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Phys Test 4
n/a
178
Physiology
Graduate
04/26/2011

Additional Physiology Flashcards

 


 

Cards

Term
5 main areas that secrete H2O, digestive juices & enzymes
Definition

mouth (salivary glands)

stomach (gastric glands)

pancreas

liver (gallbladder)

small intestine

Term
What gland secretes each?

1. Serous, watery secretion
2. produce a mixed serous/mucus secretion
3. predominantly mucus secretion
Definition

parotid

submandibular

sublingual

Term
What are the secretory units ofo the salivary glands
Definition
acini
Term
___ controls the viscosity of mucus
Definition
mucin
Term
3 functions of saliva

1. Initial digestion of ___ by the salivary enzyme ___. Breaks down polysaccharides into disaccharides (maltose)
2. ___ & ___ of ingested foods
3. ___ of ingested food to aid its movement
Definition

starches by a-amylase

dilution and buffering

lubrication

Term
Starch and glycogen are polysaccharides that fxn to ___.
Definition
store energy
Term
how much saliva is produced/day?
Definition
1 L
Term
Components of saliva
Definition

water

mucin - glycoprotein, mucus-rich secretion

protein: amylase enzymes

salts: Na, Cl, K, HCO3

Term
Two secretory cells composed of acinus in salivary glands

1. ___: secrete water fluid containing digestive enzymes like amylase

2. ___: secrete mucin
Definition

serous cells

mucus cells

Term
Amylase is synthesized and stored in the ___ granules
Definition
zymogen
Term
The ___ modifies electrolye concentrations of the saliva.
Definition
salivary duct
Term
Primary secretion of saliva produced by acinar cells is __tonic, with salt concentrations that are close to that of the plasma.

The ductal cells modify the composition of the saliva, causing __tonic character, at the low flow rate of 1ml/min.

To do this, the ductal cells extract __ and __, making their concentrations less than that in the plasma, and they add __ & __, resulting in concentrations greater than that in the plasma.
Definition

isotonic

hypotonic

 

Na, Cl

K, HCO3

Term
Relationship between saliva and salivary flow rate:


The less difference in ion concentration between saliva and plasma, the more/less modification is done by the ductal cells.

The higher the flow rate, the less time there is for modification by ductal cells.

Therefore, ionic concentraiton is __-dependent
Definition

less

flow rate

Term
What is a high or low salivary flow rate?
Definition

high = >1 ml/min

low = < 1 ml/min

Term
REgulation of salivary secretion:

1. Both parasympathetic and sympathetic stimulation of salivary glands increases/decreases activity of acinar and ductal cells, thereby increasing/decreasing salivary secretion

- the ___ system predominantly controls salivary secretion

___ is an anti-cholinergic acent (Ach-M receptor antagonist) and is a protein inhibitor of salivary secretion.

2. ___ causes reflex secretion of saliva.
Definition

increase, increase

 

parasympathetic

atropine

 

food in the mouth

Term
Relatively common, chronic, autoimmune systemic inflammatory disorder of unknown cuase

characterized by dryness of the mouth, eyes, and other mucus membranes due to ___ of the exocrine galnds and secondary gland dysfunction.

Pathophysiology:
Salivary lacrimal, and other exocrine glands become infiltrated with CD4 cells and with B cells, resulting in ____.

Symptoms:
Diminished saliva (xerostomia) results in difficulty chewing, swallowing, candida infection, tooth decay, calculi in salivary ducts. possible diminished taste and smell.
Definition

sjogren's syndrome

 

lymphocytic infiltration

 

ductal luminal narrowing and atrophy of glands

Term
Storage capacity of the stomach?

How much gastric juice does it secrete per day?
Definition

4 cups

2000-2500 ml (2- 2.5L)

Term
Functions of the stomach:

Serves as a ___, mixes and subdivides food

Secretes 5 things

Digests ___

Empties food at a controlled rate into the duodenum
Definition

reservoir

 

HCL, pepsinogens, mucus, HCO3, intrinsic factor

--> HCL kills micro-organisms

 

proteins

Term
___ is the pre-proenzyme precursor of pepsin
Definition
pepsinogen
Term
What is the optimal pH of the stomach?

What happens if the pH is above this?
Definition

1-4

 

higher pH = significant

Term
What is a possible outcome of achlorhydria, gastrectomy, or GI disease?
Definition
increased risk of bacterial overgrowth in the intestines due to decreased acid
Term
Protein digestion begins with ___ which is converted to active pepsin in acidic stomach environment.
Definition
pepsinogen
Term
Gastric mucosa has numerus openings called ___.

__ secrete a fluid called gastric juice.

4 major components of gastric juice?
Definition

gastric pits

gastric (oxyntic) glands

 

acid (HCl)

enzymes (gastric lipase)

mucus (protects stomach and forms chyme)

hormones (gastrin, intrinsic factor)

Term
4 types of secretory epithelial cells that cover the surface of the stomach and extend down into gastric pits and glands:

1. __: secrete alkaline mucus that protects the epithelium against shear stress and acid.

2. __: secrete HCl

3. __: secrete pepsinogen

4. __: secrete gastrin
Definition

mucus

parietal

chief

g cell

Term
Mechanism of HCl secretion by gastric parietal cells:

1. Within parietal cells CO2 produced from aerobic metabolism combines with H2O to form H2CO3. This reaction is catalyzed by ___. H2CO3 then dissociates into H+ and HCO3.

