LARGE INTESTINE Flashcards

Describe the gross and microscopic anatomy of the large intestine and its function

1
Q

Large intestine

A
  • begins at cecum inferior to ileocecal valve
  • appendix attached to lower end of cecum
  • densely populated with lymphocytes and is a significant source of immune cells
  • ascending colon, right colic (hepatic) flexure, transverse colon, left colic (splenic) flexure, and descending colon frame the small intestine
  • sigmoid colon is S-shaped portion leading down into pelvis
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2
Q

Rectum

A

portion ending at anal canal

has three curves and three infoldings, called the transverse rectal folds (rectal valves)

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3
Q

Anal canal

A
  • final 3 cm of the large intestine
  • passes through levator ani muscle and pelvic floor terminates at the anus
  • anal columns and sinuses—exude mucus and lubricant into anal canal during defecation
  • large hemorrhoidal veins for superficial plexus in anal columns and around orifice
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4
Q

Bacterial flora

A

populate large intestine

about 800 species of bacteria

digest cellulose and other undigested carbohydrates

body absorbs resulting sugars

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5
Q

Flatus

A

intestinal gas

average person produces 500 mL per day (flatus) from 7 to 10 L of gas present but reabsorbed

hydrogen sulfide, indole, and skatole produce odor

others are odorless

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6
Q

Absorption and motility

A

large intestine takes about 12 to 24 hours to reduce the residue of a meal to feces

does not chemically change the residue

reabsorbs water and electrolytes

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7
Q

Feces

A

consist of 75% water and 25% solids, of which 30% is bacteria, 30% undigested fiber, 10% to 20% fat, small amount of mucus, and sloughed epithelial cells

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8
Q

Haustral contractions

A

occur every 30 minutes

this kind of colonic motility is a form of segmentation

distension of a haustrum stimulates it to contract

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