Digestive Hormones and Bile Function

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Questions and Answers

What initiates the peristaltic rush in the small intestine?

Relaxation of smooth muscle

Inhibition of the enteric nervous system

Irritation of the intestinal mucosa (correct)

Increased digestive enzyme secretion

Which enzyme is involved in the digestion of sucrose?

Sucrase (correct)

Lactase

Alpha-dextrinase

Maltase

What type of transport is primarily used for the absorption of sodium in the small intestine?

Osmosis

Facilitated diffusion

Active transport (correct)

Passive diffusion

Which of the following ions is absorbed via active transport in the small intestine?

Calcium Signup and view all the answers

What is the primary role of enterokinase in the small intestine?

Converting trypsinogen to trypsin Signup and view all the answers

What is the primary component of feces by weight?

3/4 water Signup and view all the answers

Which factor is responsible for the brown color of normal feces?

Stercobilin & Urobilin Signup and view all the answers

What triggers the secretion of pancreatic digestive enzymes?

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

Which enzyme is NOT classified as a proteolytic enzyme in pancreatic juice?

Pancreatic Amylase Signup and view all the answers

What is the daily secretion of pancreatic juice?

1000 mL Signup and view all the answers

What color change of feces indicates potential obstructive jaundice?

Clay/Pale Signup and view all the answers

Which regulator of pancreatic secretion is NOT a hormonal regulation?

Vagal stimulation Signup and view all the answers

Which of the following is a lipolytic enzyme secreted by the pancreas?

Pancreatic Lipase Signup and view all the answers

What is the primary function of secretin in digestive processes?

Encouraging pancreas to secrete bicarbonate Signup and view all the answers

Which of the following accurately describes the role of bile in digestion?

It emulsifies fats for better absorption Signup and view all the answers

What is one of the key metabolic functions of the liver?

Glycogen storage and synthesis Signup and view all the answers

Which hormone is responsible for stimulating the secretion of digestive enzymes and bile from the pancreas?

Cholecystokinin Signup and view all the answers

What is a characteristic of bile composition?

It has a high concentration of bile pigments Signup and view all the answers

Which of the following is NOT a function of cholecystokinin?

Increasing gastric acid secretion Signup and view all the answers

What is one of the outcomes of liver dysfunction concerning ammonia?

Decreased detoxification of ammonia Signup and view all the answers

Which digestive phase is characterized by the secretion of gastrin?

Gastric phase Signup and view all the answers

Study Notes

Secretin, Cholecystokinin, and Gastrin

Secretin stimulates pancreas to release large volumes of fluid rich in bicarbonate (HCO3-) in response to acidic chyme.
Cholecystokinin triggers pancreas to secrete digestive enzymes and bile when fat and peptides are detected in chyme.
Gastrin is released during gastric phase and promotes secretion of pancreatic enzymes.

Gallbladder and Bile

The gallbladder is a storage organ for bile, which is produced by the liver.
Functions of bile:
- Emulsifies fats, aiding absorption by forming micelles.
- Excretes metals, toxins, bacteria, and bile pigments.
- Stimulates intestinal peristalsis.
- Neutralizes acidic chyme.
Composition of bile:
- Water, inorganic salts, bile salts, bile pigments (bilirubin and biliverdin), and lipids (cholesterol, lecithin).
Daily bile secretion ranges from 700 to 1200 ml, with a pH between 7.7 and 8.6.

Liver Functions

Central to metabolism, including glycogen storage, plasma protein synthesis, and drug detoxification.
Possesses regenerative capabilities.
Metabolic roles:
- Converts certain amino acids, lactate, or glycerol into glucose (gluconeogenesis).
- Breaks down glycogen to glucose (glycogenolysis).
- Synthesizes glycogen from glucose (glycogenesis).
Lipid metabolism includes cholesterol and triglyceride synthesis.
Converts ammonia to urea and metabolizes drugs and toxins.
Displays immunologic effects through reticuloendothelial cells, filtering antigens from blood.

Peristaltic Rush

A strong peristalsis in the small intestine triggered by intestinal mucosa irritation, such as diarrhea.
Initiated by autonomic nervous system reflexes and myenteric plexus activity.
Aims to expel irritating chyme and relieve intestinal distention.

Enzymes in Small Intestinal Secretions

Secreted by epithelial cells of the small intestine, particularly those on villi.
Include:
- Enterokinase.
- Proteolytic enzymes (aminopolypeptidase, dipeptides).
- Carbohydrate-splitting enzymes:
  - Lactase converts lactose to glucose and galactose.
  - Sucrase converts sucrose to glucose and fructose.
  - Maltase converts maltose to glucose.
  - Alpha-dextrinase also converts to glucose.

Absorption

Water is absorbed mainly through osmosis (99% absorption).
Sodium absorption (25-35 gm/day) occurs via active transport and diffusion.
Ion absorption:
- Calcium and iron via active transport.
- Potassium, magnesium, and phosphate also absorbed actively.
Glucose and galactose absorbed through sodium-glucose co-transport; fructose via facilitated diffusion.
Proteins are absorbed as amino acids through sodium-amino acid co-transport.
Defecation reflex is influenced by parasympathetic nervous system.

Composition of Feces

Consists of approximately 75% water and 25% solids.
Solid composition: 30% dead bacteria, 10-20% fat, 10-20% inorganic material, 2-3% protein, and 30% undigested roughage.
Normal color due to stercobilin and urobilin; odor caused by indole and mercaptans.
Abnormal fecal colors indicate potential health issues:
- Clay/pale - obstructive jaundice.
- Green - biliverdin presence.
- Yellow - bilirubin.
- Black - iron or upper GI hemorrhage.
- Red - lower GI bleeding.

Pancreas

Pancreatic enzymes are secreted by acini in response to chyme in the small intestine.
Contains enzymes for digesting proteins, carbohydrates, and fats.
Daily secretion is about 1000 ml with a pH of around 8.0.
Types of enzymes include:
- Proteolytic enzymes like trypsinogen (activated to trypsin) and chymotrypsinogen (activated to chymotrypsin).
- Carbohydrate-splitting enzyme: pancreatic amylase (starch to maltose).
- Lipolytic enzymes (e.g., pancreatic lipase) that break down fats with bile assistance.

Regulation of Pancreatic Secretion

Regulated by nervous system signals during cephalic and gastric phases.
Hormonal secretions also play a role in stimulating pancreatic functions.

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Description

This quiz covers the roles of secretin, cholecystokinin, and gastrin in digestion, as well as the crucial functions of the gallbladder and bile. Understand the composition of bile and its importance in fat emulsification and metabolic processes. Test your knowledge on how these elements interact within the digestive system.