2. At the apical membrane, H+ is secreted into the lumen of the stomach via the ___. Cl follows H+ into the lumen by diffusing through ___ in the apical membrane.

3. At the basolateral membrane, HCO2 is absorbed into the blood via a ___ exchanger. The absorbed HCO3 is responsible for the ____ (high pH) that can be observed in gastric venous blood after a meal. Eventually this HCO3 will be secreted back into the GI tract in pancreatic secretions
Definition

1. carbonic anhydrase

2. H+ K+ ATPase, Cl- channels

3. Cl-HCO3 , alkaline tide

Term
H+-K+ ATPase in step 2 of HCl secretion by gastric parietal cells is inhibited by the drug ___, which is used to treat ulcers to reduce H+ secretion.
Definition
omeprazole
Term
Net results from gastric parietal cell events are?
Definition

net secretion of HCl

Net absorption of HCO3-

Term
Regulation of HCl secretion:

ACh:
release by __ nerve
binds to receptors on __ cells
produces H+ secretion by ___ cells
___ blocks the action of ACh by blocking muscarinic receptors on these cells
Definition

vagus

parietal

parietal

atropine

Term
Regulation of HCl secretion:

Histamine:

Released from ___ cells in gastric mucosa
Binds to __ receptors on parietal cells
stimuates parietal cells to secrete __
__ blocks these receptors
Definition

mastlike cells

H2

H+

cimetidine

Term
Regulation of HCl secretion:

Gastrin:

Released into circulation by __ cells of the stomach antrum
Binds to receptors on __ cells
Stimulates __ secretion
Definition

G cells

parietal

H+

Term
___ is a glycoprotein produced by the parietal cells

It is necessary for the absorption of B12, which takes place in the terminal ileum

Lack of this substance is seen in ____, an autoimmune disease. Deficiency can also lead to malabsorption of B12 and subsequent ___.
Definition

intrinsic factor

pernicious anemia

megaloblastic anemia

Term
Lack of intrinsic factor or B12 deficiency or something can result in CNS disease via damage to the ___, resulting in problems with balance and 2 point discrimination
Definition
Term
The gastric mucosal barreir in physiological conditions:

The innermost layer of gastric mucosa (epithelia) is impermeable to the acid it secretes. the protective effects are attributed to the following factors:

___ - prevent acid penetration
The epithelia are covered with the _____, which is an impermeable hydrophobic lipid layer to prevent from ionized water-soluble molecules
Definition

tight junctions

gastric mucosal barrier

Term
Pathophysiology of peptic ulcer:

Gastric secretions induce ___ damage.

Occur in what three places?
Definition

mucosal barrier

 

first few cm of duodenum (most common), antrum of stomach, lower esophagus

 

 

Term
Causes of peptic ulcer:

1. Disruption of mucosal barrier:
- ___ cuases 75-95% of all ulcers
- risk factors?
- ischemia

2. Excess H+ and pepsin
- ___ disease: rare gastrinoma, gastrin-producing tumor
- psychic stress-increased parasympathetic stimulation
Definition

H. pylori

smoking, alcohol, NSAID, stress, reflux or bile salts, proteases, free radicals

 

zollinger-ellison

Term
Gastric ulcers:

Mucosal barrier is defective allowing H+ and pepsin to digest part of the mucosa

H. pylori produces __ from urea, which breaks down mucosal barrier
Definition
NH4
Term
Duodenal ulcers:

__ secretory rates are higher than normal
- Excess damage to mucosa, often confused wtih pain of being hungry
Definition
H+
Term
What diesase?

Prevalence of middle aged adults is 20-50% in industrialized countries.

Transmission via vomit, saliva, feces, H2O

Inflammation occurs in antrum and body of stomach, leading to gastric atrophy and peptic ulcer
Definition
H pylori gastritis
Term
What disease?

Rare condition caused by a gastrinoma. the tumors most likely exist in the pancreas but can also be found in stomach or duodenum.

Elevation of serum gastrin level and basal gastric acid in staomch

peptic ulcer
Definition
Zollinger-Ellison Syndrome
Term
Fxns of the GI system
Definition

Primary: serve as portal whereby nutrients and water can be absorbed into the body

 

- mix food with a variety of secretions from the GI tract and digestive secretions

- move food along the GI tract

- Absorb nutrients to supply metabolic needs

- Excrete waste

Term
Organs of the GI system
Definition

mouth

salivary glands

pharynx

esophagus

stomach

exocrine pancreas

liver

small intestine

large intestine

Term
What do the bacteria in the GI tract accomplish?
Definition

metabolic fxns that can't be performed by mamallian enzymes

resistance to infection

Term
Components of the immune system of the GI tract
Definition

Enteric immune system (little brain): myenteric and submucosal plexi

 

splanchnic circulation

 

Neuroendocrine system including VIP

Term
4 basic digestive processes
Definition

motility

secretion

digestion

absorption

Term
4 layers of the GI tract wall
Definition

mucosa (mucus membrane, lamina propria, and

muscularis mucosa)

submucosa

muscularis externa (outer longitudinal and inner circular muscles)

serosa

 

listed in to out

Term
GI tract layers: Mucosa

Components?
Functions?
Definition

COmponents: Epithelium

lamina propria (loose connective tissue contains lymph nodes and capillaries)

muscularis mucosa (smooth muscle that contracts to change shape and surface areas)

