Term
| Three Types of Digestion within the GI |
|
Definition
1. Mechanical - chewing and churning
2. Chemical - hydrolysis
3. Fermentation - ruminants and hind-gut fermentors |
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Term
|
Definition
1. Myenteric plexus (Auerbach)
2. Submucosal plexus (Meissner) |
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Term
| Two kinds of Afferent (sensory) neurons within the ENS and location |
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Definition
1. Mechanoreceptors - within muscle layers
2. Chemoreceptors - within mucosa |
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Term
| Efferent (Motor) Neuron innervation in the ENS |
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Definition
| Inhibition OR excitation of vascular muscle, gut muscle, and glands. |
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Term
| Excitatory Neurotransmitters of the ENS |
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Definition
1. Acetylcholine (most potent in the GI tract)
2. Substance P (tachykinins) |
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Term
| Inhibitory Neurotransmitters of the ENS |
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Definition
1. Peptides: Somatostatin, PACAP
2. Non-peptides: Nitric Oxide, ATP |
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Term
| Vasoactive Intestinal Peptide (VIP) |
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Definition
| Neurotransmitter that both inhibits gut muscle and stimulates secretions. Works to increase GI motility. |
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Term
| Parasympathetic Innervation of the GI Tract |
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Definition
1. Mostly vagus nerve (CN X)
2. Pelvic Nerve (S2-S4) innervates descending colon and rectum. |
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Term
| Chief Neurotransmitter of the PSNS of the GI Tract |
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Definition
| Acetyl-choline (ACh) - increase peristalsis, stimulate secretions, relax sphincter |
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Term
| Chief Neurotransmitter of the SNS of the GI Tract |
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Definition
| Norepinephrine - decrease peristalsis, inhibit secretion, contract sphincters |
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Term
| Location of PSNS Neurons that Innervate the GI Tract |
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Definition
| Preganglionic PSNS fibers integrate to the ENS. |
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Term
| Location of SNS Neurons that Innervate the GI Tract |
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Definition
| SNS fibers are primarily postganglionic. |
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Term
| Vagal and Pelvic Afferent Nerves of the GI Tract |
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Definition
| Parasympathetic; include chemoreceptors and mechanoreceptors. |
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Term
| Splanchnic Afferent Nerves (excluding the pelvic nerve) of the GI Tract |
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Definition
| Sympathetic; include chemoreceptors and mechanoreceptors |
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Term
| Eneteroendocrine, AKA APUD (Amine Precursor Uptake Decarboxylase) Cells |
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Definition
| Cells releasing intrinsic gut hormones for GI control. |
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Term
| Three types of hormone secretion by enteroendocrine cells |
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Definition
1. Endocrine
2. Paracrine
3. Autocrine |
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Term
| Endocrine Secretion Method |
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Definition
| Secretory cell release hormone which travels through bloodstream to distant target cell. |
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Term
| Paracrine Secretion Method |
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Definition
| Secretory cell releases hormone which travels by intercellular diffusion to nearby target cell. |
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Term
| Autocrine Secretion Method |
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Definition
| Secretory cell releases hormone which binds to receptors on the same cell. |
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Term
| Intrinsic Gut Hormone Types |
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Definition
1. Peptides (proteins)
2. Non-peptides |
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Term
| Intrinsic Peptide Hormones of the GI Tract |
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Definition
1. Gastrin (stomach)
2. Ghrelin (stomach)
3. Tachykinins (AKA substance P, all GI)
4. Secretin (duodenum)
5. Gastric Inhibitory Peptide (GIP, proximal small intestine)
6. Motilin (proximal small intestine)
7. Somatostatin
8. Cholecystokinin (CCK, small intestine)
9. PYY (small intestine and colon) |
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Term
| Intrinsic Non-Peptide Hormones of the GI Tract |
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Definition
1. ACh
2. NO (Nitric Oxide)
3. ATP
4. Seratonin (5-HT) |
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Term
| Intrinsic Rhythmic Depolarizations |
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Definition
| Slow waves traveling in an aboral direction within the smooth muscle of the GI tract. |
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Term
| Interstitial Cells of Cajal (ICC) |
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Definition
| "Pacemakers" which start slow waves. They are located in or near smooth muscle and link to the muscle by Gap Junctions. |
