Digestion and Its Processes

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Questions and Answers

What is meant by a balanced diet?

A balanced diet is one that provides all the essential nutrients the body needs in the right proportions.

What are the principal dietary sources of carbohydrates?

Sources include grains, fruits, vegetables, and legumes.

What is the importance of carbohydrates?

Carbohydrates are essential for providing energy and supporting the functioning of vital organs.

What is the importance of fats and oils?

Fats and oils are important for energy storage, insulation, and supporting cell structure. Signup and view all the answers

What is the importance of proteins?

Proteins are vital for building and repairing tissues, producing enzymes and hormones. Signup and view all the answers

What are the importance of vitamins C and D?

Vitamin C is important for immune function and skin health, while vitamin D is essential for calcium absorption and bone health. Signup and view all the answers

What are the importance of calcium and iron?

Calcium is critical for bone health, while iron is essential for transporting oxygen in the blood. Signup and view all the answers

What is the importance of fiber?

Fiber aids in digestion and helps prevent constipation. Signup and view all the answers

What is the importance of water?

Water is essential for hydration, regulating body temperature, and facilitating chemical reactions. Signup and view all the answers

What causes scurvy?

Scurvy is caused by a deficiency of vitamin C. Signup and view all the answers

What causes rickets?

Rickets is caused by a deficiency of vitamin D, calcium, or phosphate. Signup and view all the answers

What is ingestion in the context of the digestive system?

Ingestion is the intake of food and drink into the body. Signup and view all the answers

What is digestion?

Digestion is the breakdown of food into smaller molecules that can be absorbed. Signup and view all the answers

What is absorption in the digestive system?

Absorption is the movement of nutrients from the intestines into the bloodstream. Signup and view all the answers

What is assimilation?

Assimilation is the uptake and use of nutrients by cells. Signup and view all the answers

What is egestion?

Egestion is the removal of undigested food from the body as faeces. Signup and view all the answers

What is physical digestion?

Physical digestion involves breaking down food into smaller pieces without chemical change. Signup and view all the answers

What is chemical digestion?

Chemical digestion is the breakdown of large insoluble molecules into small soluble ones using enzymes. Signup and view all the answers

What is the function of teeth in the digestive system?

Teeth help with the ingestion and physical digestion of food by biting, chopping, and grinding. Signup and view all the answers

What role does saliva play in digestion?

Saliva helps dissolve food, softens it for easier swallowing, and contains enzymes that start digestion. Signup and view all the answers

What is peristalsis?

Peristalsis is the wave-like contraction and relaxation of muscles that moves food through the digestive tract. Signup and view all the answers

What is the function of gastric juice?

Gastric juice helps to kill microbes, activates pepsinogen into pepsin, and aids in digesting proteins. Signup and view all the answers

What is bile?

Bile is a digestive fluid produced by the liver that helps emulsify fats. Signup and view all the answers

What are villi?

Villi are small, finger-like projections in the small intestine that increase the surface area for absorption. Signup and view all the answers

What is the function of the liver?

The liver detoxifies harmful substances, produces bile, and regulates blood glucose levels. Signup and view all the answers

What is diarrhea?

Diarrhea is the excessive loss of watery feces, often caused by an infection. Signup and view all the answers

How does cholera cause diarrhea?

Cholera bacteria release toxins that stimulate the intestine to secrete chloride ions, leading to loss of fluid. Signup and view all the answers

Study Notes

Digestion

The digestive system is involved in: ingestion, digestion, absorption, assimilation, and egestion.
Ingestion is the intake of food and drink.
Digestion is the breakdown of food into smaller, soluble molecules.
Absorption is the movement of nutrients from the intestines into the blood.
Assimilation is the uptake and use of nutrients by cells.
Egestion is the removal of undigested food from the body as faeces.
There are two types of digestion: physical and chemical.
Physical digestion breaks down food into smaller pieces without changing the chemical composition of the food molecules.
Chemical digestion breaks down large, insoluble molecules into smaller, soluble molecules using enzymes.

Physical Digestion

Teeth are involved in physical digestion by biting, chopping, and grinding food.
Stomach churns food by contraction and relaxation.
Bile breaks down large fat droplets into smaller ones through emulsification.

