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Gastrointestinal Physiology
Physio Midterm/Final
772
Physiology
Professional
09/16/2010

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Term
What is the function of the digestive system?
Definition
Supply nutrients from the environment to the circulatory system
Term
The digestive system is a long tube resembling a _____.
Definition
Processing Plant
Term
The digestive sys converts ____ into ____.
Definition
Macromolecules; Micromolecules
Term
Give some examples of macromolecules.
Definition
Proteins, Fats, Carbohydrates
Term
Give some examples of micromolecules.
Definition
Amino acids, Fatty acids, Monosaccharides
Term
Macromolecules are converted to micromolecules by _____ means, assisted by _____.
Definition
Mechanical & Chemical; Accessory Organs
Term
What are the 3 fundamental processes of the digestive sys?
Definition
Motility, Secretions, Absorption
Term
Motility; = _____ digestion
Definition
Smooth m. contractions to crush, mix, & propel contents = mechanical digestion
Term
Secretions; = ____ digestion
Definition
Delivery of digestive enzymes, mucus, ions & fluid to create an aqueous phase = chemical digestion
Term
Absorption
Definition
Transport of nutrients, water, ions across the epithelium
Term
Digestion requires tight ____ systems involving ____ & ____ messages.
Definition
Control; Hormonal & Neural
Term
What are the 2 main functions of control systems in the digestive sys?
Definition
Adjust GI activity to quality/quantity of incoming food; Facilitate communication btw GI sections a/o CNS
Term
What type of molecules are absorbed in the GI tract?
Definition
Micromolecules
Term
What are the basic parts of the GI tract?
Definition
Mouth, Esophagus, Stomach, Liver/Bile, Pancreas, SI, LI, (Forestomach/Rumen)
Term
What is the function of the mouth?
Definition
Mechanical breakdown of food, Addition of saliva as a lubricant
Term
What is the function of the esophagus?
Definition
Conduit mouth/stomach (Conveyer belt)
Term
What is the function of the stomach?
Definition
Chemical digestion of proteins, liquefaction of food (Food grinder)
Term
What is the first "centerpiece" of digestion?
Definition
The stomach
Term
What is the function of the liver?
Definition
Provision of bile salts for digestion/absorption of fats
Term
What is the function of the pancreas?
Definition
Provision of major digestive enzymes
Term
What is the function of the SI?
Definition
Provision of enzymes, Chemical digestion & absorption of nutrients & water
Term
By what point in the GI tract should chemical digestion & absorption of nutrients be completed?
Definition
SI
Term
What is the function of the LI?
Definition
Absorption of water, feces formation, bacterial fermentation (major species differences)
Term
What is the function of the forestomach/rumen?
Definition
Bacterial fermentation of nutrients & absorption of fermentation products
Term
Most ingested nutrients are in the form of _____.
Definition
Huge macromolecules
Term
Macromolecules need to be ____ by ____ into simple molecules before they can be ____.
Definition
Hydrolyzed; Enzymes; Absorbed
Term
What is the structure of a protein?
Definition
Amino Acids (amino & carboxyl group) linked by peptide bonds
Term
What is the structure of a triglyceride?
Definition
3 fatty acids w/ a glycerol backbone
Term
What is the structure of glucose?
Definition
6 C ring linked @ C1 & C4 (alpha linkage)
Term
Hydrolysis
Definition
Splitting a bondage by add'n of H2O
Term
What is the prefix for a peptide >25?
Definition
Poly
Term
What is the prefix for a peptide <25?
Definition
Oligo
Term
Most fatty acids have a ____ # of Cs.
Definition
Even
Term
The digestive tract is mostly a long, _____ tube, geared towards ______.
Definition
Smooth m., Coordinated Motility
Term
The GI tract is a single-unit type ____.
Definition
Syncytium
Term
GI smooth mm. are ______ cells w/ _____ resting membrane potentials.
Definition
Self-Excitatory; Undulating
Term
The smooth m. cells of the GI tract exhibit ____ & ____.
Definition
Slow Waves; Spike Potentials
Term
What is resting membrane potential?
Definition
-70 mV
Term
Where is the midline of the GI cell undulations?
Definition
~ -50 to -60 mV
Term
What generates the resting membrane potential in the GI tract?
Definition
Specialized smooth m. cells (Cajal)
Term
b/o ____, slow waves are conducted along a GI section.
Definition
Gap Junctions
Term
Slow waves occur w/ a frequency of ____, d/o the gut section.
Definition
3-12 min
Term
Are slow waves contractions?
Definition
No
Term
Only when a slow wave peak reaches _____, contractions occur.
Definition
Critical Threshold Potential (-40/-35mV)
Term
What happens when slow wave peaks reach threshold?
Definition
Voltage-gated Ca ch's open --> Rapid influx of Ca causes spike potentials & elicits m. contractions, which spread along GI section
Term
# of contractions is determined by _______.
Definition
# of peaks/waves reaching threshold
Term
What can the amplitude of slow waves be modulated by?
Definition
Priming Factors & Hyperpolarizing Factors
Term
What do priming factors do?
Definition
Depolarize smooth m. membrane
Term
With priming factors, GI motility _______.
Definition
Increases
Term
With hyperpolarizing factors, GI motility _____.
Definition
Decreases
Term
Examples of priming factors:
Definition
Gut wall stretching, Parasympathetic stimulation, some GI hormones
Term
Examples of hyperpolarizing factors:
Definition
Sympathetic stimulation, some GI hormones
Term
What are the 2 basic patterns of GI motility?
Definition
Segmentation/Mixing; Peristalsis/Propulsion
Term
Segmentation/Mixing
Definition
Localized contraction of mostly circular mm.
Term
Segmentation/Mixing travels over ___ distances & has a _____ effect on gut content.
Definition
Short; Chopping/Mixing
Term
Peristalsis/Propulsion
Definition
Circular contraction Cr to a bolus w/ relaxation Cd to the bolus
Term
In Peristalsis/Propulsion, contraction travels ____ over ___ distances; bolus moves _____.
Definition
Analwards; Longer; Aborally
Term
Bolus moves aborally = strong local reflex called ____.
Definition
Adaptive Relaxation
Term
The secretory & motor functions of the GI tract are tightly controlled by ____, ____, & ____.
Definition
Endocrine System, Nervous System (Enteric & Autonomic), & Immune System
Term
Which system controls digestive functions by secreting endocrines & paracrines?
Definition
Enteric Endocrine System
Term
The enteric endocrine system controls digestive functions by secreting ____ & ____.
Definition
Endocrines & Paracrines
Term
Regulatory peptides that act via blood stream =
Definition
Endocrines
Term
Regulatory peptides that act via Diffusion =
Definition
Paracrines
Term
Enteric Endocrine system can also be stimulated via ____.
Definition
Enteric Plexus
Term
How many regulatory peptides of the enteric endocrine system are known to date?
Definition
~35
Term
Name some GI endocrine regulatory peptides.
Definition
Gastrin, Somatostatin, Secretin, Cholecystokinin, Gastric Inhibitory Peptide, Motilin, Enteroglucagon, Peptide YY
Term
What do the regulatory peptides of the GI endocrine cells affect?
Definition
Secretions of the GI tract & accessory organs, & their motility functions
Term
What do duodenal endocrine cells react to?
Definition
Low pH
Term
Duodenal endocrine cells react to low pH values & release ____ into circulation
Definition
Secretin
Term
What does secretin do?
Definition
Stimulates pancreas & liver to release buffers into the gut
Term
What is considered the brain of the gut? What does it consist of?
Definition
Enteric (Intrinsic) NS; Myenteric & Submucosal Plexus
Term
What is the unique NS of the GI system?
Definition
Enteric (Intrinsic) NS
Term
Where is the submucosal plexus located?
Definition
Between Submucosa & 1st m. layer
Term
Whee does the enteric NS lie?
Definition
In the gut wall extending btw esophagus & anus
Term
How many neurons does the Enteric NS contain?
Definition
As many as the spinal cord
Term
The enteric NS is ____ & regulates GI _____, _____, & ____.
Definition
Autonomic; Smooth mm., Endocrine & Secretory cells
Term
What does the enteric NS enable?
Definition
Communication among adjacent GI sections (=local reflexes)
Term
The enteric NS uses _____.
Definition
NT's
Term
What are the NT's of the enteric NS?
Definition
ACh (mostly excitatory), Norepinephrine (mostly inhibitory), Serotonin, Dopamine, CCK, ATP, Somatostatin, Bombesin, Motilin, Substance P, Vasoactive Intestinal Peptide
Term
The Enteric NS is a ______ consisting of _____
Definition
Simple Reflex System; Sensory R's, Afferent Fibers, Ganglia Cells, Efferent Fibers, Effectors
Term
What are the effectors of the enteric NS?
Definition
Smooth m. cells, Secretory cells
Term
What does the myenteric plexus influence?
Definition
GI Motility
Term
What does the submucosal plexus influence?
Definition
GI Secretions
Term
What type of R's are involved w/ the myenteric plexus? What do they do?
Definition
MechanoR's; Monitor degree of m. stretching
Term
What type of R's are involved w/ the Submucosal Plexus? What do they do?
Definition
ChemoR's; Monitor chemicals (nutrients, pH)
Term
(Myenteric Plexus): m. stretching --> ______ --> _______ --> ______
Definition
Afferent neurons --> Cell Body --> Efferent neurons to m. cells
Term
(Submucosal Plexus): chemicals --> ____ --> _____ -->_____
Definition
Afferent neurons --> Cell body --> Efferent neuron to secretory, endocrine, & mucus cells
Term
Many ____ exist btw Myenteric & Submucosal plexuses to coordinate ____ & ____ activity.
Definition
Interneurons/Collaterals; Muscle & Secretory
Term
Can endocrine cells be stimulated/inhibited by NS?
Definition
Yes (even though they are autonomous)
Term
Although the Enteric NS works ____, the GI tract is also innervated by ______. (= _____ & _____)
Definition
Independently; Autonomic NS; Parasympathetic & Sympathetic innervation
Term
What is the parasympathetic system supplied by?
Definition
Vagus n. & Pelvic nn.
Term
What type of fibers does the parasympathetic system contain?
Definition
Sensory (from ChemoR's, MechanoR's); Motor (to m. cells, gland cells)
Term
What is the main transmitter of the parasympathetic system?
Definition
ACh
Term
What does stimulation of the parasympathetic nn. do to GI functions?
Definition
Increases motility & secretion rates; Decreases sphincter tones
Term
Where does the sympathetic NS originate?
Definition
T5-L2
Term
Where does sympathetic NS pass to?
Definition
Mesenteric Ganglia
Term
What is the major transmitter of the SNS?
Definition
Norepinephrine
Term
Stimulation of the parasympathetic nn. mostly _____ GI functions.
Definition
Stimulates
Term
Stimulation of the sympathetic nn. mostly _____ GI functions.
Definition
Inhibits
Term
What does stimulation of the sympathetic nn. do to GI functions?
