Gastrointestinal Tract Overview

Questions and Answers

Which part of the gastrointestinal tract directly processes food and waste?

Liver

Large intestine (correct)

Pancreas

Salivary glands

What is the primary function of bile acids in digestion?

Transport nutrient molecules

Solubilize lipids (correct)

Secrete electrolytes

Hydrolyze macromolecules

Which organs are essential for the digestion and absorption of all basic nutrients?

Teeth and tongue

Gallbladder and salivary glands

Pancreas and small intestine (correct)

Stomach and esophagus

Which of the following processes is NOT part of the sequence of events for digestion and absorption?

Nutrient molecule secretion Signup and view all the answers

Which type of cells in the salivary glands, gastric mucosa, and pancreas support enzyme secretion?

Exocrine cells Signup and view all the answers

What primarily controls salivary secretion?

Autonomic nervous system Signup and view all the answers

Which area of the brain is responsible for controlling salivary secretion?

Medulla oblongata Signup and view all the answers

Which of the following agents inhibits salivary secretion?

Atropine Signup and view all the answers

What is xerostomia?

Absence of saliva Signup and view all the answers

How does sympathetic stimulation affect salivary secretion?

It has a smaller increase compared to parasympathetic stimulation Signup and view all the answers

What is the primary function of kallikrein in the salivary glands?

To induce vasodilation Signup and view all the answers

Which factors are known to inhibit salivary secretion?

Sleep, fatigue, and fear Signup and view all the answers

What effect does pilocarpine have on salivary secretion?

Enhances salivary secretion Signup and view all the answers

What is the primary product of endopeptidase activity in the stomach?

Peptones Signup and view all the answers

What happens during the phenomenon known as alkaline tide?

HCO3- is added to the bloodstream Signup and view all the answers

Which of the following factors does NOT contribute to the secretion of H+ in the stomach?

Somatostatin Signup and view all the answers

What is the main function of the gastric mucosal barrier?

Prevents H+ ions and pepsins from damaging the gastric mucosa Signup and view all the answers

What initiates the secretion of somatostatin in the stomach?

Gastric luminal pH falling below 3 Signup and view all the answers

How thick is the mucus gel layer that protects the gastric mucosa?

0.2 mm Signup and view all the answers

What is the consequence of the absence of gastrin, histamine, or acetylcholine on H+ secretion?

Reduced acid secretion Signup and view all the answers

What percentage of lipid digestion occurs in the stomach due to gastric lipase?

10% Signup and view all the answers

What is the primary function of Brunner's glands in the small intestine?

Producing alkaline mucus to protect the mucosa Signup and view all the answers

Which of the following enzymes is responsible for breaking down disaccharides into monosaccharides?

Sucrase, maltase, lactase Signup and view all the answers

What is the pH range of intestinal juice?

7.5 - 8.0 Signup and view all the answers

Which hormone does NOT inhibit acid secretion in the stomach?

Gastrin Signup and view all the answers

Which of the following components is NOT a part of the composition of intestinal juice?

Bile salts Signup and view all the answers

Which gland secretes substances in response to irritating stimuli and vagal stimulation?

Brunner's glands Signup and view all the answers

What is the main role of cholecystokinin in digestion?

Releasing pancreatic enzymes Signup and view all the answers

How much intestinal juice is typically produced per day?

1800 ml Signup and view all the answers

What is the primary composition of bile from the liver?

97% water and 3% solids Signup and view all the answers

What is one of the roles of bile salts in digestion?

They act as emulsifying agents for fats. Signup and view all the answers

Which of the following substances is considered a powerful choleretic?

Bile salts Signup and view all the answers

What is the capacity of the gallbladder?

50 ml Signup and view all the answers

Which statement describes a change that occurs in bile when stored in the gallbladder?

Bile concentration increases by absorbing water. Signup and view all the answers

What role does secretin play in biliary secretion?

