Chapter 23 the digestive system: large intestine Flashcards
Where is the large intestine located?
extends from ileum of small intestine to anus as it
mainly surrounds small intestine
What are the functions of the large intestine?
propulsion—through peristaltic actions of muscularis externa
absorption—mainly of water; also salts/electrolytes and vitamins B and K
chemical digestion—by bacteria mainly
defecation—functions with anus to move feces out of body
What is the cecum of the large intestine?
saclike first subdivision; mucosa forms ileocecal valve
What is the appendix?
extends from cecum; contains bacteria; functions in immune system
What is the rectum?
extends down from sigmoid colon to anal canal; 3 internal folds/rectal valves
What are the 4 segments of the colon in the large intestine?
ascending colon—extends superiorly from cecum to right colic/hepatic flexure
transverse colon—extends transversely across abdominal cavity to left colic/splenic flexure
descending colon—extends inferiorly to pelvic cavity
sigmoid colon—forms S shaped part in pelvic cavity extending from descending colon to rectum
What is the anal canal?
last subdivision; narrowed part extending from rectum through anus
What are anal columns?
folds of mucosa joined at anal valves which form anal sinuses
what is pectinate line?
inferior line on which anal valves lie
What is the mucosa layer of the large intestine wall?
inner epithelium mainly simple columnar epithelium forming intestinal crypts/glands made up
mainly of 2 cell types, goblet cells and colonocytes/absorptive cells
What is the submucosa layer of the large intestine wall?
mainly made up of areolar connective tissue
What is the muscularis externa of the large intestine wall?
2 layers—typical inner circular layer
outer longitudinal layer—3 thickened strips, tenia coli, extend from cecum through sigmoid colon;
muscle tone causes sacs/haustra to form
What is the serosa of the large intestine wall?
2 layers—inner areolar connective tissue and outer simple squamous epithelium
epiploic appendages—saclike projections from serosa containing fat
mesenteries—transverse mesocolon, sigmoid mesocolon extend from serosa
What is the function of the anus?
functions in defecation as surrounds anal canal; mainly made up of 2
muscles
internal anal sphincter
inferior smooth muscle thickening of circular layer of muscularis externa of
large intestine
