large intestine

• after food leaves the small intestine, it enters the large intestine

• the large intestine has 3 major sections:

  • cecum

  • colon - ascending colon, transverse colon and descending colon

  • rectum

processes in colon

• 2 major functions of large intestine:

  • absorption of water back into the body

  • removal of waste (feces) through the rectum and anus

• large amounts of bacteria (about 3 pounds worth) are located in the large intestine that help to produce vitamins B and K.

  • strong doses of antibodics can disrupt these bacteria and cause vitamin deficiencies

• The haustra are the small pouches that give the large intestine its lumpy intestine

• Haustral contractions are slow, segmenting movements that last only about 30 minutes after food moves into the large intestine

• mass movements, however, are slower and more powerful movements that push waste towards the rectum 3 or 4 times a day

rectum and anus

• the rectum collects and stores undigested waste and bacteria

• as the rectum fill, pressure is placed on the internal anal sphincter, causing it to relax

• the external anal sphintor, luckily, needs to be voluntarily relaxed to relaese the built up feces through the anus