Definition
Decreases motility & secretions; Increases sphincter tone
Term
Enteric NS = ____ Reflexes; Autonomic NS = ____ Reflexes.
Definition
Local; Central
Term
Are the Enteric & Autonomic NS controlled by the same or different ChemoR's & MechanoR's w/i GI wall?
Definition
Same
Term
What type of signals do the MechanoR's & ChemoR's send to the Enteric & Autonomic NS?
Definition
Sensory signals
Term
What is the main stimulation for GI movements?
Definition
Distension of GI wall
Term
What does distention of GI wall stimulate? Via what?
Definition
Enteric & Autonomic NS via MechanoR's
Term
Distension of GI wall --> Stimulation of NS via MechanoR's --> ________
Definition
Release of Priming Factors
Term
What results from the release of priming factors?
Definition
Opening of ligand-gated ion channels --> Depolarization of smooth m. membranes --> Passing slow waves will reach threshold
Term
What happens when passing slow waves reach threshold?
Definition
Spike Potentials --> Contractions
Term
What does the enteric immune system consist of?
Definition
Mesenteric lnn.; Peyer's Patches; Diffuse Lymphoid Tissue; Intraepithelial Leukocytes
Term
What is the enteric immune system concerned w?
Definition
Potential Pathogens (Defense Sys)
Term
If challenged, what does the enteric immune sys do?
Definition
Releases inflammatory mediators (prostaglandins, histamine, cytokines, chemokines)
Term
What do prostaglandins, histamine, cytokines, etc. act as in the GI tract?
Definition
Paracrines; typically stimulating secretory & motility functions
Term
What does stimulation of secretory & motility functions of the GI by the enteric immune sys lead to?
Definition
Peristaltic Rush
Term
What is Peristaltic Rush?
Definition
Powerful & Rapid Peristaltic movements of the SI caused by intense mucosal inflammation
Term
What type of response is peristaltic rush?
Definition
Protective response to quickly push potentially harmful contents into the LI
Term
GI blood flow is largely _____.
Definition
Autoregulated & Adjusts to the level of local activity
Term
How much can the GI blood flow increase between inactivity & active digestion?
Definition
By a factor of 8 (8-10)
Term
What stimulates GI blood flow?
Definition
Pumping action of GI mvmt; Several endocrines; Decreased O2/increased CO2 conc during activity phases
Term
What are some endocrines that stimulate GI blood flow?
Definition
Bradykinin; Kallidin
Term
Sympathetic stimulation leads to _____ of GI blood vessels.
Definition
Constriction
Term
How long can GI blood vessels remain constricted w/o causing damage?
Definition
1 hr
Term
What can overrule the effect of sympathetic stimulation constricting GI blood vessels? What does this do?
Definition
Autoregulatory Mechanism; Protect Mucosa
Term
What are some causes of long disruption of GI blood supply?
Definition
R Heart failure; Hepatosis; Ileus
Term
What type of tissues suffer the most from hypoxia?
Definition
Highly active tissues
Term
What is the term for blockage of the gut by a foreign object?
Definition
Ileus
Term
What does ileus lead to?
Definition
Permanent distension & ingesta back-up
Term
Colic
Definition
Abdominal Pain/Discomfort
Term
What is another name for the cephalic phase?
Definition
Pregastric phase
Term
What does the cephalic phase involve?
Definition
Grasping, Chewing & Mixing food w/ saliva in preparation for swallowing
Term
What is the first step of mechanical digestion?
Definition
Cephalic phase (Mastication/Chewing)
Term
What type of digestion is included in the cephalic phase?
Definition
Mechanical; Chemical in some spp. (omnivores)
Term
Where does the cephalic phase send signals? What is the purpose of this?
Definition
Stomach, accessory glands, SI to prepare for incoming food; "warming up"
Term
Disturbances in _____ can hamper adequate food intake.
Definition
Pregastric functions
Term
How many pairs of salivary glands do most animals have? Name them.
Definition
3; Parotid, Mandibular, Sublingual
Term
What extra salivary gland is present in ruminants & birds?
Definition
Buccal
Term
What are the functions of saliva?
Definition
Moisten, lubricate, bind food into bolus; Control bacterial growth; Start carbohydrate digestion in omnivores; Cool body; Protect Mucosa; Vocalization
Term
How does saliva start carbohydrate digestion?
Definition
Via salivary amylase
Term
How does saliva cool the body?
Definition
Evaporation
Term
In what animals does saliva play a role in thermoregulation?
Definition
Carnivores, Birds, Reptiles
Term
What do salivary acini secrete?
Definition
Mucus & plasma-like fluid (primary saliva)
Term
When is primary saliva altered?
Definition
During duct passage
Term
During duct passage, what is exchanged in saliva?
Definition
Na & Cl against K & HCO3
Term
Saliva is slightly ____, slightly ____, & ____-rich.
Definition
Hypotonic; Alkaline; K+
Term
What animals have slightly acidic saliva? What does this cause?
Definition
Humans; Enamel Defects
Term
In humans & horses, what is the daily volume of saliva produced?
Definition
1.5L
Term
In horses, what is the daily volume of saliva produced?
Definition
10L
Term
What is the pH of saliva?
Definition
7.2-8.4
Term
Saliva is ____ compared to plasma.
Definition
Hypo-osmolar
Term
What is the daily volume of saliva produced in ruminants?
Definition
100-200L
Term
Salivation is ____, but greatly stimulated during _____, controlled by the _____ in 2 ways.
Definition
Continuous; Food-intake; ANS
Term
In what 2 ways is salivation controlled by the ANS?
Definition
Parasympathetic Reflex; Conditional Reflex
Term
What type of R's are involved w/ the parasympathetic salivary reflex? Where are they located?
Definition
ChemoR's & MechanoR's in the mouth (oral mucosa)
Term
(Parasympathetic Salivary Reflex): ChemoR's & MechanoR's in mouth -->
Definition
Salivary center/Brain stem
Term
Salivary center in the BS sends _____ efferents via _____ nn., causing ____.
Definition
Parasympathetic; CrN 7 & 9; Salivation
Term
What contributes to the conditioned salivary reflex?
Definition
Anticipation & Smell of food
Term
(Conditioned Salivary Reflex): Anticipation & Smell -->
Definition
Higher CNS --> Salivary Center --> Salivation
Term
The stimuli that cause increased salivation also activate _____ & initiate _____.
Definition
Vagus n.; Vagal Reflexes
Term
Vagal reflexes lead to ___ stimulation of ____. This is called ____.
Definition
Mild; Stomach, SI, Pancreas, Bile; Warming-up Phase
Term
What is ruminant saliva rich in? What is this essential for?
Definition
Bicarbonate & Phosphate buffers; Neutralization of Fermentation products in the rumen
Term
What can the continuous production of large amounts of saliva in ruminants lead to when a foreign body is lodged in the esophagus?
Definition
Fluid Loss
Term
_____ of food req's highly coordinated mvmts of voluntary mm., using lips, tongue, teeth, forelimbs, nose.
Definition
Prehension
Term
What does mastication do?
Definition
Breaks down food & lubricates it for swallowing
Term
What structures are involved in mastication?
Definition
Teeth, Jaws, Palate, Tongue & Cheeks
Term
Mastication is mainly controlled by ____, involving ___ n.
Definition
Chewing Reflex; CrN 5
Term
What is the chewing reflex?
Definition
Presence of bolus creates pressure against palate which inhibits cheek mm.; Lower jaw drops & stimulates stretch R's in cheek mm. leading to contraction, pressure against palate, etc.
Term
Describe the comparative width of the jaws in carnivores.
Definition
Equally wide jaws
Term
Describe the comparative width of the jaws in herbivores.
Definition
Lower jaw narrower/Upper jaw wider
Term
Describe the jaw movements in carnivores.
Definition
Vertical --> Cutting Action
Term
Describe the jaw movements in herbivores.
Definition
Horizontal & Vertical --> Grinding Action
Term
What is another word for swallowing?
Definition
Deglutition
Term
What phases are involved in swallowing?
Definition
Voluntary & Reflex
Term
The voluntary + reflex phases of swallowing guarantee _____.
Definition
Correct closure of nasal & tracheal passageways
Term
What can occur if the nasal & tracheal passageways do not close during swallowing?
Definition
Fatal Aspiration Pneumonia
Term
What is the voluntary phase of swallowing?
Definition
Tongue moves bolus into pharynx
Term
What is the 1st step of the reflex phase of swallowing?
Definition
Touch R's stimulate swallowing center (MO) via CrN 9 (Gag Reflex)
Term
What does the gag reflex initiate?
Definition
Lifting of soft palate & closure of larynx; peristaltic wave moves over pharynx; upper esophageal sphincter relaxes; Bolus enters esophagus
Term
What m. is the esophageal sphincter a part of?
Definition
Cricopharyngeal m.
Term
In the esophageal phase of swallowing, the bolus is propelled by ____ towards ____.
Definition
Peristalsis; Stomach
Term
_______ relaxes ahead of peristalsis to allow entry of bolus into stomach.
Definition
Lower esophageal sphincter
Term
When not in swallowing process, ______ are tightly closed to avoid entry of air & esophageal reflux of gastric contents.
Definition
Upper & Lower Esophageal Sphincters
Term
What nerve is tested by the gag reflex?
Definition
CrN 9
Term
How common are disturbances in pregastric digestion?
Definition
Common
Term
What can result from disturbances of pregastric digestion?
Definition
Reduced nutrient intake &/or insufficient mechanical preparation of food.
Term
What are some examples of pregastric disturbances related to teeth problems or injuries of oral mucosa? What is often caused?
Definition
Broken teeth, Enamel points, Plaque/Inflammations; "Woody Tongue;" Pain
Term
What are some examples of pregastric disturbances related to nerve or CNS damage?
Definition
Encephalitis, Tetanus, Rabies, Trigeminal Paralysis
Term
What is blocked during deep anesthesia?
Definition
Swallowing reflex
Term
What are 4 causes of megaesophagus?
Definition
Achalasia; PRAA; MG; Idiopathic
Term
Achalasia
Definition
Lower esophageal sphincter fails to relax due to genetic malfunction of myenteric plexus
Term
PRAA --> ____ of esophagus
Definition
Mechanical obstruction
Term
MG
Definition
Myasthenia Gravis
Term
What is MG?
Definition
ACh R deficit or damage
Term
What m. is innervated by the trigeminal n? What results from damage to this n?
Definition
Masseter; Dropped Jaw
Term
Rabies --> ____ m. paralysis
Definition
Pharyngeal m.
Term
What is the most common disturbance of pregastric digestion related to?
Definition
Teeth Problems
Term
Regurgitation is from _____, where as vomiting is from ____.
Definition
Esophagus; Stomach
Term
What are the 4 functions of the stomach?
Definition
Temporary Storage of food; Mixing of food w/ gastric secretions & liquefaction of ingesta into chyme; Chemical & enzymatic digestion; Controlled release of liquefied chyme into SI
Term
What is particularly digested by chemical & enzymatic means in the stomach?
Definition
Protein
Term
What part of the stomach stores food?