 

Functions:

Produce mucus

secrete enzymes

absorb nutrient

protect pathogens from entry - first line of defense of the immune system

Term
GI tract layers: Submucosa

components?
Definition

connective tissue

blood vessels

glands

submucosal nerve plexus (meissner's plexus)

Term
GI tract layers: muscularis

2 layers?
nerve plexus?
Definition

inner circular layer

outer longitudinal layer

 

myenteric nerve plexus (auerbach's plexus) - located between the layers

Term
GI tract layers: serosa
components?
Definition

single layer of sqamous cells called mesothelium

 

small amount of connective tissue

 

 

Term
What is the function of the enteric nervous system?

what are the targets?
Definition

function: itegrate motor and secretory activity of GI tract

 

Targets; smooth muscle and glands

Term
2 nervous system controls of digestion - intrinsic and extrinsic
Definition

Intrinsic: enteric nervous system

- myenteric plexus, submucosal plexus

 

extrinsic: autonomic nervous system

Term
The autonomic ns influences motor and secretory activities through the ____
Definition
 ens
Term
___ is the minibrain
Definition
enteric NS
Term
Can enteric NS work in absence of ANS?
Definition
yes
Term
4 types of neurons of the ENS
Definition

motor - innervate smooth muscle

secretory - regulate endocrine and exocrine secretion

sensory - detect stretch, tonicity, glucose, or amino acids

interneurons - interact among neurons

Term
Where do the different parts of the ENS (myenteric and submucosa plexuses) exist?
Definition

myenteric - everywhere

 

submucosa - mainly in intestines. sparse in stomach. not in esophagus

Term
HIstamine is an example of a ___ substance

Insuline is an example of a ___ substance
Definition

paracrine

endocrine (hormoen)

Term
What substance?

contraction of SMC in wall
relaxation of spincters
stimulation of secretions
Definition

ACh (cholinergic)

 

Term
What substance?

relaxation of smc in wall
contraction of sphincters
inhibition of salivary secretion
Definition

norepinephrine

(adrenergic)

Term
What substance?

relaxation of SMC
stimulation of secretions
Definition
VIP & nitric oxide
Term
Which substance causes stimulation of gastrin secretion?
Definition
gastrin-releasing peptide
Term
Which substance?

contraction of smooth muscle
stimulation of salivary secretion
Definition
substance P (cosecreted with ACh)
Term
2 types of neurons in the ENS

1. ___: multiple axons, long-lasting hyperpolarization, interneurons, largest proportion in myenteric plexus

2. ___: single long axon, no hyperpolarization, most of submucosal plexus
Definition

after-hyperpolarization neurons (AH-type)

 

synaptic neurons (S-type)

Term
What substance bocks S-type neurons?
Definition
TTX (na channel blocker)
Term
Similarities between sympathetic and parasympathetic NS:

1. Both are __ (motor) systems

2. Both involve regulation of the ___ environment, out of our conscious control.

3. Both involve 2 neurons that synapse in a ___

4. Both innervate __ & ___
Definition

efferent (visceromotor)

internal

peripheral ganglion

glands & smooth muscle

Term
Differences between sympathetic and parasympathetic:

Lengths of neurons.

____ has a short preganglionic neuron and a long postganglionic neuron

___ has a long preganglionic neuron and a short postganglionic neuron
Definition

sympathetic

parasympathetic

Term
The ____ NS consists of craniosacral nerves: Vagus, plus S2-S4.

The ___ consists of thoracolumbar nerves: T1-L2/3
Definition

parasympathetic

sympathetic

Term
3 prevertebral sympathetic ganglia
Definition

celiac

superior mesenteric

inferior mesenteric

Term
Acetylcholine is involved in the sympathetic/parasympathetic ns

NE is involved in the sympathetic/parasympathetic NS
Definition

ACh

NE

Term
Symptoms associated wtih motility disorders
Definition

heartburn

nausea

vomiting

stomach pain

constipation

diarrhea

Term
The electrical output of GI muscles is a product of contributions from two electrically coupled cell types:
Definition

Smooth mucle cells

interstitial cells of Cajal (ICC)

Term
What type of cell?

- type of interstitial, modified smooth muscle cell
- is the pacemaker cell of the GI tract (generates AP)
- forms a network among one another
- is responsible for slow wave GI tract smooth muscle AP
Definition
interstitial cell of cajar (ICC)
Term
What type of cell?

- respond to the depolarization/repolarization (ap) cycle imposed by ICC
- are organized as a structural and functional unit (an electrical syncytium)
- are electrically conducted via low-resistance gap junctions between cells
- circular and longitudinal cell contraction result in decreased diamenter and shortening length the that segment of tube.. which moves food forward
Definition
smooth muscle cells
Term
Phases of AP of SMC

Phase 0
Phase 1
Phase 2
Phase 3
Phase 4
Definition

0: resting MP

1: upstroke: voltage gated Ca2+ channels and voltage gated K+ channels open

2: transient outward K+ current. early repolarization

3: inward Ca current and outward K current - plateau

4: inactivation of voltage-gated Ca channels and activation of Ca gated K channels

Term
When membrane potential of a slow wave is lower than threshold, no AP is generated, but the muscle undergoes ___, characterized by small contraction and incomplete relaxation

When threshold is reached, an AP is generated and the the muscle undergoes ___.

