Stomach Anatomy and Function

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Questions and Answers

What is the function of the pyloric sphincter in the stomach?

To produce and secrete hydrochloric acid

To absorb nutrients into the bloodstream

To churn and mix food with gastric juice

To regulate the passage of food into the small intestine (correct)

What is the pH range of the gastric juice secreted by the stomach?

pH 2-3 (correct)

pH 7-8

pH 9-10

pH 5-6

What is the function of intrinsic factor secreted by parietal cells in the stomach?

To convert iron into a soluble form

To activate pepsin in protein digestion

To produce hydrochloric acid

To facilitate the absorption of vitamin B12 (correct)

What is the function of goblet cells in the stomach?

To produce mucus that protects against acid Signup and view all the answers

What is the function of the submucosal plexus in the stomach?

To activate waves of peristalsis and gastric juice flow Signup and view all the answers

What is the function of the simple columnar epithelial cells in the stomach?

To provide a lining for the stomach that is replaced every three days Signup and view all the answers

What is the function of gastric acid in the stomach?

To increase the solubility of iron Signup and view all the answers

What is the function of chemoreceptors in the stomach?

To monitor pH changes in the stomach Signup and view all the answers

What is the role of trypsin in the digestive system?

Digesting proteins Signup and view all the answers

What is the purpose of the enteric nervous system in the stomach?

To monitor pH changes and activate neural feedback Signup and view all the answers

What is the function of the hormone gastrin?

To stimulate gastric juice secretion and gastric motility Signup and view all the answers

What is the main function of the pancreas in the digestive system?

To produce digestive enzymes and hormones Signup and view all the answers

What is the function of pancreatic lipase?

Digesting lipids Signup and view all the answers

What is the role of the hormone somatostatin in the digestive system?

Regulating growth hormone levels Signup and view all the answers

What is the function of the small intestine in the digestive system?

Absorption of nutrients from the diet Signup and view all the answers

What is the main component of pancreatic juice?

Sodium bicarbonate Signup and view all the answers

Where is vitamin B12 absorbed in the small intestine?

Terminal ileum Signup and view all the answers

What is the function of the ileocaecal valve?

One-way flow of materials from small to large intestine Signup and view all the answers

What is the mechanism of water absorption in the GI tract?

Osmosis Signup and view all the answers

What is the primary function of the large intestine?

Absorption of water and electrolytes Signup and view all the answers

What is the role of the mucosa in the small intestine?

Absorption of vitamins and minerals Signup and view all the answers

What is reabsorbed and recycled from the ileum?

Bile salts Signup and view all the answers

What determines the absorption of water in the GI tract?

Osmotic balance and concentration gradient Signup and view all the answers

What is synthesized in the large intestine through bacterial activity?

Some vitamins Signup and view all the answers

Study Notes

Stomach

Has three layers of muscle, unlike the rest of theGastrointestinal tractwhich has two.
Churns and mixes food with gastric juice.
Has two sphincters: cardiac and pyloric.
Pyloric sphincter is a ring of muscle that normally maintains constriction of a body passage.

Neural Feedback

Food distends the stomach, stimulating stretch receptors in its walls.
Chemoreceptors monitor pH changes.
Activates submucosal plexus, causing waves of peristalsis and gastric juice flow.

Stomach Secretions

Secretes 2-3L of highly acidic (pH 2-3) gastric juice and mucus per day.
Mucus provides a barrier against acidity within the stomach.
The stomach lining constantly renews itself through apoptosis, replacing old cells with new to maintain a healthy gastrointestinal tract and efficient digestion, happening every three days.

Exocrine Cells

Parietal cells secrete hydrochloric acid (HCl) and intrinsic factor (IF) for vitamin B12 absorption.
Chief cells secrete pepsinogen, which is converted to the active enzyme pepsin for protein digestion.
Goblet cells secrete mucus for protection against acid.

Stomach Functions

Mixing chamber: churns up food.
Holding reservoir: storage.
Defence: non-specific defence against gastric acidity.
Absorption (limited): water, alcohol, drugs (e.g., aspirin).
Digestion: mechanical and chemical digestion of proteins and lipids.
Iron: made more soluble with stomach acid.
Satiation: tells you to stop eating.

Hormones

Ghrelin: stimulates hunger.
Gastrin: responds to stomach distension, stimulating gastric juice secretion and gastric motility.

Pancreas

An accessory digestive organ with both exocrine and endocrine functions.
Exocrine function: secretes pancreatic juice (1.2-1.5L/day) containing sodium bicarbonate, water, and protease enzymes.
Endocrine function: secretes hormones insulin, glucagon, and somatostatin into the blood.

Pancreatic Enzymes

Secreted into the duodenum in their inactive form.
Enzymes include pancreatic amylase (breaks down starches into sugars), pancreatic lipase (lipid/fat digestion), trypsin and chymotrypsin (protein digestion), ribonuclease (digests RNA), and deoxyribonuclease (digests DNA).

Small Intestine: Absorption

Vitamin B12 is absorbed in the terminal ileum (with the help of intrinsic factor).
Vitamins, mineral salts, and water enter blood capillaries and are sent to the liver (hepatic first pass).
Bile salts are reabsorbed and recycled from the ileum.

Fluid Movement

All water absorption in the GI tract occurs via osmosis from the lumen into absorptive cells and into blood capillaries.
Osmosis is bi-directional, so absorption of water depends on electrolyte, monosaccharide, and amino acid levels to maintain an osmotic balance/concentration gradient with the blood.

Large Intestine

The final stage of digestion, absorption, some vitamin synthesis (through bacterial activity), and stool formation occurs.
The ileocaecal valve allows one-way flow of materials from the small to large intestine.
Mucus is produced, but no enzymes are secreted.
Absorption of water, minerals, vitamins, and some drugs occurs.
Four regions: caecum, colon, rectum, and anal canal.

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Description

This quiz covers the structure and function of the stomach, including its layers of muscle, sphincters, and neural feedback mechanisms that aid in digestion. Topics include the role of gastric juice, pH changes, and the enteric nervous system.