Nutrition in Animal -Important points and Notes

Nutrition in Animal

Animal nutrition comprise of nutrient requirement, mode of intake of food and its utilisation in the body.

The components of food such as carbohydrates are complex substances. These complex substances cannot be utilised as such. So they are broken down into simpler substances. The breakdown of complex components of food into simpler substances is called digestion. 

Different Ways Of Taking Food:

The mode of taking food into the body varies in different organisms-

• Bees and humming-birds suck the nectar of plants,  
• Infants of human and many other animals feed on mother's milk.
• Snakes like the python swallow the animals they prey upon. 
• Some aquatic animals filter tiny food particles floating nearby and feed upon them. 

Interesting Facts: 

Starfish feeds on animals covered by hard shells of calcium carbonate. After opening the shell, the starfish pops out its stomach through its mouth to eat the soft animal inside the shell. The stomach then goes back into the body and the food is slowly digested. 

Digestion In Humans:  

We take in food through the mouth, digest and utilise it. The food passes through a continuous canal which begins at the buccal cavity and ends at the anus. The canal can be divided into various compartments:

1. The buccal cavity , 
2. Food pipe or Oesophagus, 
3. Stomach, 
4. Small intestine, 
5. Large intestine ending in the rectum and 
6. The anus. 

These parts together form the alimentary canal (digestive tract). 

The inner walls of the stomach and the small intestine, and the various glands associated with the canal such as salivary glands, the liver and the pancreas secrete digestive juices. The digestive juices convert complex substances of food into simpler ones. The digestive tract and the associated glands together constitute the digestive system.

1. The mouth and Buccal cavity: 

Food is taken into the body through the mouth the process of taking food into the body is called ingestion. The saliva breaks down the starch into sugars.

Tongue:

• The tongue is a fleshy muscular organ attached at the back to the floor of the buccal cavity. 
•  It is free at the front and can be moved in all directions. 
• We use our tongue for talking. Besides, it mixes saliva with the food during chewing and helps in swallowing food. We also taste food with our tongue.

Milk teeth and Permanent teeth :

• The first set of teeth grows during infancy and they fall off at the age between six to eight years. These are termed Milk teeth. 
• The second set that replaces them are the permanent teeth. The permanent teeth may last throughout life or fall off during old age or due to some dental disease. 

Arrangement and Different Type of Teeth

Sweets and tooth decay:

• Normally bacteria are present in our mouth but they are not harmful to us. However, if we do not clean our teeth and mouth after eating, many harmful bacteria also begin to live and grow in it. These bacteria break down the sugars present from the leftover food and release acids. The acids gradually damage the teeth. This is called tooth decay. 
•  If it is not treated in time, it causes severe toothache and in extreme cases results in tooth loss.
• Chocolates, sweets, soft drinks and other sugar products are the major culprits of tooth decay. 

Do You Know This:

Sometimes when you eat in a hurry, talk or laugh while eating, you may cough, get hiccups or a choking sensation.  

This happens when food particles enter the windpipe. The windpipe carries air from the nostrils to the lungs. It runs adjacent to the food pipe. But inside the throat, air and food share a common passage. During the act of swallowing a flap-like valve closes the passage of the windpipe and guides the food into the food pipe. If, by chance, food particles enter the windpipe, we feel choked, get hiccups or cough.

2. The Food pipe / Oesophagus:

The swallowed food passes into the food pipe or oesophagus. The food pipe runs along the neck and the chest. Food is pushed down by movement of the wall of the food pipe.

3. The stomach:

• The stomach is a thick-walled bag. Its shape is like a flattened U and it is the widest part of the alimentary canal.
• It receives food from the food pipe at one end and opens into the small intestine at the other.
• The inner lining of the stomach secretes mucous, hydrochloric acid and digestive juices. 
• The mucous protects the lining of the stomach. 
• The acid kills many bacteria that enter along with the food and makes the medium in the stomach acidic and helps the digestive juices to act. 
• The digestive juices break down the proteins into simpler substances.

