GRIN APPLE PUBLIC SCHOOL
Science Nutrition in Animals Notes Class -VII
Alimentary canal (digestive tract): 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: the buccal
cavity, foodpipe or oesophagus, stomach, small intestine,large intestine ending in the rectum and
the anus. These parts together form the alimentary canal (digestive tract).
Digestive system: The digestive tract and the associated glands together constitute the digestive
system
Digestive Processes
1) Ingestion: The process of taking food into the body is called ingestion.
2) Digestion: The breakdown of complex components of food into simpler substances is called
digestion.
3) Absorption: The digested food can now pass into the blood vessels in the wall of the
intestine. This process is called absorption.
4) Assimilation the process where digested food molecules are absorbed into the cells and
utilized by the body for various functions, like energy production and building new cells.
5) Egestion: The faecal matter is removed through the anus from time-to-time. This is called
egestion.
Foodpipe: The foodpipe runs along the neck and the chest. Food is pushed down by movement of
the wall of the foodpipe. It is a muscular tube, about 25 cm long, with a sphincter (valve/opening) at
each end.
The stomach:
The stomach is a thick-walled bag. Its shape is like a flattened J 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.
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.
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.
Anus
• The removal of faecal matter from the large intestine occurs through the anus and this
process is called egestion.
Saliva and Salivary glands
• Three pairs of salivary glands are present around the mouth and they pour their secretion,
saliva, into the mouth by salivary ducts.
Gall Bladder
• The gallbladder is a small pear-shaped organ present under the liver, on the right side of the
body.It stores bile juice secreted by the liver.
• Bile plays an important role in the digestion of fats.
Digestion in Grass-Eating Animals
• They swallow the grass very fast and store it in a chamber called Rumen.
• In the rumen, the bacteria partially digest the food, and now it is called as cud.
• This phenomenon is referred to as rumination, and the animals are called ruminants.
• They also have a very long small intestine, which helps in the complete digestion of cellulose,
the main component of grass.
Cud: Partially digested food, returned from the rumen into the mouth, for further chewing is called
cud.
Rumination: Rumination is the process by which the cattle regurgitate previously consumed feed
and chew it again second time.
Amoeba
• Amoeba is a single-celled organism, microscopic in nature, found in pond water.
• Amoeba regularly changes its shape and position.
Process of Digestion in Amoeba
• Amoeba captures the food particles with the help of pseudopodia. The process is called
phagocytosis.
• A food vacuole is thus created with the food material inside.
• Digestive juices are produced into the food vacuole when it is moving through the cytoplasm.
• They act on the food and disintegrate it into simpler substances, and the digested food is
then absorbed.
• Finally, the food vacuole opens to the outside and undigested food is released into the
surrounding water
