Physio - Pernuske

Question 1

What constitutes the upper and lower GI tract?

Answer 1

Upper: Oral Cavity, Pharynx, Esophagus, Stomach, Small intestine Lower: Large Intestine

Question 2

What are the accessory organs to the GI tract?

Answer 2

• Salivary glands (parotid, submandibular, sublingual) - Exocrine Pancreas - Liver- Hepatic system - Gallbladder- Biliary system

Question 3

Which sphincters are voluntary? What controls involuntary vs voluntary?

Answer 3

Upper esophageal and external anal Voluntary sphincters are supplied by somatic nerves. Involuntary sphincters are stimulated by autonomic nerves.

Question 4

Name these layers

Answer 4

Serosa

Longitudinal muscle

Circular muscle

Submucosae

Muscularis mucosae

Lamina propia

Epithelium

Question 5

In what layer are major blood vessels and lymphatics found in the GI system?

Answer 5

The submocosa layer

Question 6

The interface between body and environment secretion, absorption, barrier, and immunologic protection specialized folds increase surface area is called what?

Answer 6

Mucosa

Question 7

Which cells have villi and crypts, and where are they located?

Answer 7

Enterocytes in the small intestine

Question 8

Explain the renewal of GI epithelial cells.

Answer 8

Stem cells at the base of the crypts divide, differentiate and migrate to the tips of the villi:

• Apoptosis occurs every 3-6 days after which the cell is shed into the lumen.
• Prevent the accumulation of mutations due to toxin exposure

Question 9

Define:

Diverticulum-
Diverticulosis-
Diverticulitis-

Answer 9

Diverticulum- single pouch protruding from alimentary tract. Usually false not true.

Diverticulosis- multiple diverticula

Diverticulitis- impacted with feces, inflamed, painful,
if blood vessel is eroded hemorrhage

(True diverticula contain all layers of bowel wall. False do not.)

Question 10

How is mucin organized? Are enterocytes coated with this?

Answer 10

Protein monomers combined into complexes by disulfide links,

2 layers in the stomach and colon, 1 layer in small intestine

• Glycosylation protects the protein core from proteases and carbohydrate side chains attract water forming a gel
• Enterocytes are coated with transmembrane mucins

Question 11

What are they broken down into, by what enzyme, and where are they sent?

Protein

Carbohydrates

Triglycerides

Answer 11

Protein –> Peptides, AA –> Capillaries

by Protease (in duodenum/jejunum)

Carbohydrates –> monosaccharides, disaccharidases –> Capillaries (by Amylase)

Triglycerides –> Fatty acid, monoglycerides –> Lymphatics

(Lipases)

Question 12

Amino acids and monosaccharides are absorbed where and by what mechanism?

Answer 12

Amino acids and monosaccharides are absorbed in duodenum and jejunum through secondary active transport

Question 13

What is absorbed in the duodenum?

Answer 13

Amino acids

Disaccarhides are formed, but not absorbed

Iron

Question 14

What is absorbed in the jejunum and ileum?

Answer 14

Monosaccharides

Calcium

Folate

Fat-soluble vitamins (ADEK)

Ileum

B12, Intrinsic Factor, Bile Acids

Water and Na

Question 15

CO2, H+, K+, adenosine are all what?

Answer 15

Vasodilators –> increase blood flow

Question 16

What are some causes and effects of mesenteric ischemia?

Answer 16

Causes:

• Occlusive mechanisms including thrombi (mesenteric infarction)
• Non-occlusive mechanisms including prolonged reflex vasoconstriction (due to hypovolemia, heart failure) or abnormal levels of circulating vasoconstrictors (e.g, epinephrine, angiotensin II)

Effects

• Postprandial Pain, Sitophobia
• Necrosis of the tips of the villi
• Loss of barrier function of the wall of the gut and uptake of vasodilator toxins (endotoxin) from the gut resulting in Septic Shock

Question 17

Average Transit time?

Esophagus

Stomach

Small Intestine

Large Intestine

Answer 17

Average Transit time

Esophagus – 10s

Stomach – 3-5hrs

Small Intestine – 2.5-3hrs

Large Intestine – 30-40hrs

Question 18

Most of the GI tract is covered by what type of muscle?

Answer 18

Non-striated Smooth Muscle
- exception is striated muscle in upper third of esophagus, pharynx, external anal sphincter

Question 19

(T/F) Basal resting tension or “tone” is maintained without elevation in intracellular Ca++ and without energy expenditure.

Answer 19

True

Question 20

What is the migrating motor complex and what hormone is at play?

Answer 20

Migrating Motor Complex: relaxation of sphincters and contractions in stomach and small intestine occurring during fasting(interdigestive) controlled by hormone motilin

This is your “clearing house” Sweeps everything out of compartment.

Question 21

Where is the Submucosal nerve plexus and Myenteric nerve plexus located? Can they operate autonomously from the CNS?

Answer 21

• Submucosal nerve plexus within small and large intestine, sensory and blood flow, Meissner’s
• Myenteric nerve plexus between circular and longitudinal muscle layer from esophagus to internal anus (aka Auerbach’s)
• Can operate autonomously to mediate short reflexes independent of input from the CNS

Question 22

Target cell and effect?

Gastrin

Cholecystokinin (CCK)

Secretin

Gastric Inhibitory Peptide or Glucose-Dependent Insulinotropic Peptide (GIP)

Motilin

Answer 22

1. Gastrin – G cells in antrum of stomach detect amino acids leading to pepsinogen and H+ release by parietal cells.
2. Cholecystokinin (CCK) - I cells in D/J detect fat and amino acids, secretion of pancreatic enzymes and bile salts involved in fat uptake
3. Secretin - S cells primarily in D/J detect acid stimulates secretion of pancreatic juice including bicarbonate and inhibits gastric motility.
4. Gastric Inhibitory Peptide or Glucose-Dependent Insulinotropic Peptide (GIP)- K cells in D/J detect carbohydrates and fat to inhibit gastric acid secretion and stimulate insulin release from pancreas.
5. Motilin – secreted by endocrine cells; released cyclically during fasting state to initiate Migrating Motor Complex