6. Nutrition in human beings - pharynx, oesophagus, stomach

The pharynx is divided into three parts:

 

a. Nasopharynx - Lies behind the nasal cavities and above the soft palate. The auditory tube or eustachian tube connects the nasopharynx with the ear.

 

b. Oropharynx - Lies behind the buccal cavity.

 

c. Laryngopharynx - Inferior part of the pharynx. It is a common passage for food and air.

 

Oesophagus also called the food pipe, is about \(25\) \(cm\) long. It is a highly muscular tube that is lined by stratified squamous epithelium. The oesophagus opening is called the gullet. It lies behind the trachea and the heart. It is composed of three parts:

 

a. Cervical part

  

b. Thoracic part

 

c. Abdominal part

 

It passes through the diaphragm and opens into the stomach. The oesophagus transfers the food from the pharynx to the stomach by peristaltic movements.

It is a J - shaped sac or organ, which is the widest organ of the alimentary canal. The longitudinal folds of the stomach are formed of the mucous membrane. The stomach contains peptic or chief cells, oxyntic cells and mucous cells.

 

The stomach has four parts:

 

a. Cardiac part - Present near the heart and thus called cardiac part. The gastroesophageal sphincter lies in the opening between the esophagus and stomach.

 

b. Fundus - Fundus is commonly filled with air or gas.

 

c. Body - The body is the main part of the stomach.

 

d. Pyloric part - The posterior part of the stomach, which is divided into the pyloric antrum and pyloric canal. Pyloric canal opens into the duodenum.