large intestine

• large intestine is the portion of the digestive tract extending from the ileocecal junction to the anus
• cecum is the proximal end of the large intestine, where it meets the small intestine
• vermiform appendix (worm-shaped) is a smaller, blind tube
• colon, about 1.5–1.8 m long, consists of four parts: the ascending colon, transverse colon, descending colon, and sigmoid colon
• ascending colon extends superiorly from the cecum and ends at the right colic flexure
• transverse colon extends from the right colic flexure to the left colic flexure
• descending colon extends from the left colic flexure to the superior opening of the true pelvis
• sigmoid colon forms an S-shaped tube that extends into the pelvis and ends at the rectum
• forms three bands, called the teniae coli
• Contractions of the teniae coli cause pouches called haustra
• Small, lipid-filled connective tissue pouches called omental appendages
• numerous, straight, tubular glands called crypts
• rectum is a straight, muscular tube that begins at the distal end of the sigmoid colon
• last 2–3 cm of the digestive tract is the anal canal and ends at the anus
• canal can become enlarged or inflamed, a condition known as hemorrhoids
• An abnormally frequent discharge of watery feces is called diarrhea
• Bacterial actions in the colon produce gases called flatus
• strong contractions, called mass movements.
• Gastrocolic reflexes are initiated by distension in the stomach
• duodenocolic reflexes are initiated by distension in the duodenum
• defecation reflex consists of local and parasympathetic reflexes
• anal sphincters prevent defecation