Mouth

The mouth is involved in both physical and chemical digestion.

Teeth

Enamel: the hardest substance made by the body, can be dissolved by acids.
Dentine: a hard substance, contains channels of cytoplasm.
Pulp: contains nerves for sensation, blood vessels, and cells that make dentine.
Cement: bone-like substance that attaches teeth to the jaw bone.
Types of teeth: incisors, canines, premolars, and molars.
Functions of teeth: help with ingestion, physical digestion, biting, chopping, crushing, grinding, and facilitate swallowing.

Chemical Digestion in the Mouth

Saliva contains:
- Water: helps in digestion and dissolving food.
- Mucus: binds chewed food together to form a bolus, lubricates food, and protects the alimentary canal.
- Amylase: digests starch in alkaline conditions and converts it into maltose.

Esophagus

Peristalsis: waves of muscle contraction and relaxation that move food through the esophagus towards the stomach.

Stomach

Physical Digestion in the Stomach: churning food through contraction and relaxation.
Chemical Digestion in the Stomach: by gastric juice, which contains:
- Hydrochloric Acid: kills microbes and activates pepsinogen.
- Pepsinogen: inactive enzyme activated by hydrochloric acid to form pepsin.
- Mucus: protects the stomach lining from hydrochloric acid and pepsin.
Pepsin: digests proteins into polypeptides.
Chyme: food mixed with gastric juice that leaves the stomach, acidic.

Small Intestine

Two parts: duodenum and ileum.
Duodenum:
- Emulsification of fats.
- Changes the pH of food coming from the stomach from acidic to alkaline.
Ileum:
- Completes digestion of all food types.
- Absorption of digested food.

Small Intestine Digested Juices

Bile: produced in the liver and stored in the gallbladder; not an enzyme but breaks down large fat droplets into smaller ones.
- Components of bile: bile pigments and bile salts.
Pancreatic Juice: produced in the pancreas.
- Components of pancreatic juice: bicarbonate, amylase, trypsin, and lipase.

Ileum Adaptations

Long: provides time for digestion and absorption.
Villi: finger-like projections that increase surface area for absorption.
Microvilli: tiny projections on villi that further increase the surface area of the small intestine, speeding up nutrient absorption.
Blood Capillaries: transport monosaccharides, amino acids, water, minerals, and vitamins to the liver.
Lacteals: part of the lymphatic system that absorbs fats.

Intestinal Enzymes

Lipase: digests lipids into fatty acids and glycerol.
Peptidase: digests polypeptides into amino acids.
Maltase: digests maltose into glucose.

Absorption of Food

Blood Route: amino acids, monosaccharides, water, minerals, and water-soluble vitamins are transported through villi to the liver via the hepatic portal vein.
Lacteal Route: fatty acids and glycerol are absorbed into the lacteals.

Large Intestine

Colon: absorption of water and salts.
Rectum: storage of faeces.
Anus: egestion.

Liver Functions

Hemoglobin Destruction: produces iron and bile pigments from broken-down hemoglobin.
Bile Production: emulsifies fats.
Detoxification: breaks down toxic materials.
Deamination: removes nitrogen from amino acids, producing urea.
Glucose Regulation: stores excess glucose as glycogen.
Plasma Protein Production: produces plasma proteins.

Hepatic Portal Vein vs. Hepatic Vein

Hepatic Portal Vein: connects small intestine and liver; carries a high concentration of glucose, amino acids, and low urea; may contain toxic materials.
Hepatic Vein: connects liver and inferior vena cava; carries a lower concentration of glucose, amino acids, and higher urea; absence of toxic materials.

Diseases Affecting Digestive System

Diarrhoea: excessive loss of watery faeces; caused by infections, like cholera.
Cholera: bacteria multiply in the small intestine, releasing toxins that cause excessive fluid secretion in the small intestine, leading to diarrhoea.
Oral Rehydration Therapy: a solution containing water, salt, and sugar helps rehydrate the body during diarrhoea.
Preventing Cholera Transmission: sewage treatment, vaccination, and antibiotics.

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Description

This quiz covers the essential functions of the digestive system, including ingestion, digestion, absorption, assimilation, and egestion. It explores the differences between physical and chemical digestion and the roles of various organs involved in the digestive process.