Questions and Answers
What is the function of the pyloric sphincter in the stomach?
What is the pH range of the gastric juice secreted by the stomach?
What is the function of intrinsic factor secreted by parietal cells in the stomach?
What is the function of goblet cells in the stomach?
Signup and view all the answers
What is the function of the submucosal plexus in the stomach?
Signup and view all the answers
What is the function of the simple columnar epithelial cells in the stomach?
Signup and view all the answers
What is the function of gastric acid in the stomach?
Signup and view all the answers
What is the function of chemoreceptors in the stomach?
Signup and view all the answers
What is the role of trypsin in the digestive system?
Signup and view all the answers
What is the purpose of the enteric nervous system in the stomach?
Signup and view all the answers
What is the function of the hormone gastrin?
Signup and view all the answers
What is the main function of the pancreas in the digestive system?
Signup and view all the answers
What is the function of pancreatic lipase?
Signup and view all the answers
What is the role of the hormone somatostatin in the digestive system?
Signup and view all the answers
What is the function of the small intestine in the digestive system?
Signup and view all the answers
What is the main component of pancreatic juice?
Signup and view all the answers
Where is vitamin B12 absorbed in the small intestine?
Signup and view all the answers
What is the function of the ileocaecal valve?
Signup and view all the answers
What is the mechanism of water absorption in the GI tract?
Signup and view all the answers
What is the primary function of the large intestine?
Signup and view all the answers
What is the role of the mucosa in the small intestine?
Signup and view all the answers
What is reabsorbed and recycled from the ileum?
Signup and view all the answers
What determines the absorption of water in the GI tract?
Signup and view all the answers
What is synthesized in the large intestine through bacterial activity?
Signup and view all the answers
Study Notes
Stomach
- Has three layers of muscle, unlike the rest of the<small>Gastrointestinal tract</small>which 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.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
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.