PNB 2265 Study Guide - Midterm Guide: Vasoactive Intestinal Peptide, Abdominal Cavity, Salivary Gland
16 May 2018
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DIGESTIVE ANATOMY
1. Gross Anatomy
a. Alimentary Canal
i. Mouth
ii. Esophagus
iii. Stomach
iv. Small & large intestines
v. Rectum
b. Accessory Organs
i. Salivary Glands
ii. Liver
iii. Pancreas
iv. Gallbladder
2. Serous Membrane: Peritoneum
a. Parietal Peritoneum → Lines Walls of Abdominal Cavity
b. Visceral Peritoneum → covers the surface of organs
c. Peritoneal Fluid: is a liquid that acts as a lubricant in the abdominal cavity.
DIGESTIVE PHYSIOLOGY
Molecules which influence Smooth Muscle Contraction
●Calcium, Cyclic Nucleotides
●Myosin Light Chain Kinase (MLCK), Myosin Light Chain Phosphotase
●Nitric Oxide
●Vasoactive Intestinal Peptide (VIP)
●Subtance P
What happens to smooth muscle contractility in the GI tract when
●Open Ca Channel: increase
●Increase MLCKinase Activity: increase
●Increase MLCPhosphatase Activity: increase??????
●Agonist for GPCR w/ a Gi : decrease
●Stimulating GPCR w/ a Gs : increase
●Inhibit Phosphodieterase : increase
1. Secretion: APICAL surface (faces outside), inside the GI tract, external
i. *** GI Enzymes
ii. Enzymatic Secretions of the GI Tract come from:
1. Salivary glands
2. Pancreas
3. Stomach
4. Small Intestine
iii. May be Zymogens: an inactive substance that is converted into an enzyme when activated by another
enzyme
iv. Many are brush border enzymes (they remain attached ot the apical membrane of the intestinal
epithelia)
2.
Absorption: BASOLATERAL surface, blood, inside the body, internal
v. Chemical digestion is breakdown of complex macromolecules into smaller units by SECRETED
ENZYMES; happens in the ESOPHAGUS, STOMACH, and SMALL INTESTINE
vi. Absorption is passage of the nutrients from the LUMEN into the TISSUES; happens in the SMALL
INTESTINE and STOMACH
1. Water & ions pass through the LARGE INTESTINE
3. Integrated Meal Response
Cephalic/Esophageal
i. Saliva Functions: Digestive (Salivary Amylase, Salivary Lipase) & Protective (Lysozyme, Fluoride, HCO3-)
1. Saliva is secreted by the Parotid, Sublingual, and Submandibular glands (Autonomic)
ii. The Sequence of Events:
1. Tongue pushes bolus against the soft palate + triggers swallow reflex
2. UPPER esophageal sphincter relaxes, epiglottis closes
3. Food moves into esophagus w/ peristaltic waves
iii. Gastroesophageal Junction:
1. Bolus Movement is due to pressure changes
2. Achalasia: Achalasia is a rare disease of the muscle of the lower esophageal body and the
lower esophageal sphincter that prevents relaxation of the sphincter and an absence of
contractions, or peristalsis, of the esophagus.
3. Esophageal Pressure reduced by
a. Caffeine
b. Alcohol
c. Cigarettes
d. Chocolate
4. Low pressure is bad since it can cause Gastroesophageal reflux disease, or GERD, is a digestive
disorder that affects the lower esophageal sphincter (LES), the ring of muscle between the
esophagus and stomach.stomach acid moves into the esophagus, causes discomfort and may
lead to precancerous changes in the lining of the esophagus
Gastric
4. How is gastric secretion regulated by hormones and other signaling molecules?
- Somatostatin
- Stops gastric acid secretion
- Secreted by D Cells
- Gastrin
- Stimulates secretion of gastric juice, and is secreted into the bloodstream by the stomach wall in response to
the presence of food
- Secreted by G cells
- Histamine
- Stimulates gastric acid secretion
- Secreted by ECL cells
- HCl
- Secreted by parietal cells
- Activates pepsinogen into the pepsin (enzyme form)
- Pepsinogen
- Secreted by chief cells which is stimulated by the presence of gastrin
- When it changes to its enzyme form -> pepsin, it digests proteins
5. What factors regulate the process of gastric emptying?
- DEFINITION
- Strong peristaltic waves
- Increased tone in gastric reservoir
- Opening of the pylorus (pyloric valve, pyloric sphincter)
- Inhibition of duodenal segmental contractions
- INCREASED BY
- Gastric volume and content
- Neural control
- Gastrin
- DECREASED BY
- Enterogastrones which include
- Secretin = pH
- In response to low pH due to stomach acid
- Brings bicarbonate into small intestine to neutralize the acid
- CCK = fat
-Cholecystokinin
- Also important for allowing us to start process of fat digestion in SI
- Gastric inhibitory peptide = carbs
- Released in response to carbs
- Inhibits gastric emptying too
- Causes insulin to get released
6. What are the major secretions from secretory organs and how are they regulated?
- Is this not the same as number 3????????
7. Describe the molecular basis of acid secretion in the stomach: what ion channels and transporters are involved and
where are they located?
-
Types of Cells + What They Secrete
●Chief Cells → Pepsinogen ( precursor of Pepsin )
●Parietal Cells → HCl ( for pH, parietal cells of Gastric Glands)
& Intrinsic Factor ( used for B12 Absorption )
●Mucus Cells → Mucus
●G-Cells → Gastrin (a hormone that stimulates secretion of gastric juice, and is secreted into the bloodstream by the
stomach wall in response to the presence of food)
●D-Cells → Somatostatin (growth hormone-inhibiting hormone (GHIH) a peptide hormone that regulates the endocrine
system)
●ECL Cells → Histamine (Allergen)
Secretions Regulate the Proton Pump
●Histamine increases cAMP Activating
●ACh + Gastrin increase Ca2+ Activating
●Somatostatin lowers cAMP Inhibitory
What happens when a bolus enters the stomach?
Bolus is a small rounded mass of a substance, especially of chewed food at the moment of swallowing
Document Summary
Digestive anatomy: gross anatomy, alimentary canal i. ii. iii. iv. v. Rectum: accessory organs i. ii. iii. iv. Parietal peritoneum lines walls of abdominal cavity a: visceral peritoneum covers the surface of organs, peritoneal fluid: is a liquid that acts as a lubricant in the abdominal cavity. Myosin light chain kinase (mlck), myosin light chain phosphotase. What happens to smooth muscle contractility in the gi tract when. Agonist for gpcr w/ a gi : decrease. Stimulating gpcr w/ a gs : increase. Secretion: apical surface (faces outside), inside the gi tract, external i. ii. Enzymatic secretions of the gi tract come from: May be zymogens: an inactive substance that is converted into an enzyme when activated by another enzyme iv. Many are brush border enzymes (they remain attached ot the apical membrane of the intestinal epithelia) Absorption: basolateral surface, blood, inside the body, internal v. vi. Chemical digestion is breakdown of complex macromolecules into smaller units by secreted.
