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ГоловнаІноземна мова - Англійська, Німецька та інші → Digestive system - Реферат

Digestive system - Реферат

The digestive system consists of the alimentary canal and accessory organs.
The alimentary canal includes the mouth, pharynx, esophagus, stomach, small intestine, large intestine and rectum.
The accessory organs are the teeth, tongue, salivary glands, hard arid soft palates, liver, gallblader and pancreas.
The organs of the digestive system are covered with the serous coat, the peritoneum. It has the visceral and parietal layers.
Important structures of the mouth arc the tongue which contains the end organ for taste and the teeth which divide and mix the food. The oral and laryngeal portions of the pharynx serve as a channel for the passage of food and air. Our food passes through it from the mouth to the esophagus and air from the nasal pharynx to the larynx.
The esophagus conveys food from the pharynx to the stomach. The stomach is a dilated portion of the alimentary canal. It lyes in the upper abdomen under the diaphragm. It is a retaining and mixing reservoir in-which the process of digestion begins. The glands of the fundus and body are very important in the secretion of gastric juice
The small intestine is a thin-walled muscular tube about 7 meters long. It has three portions, such as duodenum, jejunum and ileum.
The large intestine is about 1,5 meters long and includes caecum, colon and rectum.
The large salivary glands consist ofthree pairs of glands which open into the mouth.
The liver secrets bile and fulfils many other important functions, such as stimulation of red bone marrow, production of fibrinogen, glycogenetic function and others. The pancreas forms an external secretion important in digestion and an internal secretion, insulin, concerned with carbohydratic metabolism.
The "medicine" of prehistoric man was probably based upon an animistic attitude towards disease. In his view, desease was caused by the evil, influence of an enemy, a demon, a god, an animal and it must be treated by means of dislodging the malevolent cause. Early man may have attributed desease to a separation of soul and body. In any case there doubtless arose a class of men who claimed skill in the art of healing, and whose methods of treatment included dancing, grimacing, sleight-of-hand, and all the tricks of the magician.
In some cases it was necessary to combine physical with psychic methods; of this we have an excellent example in trephining, which originated as a means of permitting the escape of an evil spirit from the head ot the victim, and which gradually became a method of treating fractures of the skull and various intracranial lesions.