Definition
Proximal (Cardia & Fundus)
Term
Is absorption a physiological gastric function?
Definition
No
Term
Can any substances be absorbed by the stomach?
Definition
Yes, but not natural diet/nutrients; Alcohol, small lipophilic drugs
Term
What is required before chyme can be passed on to the duodenum?
Definition
Thorough mixing w/ gastric juices
Term
The duodenum has a limited capacity. What does this necessitate?
Definition
Temporary Storage
Term
Where does storage of food mostly occur? Facilitated by what?
Definition
Proximal stomach; Accommodation reflex
Term
What is the accommodation reflex?
Definition
Food enters the stomach & stimulates mechanoRs which initiate a vago-vagal reflex
Term
What is the vago-vagal reflex of the accommodation reflex?
Definition
Reduction in m. tone in proximal parts of stomach --> Relaxation --> Expansion of stomach w/o pressure increase
Term
What is most likely the NT of the vago-vagal reflex?
Definition
NO or VIP
Term
What reduces the accommodation reflex?
Definition
Suppression of vagus or Stimulation of Sympathetic sys --> Increased gastric pressure after food intake --> Satiety feeling
Term
VIP
Definition
Vasoactive Intestinal Peptide
Term
In what part of the stomach does mixing occur?
Definition
Distal
Term
What type of foods require grinding & mixing?
Definition
Semi-solid & Solid
Term
What are semi-solid & solid foods mixed with in the distal stomach?
Definition
Gastric Juices
Term
Describe the pylorus
Definition
Strong, sleeve-like sphincter
Term
What does presence of food in the distal stomach stimulate?
Definition
Local & Central Reflexes --> Enhance peristalsis originating in pacemaker area
Term
Peristalsis originating in the pacemaker area of the distal stomach travel towards the _____.
Definition
Antrum
Term
What happens when peristalsis reaches the antrum?
Definition
Pylorus contracts ahead of peristaltic wave --> Content is kneaded & squirted back (Retropulsion)
Term
What does mixing in the distal stomach do to content?
Definition
Liquefy
Term
When content of the distal stomach is liquefied, peristalsis begins to include _____ & becomes ____.
Definition
Prox stomach; More Intense
Term
When peristalsis includes the proximal stomach, small amounts of ____ are passed through the _____ ahead of strong peristaltic waves & chyme enters _____.
Definition
Fluid; Pylorus; Duodenum
Term
How long after a solid meal until the stomach is empty?
Definition
6-8 hours
Term
What occurs during fasting phases/empty stomach? What is this called?
Definition
Occasional strong peristaltic waves btw stomach & ileum while pylorus is relaxed; Migrating Motility Complex
Term
MMC
Definition
Migrating Motility Complex
Term
What initiates the MMC? What does the MMC do?
Definition
Motilin; Clear stomach & SI of undigested food particles
Term
How long does a ferret take from eating to defecation?
Definition
4 hours
Term
What can be done <30 min after a foreign object is ingested?
Definition
Induce vomiting
Term
What are CS of ileus?
Definition
Distension, Pain, Unstoppable Vomiting
Term
What is another name for the MMC?
Definition
Housekeeping Function
Term
How many types of mucosa does the stomach contain? What are they?
Definition
2; Non-Glandular & Glandular
Term
What is another name for non-glandular mucosa of the stomach?
Definition
Cutaneous mucosa
Term
What is the function of the non-glandular stomach?
Definition
Unclear (Storage/Fermentation?)
Term
What monogastric has a particularly large non-glandular stomach?
Definition
Horse
Term
What is the glandular mucosa of the stomach composed of?
Definition
Cardiac, Parietal, & Pyloric Region which contain tubular glands
Term
What type of cells are in the glandular mucosa of the stomach?
Definition
Mucus, Parietal, Enterochromaffin-like, Chief, & G (Endocrine) Cells
Term
What type of cells are in the glandular mucosa of the stomach?
Definition
Mucus, Parietal, Enterochromaffin-like, Chief, & G (Endocrine) Cells
Term
What are the mucus cells of the stomach? How many are there?
Definition
Surface & Neck cells; Very numerous
Term
What do parietal cells of the stomach secrete?
Definition
HCl & IF
Term
IF
Definition
Intrinsic Factor
Term
What do enterochromaffin-like cells secrete?
Definition
Histamine
Term
What do chief cells secrete?
Definition
Pepsinogen or Prochymosin
Term
What do G/Endocrine Cells secrete? Where are they present?
Definition
Gastrin; Pyloric Region only
Term
What are very numerous throughout the GI mucosa, enabling continual replenishment of all GI cells?
Definition
Stem cells
Term
Stem cells give the GI mucosa a high _______.
Definition
Regenerative capacity
Term
The mucus layer is absolutely essential to protect the gastric mucosa against _________.
Definition
Mechanical stress, Acids, Digestive enzymes, Diffusion of damaging chemicals
Term
What is mucus produced by?
Definition
Mucus/Goblet cells covering the entire glandular mucosa
Term
What is mucus?
Definition
A coat of highly viscous, adherent, nearly insoluble mucins
Term
What are mucins? What do they provide?
Definition
Glycoproteins; Protection against mechanical stress & diffusion of damaging chemicals
Term
Is mucus acidic or alkaline? Why?
Definition
Alkaline, contains bicarbonate = protection against protons
Term
What controls mucus secretion?
Definition
Local Reflexes (Enteric NS) & Central Reflexes (Vagus)
Term
What increases mucus & bicarbonate release?
Definition
Synthesis of Prostaglandin (PGE2) in goblet cells
Term
PG
Definition
Prostaglandin
Term
Drugs interfering w/ PG synthesis will affect _____.
Definition
Mucus production
Term
NSAIDs interfere _____ w/ ______, leading to ______.
Definition
Non-selectively, PGs; decreased mucus layer & protection, ulcers, erosion, inflammation
Term
Parietal cells secrete into the stomach lumen a(n) ______ sol'n of pH _____.
Definition
Isotonic; <1
Term
What is involved w/ parietal cell secretion of isotonic sol'n?
Definition
Proton Pump (H+/K+ exchanger)
Term
What are the functions of HCl?
Definition
Macerate ingesta into fluid, Denature proteins, Begin emulsification of fats, Activate proteolytic enzymes pepsinogen or prochymosin, Bactericidal
Term
Stimulation of parietal cells -->
Definition
HCl Secretion
Term
What are some factors that stimulate parietal cells?
Definition
ACh, Gastrin, Histamine
Term
ACh is released via ____ & ____ reflexes.
Definition
Central & Local
Term
What is one of the main stimulators of the gut?
Definition
ACh
Term
Gastrin is released from _____ into ____ in response to ____ (____ stimulus).
Definition
G Cells; Blood; Peptides (mild direct stimulus)
Term
Histamine is released from _______ (= ____stimulus) in response to _____.
Definition
Enterochromaffin-like cells; Strong; Gastrin
Term
What is the pH of the stomach in pigs & humans? In carnivores?
Definition
3-4; 1-2
Term
Fats must be _____ for enzymes to work on them.
Definition
Emulsified
Term
What is one of the main factors in combating incoming pathogens?
Definition
HCl
Term
Pepsinogens are precursors of _____.
Definition
Pepsins
Term
Activation from pepsinogens to pepsins req's ______ environment.
Definition
Acidic (HCl)
Term
Pepsins' pH optimum lies btw _____.
Definition
1-3
Term
What type of enzymes are pepsinogens?
Definition
Proteolytic --> Initiate protein digestion
Term
How do pepsinogens hydrolyze collagen?
Definition
Splitting large polypeptides into smaller polypeptides & some oligopeptides
Term
How many peptides are in an oligopeptide?
Definition
<25
Term
Nursing animals secrete ______ instead of pepsinogen, which is specific for _____.
Definition
Prochymosin (Rennin in calves); Coagulation of casein
Term
IF is released from ____ cells & co-secreted w/ _____.
Definition
Parietal; HCl
Term
What is IF essential for?
Definition
Intestinal absorption of Vit B12 (necessary cofactor for erythropoiesis)
Term
Suppression of HCl & IF can lead to _____.
Definition
Anemia
Term
Casein
Definition
Milk Protein
Term
What is the purpose of tight control of gastric motility & secretions?
Definition
Prepare stomach for incoming food; Match rate of gastric secretions & grinding w/ quantity & quality of ingested food; Match emptying of chyme w/ digestive & absorptive capacity of SI
Term
What are the 3 components of the gastric motility/secretion control system?
Definition
Cephalic Phase, Gastric Phase, Intestinal Phase
Term
What is the cephalic phase of the stomach?
Definition
Anticipation of food, smell, taste, or touch stimulate Vagus, which mildly stimulates gastric motility & secretions
Term
Describe motility & secretions in the cephalic phase in the stomach.
Definition
Proximal relaxation/distal peristalsis; Mucus, Gastrin, Histamine, HCl, Pepsinogen
Term
How much stomach juice do humans produce each day?
Definition
1-2L
Term
What is the gastric phase of the stomach?
Definition
Arrival of food in stomach --> Stimulation of gastric mechano- & chemoRs --> Strong stimulation of local (plexus) & central (vagal) reflexes
Term
What are the effects of the gastric phase on the stomach?
Definition
Relaxation of mm. (accommodation) in proximal parts; Vigorous m. contractions (mixing/grinding) in distal parts; Strong stimulation of all gastric secretions w/ massive HCl release
Term
Describe the self-limitation of the gastric phase in the stomach.
Definition
When pH <2, gastrin release becomes blocked & vagal & local reflexes become inhibited to prevent excessive acidification
Term
When gastrin is blocked, ____ & ____ are subsequently blocked.
Definition
Histamine & HCl
Term
The SI has a ____ capacity.
Definition
Low
Term
What is the intestinal phase of digestion?
Definition
Chyme arrives in duod --> inhibition of gastric glands & motility due to activation of R's in SI to prevent overloading of SI (Negative feedback)
Term
What are the stimuli of the intestinal phase?
Definition
Distension of SI, High Acidity, High Nutrient Content, Irritation of Mucosa (Enterogastric Reflex)
Term
Intestinal phase is transmitted largely by ______.
Definition
Endocrines
Term
What endocrines are involved w/ the intestinal phase?
Definition
Secretin & CCK
Term
What stimulates secretin, & what does secretin do?
Definition
Low pH; Reduces gastric secretions
Term
CCK
Definition
Cholecystokinin
Term
What stimulates CCK & what does it do?
Definition
Fats & Proteins; Reduces gastric motility
Term
What is vomiting?
Definition
The forceful expulsion of stomach/SI contents through the mouth
Term
Vomiting involves coordination of _____.
Definition
Many m. groups
Term
Coordination of m. groups in vomiting:
Definition
Contraction of duod, Closure of pylorus, Gastric wall & Cardia relax, Abd mm. contract, Diaphragm fixed, Reversal of swallowing
Term
Vomiting is a reflex under the control of the _____.
