Digestive System and Digestion

The human body needs energy for its functioning. Our body assimilates proteins, fats, carbohydrates and other nutrients. The digestion of the starchy parts of food begins in the mouth where it is moistered with saliva. In the tongue papillae (lingual papillae) there are the taste receptors. Over the mucous membrane of the oral cavity there are many tactile, temperature and pain receptors. The teeth, the gums, the soft and hard palates and the salivary glands are important structures located in the oral cavity. In the oral cavity the food must be well chewed between the teeth. Then the food passes through the pharynx (throat) and down through the esophagus (gullet) into the stomach which is a dilated portion of the alimentary truct pyriform in shape. The stomach is composed of a fundus (upper part), a body (middle part) and an antrum (lower, distal part). The upper opening of the stomach is called the cardiac sphincter and the lower one – pyloric. The folds in the mucous membrane lining the stomach are called rugae.

In the stomach the components of food are dissolved and hydrolysed by enzymes of saliva and gastric juice. Different gastric glands are found in the stomach. They produce hydrochloric acid and pepsin to digest food. The gastric juice secreted by the stomach possesses antibacterial activity. Pepsin converts proteins to smaller substances called peptones. But food does not enter the bloodstream through the stomach.

Further digestion and absorbtion of food into the blood takes place in the small intestine. After portions of the stomach contents enter into the duodenum they turn acid, but then the reaction rapidly changes because the hydrochloric acid of the gastric juice is neutralized by the bile, the juice of the pancreas, the juice of the duodenal glands and intestinal crypts. The bile comes from the liver and gallbladder by means of special ducts. The pancreatic juice, a colourless clear fluid contains sodium, potassium chlorides and is rich in enzymes which digest proteins, fats and carbohydrates.

Food passes in peristaltic waves from the duodenum to the jejunum and the ileum, which is attached to the large intestine. The entire small intestine has many projections called villi. It is in the small intestine where the so-called cavital.and membrane hydrolyses of nutrients takes place. The products of digestion are absorbed into the blood and lymph.

The remaining part of food (the fluid by-products of digestion) from the small intestine pass into the large intestine which consists of cecum, colon (ascending, transverse, descending), sigmoid colon and rectum. The vermiform appendix hags from the cecum. The rectum ends in the anus. The process of digestion is completed in the large intestine by the absorption of water. The unabsorbed and undigested components of food, the remains of the digesting fluids are evacuated from the body.

Post-text assignments

1 Choose the anatomic terms for the following:

1 The organ of chewing and tasting. 2 The movable muscular structure attached to the floor of the mouth; an important organ in the articulation of speech sounds. 3 The muscular membranous cavity leading from the mouth and nasal passages to the larynx and esophagus. 4 The roof of the mouth. 5 The tube through which food passes from the pharynx to the stomach. 6 Any of numerous hairlike or fingerlike vascular processes in the small intestine. 7 The first section of the small intestine between the stomach and the jejunum. 8 A large, elongated gland: some cells (beta cells) islets of Langerhans in the gland produuce the hormone insulin. 9 The largest glandular organ which secretes bile. 10 The organ for containing food and digestion of it.

(a – palate; b – duodenum; c – stomach; d – pharynx; e – esophagus; f – mouth; g – tongue; h – liver; i – pancreas; j – villus (pl villi)

2 Say what organ is spoken about:

a) This organ is the largest gland in the human body. It is in the upper part of the abdominal cavity under the diaphragm in the right side of the abdomen. Its upper surface is convex. This organ consists of small lobules connected together by connective tissue, different vessels and nerves.

b) This organ is pyriform in shape. It is a dilated portion of the alimentary canal. It is in the upper part of the abdomen under the diaphragm. The liver is above this organ, and the colon is below it. The pancreas is behind this organ.

3 Translate the following without consulting the dictionary:

1 Digestive juices are secreted into the alimentary canal by various glands and accessory organs. 2 The digestive system includes the organs that promote digestion and absorb the products of this process. 3 The alimentary canal includes the mouth, pharynx, esophagus, stomach, small intestine and large intestine. 4 The accessory organs include the salivary glands, liver, gallbladder and pancreas.