What is the purpose of this process?
Definition

tonic contraction

phasic contraction

 

makes sure contraction of some sort is always happening so peristalsis can continue

Term
____ of muscles generated by slow wave are the basis for peristalsis and segmentation
Definition
phasic contraction
Term
4 patterns of GI motility

___: controlled movment of content in GI tract from stomach to large intestine

___: crushing and grinding of ingested food

___: segmentation

___: tonic movement. movements consist of a constant level of contraction or tone wtihout regular periods of relaxation. Found in lower esophagus and upper stomach and ileocecal valve and internal anal sphincter.
Definition

propulsion

trituration

mixing movment

reservoir function

Term
Where does carbohydrate digestion begin?
Definition
mouth - when carbs mix with salivary amylase
Term
3 phases of swallowing:

1. ___: (voluntary) in the mouth. the Bolus is collected at the back of the mouth so the tongue can lift the food upward and into the pharynx to stimulate the swallowing reflex

2. ___: (involuntary). upper esophageal sphincter relaxes. superior constrictor muscle contracts forcing food into esophagus.

3. ___: (involuntary). peristalsis moves food through the esophagus into the stomach
Definition

oral phase

pharyngeal phase

Esophagus phase

Term
During the pharyngeal phase of swallowing, food movement into the respiratory passage is prevented by what?
Definition
the tongue elevates and presses against the soft palate, closing the epiglottis
Term
swallowing reflex arc:
Definition

Receptor near pharynx are activated.

afferent nerves (CN IX and X) are activated

Integrator/controller located in medulla

Efferent nerve

Contraction of pharyngeal skeletal muscle

Relaxation of upper esophageal sphincter

Term
Primary and secondary peristalsis
Definition

Primary follows reflexes, is controlled by swallowing center in brainstem

 

secondary occurs when primary is inadequate to move food through esophagus (esophageal obstruction)

Term
___: (heartburn) - common esophageal discomfort

is the result of regurgitation of food and gastric fluid into the lower esophagus
Definition
pyrosis
Term
Volume of stomach
Definition
50 - 1000ml
Term
3 layers of stomach muscle
Definition

longitudinal

circular

oblique

Term
4 functions of stomach
Definition
reservoir, mixing, subdividing, controlled emptying into duodenum
Term
Reservoir fxn of stomach (receptive relaxation) is mediated by ___ & ___. How does it work?

2 stimuli?
Definition

vagus and VIP (vasovagal reflex)

 

once food gets into the stomach, it stimulates stretch, osmotic, and chemical receptors to send signals to the medulla through afferent vagus nerves, which sends signal through the vagus motor nerve to tell stomach wall to distend

 

stimuli: stretch and CCK

Term
___ - the semi-liquid food mixture in the stomach

___ - needed to digest fat and protein (not carbs) stimulate receptive relaxation
Definition

chyme

 

CCK

Term
___ - phasic contraction that begins in the middle of the stomach. Necessary for mixing and trituration of the gastric contents.
Definition
antral pump
Term
___: the wave of contraction that closes the pylorus, resulting in most of the chyme propelled back, further mixing reduction of particular size
Definition
retropulsion
Term
Emptying of chyme into the duodenum takes about __hr after a meal

The rate of emptying depends on what two factors?
Definition

3 hr

 

on the time for neutralization of H+ (by pancreatic HCO3) and the content of the food (liquid food faster than solid)

Term
Gastric emptying:

More H+ and CCK induced by fat in the duodenum = more/less time for emptying
Definition
more
Term
Autonomic control of gastric motility:

___ enhances peristatltic contractions (rest and digest)

___ inhibits peristaltic contractions (fight or flight)
Definition

parasympathetic

sympathetic

Term
Differences in motility in fed vs. fasting states
Definition

fed - antrum contracts at a rate of 3/min

 

Fasting - antrum is quiescent for 1-2 hrs, then a 10-20 min period of intense contractions with a relaxed pyloric sphincter when indigestible objected remained from previous meal get emptied into stomach, followed by another quiescent period

 

 

Term
The fasting motility pattern is called the ____
Definition
migrating myoelectric complex (MMC) - contractions that occur every ~90 min and fxn to clear stoamch of residue remaining from previous meal
Term
Formation of duodenal v. gastric ulcers
Definition

Duodenal - duodenum is basic, so when gastric emptying is too rapid, a duodenal ulcer develops due to excess acid

 

Gastric - the stomach is acidic, so when duodenal contents are regurgitated into the stomach, an ulcer develops due to excess base. Gastric ulcers may be exacerbated by slow gastric emptying

Term
2 primary fxns of small intestine
Definition

digestion

absoprtion of nutrients

Term
frequency of small intestine peristalsis

contraction pattern?

how is it regulated?
Definition

12/min (constant)

 

primary contraction - segmentation (mixing)

Secondary - peristalsis (moving fwd)

 

 

regulated by enteric reflex:

