Alimentary Canal Functions and Mouth Anatomy

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Questions and Answers

What is formed during mastication that prepares food for swallowing?

Chyme

Digested food

Bolus (correct)

Saliva

Which sphincter separates the stomach from the small intestine?

Pyloric sphincter (correct)

Ileocecal sphincter

Cardiac sphincter

Oesophageal sphincter

What role do rugae play in the stomach?

Absorbing nutrients

Transporting food

Allowing for expansion (correct)

Secreting gastric juice

What type of cells in the gastric glands produces hydrochloric acid?

Parietal cells Signup and view all the answers

Which substance is NOT primarily absorbed in the stomach?

Proteins Signup and view all the answers

Which digestive enzyme is responsible for breaking down starch into maltose?

Amylase Signup and view all the answers

Where does the digestion of carbohydrates begin?

In the mouth Signup and view all the answers

What type of food molecules does lipase primarily act upon?

Lipids Signup and view all the answers

Which enzymes are responsible for breaking down proteins in the digestive system?

Pepsin, trypsin, and chymotrypsin Signup and view all the answers

What are monosaccharides primarily produced from in the digestive process?

Disaccharides Signup and view all the answers

What is the major function of the small intestine apart from digestion?

Absorption of nutrients Signup and view all the answers

What triggers the gall bladder to release bile?

Release of cholecystokinin from mucosal cells Signup and view all the answers

What is the primary composition of bile?

Bile salts, pigments, and phospholipids Signup and view all the answers

What is the function of bile salts in the digestive process?

They emulsify fats for absorption Signup and view all the answers

What prevents the loss of bile acids during digestion?

Reabsorption of bile acids in the ileum Signup and view all the answers

Which function does the exocrine pancreas NOT perform?

Secretion of insulin Signup and view all the answers

What causes gallstones to form?

Cholesterol crystallization Signup and view all the answers

Which of the following statements about pancreatic enzymes is true?

They aid in the digestion of fats, starches, and proteins Signup and view all the answers

What substance is secreted by the pancreas to help neutralise stomach acid in the small intestine?

Sodium bicarbonate Signup and view all the answers

What is the primary function of pancreatic lipase?

Break down lipids into fatty acids and glycerol Signup and view all the answers

Which vitamin is primarily absorbed in the large intestine produced by gut bacteria?

Vitamin K Signup and view all the answers

What is one of the roles of goblet cells in the large intestine?

Secreting mucus for lubrication Signup and view all the answers

What is a major reason for gas production in the large intestine?

Bacterial fermentation of undigested material Signup and view all the answers

What role does pancreatic amylase play in digestion?

Converts carbohydrates into simple sugars Signup and view all the answers

During the final stages of digestion, what is primarily absorbed by the large intestine?

Electrolytes and remaining water Signup and view all the answers

What causes the color of feces in the large intestine?

Bile pigments Signup and view all the answers

What primary function do teeth serve during the mechanical process in the mouth?

To tear, rip, and chew food Signup and view all the answers

Which enzyme in saliva initiates the digestion of carbohydrates?

Salivary amylase Signup and view all the answers

What is the term for the mass of food formed in the mouth after thorough chewing?

Bolus Signup and view all the answers

Which structure prevents food from entering the nasal cavity?

Uvula Signup and view all the answers

What is the main purpose of the salivary glands?

To produce saliva for digestion Signup and view all the answers

What action is primarily responsible for moving the bolus down the esophagus?

Peristalsis Signup and view all the answers

What type of muscle contraction occurs during peristalsis?

Smooth muscle contraction Signup and view all the answers

What occurs during the first phase of swallowing?

Voluntary forcing of food into the pharynx Signup and view all the answers

What is segmentation in the small intestine primarily responsible for?

Mixing food without propelling it Signup and view all the answers

What is the primary role of the esophagus in digestion?

To transport the bolus to the stomach Signup and view all the answers

Which of the following best describes a function of the tongue?

It aids in mastication and swallowing Signup and view all the answers

How does saliva contribute to digestion?

It moistens and begins the digestion of carbohydrates Signup and view all the answers

What happens to the bolus once it enters the stomach?

It transforms into chyme Signup and view all the answers

What is the role of the epiglottis during swallowing?

To prevent food from entering the trachea Signup and view all the answers

Study Notes

Alimentary Canal Activities

Ingestion: Taking food into the mouth.
Digestion: Breaking down food into smaller molecules that can be absorbed.
Absorption: Taking in the digested nutrients into the bloodstream.
Assimilation: Using the absorbed nutrients to build and maintain body tissues.
Egestion: Eliminating undigested waste products.

The Mouth - Mechanical

Teeth: Mechanically break down food into smaller pieces.
Uvula: Prevents food from entering the nasal cavity.
Tongue: Plays a crucial role in mastication and swallowing.

The Mouth - Chemical

Salivary Amylase: Breaks down starch into maltose.
Taste Buds: Allow us to appreciate food and detect potential hazards.