Definition
Vomiting Center in the brain stem
Term
The vomiting center receives afferent signals from:
Definition
GI mechano- & chemoR's, Viscera other than GI tract, Extramedullary centers (psychogenic), ChemoR trigger zones
Term
What is one factor that stimulates GI mechano- & chemoR's leading to vomiting?
Definition
Mucosal irritation
Term
What are some factors that stimulate vomiting via viscera other than GI tract?
Definition
Inflammation of liver & kidneys
Term
In what animals is extramedullary cortex/psychogenic center a factor in vomiting?
Definition
Humans
Term
What stimulates the ChemoR trigger zone of the vomiting center?
Definition
Drugs, Toxins, Inflammation products
Term
Is regurgitation voluntary? Vomiting?
Definition
Yes; No
Term
What are some consequences of severe vomiting?
Definition
Loss of fluid, Loss of K+, Loss of H+
Term
What results from loss of fluid?
Definition
Hypovolemia, decrease BP, Circulatory Shock
Term
What results from loss of K+?
Definition
Hypokalemia, Hyperpolarization of membranes, Reduced excitability of n/m cells, Weakness & Hyporeflexia
Term
What results from loss of H+?
Definition
Metabolic Alkalosis & Hypoventilation
Term
Why is vomiting nearly impossible in horses?
Definition
Acute angle btw esophagus/stomach & clamp-like structure of diaphragm --> danger of stomach rupture
Term
During vomiting, what happens to protect the respiratory tract?
Definition
Soft palate lifts, Trachea & Epiglottis close
Term
What can be used to induce vomiting? Examples?
Definition
ChemoR trigger zone; morphine, xylazine in cats
Term
What ceases to function in the absence of K+?
Definition
Proton Pump
Term
Describe the GI Barrier
Definition
The GI mucosa forms a barrier btw the gut lumen & body, allowing transfer of nutrients while protecting the body against harmful chemicals & bacteria
Term
What are the components of the GI barrier?
Definition
Mucus & bicarbonate, PGE2, Epithelial cells w/ tight junctions & stem cells, Bactericidal peptides/IgA
Term
What do mucus & bicarbonate do in the GI barrier?
Definition
Coat cells, neutralize acids, bind to bacteria
Term
What does PGE2 do in the GI barrier?
Definition
Increase blood flow, mucus, & bicarb secretions
Term
What do stem cells do in the Gi barrier?
Definition
Supply high regenerative capacity
Term
What do the tight junctions btw epithelial cells do in the GI barrier?
Definition
Make tract impenetrable to large particles
Term
What is the #1 cause of disruptions to the GI barrier?
Definition
Stress
Term
What are some causes of disruptions to the GI barrier?
Definition
Stress, NSAIDs, Ischemia, Infections
Term
How does stress disrupt the GI barrier?
Definition
Sympathetic stimulation & cortisol release --> reduced blood flow, mucus, HCO3, healing
Term
What, in particular, does cortisol impede?
Definition
Cell division & Healing
Term
What is ischemia?
Definition
Total lack of blood supply
Term
How does ischemia disrupt the GI barrier?
Definition
Cell damage
Term
How do infections disrupt the GI barrier? What is one such infection?
Definition
Tissue damage; Helicobacter pylori
Term
What are consequences of disruption of the GI barrier?
Definition
Cell injury, Gastritis, Auto-digestion, Erosion, Ulceration, Enteritis
Term
Ulcer
Definition
Deep, crater-like wound
Term
What is the Tx for disruption of the GI barrier?
Definition
Stress relief, Histamine (H2) blockers, Proton pump blockers, Antibiotics
Term
What do NSAIDs inhibit?
Definition
All PGs
Term
Give 2 examples of NSAIDs
Definition
Aspirin, IBU Profen
Term
What are some causes of stress in animals?
Definition
Transportation, Food changes, Dz, Abnormal feeding patterns
Term
What is a major damaging factor in the stomach?
Definition
HCl
Term
What is the pH of chyme entering the SI?
Definition
Highly acidic
Term
When leaving the stomach, chyme is a fluid mixture of:
Definition
Polypeptides (via action of HCl & pepsins), Large emulsified fat globules (via action of HCl), Unchanged dietary carbohydrates (respectively some oligosaccharides in omnivores via salivary amylase)
Term
Can chyme that leaves the stomach be absorbed in the SI?
Definition
No
Term
What 2 events must occur to chyme leaving the stomach?
Definition
Neutralization of gastric acid; Hydrolysis of macromolecules into micromolecules
Term
Why must neutralization of gastric acid in the chyme leaving the stomach take place?
Definition
To avoid mucosal damage
Term
Why must macromolecules be hydrolyzed into micromolecules?
Definition
For absorption (Monosaccharides, tri/dipeptides and aa's & FFAs/monoglycerides)
Term
To achieve neutralization of gastric acid & hydrolysis of macromolecules, _____, _____, & _____ must cooperate.
Definition
Pancreas, Bile, & SI Mucosa
Term
What does the pancreas provide for chyme leaving the stomach?
Definition
Buffers & Major digestive enzymes
Term
What does bile provide for chyme leaving the stomach?
Definition
Buffers & Fat emulsifier
Term
What does the SI mucosa provide for chyme leaving the stomach?
Definition
Buffers, Final digestive enzymes, Absorptive mechanisms
Term
What mildly stimulates the exocrine pancreas to secrete enzymes & bicarb ("warming up")? Via what?
Definition
Cephalic phase via vagal stimulation & Gastric phase via gastrin release
Term
What is the main phase of pancreatic stimulation?
Definition
Intestinal Phase
Term
The intestinal phase stimulates the pancreas via _______
Definition
Secretin & CCK
Term
wrt pancreatic stimulation, what role does Secretin play?
Definition
Released from duodenal endocrine cells into blood when pH of chyme is low (<4.5) --> Stimulates bicarb secretion
Term
wrt pancreatic stimulation, what role does CCK play?
Definition
Proteins & fats stimulate release of CCK from duodenal endocrine cells into blood --> Stimulates release of pancreas enzymes
Term
How much pancreatic fluid do humans produce per day?
Definition
~1L
Term
What are the direct digestive functions of the liver? Via what?
Definition
Facilitate digestion & absorption of fats & lipophilic vitamins via secretion of bile acids; Neutralize acidic chyme via bicarb secretion
Term
What are the fat soluble vitamins?
Definition
A, D, E, K
Term
What cell types secrete bile juices?
Definition
Hepatocytes & Duct cells
Term
What type of bile juices do hepatocytes secrete?
Definition
Bile acids (>50% of solutes); Lipophilic waste products (bile pigments/bilirubin, cholesterol)
Term
What type of bile juices do duct cells secrete?
Definition
Bicarb, Electrolytes & Water
Term
Where is bile juice temporarily stored? Until when? Which animals lack this structure?
Definition
Gall Bladder; Until needed; Horses, Deer, Elephants, Giraffes
Term
What happens in horses since they lack a GB?
Definition
Continuous absorption of electrolytes & water leads to concentration of organic compounds
Term
What does the gall bladder do to bile?
Definition
Store & Concentrate
Term
What are bile acids derived from?
Definition
Cholesterol
Term
Cholesterol --> ____ --> ____
Definition
Cholic acid --> Conjugated w/ aa's
Term
What aa's is cholic acid conjugated w/?
Definition
Glycine or Taurine
Term
Bile acids act as ______
Definition
Detergents
Term
Detergent has a ______ & _____ end.
Definition
Hydrophilic & Lipophilic
Term
What are the functions of bile acids?
Definition
Emulsification & Transport
Term
Where do bile acids attach to fat globules?
Definition
Surface
Term
Bile acids attach to fat globules --> ______ --> _____
Definition
Vigorous mixing in aqueous chyme --> Globules break up into smaller pieces
Term
What does breaking up of fat globules into smaller pieces accomplish?
Definition
Increases SA for action of pancreatic lipases
Term
After hydrolysis by lipases, fatty acids & monoglycerides form _____ w/ _____ (=____).
Definition
Aggregates; Bile Acids; Micelle
Term
Micelles have ___ ends pointing outward & ____ ends pointing inward.
Definition
Hydrophilic; Lipophilic
Term
What is the importance of having the lipophilic ends inside the micelle?
Definition
Keeps lipids in sol'n & enables their transport w/i aqueous chyme
Term
Micelle formation allows for _____.
Definition
Transport to & absorption from mucosa
Term
Some bile juice is released during ______ phase(s). The main stimulation occurs during _____ phase(s).
Definition
Cephalic & Gastric; Intestinal
Term
The main stimulation of bile juice release occurs during the intestinal phase via what hormones?
Definition
CCK & Secretin
Term
wrt bile release, CCK stimulates _____.
Definition
Gall bladder contraction & release of stored bile
Term
Chole
Definition
Bile
Term
Cyst
Definition
GB
Term
Kinin
Definition
Movement
Term
In animals w/o GB, the ____ is not an efficient barrier & bile is continuously release into duod.
Definition
Sphincter of Oddi
Term
wrt bile secretion, what does secretin stimulate?
Definition
Bicarb secretion into bile system when pH of chyme is low
Term
Secretion of pancreatic & bile juices are _____.
Definition
Coordinated
Term
What % of bile acids are reabsorbed? Where?
Definition
95% in ileum
Term
Once reabsorbed, where do bile acids re-enter?
Definition
Liver
Term
Bile acids are recycled and secreted again & again up to _____ times.
Definition
20
Term
What % of bile acids are shed w/ feces?
Definition
5%
Term
What is the choleretic effect of bile acids?
Definition
Re-uptake of bile acids stimulates hepatocytes to secrete more bile juice (positive feedback)
Term
What are damaged hepatocytes incapable of? What does this lead to?
Definition
Extracting bile acids from portal blood; Bile acids may increase in plasma
Term
What is one diagnostic indicator of liver dz?
Definition
Increased bile acids in plasma
Term
Inflammation of the pancreas leads to liberation of _______,which are then in contact w/ digestive enzymes leading to ___ & ___.
Definition
Proteolytic enzymes; Activation & Autodigestion
Term
What is found PM when an animal had pancreatitis?
Definition
Mushy, soft organs
Term
How common are GB inflammation & stones in vet med?
Definition
Extremely rare
Term
Typically, bile issues are secondary to _____.
Definition
Liver Problems
Term
What is the strongest stimulator of HCl secretion from parietal cells?
Definition
Histamine
Term
Gastrinoma leads to increased secretion of ____, which causes increased production of _____ & _____.
Definition
Gastrin; HCl; Corrosion, Erosion, Ulcers
Term
What can be used to decrease or stop HCl production?
Definition
H2 Antagonists
Term
Gastrin stimulates ___ cells to secrete ____.
Definition
ECL, Histamine; Parietal, HCl
Term
What is the center of the food processing plant?
Definition
SI
Term
Where are macronutrients digested & absorbed as simple molecules?
Definition
SI
Term
What are the main tasks of the SI?
Definition
Receive, mix, & propel chyme, pancreatic enzymes, bile juice, & buffers; Add lg volumes of buffered fluid; Provide add'l means to finalize digestive process started by gastric & pancreatic enzymes (i.e. its mucosal enzymes); Absorb virtually all micromol's & the majority of H2O & electrolyes
Term
What does the large volume of buffered fluid added by the SI do?
