Anatomy and physiology

 

Anatomy and Physiology

The Human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. (The "digestive system" is a broader term that includes other structures, including the accessory organs of digestion). In an adult male human, the gastrointestinal (GI) are 5 metres (20 ft) long in a live subject, or up to 9 metres (30 ft) without the effect of muscle tone, and consists of the upper and lower GI tracts. The tract may also be divided into foregut, midgut, and hindgut, reflecting the embryological origin of each segment of the tract. The GI tract releases hormones as to help regulate the digestion process. These hormones, including gastrin, secretin, cholecystokinin, and grehlin, are mediated through either intracrine or autocrine mechanisms, indicating that the cells releasing these hormones are conserved structures throughout evolution.

The lower gastrointestinal tract includes most of the small intestine and the entire intestine. According to some sources, it also includes the anus.  anus.   



Bowel or intestine Small intestine, which has three parts: o    Duodenum - Here the digestive juices from pancreas and liver mix together   Jejunum - It is the midsection of the intestine, connecting duodenum to ileum.   Ileum - It has villi in where all soluble molecules are absorbed into the blood. Large intestine, which has three parts: o    Cecum (the vermiform appendix is attached to the cecum).   Colon (ascending colon, transverse colon, descending colon and sigmoid flexure)  flexure)  









 



 



Anus

Rectum

The large intestine is the second-to-last part of the digestive system  —  the final stage of  the alimentary canal is the anus  —  in vertebrate animals. Its function is to absorb water from the remaining indigestible food matter, and then to pass useless waste material from the body. This article is primarily about the human gut, though the information about its processes are directly applicable to most mammals. The large intestine consists of the cecum and colon. It starts in the right iliac region of the pelvis, just at or below the right waist, where it is joined to the bottom end of the small intestine. From here it continues up the abdomen, then across the width of the abdominal cavity, and then it turns down, continuing to its endpoint at the anus.

 

The large intestine is about 1.5 metres (4.9 ft) long, which is about one-fifth of the whole length of the intestinal canal. In Terminologia Anatomica the large intestine includes the cecum, colon, rectum, and anal canal. However, some sources exclude the anal canal. Function and relation to other organs

The large intestine takes about 32 hours to finish up the remaining processes of the digestive system. Food is no longer broken down at this stage of digestion. The large intestine absorbs water and electrolytes from the approximate 1.5L of chyme passing through the ileocecal valve daily. The colon absorbs vitamins which are created by the colonic bacteria - such as Vitamin K (especially important as the daily ingestion of Vit. K is not normally enough to maintain adequate blood coagulation), Vitamin B12, thiamine and riboflavin. It also compacts feces, and stores fecal matter in the rectum until it can be discharged via the anus in defecation. The large intestine differs in physical form from the small intestine in being much wider and in showing the longitudinal layer of the muscularis have been reduced to 3 strap-like structures known as the taeniae coli. The wall of the large intestine is lined with simple columnar epithelium. Instead of having the evaginations of the small intestine (villi), the large intestine has invaginations (the intestinal glands). While both the small intestine and the large intestine have goblet cells, they are abundant in the large intestine. The vermiform appendix is attached to its posteromedial surface of the large intestine. It contains masses of lymphoid tissue. It is a part of mucosa-associated lymphoid tissue, which gives the appendix an important role in immunity. Appendicitis is the result of a blockage that traps infectious material in the lumen. The appendix can be removed with no damage or consequence to the patient. The large intestine extends from the ileocecal  junction to the anus and and is about about 1.5m long. long. On the surface, surface, bands of longitudinal longitudinal muscle fibers called taeniae coli, each about 5 mm wide, can be identified. There are three bands, and they start at the base of the appendix and extend from the cecum to the rectum. Along the sides of epiploicae) the taeniae,are tagsfound. of peritoneum filled with fat, called epiploic appendages (or appendices The sacculations, called haustra, are characteristic features of the large intestine, and distinguish it from the small intestine. It is also found in the digestive system. Parts and location

Parts of the large intestine are: Cecum  –  the first part of the large intestine    

 



 

Taeniae coli  –  three bands of smooth muscle Haustra  –  bulges caused by contraction of taeniae coli Epiploic appendages  –  small fat accumulations on the viscera

 

Locations along the colon are:          

 

  



   



The ascending colon The right colic flexure (hepatic) The transverse colon The transverse mesocolon The left colic flexure (splenic) The descending colon The sigmoid colon  –  the v-shaped region of the large intestine