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CLASS 7-Nutrition in Animals Class-CHAPTER NOTE
Chapter Note
Nutrition in Animals
· Nutrition in Animals includes nutrient requirement,
mode of intake of food and its utilization in the body.
·
The components of food like carbohydrates are
complex substances. It cannot be utilized as such. therefore It is broken down into simpler substances.
·
The breakdown of complex components of food into
simpler substances is called digestion.
Human digestive system
· The food Which we eat passes through a Canal inside our body.
· This Canal is often known as the Alimentary Canal or the Digestive Tract. Food is processed in alimentary Canal and utilized in the body and unused food is collected inside the canal only.
· The alimentary Canal is divided into different parts:
1. The Mouth or
Buccal Cavity
2. Food Pipe or
Oesophagus
3. Stomach
4. Small Intestine
5. Large Intestine
6. Anus
Gland: It is an organ which
produces and releases substances that perform a specific function in the body.
1.
Liver :-
·
The liver is a reddish brown gland located in
the upper part of the abdomen on the right side.
· Liver is the largest gland in the body.
·
It releases (secretes) bile juice that is stored in a sac
called the gall bladder.
·
The bile juice plays an important role in the
digestion of fats.
2.
Pancreas :-
·
The pancreas is a large cream color gland
situated just below the stomach.
· The pancreatic juice acts on carbohydrates, proteins and fat and changes them into simpler forms.
3.
Salivary glands:-
·
Salivary glands play very important role in digestion because
they make saliva.
·
Saliva helps to moisten food so we can swallow it
more easily.
·
It also contains an enzyme called amylase that makes
it easier for the stomach to break down starches in food.
The mouth and buccal cavity
·
Food is taken in the body through the mouth.
·
The process of taking food into the body is
called as ingestion.
·
Teeth chews the food and breaking it down by biting,
cutting, piercing and tearing.
·
Tooth are rooted into each separate socket in the
gum.
·
Mouth contain set of teeth as:- upper
and lower jaw.
·
There are two kind of teeth milk teeth and
permanent teeth
·
First set of teeth grows during infancy and fall off at the age between six to eight years. These are called milk
teeth.
· The second set teeth which replaces them are the permanent teeth. The permanent teeth may exist throughout life or fall off during old age or due to some dental disease.
·
Each
jaw contains :- Four Incisors, two Canine,four Premolar and six Molars
·
Mouth has the salivary glands that secrete
saliva.
The food pipe/
·
The swallowed food run through the food pipe or
esophagus.
·
The food pipe passes along the neck and the chest.
·
Food is pushed downward by movement of the wall of
the food pipe.
The stomach
·
The stomach is a thick-walled bag. It has shape like a flattened J and is the widest part of the alimentary canal.
· It receives food from the food pipe and ends into the small intestine .
· The inner lining of the stomach secretes hydrochloric acid and digestive juices, mucous.
·
The mucous help to protects the lining of the stomach.
· The acid kills many kinds bacteria which enter along with the food and makes acidic medium in the stomach and also helps the digestive juices to act.
·
The digestive juices help to break down the proteins
into simpler substances.
The small intestine
·
The small intestine is coiled type structure and is
about 7.5 meters long.
· It receives secretions from the the pancreas & liver .
·
The partly digested food when reaches the lower
part of the small intestine , intestinal juice completes the digestion
of all components of the food.
·
The carbohydrates convert 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 (nutrient) now pass into the blood
vessels in the wall of the intestine. This process is known as absorption.
·
The inner walls of the small intestine contains thousands of finger-like outgrowths. It is called villi (singular villus).
·
The villi increase the surface area for
absorption of the digested food.
·
The function of surface of villi is absorbs the digested
food materials.
·
Assimilation is the process of movement of
digested food molecules into the cells of the body where they are used.
Large intestine
·
The large intestine is shorter as well as wider than
small intestine.
·
It is
approximately 1.5 metre in length.
·
It has function to absorb water and some salts
from the undigested food material.
·
The undigested waste passes into the rectum and
remains there as semi-solid faces.
· Time-to-time, the faecal matter is removed out through the anus . It is called egestion.
DIGESTION IN GRASS-EATING ANIMALS
· Grass-eating animals swallow the grass quickly and store partially digested it in a part of the stomach called rumen.
· Partially digested is called cud.
·
Further the cud returns to the mouth in small
lumps and the animal chews it.
·
The process is known rumination and these
animals are known as ruminants.
·
The grass contain higher amount of cellulose, a type of
carbohydrate.
·
In ruminants like deer & cattle etc. bacteria
present in rumen helps to digestion of cellulose. Many animals, such as humans, cannot digest cellulose.
· Animals like rabbit, horses, etc., contain a large sac-like structure called Caecum between the esophagus and the small intestine.
·
The cellulose that food contain is digested here by
the action of certain bacteria which are not present in humans.
FEEDING AND DIGESTION IN AMOEBA
·
Amoeba is a kind of microscopic single-celled organism
found in pond water.
·
Amoeba contains a cell membrane, a rounded, dense
nucleus and many small bubble-like vacuoles in its cytoplasm.
·
Amoeba frequently changes its shape and position.
· It has finger-like projections, called pseudopodia or false feet for movement and capture of food.
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