Question

Draw a labelled diagram of the human digestive system. With the help of this diagram, describe the process of digestion of food in man (humans).

Answer 1

1. Ingestion & Mouth: The process begins here. Teeth mechanically break down the food, while saliva releases an enzyme (salivary amylase) that begins the chemical digestion of carbohydrates.
2. Oesophagus (Food pipe): The swallowed food is pushed down to the stomach through continuous, wave-like muscular contractions known as peristalsis.
3. Stomach: Food is churned and mixed with acidic gastric juices. Hydrochloric acid (HCl) kills harmful bacteria, and the enzyme pepsin begins breaking down proteins, turning the food into a semi-liquid paste called chyme.
4. Liver, Gallbladder, & Pancreas: These organs send crucial chemicals into the small intestine. The liver produces bile (stored in the gallbladder) to break down large fat drops, while the pancreas releases juices containing enzymes to further digest proteins, carbs, and fats.
5. Small Intestine: This is the primary site of complete digestion and nutrient absorption. The inner walls are lined with millions of tiny, finger-like projections called villi. These vastly increase the surface area to absorb the digested nutrients directly into the bloodstream.
6. Large Intestine: The leftover, undigested food passes here. The large intestine absorbs excess water and essential minerals, leaving behind solid waste.
7. Rectum & Anus: The solid waste (faeces) is stored in the rectum until it is eliminated from the body through the anus.