Answer:
Alimentary canal is a long tube with muscular walls, glandular epithelium lining, it opens out from the upper and lower end and lies in the abdomen in a coiled form. It consists of several organs:- Mouth, vestibule, oral cavity, pharynx, Oesophagus, stomach, small intestine, large intestine and anus.
Oral or buccal cavity: It is large space and consists of hard and soft palate, tongue, teeth and salivary glands which secretes salivary amylase enzyme which helps in the breakdown of food into the fine particles or starch into simple sugar by the mastication process.
Pharynx: It is 12cm long. It functions as the part of the digestive tract which serves as the passageway for the food from the buccal cavity to the oesophagus.
Oesophagus: It is 25cm long, narrow, muscular or straight tube lined by stratified squamous epithelium which contains mucous gland. It plays the important role to convey the food by the peristalsis movement from pharynx to the stomach.
Stomach: Stomach is wide, J- shaped, distensible and placed on the left side in the upper part of the abdomen. It has 4 parts:- Cardiac part, Fundus, body and Pyloric part. It helps in the storage of food, mechanical churning of food. It contains gastric glands which secretes HCL, pepsin and mucus which helps in the digestion of food.
Small intestine: it is 6m long, highly coiled and narrow tube. It is the longest part of the alimentary canal and consists of three parts:- Duodenum, Jejunum and Ileum. Small intestine helps in the absorption of the digested food due to numerous folds and completion of digestion. It secretes some hormones like secretin, villikinin, enterocrinin etc.
Large intestine: It is shorter than the small intestine but wider than the small intestine and present in the form of question marks. It contains three regions:- Caecum, colon and rectum. It helps in the absorption of water; formation, storage and elimination of faeces; production of mucus for the lubrication; digestion; absorption; and excretion.
Anus: it lies at the base of abdomen in a fold between the nates.
Diagram:
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