Digestive System Quiz

Digestive System

• The human digestive system is a long, muscular tube (alimentary canal) starting at the mouth and ending at the anus.
• Parts include the mouth, esophagus, stomach, small intestine, large intestine, and anus.
• Other organs like the liver, gallbladder, and pancreas are also part of the system.
• Salivary, gastric, and intestinal glands secrete digestive juices into the alimentary canal.

Digestion

• Digestion breaks down large, complex food pieces into smaller, absorbable pieces.

• It has two components: physical and chemical digestion.

• Physical digestion involves mechanical breakdown of food, like chewing and peristalsis (muscle contractions).

• Chemical digestion breaks down complex molecules into simpler ones using enzymes.

Carbohydrate Digestion (in the Mouth)

• The digestive process begins in the mouth.
• Food presence in the mouth stimulates salivary glands to release saliva.
• Saliva contains salivary amylase, which hydrolyzes starch into maltose.
• The optimal pH for salivary amylase is 6.5-7.5.
• Saliva also forms bolus, making swallowing easier.
• The epiglottis closes the trachea during swallowing to prevent food from entering the airway.

Protein Digestion (in the Stomach)

• The stomach wall has epithelial cells (gastric glands) consisting of chief cells, parietal cells, and mucous cells.
• Chief cells secrete pepsinogen, which is activated by hydrochloric acid (from parietal cells) to become pepsin.
• Pepsin hydrolyzes proteins into polypeptides.
• Mucous cells secrete mucus to protect the stomach lining from HCl's acidic effects.

Digestion in the Small Intestine

• The small intestine (duodenum, jejunum, and ileum) receives chyme from the stomach.
• Duodenum also receives bile from the liver and pancreatic juices.
• Pancreatic amylase hydrolyzes starch to maltose.
• Trypsin hydrolyzes polypeptides into shorter peptides.
• Lipase hydrolyzes lipids into fatty acids and glycerol.
• Bile emulsifies lipids, increasing the surface area for lipase action.

Absorption in the Small Intestine

• The ileum's villi and microvilli increase the surface area for nutrient absorption.
• The epithelial layer is one cell thick to enhance absorption rate.
• Goblet cells secrete mucus to aid in digestion and protect the lining.
• Blood capillaries absorb amino acids, glucose, and water.
• Lacteals absorb fatty acids and glycerol.
• Enzymes in the intestinal juice (like maltase, sucrase, lactase) further digest carbohydrates.

Assimilation and Liver Function

• The liver controls the amount of nutrients entering the bloodstream.
• Metabolises glucose for cellular respiration; amino acids for protein synthesis; excess amino acids to urea for excretion.
• The liver detoxifies substances from the blood.
• Stores glycogen from excess glucose.

Defaecation and Large Intestine Functions

• The large intestine absorbs water and minerals.
• Beneficial bacteria synthesize vitamins (B and K).
• The remaining waste (faeces) forms as undigested materials.
• Peristaltic movement in the large intestine pushes the faeces toward the rectum and then out through the anus (defaecation).
• Fibre stimulates peristalsis and helps regulate glucose absorption (especially useful for diabetics).

Balanced Diet

• A balanced diet comprises all food classes (carbohydrates, fats, proteins, vitamins, minerals, fibre, and water).
• Proportions and quantities should meet individual needs for optimal health.
• Energy value of food is the total energy released when a gram is completely oxidized.
• Food energy value is measured in kilojoules per gram (kJ/g).
• Other units include calories.
• One calorie = 4.2 joules, and is equal to the amount of energy needed to raise water temperature of 1 g by 1°C.

Health Issues

• Obesity: Excess fat storage due to imbalanced energy intake and energy expenditure.
• Gastritis: Stomach lining inflammation from factors like irregular food intake, alcohol or painkillers.
• Anorexia nervosa: Obsessive fear of gaining weight, leading to food avoidance and potential health problems.
• Bulimia nervosa: Cycles of binge eating and compensatory behaviours (vomiting or laxative use) to control weight.
• Muscle dysmorphia: Obsessive desire to gain muscle mass through extreme exercise.

Test your knowledge about the human digestive system, including its parts and functions. This quiz will cover aspects of digestion, including both physical and chemical processes, along with specifics about carbohydrate digestion in the mouth. Challenge yourself and learn more about how our body processes food!