Page 213 - Biology_F5

Biology for Advanced Level Secondary Schools

Bile duct
Oesophagus
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Stomach
Hepatic portal vein Pancreas
Pancreatic ducts Jejunum
Duodenum
Hepatic portal Ileum
vein from rectum
Rectum Chain of lymph nodes
Colon covering hepatic portal vein
Spermatic cord Tributary of hepatic portal
vein in mesentery
Caecum

Appendix

Figure 3.73: The digestive system of a mouse

The liver has four lobes; one on the left, two which pass through the numerous small
on the right, and one in the centre. The liver pancreatic ducts that enter the duodenum for
has two functions in digestion: secretion digestion. The main functions of the small
of bile and receiving the absorbed food intestine are digestion and absorption of
from the small intestine through hepatic the products of digestion. Duodenum is the
portal vein. It lacks gall-bladder, instead first part of the small intestine, connected
the cystic ducts from the liver lobes join to the stomach by a pyloric sphincter;
to form the bile duct which conveys bile to which receives and digests the released
the duodenum. The hepatic portal vein runs food from the stomach using bile and
from the liver to the intestines; covered by other digestive juices. Jejunum and ileum
a chain of lymph nodes and form branches are similar in both structure and function.
in the mesentery (plural mesenteries) and They are both involved in digestion of
other parts of the intestine. food as well as absorption of nutrients. The
overall functions of the large intestine is to
The mesenteries are the continuous set of complete absorption of water mainly from
support tissues, which attach the intestines undigested food particles, manufacture of
to the posterior wall of the abdomen. They certain vitamins, formation of feaces and
support efficient digestion and maximum expelling faeces from the body through
absorption of digested food by helping in the anus. The main role of caecum is the
storage of fat and allowing lymphatics, blood absorption of water and salts remained
vessels, and nerves to supply the intestines. after completion of digestion in the small
The pancreas secretes digestive enzymes, intestine, as well as mixing and lubricating

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