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Term
| Contraction of GI Smooth Muscle Requires |
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Definition
1. Excitatory neurotansmitters affecting Interstitial Cells of Cajal (ICC) and/or smooth muscle.
2. Simultaneous slow wave occurrence. |
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Term
| Motility in the Mouth, Pharynx, Larynx is Provided by |
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Definition
| Skeletal muscle controlled by the CNS |
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Term
| Motility in the Esophagus of Dogs and Ruminants is Provided by |
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Definition
| Skeletal muscle under CNS control. |
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Term
| Motility in the Esophagus of Cats and Horses is provided by |
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Definition
A mix of:
1. Proximal skeletal muscle under Vagus Somatic control
2. Distal smooth muscle under ANS and ENS control. |
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Term
| Motility in the Stomach and Intestines is provided by |
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Definition
| Smooth muscle mostly under ENS control. |
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Term
| Prehension of food by Lips (Horse) and Tongue (Cattle) is Controlled by these Nerves |
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Definition
| Facial (VII), Glossopharyngeal (IX), and the motor branch of Trigeminal (V). |
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Term
|
Definition
| Breaks down, moistens, and lubricates food. |
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Term
|
Definition
| Swallowing; has both voluntary and involuntary stages. |
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Term
| Voluntary Phase of Deglutition is: |
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Definition
| Food is formed into a bolus and pushed into the oropharynx by the tongue. |
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Term
| Involuntary Phase of Deglutition is ________ and Controlled by these Nerves |
|
Definition
The swallowing reflex;
1. Trigeminal (V)
2. Facial (VII)
3. Glossopharyngeal (IX)
4. Vagus (X)
5. Hypoglossal (XII) |
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Term
| Four Most Common Areas for Esophageal Obstruction |
|
Definition
1. Back of the Pharynx
2. Thoracic Inlet
3. Arch of the Aorta
4. Passage through the Diaphragm. |
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Term
| Segmental Contractions of the Gut are |
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Definition
| Non-propulsive movements responsible for mixing and fragmenting of the ingesta. |
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Term
|
Definition
1. Lubrication
2. Antibacterial Action
3. Digestive enzymes
4. Thermoregulation (panting)
5. Grooming |
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Term
| Digestive Enzymes of Saliva |
|
Definition
| Amylases and Lipases (Neonates) |
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Term
| Three Major Salivary Glands |
|
Definition
1. Parotid
2. Mandibular
3. Sublingual |
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Term
| Salivation is Stimulated By |
|
Definition
| ACh from PSNS fibers of Facial (VII) and Glossopharyngeal (IX). |
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Term
| Salivation is Inhibited by |
|
Definition
| SNS release of Epinephrine and Norepinephrine. |
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|
Term
| Salivary Glands Secrete a Mixture of |
|
Definition
1. Mucus
2. Enzymes
3. Electrolytes
4. Water |
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Term
| Collecting Ducts in Salivary Glands Add and Remove these Electrolytes |
|
Definition
Add into Lumen: Potassium and Bicarbonate
Remove into Blood: Sodium and Chloride |
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Term
| Tonicity and pH of Saliva |
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Definition
| Generally hypotonic with a neutral to alkaline pH (high potassium and bicarbonate). |
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Term
| Types of Saliva Based on Secreting Gland |
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Definition
1. Parotid - serous saliva
2. Mandibular, Sublingual - mucous/mixed saliva |
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Term
| Ruminant Saliva Characteristics |
|
Definition
| Voluminous and alkaline as a rumen buffer |
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Term
| Four Functions of Stomach |
|
Definition
1. Food Storage
2. Mechanical breakdown of food
3. Chemical digestion by HCl and proteolytic enzymes
4. Controlled dispensing of chyme to small intestine |
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Term
| Movements of the Stomach Controlled by: |
|
Definition
1. Autonomic NS (SNS & PSNS)
2. Enteric NS
3. Gut Hormones |
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Term
| Two Functional Parts of the Stomach |
|
Definition
1. Proximal Stomach (Fundus and most of Body)
2. Antrum (Distal Body and Pylorus) |
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Term
| Function of Proximal Stomach |
|
Definition
| Storage (made possible by relaxation through PSNS Vagal Reflex) |
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Term
| Function of Distal Stomach |
|
Definition
1. Mixes and grinds food
2. Pushes chyme toward Pylorus
3. Moves chyme into small intestine |
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Term
| Stomach Emptying is Promoted by |
|
Definition
Gastric factors such as:
Large volume of food in stomach
Secretion of Gastrin |
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Term
| Stomach Emptying is Inhibited by |
|
Definition
Duodenal factors (3)