Activated by PSNS

inhibited by SNS

Term
Fxns of large intestine


Mucosa contains tubular glands called ___ that are responsible for mucus secretion
Definition

reabsorb water and electrolytes

eliminate waste

storage

 

crypts

Term
Colon:

Segmental contractions of ___ facilitate H2O absoprtion

Mass movment is the forecful peristaltic contraction over long distances after a meal, called the ____. Happens 1-3 times/day.
Definition

haustra

gastric-colic reflex

Term
Anal reflexes:

Distention of the rectum results in ____

Reflex relaxation of ___ sphincter

Reflex constriction of ___ sphincter
Definition

urge to defecate

internal anal

external anal

Term
Where is vomitting controlled?
Definition
vomiting center in medulla
Term
Small intestine:

___: finger-like projections of the mucosa that contain capillaries

___: tiny projections on the luminal membrane of each cell that give the apical region a striated apearance called the ___.
Definition

villi

microvilli

brush border

Term
___ - a lymphatic capillary that absorbs ingested fat
Definition
lacteal
Term
GI Peptides:

Include what 3 things?

Regulate what 5 fxns of the digestive tract?
Definition

hormones, neurocrines, paracrines

 

contraction and relaxation of smooth muscle wall and sphincters

secretion of enzymes for digestion

secretion of fluid and electrolytes

trophic (growth) effects

Some regulation secretion of other peptides

Term
What are some hormones that are released by the GI tract to act either on the GI tract or elsewhere in the body?
Definition

Gastrin

CCK

secretin

GIP (gastric inhibitory peptide)

 

Term
___ are secreted by the endocrine cells of the GI tract and they act locally within the same tissue that secreted them.

An example is ___, which is inhibitory and is released from the small intestine
Definition

paracrine

somatostatin

Term
____ are peptides released by neurons of the GI tract following an AP

They include... (6)?
Definition

neurocrines

 

ACh

NE

VIP

GRP

Neuropeptide Y

Substance P

Term
Gastrin:

Secreted by __ cells in the stomach in response to eating
___ is released from vagal nerve endings onto these cells to stimulate gastrin release.

___ inhibits gastrin secretion

Gastrin promotes ___ secretion by gastric parietal cells
Gastrin promotes ___ also
Definition

G cells

GRP (Gastrin releasing peptide)

low pH in stomach

H+

growth of gastric mucosa

Term
CCK:

Secreted by __ cells of the small intestine in response to fatty acid and small peptides

5 actions?
Definition

I cells

 

contraction of gallbladder to eject bile into small intestine to emulsify lipids

 

Secrete pancreatic enzymes to digest lipids, CHO, and proteins

 

Secretion of bicarbonate (HCO3) from pancreas

 

 

Growth of exocrine pancreas and gallbladder

 

Inhibition of gastric emptying (slows rate) to ensure adequate time for digestion

Term
Secretin:

Secreted by __ cells of the duodenum in response to H+ and fatty acids

Promotes secretion of ____ from the pancreas to neutralize H+ and allow for pancreatic enzymes to digest fat

INhibits effects of __ on parietal cells by inhibiting H+
Definition

S cells

HCO3

gastrin

Term
Gastric INhibitory Peptide (GIP)

Secreted by the small intestine in response to ___, ___, and ___

Stimulates ___ secretion by the pancreas

Inhibits ___ secretion
Definition

CHO, amino acis, fatty acids

 

insulin

 

gastric H+

Term
Somatostatin:

Secreted by __ cells in the gastric antrum in response to decreased luminal pH

Inhibits secretion of ____ & ____
Definition

D

 

other GI hormones and gastric acid

Term
Histamine:

Secreted in ___ region of stomach

Stimulates __ secretion by gastric parietal cells (along with ___ & ___)
Definition

H+-secreting region

 

H+, gastrin, ACh

Term
The pancreas is an exocrine and endocrine gland.

Exocrine fxn done by ___ cells:
- secrete essential digestive enzymes through pancreatic duct into the duodenum

Endocrine fxn done by ___:
- secrete insulin and glucagon into the blood stream
Definition

acinar cells

islets of langerhans

Term
Exocrine pancreas:

- secretes _L/d into the duodenum
- Fluid consists of __ to neutralize H+ in the duodenum from the stomach and ___ which digest CHO, proteins, and lipids into absorbable molecules

Exocrine glands make up about __% of the pancreas

___ cells line the blind end of the branching duct system and secrete the enzymatic portion
___ cells line the ducts and secrete the aqueous HCO3 component
Definition

1 L/d

HCO3-, enzymes

 

90%

Acinar cells

Ductal cells

Term
The optimal pH for pancreatic enzymes is ___
Definition
7
Term
HCO3- secretion by pancreatic ductal cells:

The ___ membrane of ductal cells contains a Cl-HCO exchanger

The ___ membrane contains a Na/K ATPase and a Na/H exchanger


How these work:
- CO2 and H2O combine to form H+ and HCO3-
- HCO3 is secreted into the pancreatic juice by the ___ (pump)
- H+ is transported into the blood by the ___ (pump), which causes acidification of pancreatic venous blood.
Definition

apical

basolateral

 

Cl-HCO3 exchanger

Na/H exchanger

Term
Regulation of enzymatic pancreatic secretions by acinar cells

Receptors for:

1. ___: most important stimulant
2. ___: also stimulates enzyme secretion

By what mechanism do these substances stimulate enzymatic secretion?
Definition

CCK

ACh

 

stimulate enzymatic secretion via IP3 and Ca2+

Term
Regulation of pancreatic aqueous secretion of HCO3 by Ductal cells:

Receptors for 3 things.
Which is most important stimulant?