Definition
Create a suitable aqueous dilution enabling digestion & absorption
Term
Where is chemical digestion finalized?
Definition
SI
Term
Digestive enzymes work via _____, therefore need ____.
Definition
Hydrolysis; Aqueous medium
Term
Should nutrients go through to the LI?
Definition
No
Term
What is stimulated in the SI by incoming chyme?
Definition
Mixing & Peristaltic Contractions
Term
What do contractions in the SI assist in?
Definition
Mixing incoming chyme w/ intestinal fluid, pancreatic juice & bile; Distributing chyme along SI; Enabling contact btw digestive products & absorptive cells
Term
What does the ileocecal sphincter do?
Definition
Controls flow of ingesta btw SI &LI; Impede flow of ingesta into LI during digestive phase/active digestion (Closed); Avoid backflow of bacteria from LI into SI
Term
The ileocecal sphincter is a "____" btw SI & LI.
Definition
Bottleneck
Term
The ileocecal sphincter is a ___-way valve.
Definition
1
Term
Are there a lot of bacteria in the SI, LI, or both?
Definition
LI
Term
What can result from backward flow through the ileocecal sphincter?
Definition
SIBO (SI Bacterial Overgrowth)
Term
What are the SI tube & its mucosa characterized by?
Definition
Vast increase in SA by having folds, villi, & microvilli (600 fold increase)
Term
What is the purpose of the Brush Border & Microvilli?
Definition
Increase SA for absorption
Term
The intestinal mucosa contains numerous stem cells found w/i the _______.
Definition
Crypts of Lieberkuhn
Term
What type of SI cells do stem cells differentiate into?
Definition
All of them
Term
How often is the SI mucosa replaced?
Definition
Every 5 days
Term
What are the consequences of stem cells in the SI mucosa?
Definition
Great regenerative capacity after injury; Highly active tissue, thus vulnerable to hypoxia, metabolic disturbances, some viral inf's
Term
How long does it typically take for diarrhea to clear itself?
Definition
4-5 days
Term
What does Parvo virus affect?
Definition
Stem cells in Crypts of Lieberkuhn --> Loss of mucosal lining
Term
What do stem cells of the SI first differentiate into? Then?
Definition
Young enterocytes (Secretory Cells); Mature Enterocytes (Absorptive Cells)
Term
As young enterocytes of SI divide, they migrate _____.
Definition
Upwards
Term
Where are the young enterocytes of the SI?
Definition
Lining Crypts of lieberkuhn
Term
Where are the mature enterocytes of the SI?
Definition
Lining the Villus
Term
After how long do mature enterocytes excoriate? To where?
Definition
~5 days --> Gut lumen to be digested
Term
Aside from enterocytes, what do SI stem cells differentiate into?
Definition
Endocrine cells, mucus cells, paneth cells
Term
What do endocrine cells of the SI produce?
Definition
Endocrines (CCK, Secretin)
Term
What cells are the "body guard" in close proximity to SI stem cells?
Definition
Paneth cells
Term
Paneth cells are ____. They secrete ____ & ____.
Definition
Protective; Bactericidal substances & Ab
Term
Some toxins (E. coli, Cholera), inflammatory mediators & viruses stimulate _____ transport --> massive _______ --> severe ______.
Definition
Cl- Transport; Secretion of fluid into gut; Secretory Diarrhea
Term
What do young enterocytes of SI secrete? For what?
Definition
Lg volumes of intestinal fluid to facilitate digestion & absorption through active Cl- secretion into gut lumen
Term
What does active Cl- secretion into the SI lumen create?
Definition
Electrical Gradient which pulls Na+
Term
What does the pull of Na+ into the SI lumen create?
Definition
Osmotic Gradient which pulls water
Term
How much H2O is osmotically pulled into the SI lumen each day in humans?
Definition
~2L
Term
What does the osmotically pulled H2O do in the SI lumen?
Definition
Dilutes Chyme
Term
What do mature enterocytes develop?
Definition
Numerous Microvilli called BBM
Term
BBM
Definition
Brush Border Membrane
Term
What does the BBM contain?
Definition
Digestive enzymes & absorptive mechanisms
Term
What is the most powerful toxin that causes secretory diarrhea?
Definition
Cholera toxin
Term
What cells in the SI create an NaCl sol'n?
Definition
Young enterocytes
Term
What animals are more vulnerable to E. coli?
Definition
Neonates
Term
What cells of the SI finalize digestion & absorption of micronutrients?
Definition
Mature enterocytes
Term
Through mixing/peristaltic action, Mature enterocytes of the SI come into contact w/ end products of _______.
Definition
Luminal digestion
Term
What are the end products of luminal digestion?
Definition
Salivary, Gastric, & Pancreatic Enzymes
Term
The end-products of luminal digestion are largely ______, & must be _____ by ____.
Definition
Non-absorbable; Hydrolyzed further by BBM enzymes
Term
What is hydrolysis of luminal digestion end-products by BBM enzymes?
Definition
Membranous/BBM Digestion
Term
Where are carbohydrates digested?
Definition
SI
Term
What is the storage form for sugar in animals?
Definition
Glycogen
Term
What is the storage form of sugar in plants?
Definition
Starch
Term
What is the most common carbohydrate?
Definition
Starch
Term
What type of carbohydrate is starch & glycogen?
Definition
Polysaccharide consisting of glucose in alpha-1-4 & alpha-1-6 (branched) glycosidic linkages
Term
What are the phases of glycogen & starch digestion?
Definition
Luminal Phase (Salivary, Pancreatic enzyme) & Brushborder Phase
Term
Luminal Phase of starch/glycogen digestion:
Definition
alpha-amylase hydrolyzes only alpha-1-4 linkages; products are oligo- & some disaccharides (mostly maltase), which cannot be absorbed
Term
Brushborder phase digestion of starch/glycogen:
Definition
Oligo- & disaccharidases w/i BBM (eg by maltose) hydrolyze alpha-1-4 & alpha 1-6 linkages; endproducts are monosaccharides (Glc) = absorbable
Term
The end products of which phase of starch/glycogen digestion are absorbable?
Definition
Brushborder Phase
Term
Can alpha amylase hydrolyze disaccharides?
Definition
No
Term
What is req'd to digest disaccharides?
Definition
Disaccharidases in BBM
Term
What is req'd to digest sucrose? What is it digested into?
Definition
BBM Sucrase; Glc & Frc
Term
What is lactose?
Definition
Milk sugar
Term
What is req'd for digestion of lactose? What is it digested into?
Definition
BBM Lactase; Glc & Gal
Term
What is the only carb-digesting enzyme in neonates?
Definition
BBM Lactase
Term
When does BBM lactase activity decline?
Definition
Around time of weaning
Term
Many adults are sensitive to _____.
Definition
Dietary Milk
Term
What is cane sugar?
Definition
Sucrose
Term
What is lactose intolerance?
Definition
Genetic lactase deficiency in kittens & humans; Lactose is fermented to lactic acid --> Mucosal irritant --> Diarrhea
Term
What happens to alpha amylase in the stomach?
Definition
Destroyed by HCl & pepsinogens
Term
In what part of the stomach does alpha-amylase continue to function in humans & pigs?
Definition
Proximal
Term
What % of carb digestion occurs in the mouth & prox stomach in humans & pigs?
Definition
25-30%
Term
Absorption of Glc & Gal into absorptive cells occurs via _______.
Definition
Secondary active Na-cotransport mechanism
Term
Secondary active Na-cotransport mechanism d/o _______
Definition
Electrochemical sodium gradient created by Na/K pump @ the basolateral side
Term
What is an exception to Secondary active Na-cotransport mechanism for monosaccharide absorption?
Definition
Fructose is absorbed via facilitated diffusion
Term
What occurs w/ monosaccharides @ the basolateral membrane?
Definition
Leave enterocytes by FD into interstitium --> Diffuse into blood --> Tissues
Term
How are structural carbohydrates digested? Why?
Definition
Fermented by microbial action; Can't be hydrolyzed by any mammalian enzyme
Term
Structural carbs
Definition
Beta glycosidic linkages
Term
Does FD req energy?
Definition
No; Needs Carrier molecule
Term
Proteins must be converted into _____ for absorption.
Definition
Tri- or dipeptides, or aa's
Term
What are the 2 phases of peptide absorption?
Definition
Luminal & BBM phases
Term
Which transporter is not inhibited by enterotoxins?
Definition
Na-Glc Transporter
Term
What is the luminal phase of protein digestion?
Definition
HCl denatures proteins & activates pepsin; Pepsin hydrolyzes proteins into polypeptides; Pancreatic endo- & exopeptidases hydrolyze polypeptides into oligopeptides
Term
What is the BBM phase of protein digestion?
Definition
Brushborder enzymes hydrolyze oligopeptides into tri- & dipeptides & aa's
Term
Neonates of some species absorb colostral Ig's by endocytosis. Digestion of these proteins is avoided by:
Definition
Limited HCl secretion; Limited pro-chymosin secretion; Trypsin-inhibitor in colostrum
Term
How are aa's & di- & tripeptides absorbed?
Definition
Similar mechanisms as Glc (Secondary Active Na-Cotransport)
Term
Absorption of the end products of carb & protein digestion d/o in tact _____, needs specific _____, d/o ______ & req's _____.
Definition
Enterocytes, Specific Transporters, Na absorption, energy
Term
What does digestion/absorption of fats d/o?
Definition
Pancreatic enzymes & bile salts (does not req BB enzymes or transporters)
Term
Fat globules are emulsified by _____.
Definition
Conjugated bile acids
Term
What attaches to the surface of fat globules? What does it do?
Definition
Pancreatic lipase/Colipase; Hydrolyze triglycerides into monoglycerides & FFAs
Term
Monoglycerides & FFAs form aggregates w/ ______ (=_____).
Definition
Conjugated bile acids (Micelles)
Term
Micelles transport _______ to ______ where they _____ into ______.
Definition
Monoglycerides & FFAs to BBM; Diffuse into epithelial cell
Term
Free conjugated bile acids return to _________.
Definition
Emulsify more fat globules or form new micelles
Term
What happens to FFAs & monoglycerides after diffusion into enterocyte?
Definition
Mostly recombined to triglycerides
Term
What aggregates into chylomicrons?
Definition
Triglycerides, cholesterol, phospholipids, fat-soluble vitamins & newly formed lipoproteins
Term
What are chylomicrons?
Definition
Transport form for lipids in plasma
Term
How do chylomicrons leave the endothelial cell? What do they enter?
Definition
Exocytosis; Lymphatic System --> Circulation (plasma can turn milky)
Term
Hepatic (bile) & Pancreatic (lipase) disorders can lead to __________.
Definition
Maldigestion/Malabsorption of dietary fats
Term
Chyle
Definition
Lymph
Term
Every day, the equivalent of up to ____% of an animal's BW enter the GI as fluid, which has to be ____ to avoid ____.