1. Afferent neurons from the brain and spinal cord (decreased Vagal input and increased sympathetic input)
2. ENS Afferent neurons.
3. Secretion of Gut Hormones from duodenal enteroendocrine cells |
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Term
| Gut Hormones Secreted in Duodenum which Inhibit Gastric Emptying |
|
Definition
1. CCK (Cholecystokinin)
2. Somatostatin |
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|
Term
| Characteristics of Duodenal Contents |
|
Definition
1. Low pH
2. High Osmolality (hypertonic)
3. Lipids |
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Term
| Size of Particles Leaving the Stomach |
|
Definition
|
|
Term
| Time for Liquids to Empty from Stomach |
|
Definition
| 1 hour (half life 18 minutes) |
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Term
| Time for Solids to Empty from Stomach |
|
Definition
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|
Term
| Interdigestive Motility Complex; Process, Stimulation, and frequency |
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Definition
| Clears bone and indigestible material from stomach. Stimulated by motilin. Cyclic, strong wave of peristalsis sweeps over antrum as pylorus relaxes. Occurs once an hour between meals, eating interrupts cycle. |
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Term
| Vomiting is a Reflex Coordinated in the: |
|
Definition
|
|
Term
| Five types of Stimuli for Vomiting: |
|
Definition
1. Mechanoreceptors in pharynx
2. Mechanoreceptors and chemoreceptors in stomach and duodenum
3. Mechanoreceptors and chemoreceptors in other organs
4. Chemoreceptor Trigger Zone in brainstem.
5. Semicircular canals in inner ears |
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Term
| Characteristics of Vomiting |
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Definition
| Salivation, anticipation, retching, semidigested food, bile, +/- blood, low pH (<5). |
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Term
| Characteristics of Regurgitation |
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Definition
| Passive (few warning signs), contains undigested food, pH (>7) |
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Term
|
Definition
|
|
Term
| Three Zones of Glands in the Glandular Mucosa: |
|
Definition
1. Cardiac
2. Parietal
3. Pyloric |
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Term
| Cardiac Zone Glands secrete: |
|
Definition
|
|
Term
| 5 Cells of Parietal Zone Glands |
|
Definition
1. Neck and surface mucous cells
2. Parietal Cells
3. Chief Cells
4. Enterochromaffin Cells
5. Mast Cells |
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Term
|
Definition
1. H, Cl (combine extracellularly to make HCl)
2. Intrinsic factor |
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|
Term
|
Definition
| Pepsinogens, and chymosinogen in cattle, (inactive proenzymes) which are cleaved into active enzymes for protein digestion. |
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Term
|
Definition
1. Pepsin
2. Chymosin
Most active at low pHs. |
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Term
| Enterochromaffin and Mast Cells Secrete: |
|
Definition
|
|
Term
|
Definition
| Stimulates HCl secretion (H and Cl secretion) by Pareital Cells via receptors. |
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Term
| Cells of the Pyloric Zone Glands and their Secretions: |
|
Definition
1. Mucous Cells - secrete mucus and some Pepsinogens
2. G-Cells - secrete gastrin. |
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Term
|
Definition
| Stimulates HCl production by Parietal cells and Histamine secretion by mast and enterochromaffin cells. |
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Term
| 2 Phases of HCl Secretion |
|
Definition
1. Cephalic (CNS)
2. Gastric |
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Term
| Process of Cephalic Phase of HCL Secretion |
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Definition
| Anticipation of food > ACh release from Vagus to Parietal Cells and G-Cells. Pareital Cells are stimulated to release HCl. Gastrin from G-Cells causes further HCl secretion. |
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Term
| Process of Gastric Phase of HCl Secretion |
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Definition