By what mechanism does this substance stimulate HCO3 secretion?
Definition

CCK, ACh, Secretin

 

Secretin is most important, but it's effects are potentiated by CCK and ACh

 

Secretin stimulates HCO3 secretion via cAMP

Term
What nutrient do these enzymes digest?

Pancreatic: amylase
Intestinal: sucrase, maltase, lactase, trehalase, a-dextrinase, amino-oligopeptidase, dipeptidase, enterokinase
Definition
carbohydrates
Term
What nutrient do these pancreatic enzymes digest?

trypsin
chymotrypsin
carboxypeptidase
elastase
Definition
proteins
Term
what nutrient do these pancreatic enzymes digest?

lipase-colipase
phospholipase
cholesterol ester hydrolase
Definition
lipids
Term
Bile:

Necessary for the digestion and absorption of ___ in the small intestine.

Composed of ___, ___, and ___

Solubilize products of __ digestion into packets called ___.
Definition

lipids

 

bile salts, bile pigments, cholesterol

 

lipid, micelles

Term
Bile:

Produced and secreted by the ____
Stored in the ___
Injected into the ___

After lipids are absorbed, bile salts are recirculated to the liver via the ____, where they are extracted from portal blood by ___.
Definition

liver

gallbladder

small intestine

 

enterohepatic circulation

hepatocytes

Term
A female pt with crohn's disease undergoes an ileectomy. Afterwards, she notices oil droplets in her diarrhea. What is this condition called and what caused it?

What are other complications of this surgery?


What would treat the diarrhea?
Definition

Steatorrhea

 

After the ileectomy, the intestine is unable to reabsorb the normal amount (95%) of bile salts. The liver cannot keep up with the increased need for making bile salts and thus lipids are not fully digested and end up in her stool as oil droplets

 

The diarrhea is caused bc the exces bile acids in the intestine stimulate Cl- secretion. Excess Cl stimulates excess Na and H2O to be secreted into the lumen, resulting in diarrhea.

 

Also the pt will not be able to absorb adequate intrinsic factor-B12 complex, bc this normally happens in the ileum... so the pt will need monthly B12 injections

 

Cholestryamine to stop diarrhea.

Pt will continue to have steatorrhea.

Term
Stomach digestion:

Different nutrients leave the stomach at different rates:

___ leave first (regulated by CCK), foloowed by ___, ___, and ___.

Protein digestion begins with ___, which is converted to active ___ in the acidic stomach environment.
Definition

CHO, protein, fat, fibrous foods

 

 

pepsinogen --> pepsin

Term
Small intestine:

__-__% of the diet is absorbed

Appx __m long
Definition

92-97%

 

7 m

Term
Cell types in villi of intestine:

___: make up the top of the villi

___: digest and absorb nutrients

___: secrete mucus

___: secrete the hormones secretin, CCK, and GIP

___: secrete lysozyme and is capable of phagocytosis
Definition

microvilli

absorptive cells

goblet cells

enteroendocrine cells

paneth cells

Term
Carbohydrate digestion:

Mouth: ___, ___, __, or __ are the substrate for alpha-amylase
___ is the product of the reaction

Stomach:
Low pH inhibits action of alpha-amylase, so ___ takes over CHO digestion

Eventually, CHO are broken down into ___, wchih are absorbed by the small intestine and sent to the liver via portal circulation OR they end up as ___ which is excreted
Definition

starch, lactose, sucrose, cellulose

maltose

 

pancreatic amylase

 

monosaccharides (glucose, fructose, galactose)

cellulose

Term
Why isn't cellulose absorbed by the small intestine?
Definition
alpha-amylase can only break down alpha linkages and cellulose is a beta linkage. thus, it is undigestable and is excreted
Term
What is lactose intolerance?
Definition
The lack of the disaccharidase that breaks down lactose in the small intestine and thus the pt is unable to digest lactose
Term
Explain the mechanism of absorption of monosaccharides by the cells of the small intestine including the SGLT and GLUT transporters
Definition

At the apical membrane, Glucose and Galactose are taken into the cell via cotransporters with Na called SGLT. Fructose is taken in wihtout a cotransporter via GLUT 5.

 

At the basolateral membrane, the monosaccharides are transported from the cell into the blood wihtout cotransporters via GLUT 2's for each individual sugar

 

(slide 12 of ppt 3)

Term
How is ATP generated from CHO?
Definition

Either:

Glycogen from liver broken down into glucose

OR

glucose from intestine

 

transported into muscle cell

Glucose broken down via glycolysis - produces 2 pyruvate + 2 ATP

 

It is then fermented into 2 lactic acids

 

OR

 

it is taken into the mitochondria via the ETC and used to make even more ATP via the citric acid cycle (something about acetyl CoA)

Term
Protein digestion:

By ___ in the stomach, which converts it to __ & ___.

By pancreatic enzymes ___, ___, ___, and ___, which converts it into __ & ___.