Definition
10%; Reabsorbed; Dehydration
Term
Massive amounts of water & electrolytes are _____ into the gut lumen via ______.
Definition
Actively Secreted; Saliva, Stomach juices, Intestinal Fluid, Pancreas & Bile juice
Term
The # of micromolecules _____ dramatically once hydrolysis of nutrients begins.
Definition
Increases
Term
Osmotic pressure of chyme ____ before absorption & water is ______ via _____.
Definition
Increases; Sucked into gut lumen; Osmotic Pull
Term
Osmolality
Definition
# of particles/V of sol'n
Term
As # of particles in V of sol'n increases, osmotic P ____.
Definition
Increases
Term
Water always follows ______ & its absorption entirely d/o absorption of _______ & _______.
Definition
Osmotic Gradients; Electrolytes & Nutrients
Term
What is the driving force for absorption of Glc, Gal, Na, Small peptides, aa's & Cl-?
Definition
Na/K pump
Term
During absorption, accumulation of electrolytes & nutrients intracellularly & then in the lateral spaces before being transported off via blood creates steep _______ --> ______ follows ______ = is ______.
Definition
Osmotic Gradients; Water, Passively; Reabsorbed
Term
When more Na is absorbed, more _____ is reabsorbed.
Definition
Water
Term
By the time chyme leaves SI, how much of its water content has been reabsorbed?
Definition
80-90%
Term
Large amounts of bicarb are secreted into the gut lumen via ________ & must be recovered to _______.
Definition
Saliva, Pancreas, Bile, Intestinal Fluid, Mucus; Maintain pH neutrality
Term
What does recovery of bicarb d/o? What is it achieved by?
Definition
Sodium gradients; Absorption of CO2
Term
How is K+ absorbed?
Definition
Passively along its chemical gradient
Term
Is it more essential to reabsorb water or bicarb?
Definition
Equally essential
Term
What type of diarrhea do laxatives create?
Definition
Osmotic
Term
Diarrhea
Definition
Softer than normal feces caused by an imbalance btw water absorption & secretion, leading to loss of body water, electrolytes, & bicarb via feces
Term
What is another name for osmotic diarrhea?
Definition
Malabsorptive
Term
If gut contains a lg # of mol's which are poorly or not absorbed --> _______ --> ______
Definition
High osmolality of chyme --> Water is sucked into lumen
Term
What causes osmotic diarrhea?
Definition
Intake of non- or low absorbable compounds; Accumulation of partially digested ingesta; Loss of absorptive cells due to mucosal damage
Term
What are some non- or low absorbable compounds that can cause osmotic diarrhea?
Definition
Fructose, Sorbitol, Lactic acid, Laxatives
Term
What could cause accumulation of partially digested ingesta & osmotic diarrhea?
Definition
Pancreatic deficiency
Term
What could cause loss of absorptive cells, resulting in incomplete digestion & malabsorption of micromol's?
Definition
Inflammations, Infections, Some Toxins
Term
What do toxins inhibit? Which one is kept in tact?
Definition
Many Na-cotransport mechanisms; Na-Glc
Term
What is secretory diarrhea?
Definition
Direct stimulation of secretory cells a/o mucus cells to secrete more fluid/mucus into gut lumen
Term
What are some causes of secretory diarrhea?
Definition
Some toxins; Mucosal irritants; Inflammatory mediators; Parasympathetic stimulation
Term
What are some toxins that cause secretory diarrhea?
Definition
E. coli toxin, Cholera toxin
Term
When are inflammatory mediators released that can cause secretory diarrhea?
Definition
Gastritis/Enteritis
Term
Describe what happens in secretory diarrhea.
Definition
More fluid is secreted than can be absorbed; Distension of GI wall; Stimulates Motility; Diarrhea
Term
Secretory diarrhea is more severe when ____ is present.
Definition
Mucosal damage
Term
What are the consequences of diarrhea?
Definition
Fluid loss; Bicarb loss; K+ loss; Epithelial defects/intestines
Term
What happens after fluid loss from diarrhea?
Definition
Hypovolemia; Hypoxia/Metabolic Acidosis/Tissue Damage + Shock & Circulatory collapse
Term
What happens after bicarb loss from diarrhea?
Definition
Loss of buffering capacity; Metabolic Acidosis; Tissue Damage
Term
What results from K+ loss from diarrhea?
Definition
Hypokalemia; Hyperpolarization of n/m membranes; Weakness & Hyporeflexia
Term
What results from epithelial defects/intestines from diarrhea?
Definition
Denuding of villi; Loss of barrier effect; Septicemia
Term
After K+ loss, are n. & m. cells more or less excitable?
Definition
Less
Term
What is the most common cause of diarrhea?
Definition
Intestinal parasites
Term
Where is enzymatic digestion & absorption of nutrients completed?
Definition
SI
Term
The LI receive largely ____ material.
Definition
Indigestible
Term
What are some indigestible materials received by LI?
Definition
Structural carbs; Trapped nutrients like whole grain
Term
Which part of the GI displays large anatomical differences across spp?
Definition
LI
Term
What are the 4 basic functions of LI in all spp?
Definition
Propulsion of chyme towards rectum; Absorption of remaining water & electrolytes; Microbial fermentation of undigested organic matter; Storage & expulsion of feces
Term
Do dogs have long or short LI? Horses?
Definition
Short; Long
Term
What does decreased blood glucose cause?
Definition
Hunger
Term
At the end of ____ digestion, an animal will typically take in the next meal.
Definition
SI
Term
Next meal --> _____ initiates _______
Definition
Gastric Distension --> Gastro-Ileal Reflex
Term
Gastro-Ileal Reflex:
Definition
Ileocecal Sphincter opens & ingesta is propelled into cecum
Term
Arrival of chyme in LI stimulates _____
Definition
MechanoR's & ChemoR's
Term
When mechano- & chemoR's in the LI are stimulated, induces _______
Definition
Increased motility to propel chyme towards rectum
Term
What is the LI motility pattern?
Definition
Mixing/Segmentation mvmts; Peristaltic & Antiperistaltic mvmts; Mass mvmts btw distal colon & rectum
Term
What is the purpose of mass mvmts btw distal colon & rectum?
Definition
Forward fecal matter
Term
What induces mass mvmts in the LI?
Definition
Gastro-Colic & Duodeno-colic Reflex (Vagal); Irritation of Colon; Stimulation of PNS
Term
What animal has a lot of anti-peristaltic mvmts in the LI?
Definition
Horse
Term
Compared to SI, mucosa of LI is much ____
Definition
Simpler
Term
Does LI mucosa contain villi? C of L?
Definition
No; Yes
Term
Do absorptive cells of the LI express BBM enzymes? Transporters?
Definition
No; No
Term
Where are the secretory & mucus cells of the LI?
Definition
Crypts of Lieberkuhn
Term
What is fermented in the LI? By what? Into what?
Definition
Indigestible matter & "escaped" nutrients; Bacterial enzymes; VFA's, CO2, CH4
Term
What type of pH does fermentation create?
Definition
Acidic
Term
What is secreted in the LI?
Definition
Bicarb-rich fluid & mucus
Term
What is the purpose of the bicarb-rich fluid & mucus in the LI?
Definition
Buffering of fermentation products to protect mucosa
Term
What is osmotic water influx in the LI b/o?
Definition
[VFA]
Term
As fermentation increases, [VFA] _____
Definition
Increases
Term
What is absorbed in the LI?
Definition
Sodium; Fermentation Products, Some vitamins produced by bacteria (K)
Term
How is sodium absorbed in the LI? What follows?
Definition
Active Na-K pump; Chloride & Water
Term
What regulates the Na-K pump in the LI?
Definition
Aldosterone
Term
How are fermentation products absorbed? Followed by what?
Definition
Simple diffusion; Water (osmotically)
Term
What, in the LI, can lead to copious secretion of mucus & fluid --> diarrhea?
Definition
Intense irritation (colitis) or psychogenic tension (anxiety)
Term
What is 1 cause of colitis?
Definition
Bacterial inf
Term
Psychogenic Tension via ____ causes _____
Definition
Limbic system; Parasympathetic stimulation
Term
When aldosterone increases, Na absorption ____.
Definition
Increases
Term
What reflexes are associated w/ defecation?
Definition
Myenteric & Parasympathetic (via pelvic nn.)
Term
What is the myenteric reflex of defecation?
Definition
Mass mvmts move feces from colon to rectum; stimulates pressure R's in rectum; stimulates myenteric plexus; Peristalsis & Internal sphincter relaxation --> Defecation
Term
The myenteric reflex is a ____ reflex, fortified by ___.
Definition
Weak; Parasympathetic Reflex
Term
What is the parasympathetic reflex of defecation?
Definition
Rectum distension --> Afferent parasymp. fibers --> spinal cord --> efferent parasy. fibers/pelvic nn. --> Intensified peristalsis
Term
What can block the defecation reflex? Via what nerve?
Definition
Voluntary constriction of external sphincter & puborectal mm. (via pudendal n.)
Term
Pelvic n. damage --> _____ --> _____
Definition
Paralyses defecation reflex --> Constipation
Term
Pudendal n. damage --> _____ --> _____
Definition
Abolishes control --> Fecal Incontinence
Term
Damage of what n. leads to constipation?
Definition
Pelvic
Term
Damage of what n. leads to fecal incontinence?
Definition
Pudendal
Term
Which of the defecation reflexes is more powerful?
Definition
Parasympathetic
Term
Is the external anal sphincter voluntary or involuntary?
Definition
Voluntary
Term
Is the inner anal sphincter voluntary or involuntary?
Definition
Involuntary
Term
Maldigestion/Malabsorption = _____
Definition
Malassimilation
Term
What, in evolutionary terms, is the most successful group of land mammals?
Definition
Ruminants
Term
What is the problem of land mammals?
Definition
The most abundant component of natural food resources, namely structural carbohydrates, can't be digested by any mammalian enzyme system
Term
What type of linkages do structural carbs have?
Definition
Beta
Term
What is the solution that ruminants developed for the problem of land mammals?
Definition
Symbiotic relationship w/ microbes, which are able to ferment structural carbs
Term
What are the compromises of ruminants?
Definition
Enormous fermentation chambers to gain sufficient energy out of a slow process; All ingested food 1st exposed to & shared w/ microbes (even if host could digest these nutrients itself)
Term
What does the ruminant's forestomach consist of?
Definition
Reticulum, Rumen, Omasum
Term
What part of the forestomach are pseudoruminants lacking? What is one pseudoruminant?
Definition
Omasum; Camel
Term
Which part of the ruminant forestomach has a honeycomb-like appearance?
Definition
Reticulum
Term
What is the size of the reticulo-omasal orifice?
Definition
small
Term
What is the volume of the reticulorumen in cattle?
Definition
250L
Term
What divides the reticulorumen into functional compartments?
Definition
Muscular folds & pillars
Term
What is the reticulorumen covered w/?
Definition
Stratified Squamous Epithelium (Aglandular)
Term
The motility pattern of the reticulorumen is ____.