Food distends stomach > ENS release ACh stimulating G-Cells and Parietal Cells
Food raises stomach pH > G-Cells release more gastrin |
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Term
| Negative feedback loop of HCl Secretion is caused by: |
|
Definition
1. Low pH >decrease in Gastrin production
2. Chyme in duodenum >Somatostatin, Secretin, CCK secretion into bloodstream >decrease in HCl and Pepsinogen secretion in stomach. |
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|
Term
| Methods for Treating Ulcers: |
|
Definition
1. Antacids - increase pH temporarily, but cause rebound HCl production
2. Surface protectants - coat the ulcer by reacting with HCl and attaching to proteins.
3. H2 Histamine Receptor Antagonists - block the action of histamine on parietal cells.
4. Proton Pump Inhibitors - block the action of the H/K/ATPase pump on parietal cells. |
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|
Term
|
Definition
1. Endocrine: regulation of blood glucose.
2. Exocrine: Secretion of proenzymes to digest complex lipids, proteins, and carbohydrates. |
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|
Term
| Secretory Components of the Exocrine Pancreas |
|
Definition
1. Acinar Cells secrete zymogens and enzymes.
2. Centroacinar and Duct Cells secrete HCO3 and H2O as buffers. In dogs they secrete Intrinsic Factor for B12 absorption. |
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Term
| 3 Main Enzymes/Proenzymes Secreted by Pancreas: |
|
Definition
1. Amylases: hydrolyze starches, simple sugars
2. Lipases: hydrolyze fats
3. Zymogens (proenzymes): hydrolyze proteins |
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|
Term
| Examples of Lipases Secreted by Pancreas |
|
Definition
1. Lipase
2. Cholesterol Esterase
3. Phospholipase |
|
|
Term
| Examples of Zymogens Secreted by Pancrease |
|
Definition
1. Trypsinogen
2. Chymotripsinogen
3. Proelastase |
|
|
Term
| Function of Trypsin Inhibitor |
|
Definition
| Packaged with zymogens to inhibit their activation and self digestion of pancreas. Diluted in small intestine for Zymogen activation. |
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|
Term
| 4 Main Factors Promoting Pancreatic Secretion: |
|
Definition
1. ACh
2. Gastrin
3. Secretin
4. CCK |
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|
Term
| Source and Effect of ACh on Pancreatic Cells |
|
Definition
| Released by Vagal stimulation and causes limited release of pancreatic enzymes and HCO3. |
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|
Term
| Source and Effect of Gastrin(Intrinsic; main secretory control mechanism) on Pancreatic Cells: |
|
Definition
| Secreted by stomach, leads to increase in pancreatic enzyme secretion. |
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|
Term
| Source and Effect of Secretin (Intrinsic; main secretory control mechanism)on Pancreatic Cells: |
|
Definition
| Low pH in duodenum leads to secretin secretion, causes increase in HCO3. |
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|
Term
| Source and Effect of CCK (Intrinsic; main secretory control mechanism) on Pancreatic Cells: |
|
Definition
| Peptides and fats in duodenum lead top secretion of CCK; increases pancreatic enzyme secretion. |
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|
Term
| 2 Factors for Negative Feedback of Pancreatic Secretion |
|
Definition
1. Increased pH
2. Digestion of Chyme |
|
|
Term
| Percentage of GI Blood Flow to Mucosa |
|
Definition
| 75% for absorption of nutrients and water. |
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|
Term
| Countercurrent Blood Flow's effect on tip of Villus in Intestine |
|
Definition
| Tip of villus becomes more HYPOXIC |
|
|
Term
|
Definition
1. Lipid Digestion by Bile Acids (bile salts)
2. Waste Elimination |
|
|
Term
| Bile Acids Conjugate with: |
|
Definition
|
|
Term
| Purpose of Bile Acid Conjugation: |
|
Definition
1. Increases bile acid solubility
2. Prevents re-absorption in the bile ducts. |
|
|
Term
| Function of Gallbladder and bile ducts: |
|
Definition
| Concentrates bile by re-absorbing water and electrolytes (except calcium). |
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|
Term
| Micelles: Form and Function |
|
Definition
Form: small, spherical globules of bile salts.
