The human digestive system consists of thegastrointestinal tractplus the accessory organs of digestion (thetongue,salivary glands,pancreas,liver, andgallbladder).[1]In this system, the process ofdigestionhasmany stages, the first of which starts in themouth. Digestion involves the breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body.Human digestive systemHuman.
digestive system Chewing, in which food is mixed withsalivabegins the process of digestion. This produces aboluswhich can be swallowed down theesophagusand into thestomach. Here it is mixed withgastric juiceuntil it passes into theduodenumwhere it is mixed with a number ofenzymesproduced by thepancreas. Saliva also contains acatalyticenzymecalledamylasewhich starts to act on food in the mouth. Anotherdigestive enzymecalledlingual lipaseis secreted by some of thelingual papillaeon the tongue andalso fromserous glandsin the main salivary glands. Digestion is helped by themasticationof food by theteethand also by themuscular actionsofperistalsisandsegmentation contractions.Gastric juicein the stomach is essential for the continuation of digestion as is the production ofmucusin the stomach.Peristalsis is the rhythmic contraction ofmusclesthat begins in the esophagus and continues along the wall of the stomach and the rest of thegastrointestinal tract. Thisinitially results in the production ofchymewhich when fully broken down in thesmall intestineis absorbed aschyleinto thelymphatic system. Most of the digestion of food takes place in the small intestine. Water and somemineralsare reabsorbed back into the blood in the colon ofthelarge intestine. The waste products of digestion (feces) aredefecatedfrom theanusvia therectum.
There are several organs and other components involved in the digestion of food. The organs known as theaccessory digestive glandsare theliver,gall bladderandpancreas. Other components include themouth,salivary glands,tongue,teethandepiglottis.The largest structure of the digestivesystemis thegastrointestinal tract(GI tract). This starts at the mouth and ends at theanus, covering a distance of about nine metres.The largest part of the GI tract is the colon orlarge intestine. Water is absorbed here and the remaining wastematter is stored prior todefecation. Most of the digestion of food takes place in thesmall intestine.A major digestive organ is thestomach. Within itsmucosaare millions of embeddedgastric glands. Their secretions are vital to the functioning of the organ.There are many specialisedcellsof the GI tract. These include the various cells of the gastric glands,taste cells,pancreatic duct cells,enterocytesandmicrofold cells.Some parts of the digestive system are also part of theexcretory system, including the large intestine.
Writen by / mahmoud khalid
