Large Intestine (21-22)

Question 1

Three distinct surface characterstics

Answer 1

Tenia Coli, Haustra, Omental (epiploic) appendcies

Question 2

Tenia Coli

Answer 2

3 bands of longitudinal smooth muscle fibers

Question 3

Haustra

Answer 3

are sacculations of the colon that bulge out between Tenia coli

Question 4

Omental (epiploic) appendcies

Answer 4

fat-filled appendices

Question 5

The inner surface of the large intestine has mucosal folds called

Answer 5

Semilunar folds (plicate semiulnares

Question 6

Mucosa of the large intestine lacks

Answer 6

villi and has a smooth muscle interior surface

Question 7

The surface epithelium invaginates into the lamina propria to form

Answer 7

the intestinal glands of Lieberkuhn

Question 8

The surface of the large intestine is lined by

Answer 8

similar columnar epithelium consisting of intestinal absorptive cells and goblet cells (Goblet cells - dominant cell type and their number increases in more distal parts of the large intestine)

Question 9

Lamina propria typically contains

Answer 9

lymphoid tissue

Question 10

Muscularis mucosae has inner circular and outer longitudinal

Answer 10

smooth muscle layers

Question 11

Muscularis Externa

Answer 11

inner circular and outer longitudinal layers of smooth muscle
The outer longitudinal layer is discontinuous forming 3 separate longitudinal bands of smooth muscle called Taeniae Coli

Between Taeniae coli, the muscle is extremely thin or absent

The myenteric plexus lies between the two muscle layers

Question 12

Serosa/adventitia

Answer 12

The cecum, transverse and sigmoid colon are covered by serosa (peritoneum) divided into regions

Question 13

Cecum

Answer 13

Cecum - a blind pouch 6-7cm long
ileum enters the cecum at ileocecal orifice
ileocecal valve guards the orifice

Appendicular orifice also in cecum,

Question 14

Vermiform appendix

Answer 14

2-20cm long, usually 8cm
position of the rest of the appendix varies
frequently inflamed - appendicitis

Question 15

Ascending colon

Answer 15

From cecum proximally to right colic (hepatic) flexure distally
Narrower than cecum

Question 16

Transverse colon

Answer 16

largest and most mobile portion of the large intestine

From right colic (hepatic) flexure to left colic (splenic) flexure

Question 17

Descending colon

Answer 17

from left colic figure to sigmoid colon
Narrowest portion of colon

Question 18

Sigmoid colon

Answer 18

S-shaped loop from descending colon to rectum

Question 19

Rectum and Anal Canal

Answer 19

Located within true pelvis
Rectum is continuous with sigmoid colon
anal canal is the inferior 1.5 inches of the GI tract; it is continuous with rectum at anorectal junction

Question 20

The changes seen at the anorectal Junction are:

Answer 20

1. the epithelium changes from similar columnar to non-keratinized stratified squamous
2. the combined lamina propria-submucosal layer (muscular mucosal disappears) contains large thin-walled veins, when dilated they are called internal hemorrhoids
3. the inner-circular layer of the muscular external enlarges form the internal anal sphincter (smooth muscle)
4. defecation involves the action of voluntary muscle comprising the external anal sphincter. At the level of subcutaneous part of the external anal sphincter is composed of striated muscle fibers