Answer:
The various processes involved in the digestion of human being
are:
(i) Ingestion: Through the help of mouth human
beings ingest food
(ii) Digestion: The teeth helps in physical
digestion of food. In mouth there are salivary glands, which secretes saliva,
in which salivary amylase enzyme is present which digest the starch present in
food into maltose sugar, i.e., the digestion of carbohydrate starts from mouth
itself. Mouth opens into a small funnel-shaped area called pharynx which leads
to a long tube called oesophagus, whose wall is highly muscular. When the
slightly digested food enters into oesophagus the contraction and expansion
movement of its wall, takes place, which is known as peristaltic movement. This
movement helps the food to move towards the stomach. Usually, in oesophagus
there is no digestion of food. From the oesophagus the food enters into the
stomach. In the stomach there is secretion of gastric juices which is a mixture
of hydrochloric acid, pepsin (protein digesting enzyme) and mucus. Now, the
partially digested food enters from stomach into the small intestine's wider
part which is known as duodenum and the remaining part of the small intestine
is termed as ileum. The duodenum, receives secretions of two glands, i.e.,
liver and pancreas. Liver secretes bile pigments and pancreas secretes
pancreatic juice which digestes the proteins, carbohydrates and emulsified
fats. Here the digestive enzymes are amylase, maltose and invertase for
digesting the carbohydrates, trypsin for proteins and lipase for fats. Thus,
food is completely digested in ileum part of small intestine.
(iii) Absorption: Now, the food enters from duodenum
into ileum part of small intestine where millions of finger-like projections
known as villi are present which absorb the food.
(iv) Assimilation: The blood carries the digested
and dissolved food to all parts of the body, where it is assimilated into the
cells which is used for obtaining energy as well as for growth and repair of
the body.
(v) Egestion: The undigested food enters into the
large intestine's wider part, where water is absorbed from the undigested food
and the food becomes solid. Now, this solid undigested food enters the last
part of large intestine known as rectum through which it moves out from the body.
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