Definition
Complex
Term
Reticulorumen has complex motility pattern in order to...
Definition
Mix & retain ingesta to enable microbiotic activity; Enable release of gas; Coordinate regurgitation; Pass on fermented matter into omasum
Term
How long does full fermentation req?
Definition
3-4 days
Term
How much saliva do ruminants produce each day?
Definition
100-150L
Term
What is stratification of ruminal ingesta b/o?
Definition
Density of food/Differences in gravity
Term
From top to bottom, what is the stratification of ruminal ingesta?
Definition
Gas Cap, Plant Mat (solid zone), Slurry zone, Potential escape zone, Liquid zone
Term
What is the solid zone of the ruminal ingesta?
Definition
D rumen receives undigested plant matter, ~1-2cm long, forming a mat of entangled fibers w/ air & gas trapped in btw (floating mat)
Term
What is the gas cap of the ruminal ingesta?
Definition
Microorganisms produce gas during fermentation, which floats to the top
Term
Which ruminal strata are plant fibers in?
Definition
Solid zone
Term
What is the liquid zone of the ruminal ingesta?
Definition
Mixing & fermentation break fibers up & small particles sediment into the liquid zone (saliva & water)
Term
Is liquid heavier or lighter than plant matter?
Definition
Heavier
Term
What is the potential escape zone of the ruminal ingesta?
Definition
Only sufficiently fermented (small) particles & fluid move from here into the omasum
Term
What is the A cycle of rumination?
Definition
Primary Contraction/Mixing Cycle
Term
What is the 1st reticulorumen mvmt of the A cycle?
Definition
Biphasic contraction of reticulum; During 2nd contraction, omasal orifice dilates & omasum relaxes (suction)
Term
What is the 1st ingesta mvmt of the A cycle?
Definition
Coarse, light particles --> D sac; Smal, heavy particles + Fluid --> Cr Sac & Omasum
Term
What is the 2nd reticulorumen mvmt of the A cycle?
Definition
Reticulum relaxes; Cr sac contracts; Cr-Cd contraction of D sac & D blindsac
Term
What is the 2nd ingesta mvmt of the A cycle?
Definition
Fluid flows back into reticulum; Coarse, light particles mixed in D rumen; Small heavy particles + fluid pressed V'ly
Term
What is the 3rd reticulorumen mvmt of the A cycle?
Definition
Cr-Cd contraction of V sac & V blind sac followed by Cd-Cr moving contraction
Term
What is the 3rd ingesta mvmt of the A cycle?
Definition
Small particles & fluid pressed D & flow back into Cr sac/reticulum; Coarse fibers remain in D sac
Term
A cycles occur w/ a frequency of ______ d/o coarseness of diet.
Definition
3 contractions/2min
Term
When are A cycles absent?
Definition
Only in deep sleep
Term
What are the overall effects of the stratification & A cycle?
Definition
Freshly swallowed food is moved into rumen & added to floating mat; Floating mat compressed & mixed; Small fermented particles pressed out & sink into fluid; Small particles & fluid move via Cr sac back into reticulum & pass through omasal orifice w/ next reticular contraction
Term
In the A cycle, how are different passage rates achieved?
Definition
D/o digestibility (fermentability) of ingesta
Term
Are coarse fibers of low digestibility or easily fermented? Lush grass & concentrates?
Definition
Low digestibility; Easily fermentable
Term
How long are coarse fibers retained?
Definition
Longer; up to 72 hrs
Term
What is the B cycle of rumination?
Definition
Secondary Contraction/Eructation contraction of the Reticulorumen & Ructus
Term
Eructation
Definition
Release of gas
Term
Gases formed during fermentation (up to ____ in cattle per day) must be _____.
Definition
350L; Released
Term
What are the B cycle movements?
Definition
Ructus
Term
The B cycle follows after how many A cycles? Depending on what?
Definition
2-3; Rate of gas formation
Term
Describe ructus
Definition
Cd-Cr contraction of rumen push gas cap fwd to cardia region; activates cardia R's; sphincter relaxation; gas enters esophagus; Antiperistaltic wave moves gas orally
Term
What can inhibit ructus?
Definition
Lateral recumbency during anesthesia, obstruction of esophagus, ruminal stasis
Term
What does inhibition of ructus lead to?
Definition
Accumulation of gas; BLOAT; pressure on thoracic organs; Circulatory failure
Term
What reflex controls reticulorumen motility?
Definition
Vagal Reflex
Term
What is involved in the vagal reflex of reticulorumen motility?
Definition
R's in mouth, forestomach, stomach, SI; Vagal afferent fibers; Motility center in MO; Vagal efferent fibers
Term
In reticulorumen motility vagal reflex, intrinsic system can ____ activity, but can't maintain ____.
Definition
Modulate; Coordinated motility pattern
Term
What are the main R's of the vagal reflex of reticulorumen motility?
Definition
Stretch R's & Chemo R's
Term
What stimulates stretch R's in the reticulorumen?
Definition
Mild to moderate distension of reticulorumen wall
Term
What do stretch R's of the reticulorumen do? What inhibits them?
Definition
Increase motility & rumination; Severe Distension
Term
What do chemoR's of the reticulorumen monitor?
Definition
pH
Term
What is the normal pH range of the reticulorumen?
Definition
5.5-6.8
Term
What pH do chemoR's in the reticulorumen respond to?
Definition
<5
Term
What do chemoR's of the reticulorumen do when pH falls <5?
Definition
Depress motility to slow down fermentation
Term
What pH is considered rumen acidosis?
Definition
<5
Term
Does the motility center in ruminants show spontaneous activity? What is it driven by?
Definition
No; Excitatory signals from R's
Term
wrt the motility center in ruminants, what results from R damage or inhibition?
Definition
Ruminal Stasis (Vagal indigestion), e.g. TRP (Traumatic Reticuloperitonitis)
Term
Aside from pH <5, what can inhibit reticulorumen activity?
Definition
Pain & Fever
Term
What is ejection/rumination? What happens?
Definition
Remastication; An extra contraction of the reticulum, cardia relaxes, glottis closes, inspiration mvmt sucks bolus into esophagus, antiperistaltic wave propels bolus into mouth, water pressed out/swallowed; rechewing
Term
Ejection/rumination is a crucial part of a ruminant's digestion to:
Definition
Break up coarse fibers, increasing SA for microbes; Stimulate saliva secretion to stabilize rumen environment (buffers)
Term
In ruminants, periods of ____ alternate w/ periods of ___. ( ___ )
Definition
Feeding; Rumination (Circadian Rhythm)
Term
Ejection/Rumination is a ______ reflex involving ________ stimulated by _______ which react to _____.
Definition
Complex Vagal Reflex; Rumination Center/MO; MechanoR's; Fiber coarseness & degree of filling
Term
When does ejection/rumination occur?
Definition
Immediately befoe an A-cycle
Term
What does rumination indicate? When is it disturbed?
Definition
Animal's well-being; Stress, Sickness, Pain
Term
A-cycle contractions involve what parts of the reticulorumen?
Definition
Reticulum, Cr Sac, D, V
Term
B-cycle contractions involve what parts of the reticulorumen?
Definition
D, V
Term
What is the most important stimulus for salivation in ruminants?
Definition
Chewing
Term
What does the host provide to microbes of the forestomach?
Definition
Shelter, Food, Water, Removes waste products, Maintains constant environmental conditions (temp, pH, osmolality, low O2)
Term
What do microbes provide to the host?
Definition
Energy through fermentation of otherwise undigestible food; Nutrients through synthesis (proteins, vitamins)
Term
What is fermentation?
Definition
Anaerobic metabolism (hydrolysis) of nutrients by microbes
Term
What is the forestomach ecosystem?
Definition
Symbiotic relationship btw host & microorganisms; Both partners benefit & would not survive w/o e/o
Term
Which part of the rumen's stomach is like the monogastric stomach?
Definition
Abomasum
Term
Does the stomach have a high or low accommodation capacity? The abomasum?
Definition
High; Low
Term
What is the function of the omasum?
Definition
Passing on of fermented particles from reticulum to abomasum; Absorption of residual VFA, H2O & bicarb; Some grinding effect
Term
What allows some grinding effect of the omasum?
Definition
Partly cornified epithelium
Term
What does passing on of fermented particles from reticulum to abomasum d/o? What can impair this?
Definition
Correct stratification of food in reticulum; TRP
Term
How important is the omasum?
Definition
Not extremely (Pseudorum's don't have one)
Term
Describe motility of the omasum.
Definition
Ingesta passes through reticulo-omasal orifice during 2nd contraction of reticulum (pushing action) while omasum relaxes (sucking action); Fluid & small particles enter omasum; Orifice closes briefly, canal contracts pressing ingesta btw leaves; body contracts pressing ingesta fwd into abomasum (pumping action)
Term
What is the retention time in the omasum?
Definition
1/2-3 hrs
Term
What controls omasal motility?
Definition
Intrinsic NS
Term
What are 3 ruminal microbes?
Definition
Bacteria, Protozoa, Fungi
Term
Which ruminal microbes are essential? Which are non-essential?
Definition
Bacteria; Protozoa & Fungi
Term
When do bacteria colonize the rumen? From what?
Definition
After birth; Environment, Food, Contact
Term
How many species of bacteria are ruminal microbes?
Definition
~200
Term
Ruminal bacteria are mostly _____
Definition
Anaerobic
Term
How are ruminal bacteria grouped? (E.g.)
Definition
According to function (Cellulolytic, Amylolytic, Proteolytic, Methanogenic)
Term
How do ruminal bacterial groups differ?
Definition
Main substrate, growth rate, fermentation speed, pH sensitivity
Term
When do protozoa colonize the rumen? How?
Definition
After birth; Contact to other ruminants
Term
How much of the microbial biomass of the rumen do protozoa constitute?
Definition
50%
Term
What do ruminal protozoa provide the host?
Definition
Essential protein source
Term
What is the fermentation pattern of protozoa similar to?
Definition
Bacteria
Term
Describe ruminal fungi.
Definition
Anaerobic, metabolize wide range of carbs
Term
What are the major VFAs? What % does each represent?
Definition
Acetate (60-70%), Propionate (20-30%), Butyrate (10%)
Term
What type of microbes ferment starch?
Definition
Amylolytic
Term
Is starch soluble or insoluble?
Definition
Soluble
Term
Amylolytic, Cellulolytic, & Hemicellulolytic microbes convert soluble & structural carbs to _____.
Definition
Fructose 1-6-bis-P
Term
What microbes ferment structural carbs? What are 3 examples of such carbs?
Definition
Cellulolytic & Hemicellulolytic; Cellulose, Hemicellulose, Pectin
Term
Microbes must enter plant matter through ____ or ____ for fermentation to begin.
Definition
Pores; Cut ends
Term
What are microbial enzymes a part of?
Definition
Outer membrane
Term
What is released when Fructose is converted to Pyruvate?
Definition
2 ATP + NADH2
Term
What are some short chain fatty acids?
