Nutrition in Animals
Animal nutrition includes nutrient requirement, mode of intake of food and its utilisation in the body.
The steps involved in digestion are: Ingestion, digestion, assimilation, absorption and egestion.
The human digestive system consists of the alimentary canal and associated digestive glands.
Alimentary canal consists of: Mouth, buccal cavity, oesophagus, stomach, small intestine, large intestine ending in rectum and anus.
The digestive glands include the salivary glands, the liver (with gall bladder) and the pancreas. The stomach wall and the wall of the small intestine also secrete digestive juices.
In the alimentary canal, the mouth leads to buccal cavity that consists of teeth and tongue.
An adult human has four different types of teeth namely, incisors (I), canine (C), premolars (PM) and molars.
The tongue is attached to the floor of the oral cavity by the frenulum.
Our mouth has salivary glands that secrete saliva.
Saliva mixes with chewed food to facilitate swallowing of food.
The food is conveyed to the pharynx and then to the oesophagus.
It passes down through the oesophagus by peristalsis and enters the stomach.
The inner lining of the stomach secretes mucous, hydrochloric acid and digestive juices.
In stomach, primarily protein digestion takes place.
Then the food enters the small intestines.
Small intestine receives secretions from the liver and the pancreas.
Liver secretes bile juice that is stored in the gall bladder and helps in digestion of fats.
Pancreas secretes the pancreatic juice that acts on carbohydrates, fats and proteins and converts them to simpler forms.
The digested end products are absorbed in the body through the epithelial lining of the intestinal villi.
Nutrients such as amino acids and glucose are incorporated into the cells by the process called assimilation.
The undigested food becomes semi-solid in nature and then enters the rectum and is finally egested out through the anus.
The grazing animals are known as ruminants.
They quickly ingest, swallow the leafy food and store it in the rumen.
Here, the food gets partially digested and is called cud.
Later, the cud returns to the mouth and the animal chews it peacefully.
Amoeba uses its pseudopodia to capture the food. The food is digested in a food vacuole.