It promotes HCO3 secretion in bile. Signup and view all the answers

What happens to bile pH during storage in the gallbladder?

It becomes neutral or acidic. Signup and view all the answers

Which of the following is a function of bile salts related to cholesterol?

Eliminating excess cholesterol via feces. Signup and view all the answers

Study Notes

GIT System Subdivisions

Alimentary Canal: Pathway for food and waste; includes mouth, pharynx, esophagus, stomach, small intestine, and large intestine.
Accessory Organs: Connected to the alimentary canal; involved in digestion but not in the passage of food; includes teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

Digestion and Absorption Sequence

Mechanical Homogenization: Mixing of food with digestive fluids throughout the GIT.
Enzyme Secretion: Over 30g of digestive enzymes produced daily to break down macromolecules into smaller units (oligomers, dimers, monomers).
Electrolyte Secretion: Acids and bases secreted to maintain an optimal environment for enzymes.
Bile Acids: Function as biological detergents to emulsify lipids for better digestion and absorption.
Intestinal Final Digestion: Completed by intestinal surface enzymes breaking down nutrients further.
Nutrient Transport: Nutrients absorbed from intestinal lumen into the bloodstream.

Specialized GIT Components

Glands and Epithelia: Specialized glands (salivary glands, stomach, pancreas, liver, intestines) support digestion.
Exocrine Cells: Produce enzymes for digestion within the GIT lumen.

Salivary Secretion Control

Autonomic Regulation: Salivary secretion controlled primarily by the autonomic nervous system, not by GIT hormones.
Parasympathetic Activation: Increased salivation initiated by the salivatory nuclei in the brainstem; stimulated by taste, smell, and chewing.
Inhibitors: Atropine inhibits saliva; agents like pilocarpine increase secretion.
Sympathetic Stimulation: Leads to a smaller increase in salivation, primarily through beta-adrenergic receptors.

Stomach Structure

Regions: Divided into Cardia (cardiac glands), Fundus and Body (oxytonic or parietal glands), and Antrum (pyloric glands).
Surface Mucous Cells: Produce neutral mucins and bicarbonate (HCO3-).
Digestive Function: Partial lipid digestion occurs via gastric lipase.

HCl Production and Regulation

Alkaline Tide: During active acid secretion, parietal cells release HCl and HCO3- into the bloodstream, causing an alkaline shift.
HCl Secretion Regulation: Driven by gastrin, histamine, and acetylcholine; absence of any factor affects H+ secretion.

Gastric Mucosa Protection

Gastric Mucosal Barrier: Mucus gel and alkaline secretions protect the mucosa from acidic contents.
Mucus Layer: About 0.2mm thick; maintains near-neutral pH for epithelial cells despite acidic luminal environment.

Intestinal Secretions

Brunner's Glands: Secrete alkaline mucus in response to irritation, vagal stimulation, and secretin.
Crypts of Liberkuhn: Produce intestinal juice with a volume of 1800 ml/day, pH 7.5-8; involved in acid neutralization and nutrient breakdown.
Enzymes Present: Include peptidase, sucrase, maltase, lactase, lipase, and enterokinase.

Bile Secretion

Composition: Roughly 97% water and 3% solids; contains bile salts, mucin, bile pigments, lipids, and inorganic substances.
Physiological Roles: Aids in lipid digestion, cholesterol elimination, fat-soluble vitamin absorption, and cholesterol solubility to prevent galls stones.

Biliary Secretion Regulation

Choleretics: Substances that enhance bile secretion; includes bile salts, secretin, gastrin, CCK, and vagal stimulation.
Gallbladder Function: Stores bile, absorbs water to concentrate bile up to 5-10 times, and regulates pH to prevent gallstone formation.

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Description

Explore the subdivisions of the gastrointestinal tract (GIT) system, including the alimentary canal and accessory organs. This quiz delves into the sequence of events for digestion and absorption, focusing on the organs involved in these processes.