MPharm Programme: Gastrointestinal System 3

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary digestive function of the liver?

Metabolism of carbohydrates

Filtration of blood

Production of bile (correct)

Storage of vitamins

Which component is NOT found in bile?

Bile salts

Cholesterol

Amino acids (correct)

Bile pigments

What role do bile salts play in digestion?

Neutralize stomach acid

Break down carbohydrates

Store vitamins

Emulsify fats (correct)

Where is bile stored before its release into the digestive system?

Gallbladder Signup and view all the answers

What is the nature of bile in terms of pH?

Alkaline solution Signup and view all the answers

Which structure primarily facilitates the process of neutralizing acidity in the duodenum?

Pancreatic bicarbonate Signup and view all the answers

What triggers the release of pancreatic enzymes in the duodenum?

Presence of fatty chyme Signup and view all the answers

What are the three main subdivisions of the small intestine?

Duodenum, Jejunum, Ileum Signup and view all the answers

What is the length of the duodenum?

10 inches Signup and view all the answers

Which of the following secretions is stimulated by the arrival of acidic chyme in the duodenum?

Secretin Signup and view all the answers

What process occurs inside the epithelial cells after the formation of monoglycerides and free fatty acids?

They are resynthesized into triglycerides. Signup and view all the answers

What is formed when triglycerides aggregate and are coated with lipoprotein?

Chylomicrons Signup and view all the answers

How do chylomicrons exit the epithelial cells?

By exocytosis. Signup and view all the answers

What prevents chylomicrons from crossing the basement membrane of capillaries?

Their large size. Signup and view all the answers

What is the primary role of the large intestine?

Water reabsorption and storage Signup and view all the answers

Which vitamins does the large intestine primarily absorb?

B vitamins and vitamin K Signup and view all the answers

What role do beneficial bacteria in the large intestine play?

They generate vitamin K and short-chain fatty acids. Signup and view all the answers

What components make up the structure of the large intestine?

Colon, appendix, and rectum Signup and view all the answers

What type of cells in the pancreas are responsible for secreting insulin?

Beta cells Signup and view all the answers

Which of the following is NOT a secretion produced by the acinar cells of the pancreas?

Insulin Signup and view all the answers

Which of the following hormones is secreted by the alpha cells of the pancreas?

Glucagon Signup and view all the answers

What is the primary function of the duct cells in the pancreas?

Secretion of aqueous bicarbonate solution Signup and view all the answers

Which enzyme is inhibited by the brush border enzymes in the intestinal mucosa?

Trypsin Signup and view all the answers

How do the pancreatic acinar cells contribute to digestion?

By secreting enzymes into the digestive tract Signup and view all the answers

What is the main role of pancreatic proteases in digestion?

To break down proteins Signup and view all the answers

Which structure in the pancreas serves as a source for endocrine secretions?

Islets of Langerhans Signup and view all the answers

What part of the small intestine predominantly absorbs bile salts and vitamin B12?

Ileum Signup and view all the answers

Which mechanism is primarily responsible for the absorption of monoglycerides and free fatty acids in the small intestine?

Passive diffusion Signup and view all the answers

What role do bile salts play during the digestion of dietary fats?

They emulsify fats into smaller droplets. Signup and view all the answers

Which of the following is NOT absorbed by the duodenum and jejunum?

Bile salts Signup and view all the answers

What is the primary function of pancreatic lipase in fat digestion?

Hydrolyzing triglycerides Signup and view all the answers

How are triglycerides initially prepared for digestion in the small intestine?

By emulsification Signup and view all the answers

What occurs when micelles approach the absorptive epithelial surface of the small intestine?

Monoglycerides and fatty acids leave micelles. Signup and view all the answers

Why is the absorption of calcium and iron in the small intestine unique?

It is regulated based on the body's needs. Signup and view all the answers

Study Notes

MPharm Programme: The Gastrointestinal System 3

The week 15 lecture covers the small intestine, its subdivisions, and the hepatopancreatic region.
The small intestine has three main subdivisions: duodenum, jejunum, and ileum.
The duodenum plays a crucial role in digestion, as it receives bile and pancreatic juice.
The hepatopancreatic region is where the common bile duct, the cystic duct, the common hepatic duct, and the pancreatic duct connect.
The pancreas produces bile and digestive enzymes, including proteases, amylase, and lipase.
Pancreatic duct cells secrete bicarbonate to neutralize stomach acid.
The duodenum is the first 10 inches of the small intestine, the primary site of digestion.
Fatty chyme in the duodenum triggers the release of CCK, a hormone stimulating bile and pancreatic enzyme release.
Acidic chyme stimulates secretin release, prompting pancreatic bicarbonate release for acid neutralization.

Structure of the Pancreas

The pancreas has exocrine and endocrine cells.
Exocrine cells secrete enzymes (e.g., lipase, amylase, proteases) into the duodenum.
Acinar cells secrete pancreatic juice containing enzymes.
Duct cells produce bicarbonate to neutralize stomach acid.
Endocrine cells, located in the islets of Langerhans, secrete hormones insulin and glucagon.
Insulin regulates blood glucose levels, while glucagon raises them.

