GIT Advanced

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Questions and Answers

Why are the enzymes pepsin and trypsin initially secreted as pepsinogen and trypsinogen (proenzymes)?

To prevent self-digestion of secreting organs. (correct)

The proenzymes break down different proteins from the enzymes.

Proenzymes act as hormones in the digestive tract.

They are secreted when the GI tract is empty and only activated when food is present.

What are the main sources of bicarbonate in the intestine?

Stomach acid and saliva.

Digested food.

Secretions of the intestinal epithelium.

Bile and pancreatic juice. (correct)

What is the main role of bicarbonate in the small intestine?

Break down proteins into amino acids.

Remove CO2 from the digestive system.

Regulate water content of the intestinal contents.

Maintain optimal pH for enzymatic digestion. (correct)

Which part of the stomach is primarily responsible for the secretion of stomach juices?

Fundus Signup and view all the answers

What is the main effect of motilin on the digestive tract?

Increased gastric motor activity. Signup and view all the answers

Which of the following two hormones have opposite effects on gastric acid secretion?

Somatostatin and CCK Signup and view all the answers

Which phase of gastric secretion does not require the presence of food in the stomach?

Cephalic phase Signup and view all the answers

Which of the following can be absorbed in the stomach?

There is no absorption of nutrients in the stomach. Signup and view all the answers

Which of the following is NOT a role of motility in the gastrointestinal system?

Digestion Signup and view all the answers

Bile is released into the duodenum by which organ?

Gall bladder Signup and view all the answers

What type of food is primarily digested in the stomach?

Protein Signup and view all the answers

The main process relating to digestion which occurs in the large intestine is:

Fermentation Signup and view all the answers

Fat is mainly absorbed by the:

Lymphatic system Signup and view all the answers

Secretions of the exocrine pancreas play a role in the digestion of:

Proteins, carbohydrates, lipids and nucleic acids Signup and view all the answers

Which branch of the nervous system regulates the function of the gastrointestinal system?

Autonomic Signup and view all the answers

Ageing of the gastrointestinal system is frequently characterised by an increased incidence of constipation. This may be caused by:

Slow peristalsis Signup and view all the answers

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

Regulation of gastrointestinal motility Signup and view all the answers

What are the roles of water in digestion?

Hydrolysis; lubrication and dilution Signup and view all the answers

Why does eating a large meal make one sleepy?

Effect of cholecystokinin (CCK) on the brain Signup and view all the answers

Pancreatitis, which causes reduced production and secretion of pancreatic enzymes, will have the following symptoms:

Decreased digestion and absorption of nutrients and diarrhoea Signup and view all the answers

Study Notes

Digestive Enzymes and Proenzymes

Pepsinogen and Trypsinogen are initially secreted as inactive proenzymes to prevent them from digesting the secreting cells in the stomach and pancreas.
They are activated only when food is present in the digestive tract.

Bicarbonate and its Role in Digestion

Bicarbonate is a crucial component of pancreatic juice and bile, contributing to the overall alkalinity of the intestinal contents.
It plays a significant role in maintaining the optimal pH for enzymatic digestion in the small intestine, essential for the proper breakdown of food.

Gastric Secretion and its Regulation

The fundus is the primary site for stomach juice secretion.
Gastric secretion is regulated by three phases:
- Cephalic phase: Initiated by the sight, smell, or thought of food, involving neural stimulation of gastric acid secretion.
- Gastric phase: Triggered by food entry into the stomach, with gastrin playing a crucial role in further stimulating acid secretion.
- Intestinal phase: Triggered by the presence of food in the small intestine, with hormones like cholecystokinin (CCK) and secretin influencing gastric acid secretion.

Motility and its Functions in the Digestive System

Motility is the movement of food through the digestive tract, involving:
- Mixing: To ensure optimal contact between food and digestive enzymes.
- Movement along the digestive tract: Propelling food towards the anus.
- Exposure for absorption: Ensuring proper contact between nutrients and the intestinal lining for absorption.

Absorption of Nutrients

The small intestine is the primary site for nutrient absorption.
Fats are primarily absorbed through the lymphatic system due to their insolubility.
Most other nutrients, including carbohydrates, proteins, and water-soluble vitamins, are absorbed into the venous system via the portal vein.

Pancreatic Secretions and their Role

The pancreas secretes enzymes essential for the digestion of various macronutrients:
- Proteins: Trypsin, chymotrypsin, carboxypeptidase
- Carbohydrates: Amylase
- Nucleic acids: Ribonuclease and deoxyribonuclease
- Lipids: Lipase

Regulation of the Digestive System

The autonomic nervous system plays a key role in regulating digestive functions.
- Parasympathetic nerves stimulate digestion, while sympathetic nerves inhibit it.

Constipation is a common occurrence in older adults.
This can be attributed to:
- Slower peristalsis: Reduced muscle activity of the gut
- Narrowing of sphincters: Affecting the ability to pass stool

Liver and its Functions

The liver is a vital organ with diverse functions, including:
- Destruction of old red blood cells
- Formation of blood plasma proteins
- Storage of glucose
- Synthesis of bile

Water and Digestion

Water is essential for several digestive processes:
- Lubrication: Facilitating the movement of food through the digestive tract.
- Dilution: Helping to dilute food and digestive secretions.
- Hydrolysis: Participating in chemical reactions breaking down food.

Postprandial Sleepiness

The feeling of sleepiness after a large meal can be attributed to:
- Increased energy requirement of the liver: As it processes nutrients from the meal.
- Effect of cholecystokinin (CCK): A hormone released after eating, which may have a mild sedative effect on the brain.

Pancreatitis

Reduced production and secretion of pancreatic enzymes due to pancreatitis can lead to:
Decreased digestion and absorption of nutrients:* Manifestation of steatorrhea (fatty stools), diarrhea, and weight loss.

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Description

This quiz covers the key concepts related to digestive enzymes, proenzymes, and the regulation of gastric secretion. Test your knowledge on the roles of pepsinogen and trypsinogen, the importance of bicarbonate in digestion, and the phases of gastric secretion. Perfect for students studying human physiology!