Chapter 2 — Nutrition in Animals

The five steps are ingestion (taking food into the body), digestion (breaking complex substances into simpler ones), absorption (digested food passing into blood vessels), assimilation (use of absorbed substances to build complex substances and release energy), and egestion (removal of undigested waste through the anus).

The small intestine is highly coiled and is about 7.5 metres long.

Villi (singular: villus) are thousands of finger-like outgrowths on the inner wall of the small intestine. They increase the surface area for absorption of digested food. Each villus has a network of thin blood vessels close to its surface that absorb the digested food materials.

Ruminants such as cows, buffaloes, and deer quickly swallow grass and store it in a part of the stomach called the rumen. Later, this partially digested food (cud) returns to the mouth in small lumps and the animal chews it. This process of rechewing the cud is called rumination.

Bile is secreted by the liver and stored in a sac called the gall bladder. It plays an important role in the digestion of fats.

The liver is the largest gland in the human body. It is reddish brown and is situated in the upper part of the abdomen on the right side.

Amoeba pushes out finger-like projections called pseudopodia (false feet) around a food particle and engulfs it. The food becomes trapped in a food vacuole. Digestive juices are secreted into the food vacuole, break down the food into simpler substances, and the digested food is gradually absorbed. Undigested residue is expelled outside.

In ruminants like cattle and deer, bacteria present in the rumen help digest cellulose. Humans do not have these bacteria, so they cannot digest cellulose.

The hydrochloric acid secreted by the inner lining of the stomach kills many bacteria that enter along with food and makes the medium in the stomach acidic, which helps the digestive juices to act.

The large intestine is about 1.5 metres long. Its function is to absorb water and some salts from the undigested food material. The remaining waste passes into the rectum and remains there as semi-solid faeces, which is removed through the anus — a process called egestion.

Bacteria in the mouth break down the sugars present in leftover food and release acids. These acids gradually damage the teeth. Chocolates, sweets, soft drinks, and other sugar products are the major culprits of tooth decay.

Salivary glands in the mouth secrete saliva. Saliva breaks down starch into sugars. The tongue mixes saliva with food during chewing and helps in swallowing.

The first set of teeth that grows during infancy is called milk teeth. They fall off at the age of six to eight years and are replaced by a second set called permanent teeth.

ORS stands for Oral Rehydration Solution. It is boiled and cooled water with a pinch of salt and sugar dissolved in it. It is given to patients suffering from diarrhoea to replace the excessive loss of water and salts from the body.

The pancreas is a large cream-coloured gland located just below the stomach. The pancreatic juice acts on carbohydrates, fats, and proteins and changes them into simpler forms.

Yes — you can read the full chapter PDF on this page for free with no sign-up required.