By ___ in the small intestine, which converts it into ___, whcih are then absorbed and transported to the liver.
Definition

pepsin (after it has been converted by pepsinogen) --> polypeptides and amino acids

 

elastase, carboxy-peptidase, trypsin, chymotrypsin __ . oligopeptides and amino acids

 

aminopeptidases --> amino acids

Term
Activation of GI proteases:

1. Intestinal protein ingestion activates ___ to its active form, ___ by the brush border enzyme ___.

2. These activated ___, convert the other inactive precursors (various zymogens) to their active enzyme states.
Definition

trypsinogen --> trypsin, via enterokinase

 

trypsin converts zymogens to their enymes v

Term
___ break down proteins into amino acids and peptides
Definition
proteases
Term
Digestion of protein begins in the stomach with the action of ___

Digestion of protein ends in the small intestine with pacreatic and brush-border ___
Definition

pepsin

 

proteases

Term
Luminal protein digestion yields:

__% amino acids and

__% oligopeptides with 2-6 AA's
Definition

40

60

Term
Absorption of Amino acids and peptides in the small intestine:

Na/AA cotransporters into small intestine epithelial cells are driven by the ___ gradient

Most ingested proteins are absorbed as di and tripeptides and are transported into the cell via a ___ cotransporter.

The di and tripeptides are then converted to amino acids via ___ in the cell and are then transported into the blood without a cotransporter
Definition

Na

 

H+/oligopeptide cotransporter

 

peptidase

Term
Disorders of protein digestion and absorption:

1. Deficiency of pancreatic enzymes:
- Ex: __ & ___.
- ___, ___, and ___ would be excreted in the feces as a result of the lack of enzymes.

2. Deficiency of Na-AA cotransporter
- ___: a genetic disorder with lack of this cotransporter
Definition

chronic pancreatitis, cystic fibrosis

triglycerides, cholesterol esters, phospholipids

 

cystinuria

Term
The major portion of fat digestion takes place in the ___ as a result of ___.

This process is more complicated than CHO/protein digestion because?
Definition

small intestine, pancreatic lipases

 

more complicated bc fats have to first be converted into a water soluble product

Term
Role of Stomach in lipid digestion:

1. Action of ___ breaks lipids into small droplets, increasing surface area for digestive enzymes.

2. Droplets are ___ by dietary proteins.

3. __ & ___ are responsible for 10% of triglyceride digestion.

4. The most important role of the stomach is to empty ___ into the small intestine at a controlled rate, rendering sufficient time for lipid digestion in the small intestine. Thus, ___ secretion depends on the contents of the food and the pH to control emptying rate.
Definition

churning

emulsified

lingual and gastric lipases

controlled rate

CCK

Term
Small intestine lipid digestion and absorption:

1. ___:
Produced by the liver and released into small intestine
Emulsify lipids
Solubilize products of lipid degestion to form a micelle
Remove waste products from the body by secretion into bile and elimination in feces.

2. ___
Definition

bile salts

pancreatic enzymes

Term
2 components of micelles
Definition

lipids

bile salts

Term
Pancreatic enzymes involved in lipid digestion:

1. ___: Hydrolyze triglycerides
- Activity is inhibited by bile salts at the lipid-H2O interface
- When bile salts are replaced by COLIPASE, this substance is active
- inactive pro-colipases secrete in pancreatic juic are activated by trypsin

2. ___: hydrolize cholesterol
- secreted as an active form of enzyme

3. ___:
secreted as an inactive form of pro-enzyme
- activated by trypsin in small intestin
Definition

pancreatic lipase

cholesterol ester hydrolase

phospholipase A2

Term
Vitamins:

Are ___ & ___ for metabolic rxns.

Must be acquired from the diet and absorbed by the GI tract

2 types:

____: include B1, B2, B6, B12, C, biotin, folic acid, nicotinic acid, and pantothenic acid
--> absorption in the small intestine via Na-dependent cotransport mechanism, similar to glucose or AA

___: include Vit A, D, E, and K
--> absorbed via the same process as lipids
Definition

co-factors and co-enzymes

 

water soluble

lipid soluble

Term
Vit B12 absorption:

1. released from food via ___ action in the stomach
2. Free B12 binds to ___ secreted by salivary juice
3. IN the duodenum, pancreatic proteases degrade this substance and B12 is transferred to ___.
4. The B12-__ complex is resistant to degradative actions of enzymes and can be absorbed in the ileum.
Definition

pepsin

R-protein

Intrinsic factor

B12-intrinsic factor complex

Term
__% of fluid/electrolytes are absorbed in the small intestine

__% of fluid/electrolytes are absorbed in the colon
Definition

80

20

Term
Mechanisms of trasnport of sodium in GI tract:

Na is primarily dependent on cotransporters with ___ & ___.
Thus, Na transport depends on the concentration of these solutes.

Absorbed sodium is rapidly exported from the cell via Na pumps - when a lot of Na is entering the cell, a lot of it is pumped out of the cell, which establishes a high ___ in the small intercellular spaces between adjacent enterocytes
Definition

glucose and AA

 

osmolarity

Term
Mechanisms of H2O transport in GI tract

H2O diffuses in response to the osmotic gradient established by ___ --- so into the intercellular space.

Most H2O absorption is ___ (through the cell) but some is ___ (between cells).

