Module 1: Anatomy and Physiology

Question 1

What are the organs of the GI tract?

Answer 1

-Mouth - chewing, hydrolysis, create a bolus
-Esophagus - muscular tube, food transport
-stomach - hydrolysis, churning, storage, making chyme (fluid form of the food)
-small intestine: duodenum, jejenum, illeum
-large intestine (colon): hydrolysis, absorption
-Rectum: storage before passing
-Anus: expulsion

Question 2

Functions of the stomach

Answer 2

churning, breaking down the bolus
-hydrolysis: enzyme-mediated breakdown
-resulting in a chyme: mix of broken-up bolus and the enzymes
-storage of chyme until it is appropriate to the duodenum (4l storage)

Question 3

Anatomy of the stomach

Answer 3

-stomach lining consists of pits increasing the surface area
-with a layer of parietal cells : secreting gastric juice (HCl-)
-also chief cells: secreting the pro-cursor-enzyme pepsinogen (-> pepsin performing hydrolysis)

Question 4

How is pepsinogen converted into pepsin?

Answer 4

with HCl, secreted by parietal cells

pepsin breaks down proteins

Question 5

What protects the stomach from the acidic gastric juice?

Answer 5

-mucous cells releasing mucin
-bicarbonate

-protection from HCl and pepsin enzyme

Question 6

Functions of the liver

Answer 6

-metabolism of nutrients (catabolism/anabolism)
-storage of nutrients (carbs, fats)
-breakdown or usage of proteins (proteins are transported via albumin in the bloodstream)

-Detoxification CYP450: modify toxins to prevent harm to the body
-bile production: absorption of fats from the food

Question 7

In which forms are nutrients stored?

Answer 7

-Glycogen
-Lipoproteins
-Triglycerides (one of the forms of fat we ingest in our food)

Question 8

How does the liver have access to nutrients?

Answer 8

-portal vein: nutrients get absorbed in the intestine -> portal vein -> supplies the liver with nutrient-rich blood

-proper hepatic artery: O2-rich blood

-hepatic vein: nutrient and O2-poor blood leaving the liver -> to the heart to replenish O2 again -> passes the intestines to receive nutrients again

Question 9

How does bile leave the liver?

Answer 9

common hepatic duct

Question 10

Layers of the mucosa of the GI tract

Answer 10

-Epithelial layer: absorbs and secrets mucus and digestive enzymes

-Lamina propria: contains blood and lymph vessels

-muscularis mucosa: smooth muscles contracting -> breakdown of food

Question 11

What are the 4 regions of the stomach?

Answer 11

-Cardia
-Fundus
-Body
-Pyloric Antrum
-Pyloric sphincter: closes while eating, keeping food inside the stomach to digest

epithelial cells in different parts contain different proportions of glands

Question 12

Which type of cells are mostly present in the Cardia?

Answer 12

Foveolar cells: secrete mucus (Glycoproteins, water)

Question 13

Which part of the stomach mostly contains parietal and chief cells?

Answer 13

-Fundus
-Body

parietal cells -> secret gastric juice (HCl-)
chief cells secrete pepsinogen

Question 14

Which cells are mostly present in the Antrium?

Answer 14

G cells: secreting gastrin -> stimulates parietal cells to secret HCl, and stimulates the growth of glands in the epithelial layer

-gastrin is also found in the duodenum and pancreas

Question 15

What are Brunner glands?

Answer 15

-in the duodenum
-secrete mucus -> containing bicarbonate ions to neutralize the acid in the stomach and the duodenum

Question 16

Function of Prostaglandins

Answer 16

-stimulate mucus and bicarbonate secretion (protection)
-vasodilation of nearby blood vessels -> allowing more blood flow for epithelial cell growth, inhibits acid secretion

Question 17

How does H. pylori cause gastric and duodenal ulcers?

Answer 17

-they colonize the mucosa and adhere to Foveolar cells
-secrete protease damaging the mucosal cells

Question 18

How do NSAIDs cause ulcers?

Answer 18

-more in the stomach than in the duodenum
-inhibits COX enzyme involved in the prostaglandin production
-over time it decreases the protective effect of prostaglandin

Question 19

Zollinger-Ellison Syndrome

Answer 19

-Tumor: Gastrinoma (neuroendocrine tumor)
-in the duodenal wall or pancreas
-secretes abnormal amount of gastrin -> stimulates parietal cells to secrete HCl-
-> Ulcers in the duodenum, distal duodenum, jejunum

Question 20

Complications of Duodenal Ulcers

Answer 20

Brunner Glands Hypertrophy
-to produce more mucus to protect the damaged area

Question 21

What causes an Ulcer to bleed

Answer 21

Erosion of the Ulcer into an underlying blood vessel
-dangerous when eroding into arteries: left gastric artery, gastroduodenal artery -> blood loss -> SHOCK

Question 22

Complication of Perforation

Answer 22

-Ulcer erodes through the cell wall -> allowing stomach content to enter the peritoneal space (sterile)
-air starts to collect under the diaphragm -> irritating the nerve -> pain in the shoulder

Question 23

Ulcers near the pyloric sphincter

Answer 23

-rare
-edema and scarring lead to an obstruction of the normal passage of gastric content into the intestine -> Gastric outlet obstruction
-leads to nausea and vomiting

Question 24

Symptoms of Ulcers

Answer 24

-Epigastric pain, Bbloating, Belching, vomiting

Gastric Ulcer:
-pain when eating due to the presence of food and HCl production - associated with weight loss

Duodenal Ulcer
-less pain when eating - associated with weight gain

Question 25

Study-guide questions
What is peristalsis?

Answer 25

wave-like muscle contraction in the esophagus, stomach, and intestines to move the food

Question 26

Function of water in the stomach

Answer 26

-dilution of acid
-activation of enzymes: pepsin
-hydration of the stomach

Question 27

Function of secretin

Answer 27

secreted by S cells in the duodenum

-pancreas: stimulates bicarbonate secretion into the duodenum
-pancreas: stimulates enzyme production: lipase, amylase, protease -> nutrient breakdown

-stomach: inhibits gastric acid production

-gallbladder: stimulation of the gallbladder to secrete bile -> emulsify fats (more accessible for enzyme for breakdown and absorption)

Question 28

What are the parts of the colon?

Answer 28

-Cecum
-Ascending Colon
-Transverse Colon
-Descending Colon
-Sigmoid Colon
-Rectum
-Anus