Describe the digestion of food in stomach.

Explanation

Mammalian (human) alimentary canal comprises mouth , buccal cavity , pharynx , oesophagus stomach , small intestine (duodenum , jejunum and ileum) , large intestine ( caecum , colon and rectum ) and anus.

Buccal cavity. The mouth is a slit-like aperture bounded by two lips. It leads to buccal cavity. Its roof is formed of hard palate, continues as soft palate, and hangs as uvula. The sides of buccal cavity are formed by cheeks. At the floor is present a musculo-sensory organ called tongue. Teeth are present for mastication of food.
Pharynx. It is a vertical tube. It is a cross passage for food and air. It has uvula and epiglottis which closes the internal nares and glottis respectively during swallowing of food to ensure the passage of food into oesophagus (food pipe).
Oesophagus. It is a 25 cm long narrow muscular straight tube. It runs downward through the chest behind heart and passes through the diaphragm into the abdomen. Here, it opens into stomach. Oesophagus propels the swallowed food into stomach.
Stomach. It is a sac-like structure situated in the upper part of abdominal cavity below the diaphragm. Large part of this sac is situated left of the median line.
Small Intestine. It is the longest part of alimentary canal. It is thin-walled and highly coiled tubular structure. It is about 3-3.5 metres long and occupies most part of abdominal cavity. It is coiled upon itself. It is differentiated into three regions, viz., duodenum, jejunum and ileum. Its inner lining is thrown into numerous villi.
Large intestine. The large intestine is about 1.5 metres long. It is divided into following parts, i.e. the vermiform appendix, the colon and the rectum. Caecum is a blind tube and represented by vermiform appendix (5-8 cms) and is present below the junction of small and large intestine. Rectum is the last part and opens to the outside by anus guarded by anal sphincter.