Function: Transport Monoglycerides and Free Fatty Acids (FFAs) to striated border of intestinal epithelium for absorption into bloodstream to prevent reverse hydrolysis. |
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|
Term
| Location and Percentage of re-absorption of Bile Acids |
|
Definition
| > 90% absorbed in Ileum. High levels of serum bile acids indicates disease. |
|
|
Term
|
Definition
1. Bile Acids
2. HCO3 and other electrolytes
3. Phospholipids
4. Cholesterol
5. Waste products (including bilirubin) |
|
|
Term
| Bile Secretion is Stimulated by |
|
Definition
1. Return of Bile Acids to Liver
2. Secretin stimulates an increase in H2O and HCO3 components of Bile. |
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|
Term
| Bile Release is Stimulated by: |
|
Definition
1. Cholecystokinin (CCK) contracts gallbladder and relaxes Sphincter of Oddi
2. PSNS Vagal stimulation. |
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|
Term
| 4 Compartments Nutrients and Water Move through during Intestinal Absorption |
|
Definition
1. Lumen
2. Cytosol
3. Lateral Space
4. Blood and Interstitial Spaces |
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|
Term
| Three Mechanisms for Sodium Absorption: |
|
Definition
1. Symports
2. Antiports
3. Simple Diffusion |
|
|
Term
| Nutrient Absorption Route in Intestine |
|
Definition
| Nutrients are absorbed via the transcellular route via active transport. |
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|
Term
| 3 types of GI tract Secretions |
|
Definition
1. Mucus
2. Digestive Enzymes and Specialized Substances (Bile, Saliva)
3. Water and Electrolytes. |
|
|
Term
| Purpose and Mechanism for Physical Breakdown of Food Particles: |
|
Definition
Purpose: prevent injury, increase surface area.
Mechanism: Chewing action, grinding of the distal stomach. |
|
|
Term
| Three Main Types of Nutrients |
|
Definition
1. Carbohydrates
2. Proteins
3. Fats |
|
|
Term
| Carbohydrate originates mainly from: |
|
Definition
|
|
Term
| Three Types of Carbohydrates |
|
Definition
1. Fiber (Cellulose; Lignin is undigestible)
2. Starches
3. Sugars |
|
|
Term
| Phases of Carbohydrate Digestion |
|
Definition
| Luminal Digestion breaks down Starch with Amylase into complex sugars > Membrane bound enzymes break down Complex sugars into simple sugars > simple sugars are absorbed into enterocyte by Na-cotransport and facilitated transport. |
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|
Term
|
Definition
|
|
Term
| 3 Phases of Protein Digestion |
|
Definition
| Luminal digestion by activated zymogens breaks proteins into peptides > membrane bound peptidases in small intestine break down peptides into amino acids and di- and tri-peptides > Absorption of Amino acids by Na-cotransporters > Absorption of Di- and Tri-Peptides by carrier proteins and digested into amino acids by cytoplasmic peptidases. |
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Term
|
Definition
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