life process for class 10 science by shailendra solanki

2. Human beings are
heterotrophic , omnivorous
organisms. Carbohydrates ,
proteins , fats , vitamins and
minerals are essential
components of human diet.
The process of nutrition
involves ingestion , digestion ,
assimilation, absorption and
egestion .

3. The human digestive system consists of the
alimentary canal and secretory glands. It
consists of the buccal cavity, oesophagus ,
stomach , small intestine , large intestine
ending in rectum and anus.
The main digestive glands which secrete
digestive juices with digestive enzymes are
the salivary glands , the liver and the
pancreas. The stomach wall and the wall of the
small intestine also secrete digestive juices.

6.  BUCCAL CAVITY :After the food is ingested through mouth,
it is crushed, softened and partially digested in the buccal
cavity.
 The buccal cavity has four types of teeth for crushing the food:
Incisors for cutting and biting ,canines for piercing and tearing
, premolars and molars for grinding. The teeth cut the food
into small pieces and makes it soft for easy swallowing.
 The tongue in the buccal cavity mixes saliva with the food and
helps in swallowing the food. It also helps in tasting the food.
 The buccal cavity has three pairs of salivary glands. The
salivary glands secrete saliva through their ducts. The saliva
contains water , salts and an enzyme salivary amylase. The
salivary amylase splits starch into sugar (maltose). Thus
carbohydrates digestion begins in the buccal cavity itself.
 Starch------------------salivary amylase--------------- Maltose (sugar)

7. OESOPHAGUS: It is a long muscular
tube which carry the food from
pharynx to the stomach. The wall of
the oesophagus is muscular. It
pushes the food forward into the
stomach by contraction and
expansion of it’s muscles. Such
movements are called peristaltic
movements. These occur all along the
alimentary canal.

8. STOMACH : The stomach is a large muscular sac present on the left side of the
abdomen. The partially digested food reaches into stomach from buccal cavity
through pharynx and oesophagus.
The stomach severs following functions:
 Storage of food
 Mechanical churning of food
 Partial digestion: the gastric glands present in the walls of the stomach secret HCl
, protein digesting enzyme and mucous.
HCl kills the microbes entering the system along with food, also it creates an acidic
medium which facilitates the action of enzyme pepsin.
Protein digesting enzyme pepsin breaks down proteins into peptones. Gastric
juices also contain gastric lipase which partially break down lipids.
Mucous covers the inner lining of the stomach and protects it from corroding
action of HCl and pepsin enzyme.

9. SMALL INTESTINE: It is the longest part of the alimentary canal. It’s length varies
in different animals depending on the type of food they eat . It is longer in
herbivores and shorter in carnivores.
The small intestine is the site of the complete digestion of carbohydrates, proteins
and fats.
It receives secretions from liver and pancreas for this purpose through a common
duct formed by the union of bile duct and pancreatic duct.
The liver secretes the bile juice and it is stored in the gall bladder . The bile helps in
breaking the fat molecules into small globules so that it becomes easy for the
enzymes to act on them . Also bile makes the acidic food coming from the stomach,
alkaline for the pancreatic juices to act.
The pancreas secretes pancreatic juice which contain various enzymes . The
pancreatic amylase cause break down of starch, pancreatic lipase breaks down
lipids and trypsin causes digestion of proteins.
The walls of the small intestine contain glands which secrete intestinal juice. The
enzymes present in it finally convert the proteins into amino acids , carbohydrates
into glucose and fats into fatty acids and glycerol.
The digested food is taken up by the walls of the small intestine.

10. The digested food is taken up by the walls of the small intestine. The inner lining of
the small intestine is has numerous finger like projections called villi which increase
the surface area for absorption.
The villi are richly supplied with blood vessels which take the absorbed food to each
and every cell of the body , where it is utilised for obtaining energy , building up of
new tissues and the repair of the old tissues.

11. LARGE INTESTINE : The
undigested and unabsorbed food
is sent into the large intestine
where more villi absorb water
from this material . The rest of
the material is removed from the
body via anus. The exit of this
waste material is regulated by
anal sphincter.