Page 65 - Biology Form Two
P. 65
Biology for Secondary Schools
3. Digestion begins in the mouth. 8. In the large intestine, water is
The teeth break down food into absorbed from the undigested
small pieces. The salivary gland and indigestible food materials
secretes salivary amylase or releasing the solid materials or
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ptyalin enzyme that begins to faeces.
digest starch.
9. In human beings there is no
4. Food is swallowed and moves diastema. The upper incisors and
through the oesophagus by the canines are missing in ruminants,
periodic contraction and relaxation but they are present in human
of the muscles in the oesophagus beings. The digestive system of
wall. This kind of movement is ruminants normally has bacteria
called peristalsis. that digest cellulose. Human beings
do not have cellulose digesting
5. In the stomach, gastric juice is
produced, which contains various bacteria. In addition, ruminants
substances including hydrochloric have the ability to regurgitate food
acid, pepsin, and rennin enzymes. that is swallowed. This is called
chewing cud. Human beings can
6. In the duodenum, food is mixed not regurgitate swallowed food.
with pancreatic and bile juice.
Bile salts from the bile juice 10. The human digestive system can
facilitate the digestion of fats and be affected by various diseases
oils into smaller droplets through and disorders including dental
emulsification process. caries, heartburn, stomach ulcers,
7. The ileum secretes intestinal indigestion, constipation and
juice which contains enzymes flatulence. Observing health tips
peptidase, lactase, maltase, sucrase and good eating habits are the major
and lipase. The inner wall of the preventive measures for most of
ileum has villi, which are finger- those problems.
like projections that facilitate the
absorption of digested food.
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