MBBS Year 1 Gastrointestinal Lectures

Questions and Answers

What is the primary function of retropulsion in the stomach?

To break down solid particles into smaller sizes (correct)

To propel food into the duodenum

To absorb nutrients into the bloodstream

To mix food with digestive enzymes

What is the primary function of pepsin in the digestive process?

Absorption of vitamins

Digestion of carbohydrates

Initiation of protein digestion (correct)

Neutralization of stomach acid

During which phase of gastric acid secretion is the majority of acid secreted?

Gastric phase (correct)

Intestinal phase

Basal phase

Cephalic phase

Which of the following is NOT a factor influencing gastric juice secretion and HCl concentration?

Presence of bacteria in the small intestine Signup and view all the answers

What is the primary role of HCO3- in gastric acid secretion?

To buffer excess acid Signup and view all the answers

What is the primary function of the gastric mucosal barrier?

Protection from the acidic environment of the stomach Signup and view all the answers

What is the purpose of the tight junctions in the gastric mucosa?

To prevent the back-diffusion of acid Signup and view all the answers

Which of the following phases of acid secretion is triggered by the sight, smell, or thought of food?

Cephalic phase Signup and view all the answers

What is the primary function of the mucus gel layer in the stomach?

To protect the stomach mucosa from acid and pepsin Signup and view all the answers

What is the role of intrinsic factor in digestion?

Absorption of vitamin B12 Signup and view all the answers

What is the term for the phase of gastric acid secretion that occurs during fasting?

Basal phase Signup and view all the answers

Which of the following cells are responsible for the production of hydrochloric acid (HCl) in the stomach?

Parietal cells Signup and view all the answers

What is the primary function of the tubulovesicles in the parietal cell?

To store HCl Signup and view all the answers

How do parietal cells adapt functionally during HCl secretion?

They form a tubulovesicular system to facilitate proton secretion. Signup and view all the answers

What is the term for the process by which food is propelled into the duodenum?

Gastric emptying Signup and view all the answers

What is the primary function of the gastric pits?

Secretion of mucus Signup and view all the answers

What type of acid is released by the G-cell?

H+ Signup and view all the answers

What is the function of somatostatin in the regulation of G-cell function?

Inhibits the release of gastrin Signup and view all the answers

What is the purpose of proton pump inhibitors in the treatment of acid reflux?

To inhibit the release of H+ ions Signup and view all the answers

What is the primary function of the ECL-cell in the regulation of G-cell function?

Releases histamine Signup and view all the answers

What is the effect of gastrin on the stomach?

Stimulates the release of H+ ions Signup and view all the answers

What is the role of the D-cell in the regulation of G-cell function?

Releases somatostatin Signup and view all the answers

What is the purpose of H2 antagonists, such as famotidine, in the treatment of acid reflux?

To inhibit the release of histamine Signup and view all the answers

What is the effect of gastrin-releasing peptide (GRP) on the G-cell?

Stimulates the release of gastrin Signup and view all the answers

Which gland is primarily responsible for the secretion of digestive enzymes in the oral cavity?

Parotid gland Signup and view all the answers

What is the primary component of gastric juice that contributes to the acidic environment of the stomach?

Hydrochloric acid (HCl) Signup and view all the answers

Which phase of acid secretion is triggered by the sight or smell of food?

Cephalic phase Signup and view all the answers

What role does bicarbonate play in gastric secretion?

It forms part of the gastric mucosal barrier. Signup and view all the answers

Which hormone is particularly responsible for stimulating the secretion of pancreatic juice?

Secretin Signup and view all the answers

Which factor does NOT influence gastric juice secretion?

Dietary fiber intake Signup and view all the answers

Cholecystokinin is known to primarily influence which aspect of gastrointestinal physiology?

Stimulate bile release Signup and view all the answers

Which component is NOT typically found in pancreatic juice?

Pepsin Signup and view all the answers

Which receptors are involved in the stimulation of gastric acid secretion according to the three receptor model?

CCK2 and M3 Signup and view all the answers

What is the role of histamine in gastric acid secretion as per the provided models?

Stimulates ECL cells to release HCl Signup and view all the answers

Which cell type is identified in the model as responsible for the release of histamine?

ECL cells Signup and view all the answers

What is the primary function of gastrin in the context of gastric acid secretion?

Stimulate H2 receptors Signup and view all the answers

Which two receptors are identified as being physiologically linked to the stimulation of gastric acid secretion?

M3 and H2 Signup and view all the answers

In the context of the three receptor model, where does gastrin primarily act to stimulate the secretion of HCl?

On the ECL cells Signup and view all the answers

Study Notes

Overview of Gastrointestinal System

The digestive system includes various organs and processes for nutrient digestion and absorption.
Key components of the digestive system include salivary glands, stomach, pancreas, and biliary system.
Gut motility plays a significant role in the digestive process.

Salivary Secretions

Salivary glands produce saliva, which contains enzymes that initiate carbohydrate digestion and lubricate food.
Saliva composition includes mucins, electrolytes, enzymes (like amylase and lysozyme).
Salivary secretion is regulated by autonomic nervous system, influenced by taste, smell, and sight.

Gastric Juice Secretion

Gastric juice consists primarily of hydrochloric acid (HCl) and pepsin, aiding in protein digestion.
Mucus and bicarbonate protect the gastric mucosa from acidic damage.
Acid secretion occurs in three phases:
- Cephalic Phase: Triggered by sight, smell, or thought of food.
- Gastric Phase: Initiated by food presence, stretching stomach walls.
- Intestinal Phase: Hormonal response from the intestine (e.g., release of secretin and cholecystokinin).

Factors Influencing Gastric Acid Secretion

Multiple factors that increase gastric acid secretion include:
- Gastrin from G cells in response to food.
- Histamine release from enterochromaffin-like (ECL) cells.
- Neurotransmitter acetylcholine (ACh) from vagus nerve stimulates acid production.

Pancreatic Secretions

Pancreatic juice contains digestive enzymes (lipase, amylase, proteases) crucial for nutrient breakdown.
Secretin and cholecystokinin are released into the bloodstream in response to the presence of fatty acids and amino acids, further stimulating pancreatic secretion.

Gastric Mucosal Defense Mechanisms

A thick layer of mucus forms a protective barrier against gastric acid, preventing mucosal injury.
Bicarbonate secretion neutralizes acid, maintaining a pH gradient across the gastric epithelium.
Blood flow to the gastric mucosa supplies nutrients and delivers bicarbonate to help buffer acidity.

Physiological Changes in Aging

Older adults may experience hyposalivation, leading to dry mouth and difficulty swallowing.
Changes in receptor sensitivity and control mechanisms may affect the physiological regulation of digestion.

Implications of Acid Secretion Regulation

Proton pump inhibitors (e.g., omeprazole) and H2 antagonists (e.g., famotidine) are used to manage excessive gastric acid conditions.
Understanding gastric secretion mechanisms is critical for diagnosing and treating gastrointestinal disorders.

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Description

This quiz covers the overview of the digestive system, digestion and absorption of nutrients, salivary, gastric and pancreatic secretions, bile and biliary system, and motility of the gut based on Physiology, 5th Edition and Medical Physiology.