4. The small intestine:

• The small intestine is highly coiled and is about 7.5 metres long. It receives secretions from the liver and the pancreas.Besides, its wall also secretes juices
• The liver is a reddish brown gland situated in the upper part of the abdomen on the right side.It is the largest gland in the body. It secretes bile juice that is stored in a sac called the gall bladder. The bile plays an important role in the digestion of fats.
• 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.
• The partly digested food now reaches the lower part of the small intestine where the intestinal juice completes the digestion of all components of the food.
• The carbohydrates get broken into simple sugars such as glucose, fats into fatty acids and glycerol, and proteins into amino acids.

Absorption in the small intestine: 

• The digested food can now pass into the blood vessels in the wall of the intestine. This process is called Absorption. The inner walls of the small intestine have thousands of finger-like outgrowths. These are called villi (singular villus).
• The villi increase the surface area for absorption of the digested food. Each villus has a network of thin and small blood vessels close to its surface. The surface of the villi absorbs the digested food materials. 
• The absorbed substances are transported via the blood vessels to different organs of the body where they are used to build complex substances such as the proteins required by the body. This is called assimilation. 

The food that remains undigested and unabsorbed enters into the large intestine.

5. Large Intestine:

• The large intestine is wider and shorter than small intestine. It is about 1.5 metre in length. 
• 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. The faecal matter is removed through the anus from time-to-time. This is called Egestion. 

Diarrhoea:

Sometime we might have experienced the need to pass watery stool frequently. This condition is known as diarrhoea. Diarrhoea should not be neglected. Even before a doctor is consulted the patient should be given plenty of boiled and cooled water with a pinch of salt and sugar  dissolved in it. This is called Oral Rehydration Solution (ORS).

Digestion In Grass-Eating Animal:

• Animals like cows, buffaloes and other grass-eating animals keep chewing continuously even when they are not eating. Actually, they quickly swallow the grass and store it in a part of the stomach called Rumen.
• The food gets partially digested and is called cud. But later the cud returns to the mouth in small lumps and the animal chews it. This process is called Rumination and these animals are called Ruminants.
• The grass is rich in cellulose, a type of carbohydrate. Many animals, including humans, cannot digest cellulose.
• Ruminants have a large sac-like structure called Rumen between the oesophagus and the small intestine. The cellulose of the food is digested here by the action of certain bacteria which are not present in humans.

Feeding And Digestion In Amoeba:

• Amoeba is a microscopic single-celled organism found in pond water. 
• Amoeba has a cell membrane, a rounded, dense nucleus and many small bubble-like vacuoles in its cytoplasm.
• Amoeba constantly changes its shape and position. It pushes out one, or more finger-like projections, called Pseudopodia or false feet for movement and capture of food. 
• Amoeba feeds on some microscopic organisms. When it senses food, it pushes out pseudopodia around the food particle and engulfs it. 
• The food becomes trapped in a food vacuole Digestive juices are secreted into the food vacuole. 
• They act on the food and break it down into simpler substances. Gradually the digested food is absorbed.
• The undigested residue of the food is expelled outside by the vacuole. 

What Have You Learnt?

• Nutrition is a complex process involving: (i) ingestion, (ii) digestion, (iii) absorption, (iv) assimilation and (v) egestion.
• Digestion of carbohydrates, like starch, begins in the buccal cavity. 
• The digestion of protein starts in the stomach. 
• The bile secreted from the liver, the pancreatic juice from the pancreas and the digestive juice from the intestinal wall complete the digestion of all components of food in the small intestine. 
• The digested food is absorbed in the blood vessels from the small intestine.
• The absorbed substances are transported to different parts of the body. Water and some salts are absorbed from the undigested food in the large intestine.
• The undigested and unabsorbed residues are expelled out of the body as faeces through the anus.
• Amoeba ingests its food with the help of its false feet or pseudopodia. The food is digested in the food vacuole.