Digestive Glands and Their Functions

Salivary Glands: Salivary glands produce saliva, which lubricates food and begins the digestion of starch.

Gastric Glands: Gastric glands secrete hydrochloric acid, mucus, and pepsinogen.

Pancreas: The pancreas produces pancreatic juice containing amylase, lipase, and proteases.

Intestinal Glands: Intestinal glands secrete enzymes that complete digestion.

Why the Oesophagus Is Not a Digestive Gland ? 

The oesophagus only transports food and secretes mucus for lubrication. It does not produce digestive enzymes.
Major Digestive Enzymes and Their Functions

Salivary Amylase: Breaks starch into maltose.

Pepsin: Breaks proteins into polypeptides.

Pancreatic Amylase: Continues carbohydrate digestion.

Pancreatic Lipase: Breaks fats into fatty acids and glycerol.

Trypsin and Chymotrypsin: Digest proteins into smaller peptides.

Maltase, Sucrase, and Lactase: Convert disaccharides into monosaccharides.

Peptidases: Break peptides into amino acids.

Digestion and Absorption of Fats

Fat digestion differs significantly from carbohydrate and protein digestion.

Emulsification of Fats: Bile salts produced by the liver break large fat globules into smaller droplets, increasing their surface area.

Role of Lipase: Lipase converts fats into fatty acids and glycerol.

Absorption of Fats: Fatty acids and glycerol are absorbed into intestinal cells and reassembled into triglycerides. They are then packaged into chylomicrons and transported through lacteals into the lymphatic system.

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Structure and Functions of Intestinal Villi

The small intestine contains millions of finger-like projections called villi that increase the surface area for absorption.

Structure of a Villus: Each villus is covered by epithelial cells with microvilli. Inside the villus are blood capillaries and a central lacteal.

Role of Blood Capillaries: Capillaries absorb glucose, amino acids, vitamins, minerals, and water-soluble nutrients into the bloodstream.

Role of Lacteals: Lacteals absorb fats and fat-soluble vitamins into the lymphatic system.

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Functions of the Large Intestine

Most digestion and nutrient absorption occur in the small intestine. The large intestine mainly absorbs remaining useful substances.

Absorption in the Large Intestine

The large intestine absorbs water, mineral salts, and vitamins produced by beneficial bacteria. The remaining material is compacted into faeces and eliminated from the body.

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Functions of the Liver in Digestion

The liver is the largest internal organ and performs many important metabolic functions.

Major Functions of the Liver

The liver regulates blood glucose levels, metabolizes fats and proteins, produces bile, detoxifies harmful substances, and breaks down old red blood cells. These functions are essential for maintaining homeostasis.

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Environmental Hazards of Chemical Fertilizers

Chemical fertilizers increase crop production but can also harm the environment.

Eutrophication: Excess fertilizers entering water bodies cause algal blooms and oxygen depletion.

Groundwater Pollution: Nitrates can contaminate drinking water and cause health problems.

Greenhouse Gas Emissions: Fertilizer use contributes to the release of nitrous oxide, a powerful greenhouse gas.

Soil Degradation: Excessive fertilizer use damages soil quality and beneficial microorganisms.

Marine Dead Zones: Fertilizer runoff can create low-oxygen zones in oceans where marine life cannot survive.

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Malnutrition and Its Health Effects

Malnutrition occurs when the body receives too little, too much, or an imbalanced amount of nutrients.

Effects of Undernutrition: Undernutrition can cause stunted growth, weakened immunity, kwashiorkor, marasmus, anemia, rickets, and night blindness.

Effects of Overnutrition: Overnutrition can result in obesity, diabetes, hypertension, and cardiovascular diseases.

Why Malnutrition Is a Health Hazard?

Malnutrition affects growth, immunity, organ function, and overall health, making individuals more vulnerable to diseases.

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Importance of Dietary Fiber

Definition

Dietary fiber, also known as roughage, is the indigestible portion of plant food.

Functions of Dietary Fiber: Fiber prevents constipation, promotes regular bowel movements, supports digestive health, reduces cholesterol levels, helps control blood sugar, lowers the risk of heart disease, and promotes a feeling of fullness that helps maintain a healthy body weight.

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Overnutrition and Health Disorders

Overnutrition occurs when a person consumes more nutrients and calories than the body requires.

Obesity: Excess calorie intake leads to fat accumulation and obesity.

Cardiovascular Diseases: High-fat diets increase the risk of atherosclerosis, heart attacks, and strokes.

Type 2 Diabetes

Excess sugar consumption can lead to insulin resistance and diabetes.

Hypertension: High sodium intake raises blood pressure and increases the risk of heart disease.

Vitamin Toxicity: Excessive intake of fat-soluble vitamins may cause serious health complications.