Definition
Valeric, Isovaleric, Isobutyric, Methylbutyric Acid
Term
What is pyruvate converted to?
Definition
Acetate, Propionate, Butyrate, Lactate
Term
What is lactate converted to?
Definition
Propionate + Acetate
Term
What is released when pyruvate is converted to acetate?
Definition
2 CO2 + ATP
Term
What is NADH2 converted to when pyruvate is converted to either propionate or butyrate?
Definition
NADH2 --> NAD
Term
How many C does acetate contain?
Definition
2
Term
Microbes are continually flushed into _____
Definition
Omasum/Abomasum/SI
Term
Rum's d/o digesting microbes to cover their own ______
Definition
Protein requirement
Term
What are 2 NPNs?
Definition
Urea, Nitrates
Term
What is NPN supply achieved by in rum's?
Definition
Dietary Supplementation; Rumino-Hepatic N recycling
Term
Urea is a waste product of _____, formed in the _____.
Definition
catabolism; liver
Term
How is urea formed?
Definition
Catabolism of endogenous aa's (m. tissue) & Ammonia absorption from the rumen
Term
What happens if ruminal [NH3] is low?
Definition
Urea is secreted directly or via saliva into rumen for bacterial growth
Term
What happens if ruminal [NH3] is high?
Definition
Urea is excreted via kidneys
Term
In ruminants, most dietary proteins are ____ by ____ into ____.
Definition
Fermented, Microbes; NH3 & VFAs
Term
For their own growth, microbes synthesize _____
Definition
Proteins
Term
What do microbes req for protein synthesis?
Definition
Carbon skeleton (VFA), N source, ATP
Term
What are some sources of N for microbial protein synthesis?
Definition
Ammonia from proteinolysis (very limited in natural diet); NPN
Term
NPN
Definition
Non-protein Nitrogen
Term
What is the bottleneck for microbial production of protein?
Definition
Nitrogen source
Term
How does absorption of VFAs occur?
Definition
As free acids (lipophilic); In ionized form
Term
What is req'd for absorption of VFAs as free acids?
Definition
Low rumen pH (pka=4.8)
Term
What is probably involved w/ absorption of VFAs in ionized form?
Definition
Bicarb/VFA Exchanger
Term
What does the increase in VFAs during fermentation do to rumen pH?
Definition
Decreases pH
Term
Because of acidification from fermentation, the rumen must be constantly ______ via _______
Definition
Buffered; Flow of saliva & bicarb secretion via rumen wall
Term
Are soluble carbs (concentrates) fermented faster or slower than structural carbs?
Definition
Faster
Term
Compared to structural carbs, fermentation of soluble carbs releases (more/less) VFAs, (more/less) energy for host, (favorable/unfavorable) for production systems.
Definition
More; More; Favorable
Term
What does rapid acid increase in the rumen challenge?
Definition
Buffering capacity; can suppress useful bacterial pop's (potentially harmful)
Term
Do concentrates stimulate chewing & remastication?
Definition
no
Term
Fermentation yields ____ via ____ p'way
Definition
ATP; Acetate
Term
What is the main p'way of fermentation?
Definition
Acetate
Term
What is ATP utilized to regenerate? Via what p'ways?
Definition
Reduced co-factors (NADH2--> NAD+) via propionate & butyrate to keep p'ways open
Term
What is a waste product of the acetate p'way?
Definition
CO2
Term
CO2 is partly reduced by _______ to ______. What is the purpose of this?
Definition
Methanogenic bacteria; CH4; Regeneration of more co-factors
Term
CH4 contains large amts of ______ (lost)
Definition
Chemical Energy
Term
What microbial waste products diffuse out into rumen fluid?
Definition
Acetic, Butyric, & Propionic Acid (or salts)
Term
What type of carbs can ruminants digest?
Definition
Soluble; not structural
Term
Waste products of fermentation contain ____ for host.
Definition
Chemical energy
Term
The rumen eventually digests _____, which are its main protein source.
Definition
Microbes
Term
What is the major energy source for the ruminant host? How much of the host's energy req's do they cover?
Definition
VFAs; 60-80%
Term
What does decreased chewing & rumination do to buffer flow?
Definition
Decreases
Term
What is the cause of rumen acidosis? Examples?
Definition
Imbalance btw VFA prod & buffering capacity; Sudden ingestion of lg quantities of highly digestible carbs (grain engorgement)
Term
In rumen acidosis, VFA ____, Salivation/Rumination ____, pH _____.
Definition
Increases; Decreases; Decreases
Term
What can cause grain engorgement?
Definition
Breaking into a grain store; Concentrate diets, esp. before slaughter
Term
What pH is considered rumen acidosis?
Definition
<5.5
Term
When rumen pH drops <5.5, VFAs shift from _____ to ____. (pka ___)
Definition
Ionic to free acid state (pka 4.8)
Term
VFAs in free acid state are (ease of absorption).
Definition
Readily absorbed (just req's a conc gradient)
Term
What is normal intracellular pH?
Definition
7
Term
VFAs in free acid state + IC pH 7 --> _____.
Definition
Dissociation of free acids to ionic form & H+
Term
When free acids dissociate to ionic form & H+, what happens to the H+/Na+ exchanger? Intracellular pH?
Definition
Becomes overloaded; Drops
Term
What does drop in pH do to Na+/K+ pump?
Definition
Inhibits, leading to further accumulation of H+ & Na+
Term
What does IC Na accumulation lead to?
Definition
Water influx into epithelial cells = swelling
Term
What do low pH & edema do to epithelial cells?
Definition
Damage --> Necrosis (Ruminitis)
Term
Low pH favors _____ & inhibits ____.
Definition
Lactate producers; Fermentation to VFA
Term
Lactic acid is (ease of absorption). --> _____
Definition
Not absorbed easily; Strong acid, pH drops further, osmolality rises, water enters rumen
Term
What are the results of rumen acidosis?
Definition
Damaged epithelium, Barrier function & absorption impaired, Systemic inf's (Liver), Metabolic acidosis, Ruminal stasis, Dehydration, Renal failure, Shock, Death
Term
What is the main contributing factor to ruminal stasis?
Definition
Distension
Term
Acute ruminal acidosis --> _____
Definition
Death w/i 24 hrs
Term
What is the solution for ruminal acidosis?
Definition
Pump out & replace reticulorumen fluid (Expensive & rarely done)
Term
What can cause chronic rumen acidosis?
Definition
Overfeeding of soluble carbs, e.g. dairy cows
Term
Describe chronic rumen acidosis.
Definition
Borderline acidotic; Cornification of epithelium & decreased absorption (parakeratosis); Liver abscesses
Term
What is the function of the hindgut?
Definition
Absorption of water & electrolytes; Fermentation (to various degrees in all mammals); Feces formation/storage
Term
What is the energy coverage through fermentation in rabbits?
Definition
30-40%
Term
What is the energy coverage through fermentation in horses?
Definition
50-70%
Term
What is the energy coverage through fermentation in pigs?
Definition
15-30%
Term
What is the energy coverage through fermentation in dogs?
Definition
6-9%
Term
What is the energy coverage through fermentation in humans?
Definition
6-9%
Term
What animals are cecum fermenters?
Definition
Rabbit, Chinchilla, Guinea Pig, Koala
Term
What animals are colon fermenters?
Definition
Horse, Elephant, Rhinoceros, Pig, Some Primates
Term
HG fermenters are always a combination of ____ & ____.
Definition
Cecum & Colon Fermentors
Term
What animal is in btw cecum/colon fermentor?
Definition
Hippo
Term
What is the most successful HG fermentor?
Definition
Horse
Term
As a general rule, HG fermentation is very similar to ________.
Definition
Ruminal fermentation
Term
How long is the horse cecum?
Definition
~1.5 m
Term
What is the horse's cecum divided into?
Definition
Base, Corpus, Apex
Term
What does the cecum receive?(Horse)
Definition
Slurry-like ingesta from SI
Term
What is the function of the cecum?(Horse)
Definition
Mixing mvmt's btw haustra; Occasional mass mvmt's - apex & corpus contract, then base --> ingesta moves through cecocolic orifice into RVC
Term
What is the sequence of the VC?(Horse)
Definition
RVC, Sternal Flexure, LVC, Pelvic Flexure
Term
What type of segmentation does the VC have? What is its function?(Horse)
Definition
Haustric; Mixing, Peristalsis & Anti-Peristalsis originating from Pelvic Flexure --> Long retention of ingesta in VC
Term
Describe the Pelvic Flexure. What is its function?(Horse)
Definition
Marked reduction of diameter; Functions similar to pylorus; Helps to retain lg particles & pass on liquid & sm fermented particles
Term
What is the sequence of the DC?(Horse)
Definition
LDC, Diaphragmatic Flexure, RDC, junction to SC
Term
Describe the function of the DC. (Horse)
Definition
Mvmt's similar to VC w/ retention of ingesta @ junction
Term
What is the total retention time in the lg colon of horses?
Definition
24-96 hrs
Term
What is the total volume of the lg colon in horses?
Definition
Up to 130L
Term
In the horse, where does most fermentation occur?
Definition
Cecum & VC
Term
What is the pacemaker area of the LC of the horse?
Definition
Pelvic Flexure
Term
What is the biggest difference of HG fermentation (compared to rumen)?
Definition
HG receives pre-digested mix of feeds, endogenous fluids & cells
Term
Describe digestion in the SI of the horse.
Definition
Not very efficient; Fast passage rate of ingesta; Pancreatic enzymes not very important; Even many soluble carbs reach LI & will be fermented
Term
What occurs in the HG during fermentation & absorption? (Different from rumen)
Definition
Large Water Mvmt's via osmosis & Cl-secretion from crypts
Term
What is the daily fluid volume entering/leaving HG?
Definition
= Total ECF volume of horse (20-25% BW)
Term
In the HG, how is buffering of VFAs achieved?
Definition
Mucosal secretion of HCO3- (ileum & HG secretion)
Term
What is the most favorable difference btw HG fermentation & ruminal fermentation?
Definition
Acetate instead of CH4 production (less energy loss): 4 H2 + 2CO2 --> CH3COOH + 2 H2O
Term
In HG fermentation, N recycling exists w/ _____ into cecum & colon.
Definition
Urea secretion
Term
In HG fermetors, are microbial proteins & vit's (K & B complex) available to the host?
Definition
Hardly
Term
What is done to make up for the deficiency of microbial proteins & vit's in Lagomorphs?
Definition
Coprophagia
Term
What is another term for Coprophagia?
Definition
Cecophagia
Term
What is Coprophagia?
Definition
Microbe-rich cecum content excreted once daily through rapid peristalsis --> Ingested --> Proteins & Vit's recovered via SI digestion/absorption
Term
Describe coprophagia in neonates.
Definition
Coprophagia from mothers --> access to microbes
Term
Horses are ____ grazers, giving them more access to ____ than cows, which are _____ grazers.
Definition
Selective; N; Bulk
Term
HG fermentors are vulnerable to antibiotics, esp. _____ specific; _______ (killed intestinal flora)
Definition
Gr +; Dysbiosis
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