Answer / guest

The long tube beginning at the mouth and ending with the
anus where waste products are expelled is the digestive
system in man. This long tube is called the food canal or
alimentary canal. It is nearly 30ft long and lies coiled on
the body. It is names in some parts and wider at other. It
is known by different names in different parts of the body.
This food canal or the alimentary canal is the chemical
laboratory of the body where all sorts of chemical changes
take place.
The first process of digestion begins in
the mouth, where the food is cut into small bits and chewed
almost to a past, simultaneously, saliva is poured over it
by the glands, which acts as a chemical agene. As the food
does not stay in the mouth very long it undergoes little
chemical change.

The second stage of digestion takes place
in the stomach, where the alimentary canal is wider. It is
actually flexible and expands when more food enters it. The
food stays here for a longer time. The tiny stomach glands
pure he gastric juice over the food and the food is
thoroughly mixed with the gastric juice by the action of the
muscular walls of the stomach which contract and relax
slowly and repeatedly. The gastric juice acts only on the
proteins and digests most of them. But the digestion is not
yet complete and the food passes slowly into the next part
of the canal known as small intestiners.

The third stage of digestion takes
place in the small intestines, where the proteins and starch
and the greater part of digestion of fats and carbohydrates
takes place. The food is subjected to the vigorous action of
number of digestive juices-pancretaic juice, the which acts
on all kinds of nutritive constituents, viz. proteins,
carbohydrates and fats. Bile acts only on fats. The
proteins, carbohydrates and fats are all attacked by these
juices and digested. The intestinal juice gives a finishing
tough to the digestion of proteins intestinal juice gives a
finishing tough to the digestion of proteins and
carbohydrates. The digested products are all assimilated in
the blood. The contents of the small of the small intestine
pass into the large intestine.
The last stage of digestion takes
place in the large intestines. Most of the nourishment of
the food has already been absorbed by the time it reaches
the large intestines. Here water and a little of the
remaining good are absorbed. The undigested material
collects in the large intestine and at intervals in
eliminated by the movements of the bowels.

Answer / abhishek dash

The digestive system comprises of the alimentary canal and it's associated glands. The parts of the alimentary canal are 1)mouth 2)pharynx 3)oesophagus 4)Stomach 5)intestines 6)anal canal.

The mouth cavity is also called as the Oral orifice. It is bound by the lips on the upper side and the lower side. Inner to the mouth cavity is present the buccopharyngeal cavity. This cavity is made up of Buccal cavity and pharyngeal cavity. The buccal cavity contains Teeth, Palate, Tongue, and the Salivary Glands. The teeth help in chewing the food, tongue helps in mixing the food with the saliva, and salivary glands secrete the saliva.

The roof of the buccal cavity is called the Palate, which is divided into anterior hard palate and posterior soft palate. The hard palate has a mucous membrane which is folded into several ridges called rugae. The soft palate is folded to form a finger like projection called uvula which closes the internal nostrils while swallowing.

The pharyngeal cavity is divided into two openings posteriorly. The upper one is called opening of Gullet and the lower one, opening of Glotis. The opening of Glotis is guarded by a cartilagenous flap called epiglotis which closes the Glotis while swallowing.

The oesophagus is a muscular tube which is 25 cm wide. No digestion takes place in the oesophagus, and it acts as a passage for the food from the buccopharyngeal cavity to the stomach.

Stomach is otherwise called as the gaster. It is divided into 4 parts- 1)Cardia 2)Fundus 3)Main body and 4)Pylorus. In the stomach, the gastric juice acts on the food in an acidic medium.

The small intestine is divided into 3 parts- 1)Duodenum 2)jejunum 3)ileum. The small intestine is about 6 m long and about 2.5 cm wide. The common bile duct from liver and gall bladder and the pancreatic duct open into the duodenum by a common aperture called the Papillae of Vater. The food is digested in a basic medium in the duodenum.

The large intestine is 1.5 m long and 6.5 cm wide. It is divided into four regions- 1)caecum 2)Vermiform apendix 3)colon 4)Rectum. The digested food is absorbed in the large intestine. The colon of the large intestine is divided into ascending colon, transverse colon and descending colon. The descending colon ends with the rectum where the undigested food is stored.

Later on the undigested food is passed out through the anus.

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