Digestive system Digestive system consists of a

Digestive system

Digestive system consists of a chain of organs which are connected to each other with a tube. This tube twists from mouth to the end part i. e. anus. There additional organs as well which help to split food and get it absorbed in the body. The digestive tract consists of the organs in the pattern given below pattern. They are namely: Mouth Esophagus Stomach Small intestine Large intestine Rectum Anus

The interior of the above organs have a coating which is known as mucosa. This mucosa has small gland which produces juice and this juice helps in the digestion of food. All these organs also have a coating of soft muscles. The function of these soft muscles is to break the food and push it from one organ to the other organ. Digestive juice is produced by liver and pancreas. Juices are passed from ducts (which are tiny tubes) to the intestines. But before it is passed on to the intestines the gall bladder store up the juice till it is required.

Two other important systems that perform main role in the digestive system are nervous system and circulatory system.

Structure of the Digestive Tract • Mucosa • Submucosa • Muscularis • Serosa

Human digestive system diagrams

The digestive system begins in the mouth.

Tongue

Parotid Gland Branched acinar gland. Its secretory portion is composed exclusively of serous cells. Containing secretory granules that are rich in proteins and have a high amylase activity. Intercalated and striated ducts are easily observed.

Submandibular (Submaxillary) Gland Branched tubuloacinar gland formed of serous and mucous cells. The serous cells are the main component. Serous cells are responsible for the weak amylolytic activity. The cells that form the demilunes in the submandibular gland secrete the enzyme lysozyme. Striated ducts are easily observed but intercalated ducts are very short.

Sublingual Gland Branched tubuloacinar gland formed of serous and mucous cells. Mucous cells predominate in this gland. Intralobular ducts are not as well developed as in other major salivary glands.

Teeth

Gingiva Mucous membrane firmly bound to the periosteum. Composed of stratified squamous epithelium and lamina propria containing numerous connective tissue papillae. Junctional epithelium bound to the tooth enamel by means of a cuticle that resembles a thick basal lamina and forms the epithelial attachment of Gottlieb. The epithelial cells are attached to this cuticle by hemidesmosomes. Between the enamel and the epithelium is the gingival sulcus.

Teeths and gingiva

Pharynx A transitional space between the oral cavity and the respiratory and digestive systems. Lined by stratified nonkeratinized squamous epithelium in the region continuous with the esophagus Lined by ciliated pseudostratified columnar epithelium containing goblet cells in the regions close to the nasal cavity. Contains the tonsils. The mucosa of also has many small mucous salivary glands in its lamina propria. The constrictor and longitudinal muscles of the pharynx are located outside this layer.

Esophagus

Sto ma ch

Pylorus Has deep gastric pits into which the branched, tubular pyloric glands open. Pyloric glands have longer pits and shorter coiled secretory portions. These glands secrete mucus as well as appreciable amounts of the enzyme lysozyme. Gastrin (G) cells which release gastrin are enteroendocrine cells intercalated among the mucous cells of pyloric glands. Other enteroendocrine cells D cells secrete somatostatin, which inhibits the release of some other hormones, including gastrin.

Small Intestine

Large Intestine

Appendix

Pancreas The pancreas is a mixed exocrine-endocrine gland that produces digestive enzymes and hormones. Enzymes are stored and released by cells of the exocrine portion, arranged in acini. The hormones are synthesized in clusters of endocrine epithelial cells known as islets of Langerhans

Liver The liver is the second-largest organ of the body and the largest gland. The liver is the organ in which nutrients absorbed in the digestive tract are processed and stored for use by other parts of the body. Most of its blood (70 -80%) comes from the portal vein, arising from the stomach, intestines, and spleen; the smaller percentage (20 -30%) is supplied by the hepatic artery. Bile is an exocrine secretion of the liver that is important for toxic substances elimination and lipid digestion. The liver also has the very important function of producing plasma proteins, such as albumin, other carrier proteins, coagulation factors, and growth factors.

The Liver Lobule

Liver Regeneration Despite its slow rate of cell renewal, the liver has an extraordinary capacity for regeneration. The loss of hepatic tissue by surgical removal or from the action of toxic substances triggers a mechanism by which hepatocytes begin to divide, continuing until the original mass of tissue is restored.

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