Digestive System and Digestion Quiz

Digestive System

• The human digestive system is a long muscular tube, starting at the mouth and ending at the anus.
• It includes the mouth, esophagus, stomach, small intestine, large intestine, and anus.
• Other organs like the liver, gallbladder, and pancreas also aid in digestion.
• Glands in the digestive system secrete digestive juices into the alimentary canal.

Digestion

• Digestion breaks down large, complex food pieces into smaller, simpler, absorbable pieces.
• This process has two components: physical and chemical digestion.
• Physical digestion involves mechanical breakdown of food, such as chewing and peristalsis.
• Chemical digestion uses enzymes to break down complex molecules like proteins into simpler molecules for absorption.
• Digestion begins in the mouth with the breakdown of carbohydrates through saliva amylase.

Digestion of Carbohydrates in the Mouth

• Food in the mouth stimulates saliva secretion from salivary glands.
• Saliva contains salivary amylase that hydrolyzes starch to maltose.
• The optimum pH range for amylase is 6.5-7.5.
• Saliva also helps form a bolus for easier swallowing.

Digestion of Protein in the Stomach

• The stomach lining has gastric glands with chief cells, parietal cells, and mucous cells.
• Chief cells make pepsinogen, which is activated to pepsin by hydrochloric acid from parietal cells.
• Pepsin hydrolyzes proteins into polypeptides.
• Mucous cells produce mucus to protect the stomach wall from acid.

Digestion in the Small Intestine

• The small intestine includes the duodenum, jejunum, and ileum. It receives chyme from the stomach.
• Duodenum also receives bile from the liver and pancreatic juice.
• Pancreatic amylase hydrolyzes starch to maltose.
• Trypsin hydrolyzes polypeptides into shorter peptides.
• Lipase hydrolyzes lipids into fatty acids and glycerol.

Carbohydrate Digestion (in the small intestine)

• Maltase hydrolyzes maltose into glucose.
• Sucrase hydrolyzes sucrose into glucose and fructose.
• Lactase hydrolyzes lactose into glucose and galactose.

Lipid Digestion (in the small intestine)

• Lipase hydrolyzes lipids into fatty acids and glycerol.

Protein Digestion (in the small intestine)

• Erepsin hydrolyzes peptides into amino acids.

Absorption

• The ileum is adapted to absorb nutrients due to its folded inner layer covered by villi.
• Villi have a one-cell-thick epithelial layer, goblet cells to secrete mucus and a network of blood capillaries.
• Microvilli further increase the surface area for absorption.
• Lacteals transport fatty acids and glycerol.
• Different nutrients are absorbed via different mechanisms (active transport, facilitated diffusion, osmosis, simple diffusion).

Assimilation

• The circulatory system transports absorbed nutrients.
• Blood capillaries in the small intestine form the hepatic portal vein, transporting blood to the liver.
• The liver controls the quantity of nutrients entering the blood circulation. Functions include metabolism of glucose, amino acids & lipids; detoxification, and storage of nutrients.

Defaecation

• Undigested food, dead cells, and fiber enter the large intestine, moving slowly through peristalsis.
• The large intestine absorbs water and vitamins.
• Waste products form feces.
• Feces moves to the rectum and are expelled through the anus.
• Fiber stimulates peristalsis, absorbs toxins and helps regulate glucose absorption in diabetics.

Balanced Diet

• A balanced diet includes all seven food groups in appropriate proportions.
• Energy value is the total energy released from the complete oxidation of 1 gm of food.
• Energy is measured in kilojoules (kJ) or calories (cal).

Health Issues Related to the Digestive System and Eating Habits

• Obesity, a significant health concern, arises from imbalanced food intake and energy use.
• Issues like gastritis (stomach inflammation), anorexia nervosa (eating disorder characterized by food avoidance), bulimia nervosa (cycle of binge eating and purging), and muscle dysmorphia (extreme dissatisfaction with body image), are all related to eating habits.
• Other issues include problems during defaecation (e.g constipation, colon cancer, rectum cancer and haemorrhoids) and poor healthy habits.

Test your knowledge on the human digestive system and its processes. This quiz covers the anatomy of the digestive tract, the stages of digestion, and the specific breakdown of carbohydrates in the mouth. Challenge yourself to understand how food is processed from intake to absorption.