The Digestive SystemThe digestive s

The Digestive System

The digestive system consists of the digestive tract and digestive glands. The digestive tract is some 8-10 m long and is divided into the following parts: oral cavity, pharynx, oesophagus, stomach, small intestine and large intestine. The structures of the different parts of the tract have some special features.

The wall of the greater part of the digestive tract consists of three coats: internal - mucous, middle - muscular, and the external - serous. The mucous coat is lined with the epithelium outside which is a connective tissue with a thin layer of smooth muscle fibres. The mucous coat is pink in colour because it has many blood vessels. The numerous small glands in this coat secrete a viscous coat of the digestive tract. It facilitates the movement of food and protects the mucous coat from the damage by solid particles of food and various chemical substances. One must remember that the mucous coat of the digestive tract begins with the esophagus, contains lymph nodules which also have a protective function.

The greater part of the muscular coat of the digestive tract consists of two layers: an internal layer with circular muscle fibres and an external layer with longitudinal muscle fibres. The wall of the pharynx and the superior part of the esophagus, and the tongue and the soft palate all contain striated muscle tissue. It is the muscular coat of the other parts of the digestive tract that consists of smooth muscle tissue. Contractions of the muscular coat move food along the digestive tract.

The serous coat that covers the digestive organs in the abdominal cavity is called the peritoneum. The peritoneum has two layers, visceral and parietal. In the esophagus the serous layer is lacking and the outer coat is fibrous in nature.

The digestive glands secrete digestive juices that contain enzymes and some other substances which take part in the chemical processes of digestion.

In addition to the small glands in the mucous coat of the digestive tract, there are also large glands: the salivary glands, the liver and the pancreas. Though these glands are situated outside the digestive tract, they communicate with it through ducts.

Any part of the digestive tract and the digestive glands are equipped with nerve fibres and their endings. The nerves of the digestive glands regulate the secretion of digestive juices. It is known that the nervous system not only regulates the activity of each organ, but also coordinates their activities.

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The Digestive SystemThe digestive system consists of the digestive tract and digestive glands. The digestive tract is some 8-10 m long and is divided into the following parts: oral cavity, pharynx, oesophagus, stomach, small intestine and large intestine. The structures of the different parts of the tract have some special features.The wall of the greater part of the digestive tract consists of three coats: internal - mucous, middle - muscular, and the external - serous. The mucous coat is lined with the epithelium outside which is a connective tissue with a thin layer of smooth muscle fibres. The mucous coat is pink in colour because it has many blood vessels. The numerous small glands in this coat secrete a viscous coat of the digestive tract. It facilitates the movement of food and protects the mucous coat from the damage by solid particles of food and various chemical substances. One must remember that the mucous coat of the digestive tract begins with the esophagus, contains lymph nodules which also have a protective function.The greater part of the muscular coat of the digestive tract consists of two layers: an internal layer with circular muscle fibres and an external layer with longitudinal muscle fibres. The wall of the pharynx and the superior part of the esophagus, and the tongue and the soft palate all contain striated muscle tissue. It is the muscular coat of the other parts of the digestive tract that consists of smooth muscle tissue. Contractions of the muscular coat move food along the digestive tract.Серозный слой, который охватывает органы пищеварения в брюшной полости, называется брюшина. Брюшина имеет два слоя, висцеральной и париетальной. В пищевод серозный слой отсутствует, и наружный слой волокнистой в природе.Пищеварительных желез секретируют пищеварительные соки, которые содержат ферменты и некоторые другие вещества, которые принимают участие в химических процессах пищеварения.В дополнение к малых желез в слизистую пищеварительного тракта, есть также большие желез: слюнных желез, печени и поджелудочной железы. Хотя эти железы находятся за пределами желудочно-кишечного тракта, они общаются с ним через вентиляционные каналы.Любая часть пищеварительного тракта и пищеварительных желез оснащены нервных волокон и их окончаний. Нервы пищеварительных желез регулируют секрецию пищеварительных соков. Известно, что нервная система не только регулирует деятельность каждого органа, но и координирует их деятельность.