H2O and Na then both diffuse into the capillary blood within the ___.
Definition

Na

transcellular, paracellular

 

villus

Term
Large intestine activities:

Absorption of __ & __

Digestion and metabolism of ___ that wasn't digested yet.

No mammalian cell can digest ___, but bacteria in the large bowel can digest it.

Bacteria also synthesize __ & ___ in the bowel.

Bacterial ___ produces gases and organic acids.
Definition

water and electrolytes

 

CHO

 

cellulose

 

Vit K and B vitamins (thiamin and riboflavin)

 

fermentation

Term
How does diarrhea result in Na and H2O being retained in the lumen of colon cells?
Definition
High flow rate of intestinal fluid in diarrhea causes increased K secretion resulting in hypokalemia, which results in Na and H2O being retained in the lumen
Term
Pancreatic insufficiency
Zollinger Ellison syndrome
Cholestasis/bile salt deficiency
lack of brush border enzymes
nutrient digestion by bacterial overgrowth


All are causes of ___
Definition
maldigestion
Term
Celiac sprue - steatorrhea
gastroenteritis
crohn's disease
lymph obstruction


all are causes of ___
Definition
malabsorption
Term
Lactose intolerance is a disease involving insufficient ___ digestion
Definition
luminal
Term
4 types of diarrhea

1. As seen in the ileum resection

2. ingestion of poorly absorbed substrate (usually a CHO or divalent ion). ex is lactose intolerance

3. Ex: cholera. occurs when secretion of water into the intestinal lumen exceeds absorption.

4. E. coli is example
Definition

decreased absorptive surface area

osmotic diarrhea

secretory diarrhea

intestinal infections

Term
2 blood supplies to the liver

1. ___: drains blood from the GI tract and spleen to the liver. Brings O2-poor and nutrient rich blood. Thus, all nutrients are processed by the liver before being released back into the central veins.

2. ___: branch of the celiac trunk. Brings O2-rich blood.
Definition

portal vein

hepatic artery

Term
Components of the hepatic triad
Definition

Portal vein

Hepatic artery

Bile drainage duct

Term
Liver lobules:

Each hepatocyte has a ___ in the middle of it

Bile produced by hepatocytes is released by ____ to be transported to ___ , which carry it to the liver.

___ make up the complex of "walls" radiating and bring blood in to the central vein. They are special liver capillaries where blood mixes and liver cells act.
Definition

central vein

canaliculi, bile duct

 

sinusoids

Term
___ cells are located in the sinusoids. The belong to the immune system and are used for ingestion of bacteria.

__ cells are located in the perisinusoid space along with the hepatocytes. They contain lipid droplets with Vit A. In inflammation, these cells become transformed to ___, which secrete collagen and extracellular matrix into the perisinusoidal space. This inflammatory response is partially responsible for ___ of the liver.


This structure facilitates rapid exchange of molecules
Definition

Kuppfer cells

stellate cells (contractile phenotype), myofibroblasts (proliferative phenotype) = scarring

Term
6 Liver fxns:
Definition

1. detoxification

2. carbohydrate metabolism

3. protein metabolism (albumin, prothrombin)

4. lipid metabolism (lipoprotein synthesis)

5. bile formation and secretion

6. blood detoxification and purification (remove old RBCs, degrade Hb to bilirubin, urea formation from ammonium)

Term
CHO metabolism in liver:

Purpose: maintain glucose homeostasis at about __ mg/dl

___: synthesis of glucose from fats, AAs, and lactate. Uses non-carbohydrate substrate to produce glucose -- done during fasting.

___: breakdown of glycogen into glucose during fasting

___: formation of glycogen from glucose to store CHO in the liver as blood glucose level rises. Uses glucose to make glycogen.
Definition

90

Gluconeogenesis

Glycogenolysis

Glycogenesis

Term
Why is it important to keep glucose levels steady?
Definition

Glucose is the energy source for RBCs and renal medulla

 

Preferred energy source for brain

Term
Protein and AA metabolism in liver

Sythesize ___ such as fibrinogen

Produce __ via ammonia (major fxn of the liver) - important for ___ metabolism. Important substrates for non-essentail AA such as tyrosine and cysteine and nucleic acids.
Definition

plasma proteins

 

urea, nitrogen,

Term
Lipid metabolism in the liver:

1. ___ synthesis to form bile salts
2. ___ & ___ production.
3. Used to generate ATP or ketone bodies - free fatty acids after a meal are used for energy
- could result in diabetic ketoacidosis
Definition

cholesterol

triglycerides and VLDL

Term
What are some ways our body uses cholesterol?

__% of body's cholesterol is endogenous
Definition

cell membranes

vit D

hormones

myelin

bile salts

 

85%

Term
How does the body make cholesterol?
Definition
Liver via acetyl-CoA
Term
How do we get LDL in our diets?

How do we get HDL in our diets?
Definition

LDL: trans and saturated fats

 

HDL: mono-unsaturated fats (olive oil, canola oil) & fiber

Term
What are some coagulation factors that the liver produces?
Definition

fibrinogen, prothrombin, V, VII, IX, X, and XI

protein C, Protein S, antithrombin

Term
What are some fat soluble vitamins that the liver stores?
Definition
A (vision), D (Ca absorption), K (synthesis of clotting factors)
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