The Bolus

Definition: A rounded mass of food formed in the mouth.
Formation: Food is crushed and ground by teeth (mastication) and moistened with saliva.

Salivary Glands

Submandibular: Produces 70% of saliva.
Sublingual: Produces 5% of saliva.
Parotid: Produces 25% of saliva.
Saliva Composition: 99.5% water, 0.5% other substances like mucin and salivary amylase.

Swallowing

Process: Involves coordinated activity of the tongue, soft palate, pharynx, and esophagus.
Phases:
- Voluntary Stage: Food is pushed into the pharynx by the tongue.
- Reflex Stage: Swallowing becomes an automatic process.

The Esophagus

Function: Transports food from the mouth to the stomach.
Structure:
- Mucous membrane lining for lubrication.
- Smooth muscle wall contracts to propel food downwards.

Peristalsis

Definition: Rhythmic contractions of smooth muscles that move food through the digestive tract.
Mechanism:
- Circular muscle contraction behind the bolus.
- Longitudinal contraction in front of the bolus.
Result: Bolus moves towards the stomach.

Digestive Tract Movements: Segmentation and Vomiting

Segmentation: Mixing movement in the small intestine. Constriction of segments without forward or backward movement.
Vomiting: Propulsion by abdominal muscle contraction.

The Stomach

Location: J-shaped organ on the left side of the abdominal cavity.
Regions: Fundus, body , pylorus.
Sphincters:
- Pyloric Sphincter: Separates stomach from small intestine.
- Esophageal Sphincter: Separates stomach from esophagus.
Environment: Highly acidic.

Structures of the Stomach

Rugae: Folds in the stomach lining that allow for expansion when eating.
Gastric Glands: Secrete gastric juice.
Types of Gastric Gland Cells:
- Parietal Cells: Produce hydrochloric acid (HCl).
- Chief Cells: Produce pepsin (for protein digestion).
- Mucus Cells: Produce mucus (protects against HCl).

Stomach Lining

Epithelium: Forms deep pits containing glands.
Secretions: Enzymes, hormones, and mucus.
Gastric Juice:
- Hormones: E.g., gastrin (increases acid secretion and stomach motility).
- Enzymes: E.g., pepsin.
Absorption: Some water, lipids, caffeine, and alcohol are absorbed in the stomach.

The Small Intestine

Key Function: Primary site for digestion and absorption of nutrients.

Accessory Organs

Liver:
- Largest solid organ and gland in the body.
- Produces bile.
- Processes nutrients and detoxifies harmful substances.
Gall Bladder:
- Stores and concentrates bile.
- Releases bile into the duodenum in response to cholecystokinin.
Pancreas:
- Endocrine and exocrine function.
- Exocrine: Secretes digestive enzymes and bicarbonate into the duodenum.
- Endocrine: Produces insulin and glucagon.

Bile

Source: Produced by the liver.
Function: Emulsifies fats for digestion.
Composition: Bile salts, bile pigments (bilirubin), cholesterol, and phospholipids.
Reabsorption: Most bile is reabsorbed and recycled by the liver.

Pancreatic Fluid

Composition:
- Sodium Bicarbonate: Neutralizes stomach acid.
- Pancreatic Amylase: Digests carbohydrates.
- Pancreatic Lipase: Digests lipids.
- Trypsin and Chymotrypsin: Digest proteins.
- Nucleases: Digest nucleic acids.

The Large Intestine (Colon)

Function:
- Absorbs water, electrolytes, and some vitamins.
- Stores and eliminates waste.
Characteristics:
- Less muscular.
- Contains goblet cells (secrete mucus for lubrication).
- No villi.
Key Processes:
- Fermentation of undigested material by bacteria.
- Formation of feces.

The Rectum

Location: Last 13 cm of the large intestine.
Function: Stores feces until elimination.
Sphincters: Relax to allow for defecation.

Digestion

Definition: The process of breaking down food into smaller molecules for absorption.
Types:
- Mechanical: Physical breakdown of food (chewing, churning)
- Chemical: Breakdown of food molecules by enzymes.

Digestive Juices

Source: Stomach, small intestine, salivary glands, gall bladder, and pancreas.
Key Components: Digestive enzymes.

Digestive Enzymes

Types:
- Amylase: Digests starches.
- Lipase: Digests lipids.
- Protease: Digests proteins.

Digestion of Carbohydrates

Step 1: Salivary amylase (mouth) and pancreatic amylase (small intestine) break down polysaccharides into disaccharides.
Step 2: Intestinal enzymes (sucrase, maltase, lactase) break down disaccharides into monosaccharides.

Digestion of Proteins

Step 1: Pepsin (stomach) and trypsin and chymotrypsin (pancreas) break down proteins into smaller peptide chains.
Step 2: Aminopeptidase (small intestine) breaks down peptides into amino acids.

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Description

Explore the key activities of the alimentary canal, including ingestion, digestion, absorption, assimilation, and egestion. Delve into the mechanical and chemical processes that occur in the mouth, highlighting the role of teeth, saliva, and taste buds in digestion.