Functional Anatomy of Pancreas

The pancreas's exocrine function involves duct cells secreting bicarbonate, ensuring proper pH conditions for enzyme action in the small intestine.
Duct cells secrete aqueous bicarbonate solution.
Acinar cells release pancreatic juice containing enzymes such as proteases, amylase, and lipase.
The endocrine function within islets of Langerhans involves beta cells (insulin secretion) and alpha cells (glucagon secretion).

Secretions of the Pancreas

The pancreas releases bicarbonate (NaHCO3) to neutralize acids into the duodenum
Acinar cells secrete digestive enzymes
Hormones like insulin and glucagon are released by the endocrine function.

Hormonal Control of Pancreatic Exocrine Secretion

Acidic chyme in the duodenum triggers secretin release, stimulating pancreatic duct cells to release bicarbonate.
Fatty or protein chyme in the duodenum triggers CCK, enhancing pancreatic acinar cell enzyme secretion.

Activation of Pancreatic Enzymes

Inactive enzyme precursors, like trypsinogen, are activated in the duodenum by enteropeptidase.
Trypsin activates other enzymes via a cascade reaction.
Trypsin inhibitors control the activation.

The Liver & Hepatic Portal Circulation

The liver processes nutrients from the digestive tract.
The hepatic artery carries oxygenated blood to the liver.
The hepatic portal vein carries deoxygenated blood containing digested nutrients from the digestive tract to the liver.
Blood exits the liver via the hepatic vein.

The Liver

The liver is the largest gland in the body.
It is composed of plates of hepatocytes, specialized liver cells.
The main digestive function of the liver is bile production.
Bile emulsifies fats.
Bile consists of bile salts, bile pigments, cholesterol, neutral fats, phospholipids, and electrolytes.
Bile is stored in the gallbladder and released into the small intestine as needed.

Fat Emulsification by Bile Salts

Bile salts emulsify fats, increasing the surface area for lipase action.
Bile salts have hydrophilic (water-loving) and hydrophobic (water-fearing) regions, allowing them to coat fat droplets.

Control of Bile Release

Cholecystokinin (CCK) stimulates gallbladder contraction and relaxes the hepatopancreatic sphincter.
Acidic, fatty chyme stimulates the release of CCK and secretin.
Vagal stimulation causes weak gallbladder contractions.
Bile salts and secretin stimulate liver.

Enterohepatic Circulation of Bile Salts

Bile salts are reabsorbed and recycled.
Approximately 95% of bile salts are reclaimed.
The remainder is excreted and lost in the feces.

Digestion & Absorption in the Small Intestine

This section outlines the processes of carbohydrate, protein, and fat digestion and absorption in the duodenum and jejunum.
Water and electrolytes are freely absorbed

Absorption in Small Intestine

The duodenum and jejunum are the main sites for nutrient absorption, absorbing carbohydrates, proteins, fats, vitamins, and water.
Calcium and iron absorption is regulated based on the body's needs.
The ileum absorbs bile salts, vitamin B12, electrolytes, and water.

Carbohydrate, Protein & Fat Digestion

Enzymes for carbohydrate, protein, and fat digestion are discussed.
Specific enzymes such as amylase, proteases, and lipases break down these nutrients into smaller components.

Carbohydrate Digestion

Dietary carbohydrates are broken down into monosaccharides.
Salivary and pancreatic amylase break down polysaccharides into disaccharides.
Enzymes like maltase, sucrase, and lactase convert disaccharides into monosaccharides.
These monosaccharides are then absorbed.

Carbohydrate Absorption

Glucose and galactose are absorbed via active transport (symport with Na+).
Fructose is absorbed via facilitated diffusion.
Monosaccharides are absorbed into blood stream.

Protein Digestion

Dietary proteins are initially broken down into smaller peptides by proteases like pepsin.
Pancreatic proteases further digest peptides into amino acids and dipeptides/tripeptides.
Aminopeptidases break down peptides into single amino acids.

Protein Absorption

Amino acids are absorbed via active transport or facilitated diffusion mechanisms.
Small peptides can also be absorbed in certain cases using H+ cotransport.

Fat Digestion and Absorption

Bile salts emulsify dietary fat.
Pancreatic lipase breaks down triglycerides into fatty acids and monoglycerides.
These products form micelles, which carry them to the intestinal lining.
Fatty acids and monoglycerides are absorbed and reassembled into triglycerides.
Chylomicrons encapsulate the triglycerides and transport them into the lymphatic system.

Iron Absorption

Dietary iron is absorbed in the ferrous form or as heme.
Ferrous iron enters cells mediated by divalent metal transporter 1.
Absorbed iron can be transported into blood by membrane protein ferroportin.
Stored iron is in the form of ferritin.
Unused iron is lost in the feces.

The Large Intestine

The large intestine (colon, cecum, appendix, rectum) is primarily a drying and storage organ.
It absorbs water, electrolytes, and several B vitamins, vitamin K, and folic acid.
It houses beneficial bacteria that aid in producing vitamin K and folic acid and producing short-chain fatty acids.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers key concepts from the week 15 lecture focusing on the small intestine and the hepatopancreatic region. Topics include the subdivisions of the small intestine, the digestive roles of the duodenum, and the functions of the pancreas in digestion. Test your knowledge on these critical aspects of gastrointestinal physiology.