Lecture 16: The Digestive System

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Questions and Answers

What is the main function of the mucosa layer in the gastrointestinal tract?

To absorb nutrients into the bloodstream

Which enzyme is responsible for breaking down proteins in the stomach?

Pepsin

What is the role of the submucosa layer in the gastrointestinal tract?

To provide mechanical support

Which of the following is NOT a function of the digestive system?

Respiration Signup and view all the answers

What is the term for the slow delivery of chyme from the stomach to the small intestine?

Peristalsis Signup and view all the answers

Which accessory organ produces bile that aids in fat digestion?

Liver Signup and view all the answers

What is the term for the breakdown of food into absorbable components?

Digestion Signup and view all the answers

Which of the following is a type of carbohydrate?

Monosaccharide Signup and view all the answers

What is the function of the muscularis externa layer in the gastrointestinal tract?

To mix and propel food through the digestive system Signup and view all the answers

What is the term for the removal of wastes as faeces?

Elimination Signup and view all the answers

What is the main function of the salivary amylase in the oral cavity?

To digest starch into maltose Signup and view all the answers

What is the primary function of the mucosa in the stomach?

To secrete mucus to protect the stomach lining Signup and view all the answers

What is the main function of the pyloric sphincter in the stomach?

To prevent backflow of chyme into the oesophagus Signup and view all the answers

What is the function of the gastric glands in the stomach?

To secrete components of gastric juice Signup and view all the answers

What is the function of the villi in the small intestine?

To increase the surface area for absorption Signup and view all the answers

What is the function of the liver in the digestive system?

To secrete bile into the small intestine Signup and view all the answers

What is the function of the pancreatic juices in the small intestine?

To secrete digestive enzymes into the small intestine Signup and view all the answers

What is the function of the gallbladder in the digestive system?

To store bile from the liver Signup and view all the answers

What is the function of the peristalsis in the oesophagus?

To propel food into the stomach Signup and view all the answers

What is the function of the bicarbonate-rich mucus in the stomach?

To protect the stomach lining from protein digestion and corrosion from HCl Signup and view all the answers

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

To store and concentrate bile Signup and view all the answers

Which enzyme is responsible for breaking down starch into maltose and maltotriose in the small intestine?

Pancreatic amylase Signup and view all the answers

What is the primary function of segmentation in the jejunum?

To promote mixing and absorption of nutrients Signup and view all the answers

Which region of the small intestine is responsible for absorbing fat-soluble vitamins and cholesterol?

Ileum Signup and view all the answers

What is the primary function of haustral contractions in the ascending and transverse colon?

To mix and absorb water and electrolytes Signup and view all the answers

Which type of contraction occurs in the small intestine at a rate of ~16 contractions per minute?

Peristalsis Signup and view all the answers

What is the primary function of the large intestine in terms of digestion?

To break down insoluble carbohydrates via fermentation Signup and view all the answers

Which region of the large intestine is responsible for storing faecal material until it is eliminated from the body?

Rectum Signup and view all the answers

What is the primary function of pancreatic lipase in the small intestine?

To break down triglycerides into fatty acids and monoglycerides Signup and view all the answers

What is the primary function of the small intestine in terms of absorption?

To absorb carbohydrates, proteins, and fats Signup and view all the answers

What is the primary consequence of rapid delivery of chyme from the stomach to the small intestine?

Increased water secretion from blood to the intestinal lumen Signup and view all the answers

Which of the following structures is responsible for the breakdown of carbohydrates into absorbable components?

Salivary glands Signup and view all the answers

What is the primary function of the serosa/adventitia layer in the gastrointestinal tract?

Protection of the tract from external damage Signup and view all the answers

What is the term for the products of lipid digestion?

Fatty acids and glycerol Signup and view all the answers

What is the role of gastrin in the digestive system?

Stimulates the secretion of gastric juice Signup and view all the answers

What is the primary function of the bile produced by the liver?

Emulsification of fats Signup and view all the answers

What is the term for the waste products produced by the digestive system?

Faeces Signup and view all the answers

What is the role of pancreatic lipase in the digestive system?

Breakdown of fats Signup and view all the answers

Study Notes

Digestive System Overview

The digestive system consists of the gastrointestinal tract (alimentary canal) and accessory organs
The gastrointestinal tract includes the oral cavity, pharynx, oesophagus, stomach, small intestine, and large intestine
Accessory organs include teeth, salivary glands, liver, gallbladder, and pancreas

Layers of the Gastrointestinal Tract

The gastrointestinal tract has 4 distinct layers: mucosa, submucosa, muscularis externa, and serosa/adventitia
The mucosa layer has epithelium, lamina propria, and muscularis mucosae
The submucosa layer is composed of loose connective tissue
The muscularis externa layer has longitudinal and circular muscle
The serosa/adventitia layer is a layer of connective tissue that covers the gastrointestinal tract

Digestive System Functions

Ingestion: taking food into the mouth
Secretion: production of digestive enzymes and hormones
Motility: movement of food through the digestive system
Digestion: breakdown of food into absorbable components
Absorption: uptake of nutrients into the bloodstream
Elimination: removal of waste products

Carbohydrates

Monosaccharides: glucose, fructose
Disaccharides: sucrose, lactose, maltose
Polysaccharides: starch, cellulose, glycogen
Digestion of carbohydrates: salivary and pancreatic amylase

Proteins

Amino acids: building blocks of proteins
Proteins are polypeptides that are folded into functional structures
Digestion of proteins: pepsin, trypsin

Lipids

Triglycerides (glycerol attached to 3 fatty acid chains)
Fatty acids: chains of hydrocarbons
Digestion of lipids: lingual, gastric, and pancreatic lipase

Digestion and Absorption

Mechanical digestion: breakdown of food into smaller particles
Chemical digestion: breakdown of food into absorbable components
Absorption: uptake of nutrients into the bloodstream

Oral Cavity

Anatomy: teeth, tongue, salivary glands
Function: ingestion, mechanical digestion, chemical digestion (salivary amylase and lingual lipase)

Pharynx

Anatomy: funnel-shaped tube of skeletal muscle
Function: shared by digestive and respiratory systems, allows bolus to move to oesophagus during swallowing

Oesophagus

Anatomy: muscular tube
Function: propulsion of bolus to stomach via peristalsis

Stomach

Anatomy: J-shaped chamber with rugae and gastric glands
Function: mechanical digestion, chemical digestion (gastric juice: pepsin, HCl, bicarbonate ions)

Small Intestine

Anatomy: 3 regions (duodenum, jejunum, ileum) with villi and microvilli
Function: chemical digestion and absorption of nutrients

Accessory Organs

Liver: secretes bile
Gallbladder: stores and concentrates bile
Pancreas: secretes pancreatic juice with digestive enzymes

Large Intestine

Anatomy: 4 regions (caecum, colon, rectum, anal canal)
Function: absorption of water and electrolytes, fermentation of insoluble carbohydrates

Waste Products

Faeces: solid or semi-solid waste
Bilirubin: pigment that is a waste product of red blood cell breakdown

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