Anatomy and Physiology of Digestive System

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Questions and Answers

What is the primary function of the mucosa layer in the digestive tract?

Protections and binding of the digestive tract

Storage of food in the digestive tract

Peristalsis and segmentation of food

Secretion and absorption of nutrients (correct)

What is the main function of the stomach in the digestive process?

Absorption of nutrients

Production of digestive enzymes

Elimination of waste products

Storage and mechanical breakdown of food (correct)

Where does starch digestion start?

Small intestine

Large intestine

Stomach

Mouth (correct)

Which of the following is NOT a function of the stomach?

Absorption of nutrients Signup and view all the answers

What is the role of the serosa layer in the digestive tract?

Protection and binding of the digestive tract Signup and view all the answers

What is the role of carbonic anhydrase in the formation of HCl in the parietal cells?

It produces carbonic acid from CO2 and H2O Signup and view all the answers

What is the function of the goblet cells in the mucosa layer?

Secretion of mucus Signup and view all the answers

What is the function of the H+/K+ ATPase pump in the parietal cells?

It couples the secretion of H+ into the gastric lumen while transporting K+ from the lumen of the stomach Signup and view all the answers

What are the three main regulators of gastric secretion?

Vagus nerve, gastrin, and histamine Signup and view all the answers

What is the term for the contraction of the walls of the digestive tract?

Peristalsis Signup and view all the answers

What is the function of the intrinsic factor secreted by the stomach lining?

Reabsorption of vitamin B12 Signup and view all the answers

What is the main function of the mucus layer in the stomach lining?

It prevents acid and pepsin from damaging the stomach lining Signup and view all the answers

What is the correct order of the parts of the GI tract?

Mouth, Pharynx, Esophagus, Stomach, Small intestine, Large intestine Signup and view all the answers

What is the approximate length of the duodenum in the small intestine?

25 cm Signup and view all the answers

What is the main function of the jejunum in the small intestine?

Most absorption occurs here Signup and view all the answers

What is the function of tight junctions between epithelial cells in the stomach lining?

They prevent the destruction of underlying tissues Signup and view all the answers

Study Notes

Digestive System: Overview

The digestive system consists of the gastrointestinal (GI) canal or tract and accessory or associated digestive organs.
The GI canal is a continuous coiled hollow tube comprising the oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine.
Accessory organs include teeth, salivary glands, pancreas, liver, and gallbladder.

Layers of the Digestive Tract

The digestive tract has four layers (tunics):
- Mucosa: inner secretory and absorptive layer with simple columnar epithelium, lamina propria, muscularis mucosae, and goblet cells that secrete mucus.
- Submucosa: very vascular, with glands and nerve plexuses.
- Muscularis: smooth muscle responsible for peristalsis and segmentation, with a nerve plexus for autonomic nervous system control.
- Serosa: outer binding and protective layer.

Functions of the Stomach

The stomach stores food, churns it to mix with gastric secretions, and begins protein digestion with pepsin.
Gastric acid kills bacteria, denatures proteins, and activates pepsinogen into pepsin.
Intrinsic factor secretion from the stomach lining helps in vitamin B12 reabsorption later in the intestine.
The stomach moves food into the small intestine in the form of chyme.

Digestion and Absorption in the Stomach

Protein digestion starts in the stomach.
Starch digestion starts in the mouth but stops in the stomach due to pH levels.
Only alcohol and NSAIDs (aspirin) are absorbed in the stomach.

Stomach: HCl Secretion

HCl secretion in the stomach involves the formation of carbonic acid from CO2 and H2O, which then dissociates into bicarbonate ion and H+.
Parietal cells couple the transport of Cl- and bicarbonate ion across the plasma membrane, secreting Cl- into the gastric lumen.
The H+/K+ ATPase pump couples the secretion of H+ into the gastric lumen while transporting K+ from the lumen of the stomach in the opposite direction.

Regulation of Gastric Secretion

HCl secretion by parietal cells is regulated by the vagus nerve (parasympathetic), hormone gastrin, and histamine secretion.

Stomach Defenses

The stomach lining has defenses to prevent damage from acid and pepsin, including:
- An adherent layer of mucus with alkaline bicarbonate.
- Tight junctions between epithelial cells to prevent underlying tissue destruction.
- Rapid epithelial mitosis (cell division) that replaces the whole stomach epithelium every three days.

Small Intestine Structure

The small intestine is divided into three sections:
- Duodenum: first 25 cm (most digestion).
- Jejunum: middle 2/5 (most absorption).
- Ileum: last 3/5.

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Description

This quiz covers the parts of the digestive system, including the gastrointestinal canal and accessory organs, as well as the processes of digestion and absorption. It's a part of the anatomy and physiology course for pharmacy students.