14

Question 1

small intestine anatomy

Answer 1

• 6-7 m long
• 3 parts - duodenum, jejunum, illeum
• completely wrapped in mesentary proper **except duodenum

Question 2

duodenum

Answer 2

• SHORTEST PART - 25 cm long - C shaped
• encloses head of pancreas
• receives chyme from the stomach, receives bile and pancreatic juice via the duodenal ampulla
• retorpariteneal

Question 3

jejunum

Answer 3

• 2.5 m long
• main site of digestion and absorbtion
• fan shaped messentary (proper)

Question 4

illeum

Answer 4

• 3.5 m long
• opens into the cecum at the ileocecal valve
• fan shaped messentary (proper)

Question 5

arterial blood supply of small intestine

Answer 5

branch of abdominal aorta - superior mesenteric artery

Question 6

venous drainage of small intestine

Answer 6

superior mesenteric vein - drains into hepatic portal vein

Question 7

lining of the intestinal wall is increased by?

Answer 7

• longitudinal folds - disappear as digestive tract fills
• circular folds called plicae circulares - permanent
• intestinal vili - fingerlike projections in the mucosa

Question 8

intestinal vili (& their epithelium?)

Answer 8

• fingerlike projections in the mucosa
• covered by simple columnar epithelium (with microvili - brush boarder) and goblet cells
• supported by a core lp which contains the capillary network and lymphatic lacteals (centre of vili)

Question 9

histology of small intestine

Answer 9

mucosa, submucosa, muscularis and serosa

Question 10

mucosa of small intestine

Answer 10

• have intestinal vili
• simple columnar epithelium called enterocytes which are absorbtive cells
• lamina propria that contains Peyer’s patches (lyphoid follicles) and forms core for each vilus (contains bvs, nerve, lacteals)
• also has intestinal glands

Question 11

intestinal glands

Answer 11

“Crypts of Leiberkuhn”

• opeinings from intestinal glands to intestinal lumen at bases of villi (crypts = btwn vili)
• serve as entrances for brush boarder enzymes
• contain different types of cells - main function = these

Question 12

cells of intestinal glands (4) (smi)

Answer 12

goblet cells

• between columnar and epithelial cells
• eject mucins onto intestinal surfaces (lubricant)

enteroendocrine cells
-produce digestive hormones (gastrin, cholecystokinin, secretin)

paneth cells
-secrete antimicrobial peptides (lysozyme - defense against bacteria)

stem cells also located here - repair of intestinal cells

Question 13

submucosa of small intestine

Answer 13

-contains duodenal (Brunner’s) glands that produce/secrete alkaline mucus (prevents digestion of GI tract cells) when chyme arrives from the stomach

Question 14

movements of the mucosa

Answer 14

microvili - move by supporting microfilaments

vili - move by muscularis mucosae

plicae circulares - move by muscularis mucosae & externa

Question 15

anatomy of large intestine

Answer 15

-horseshoe shaped 
\+/- 1.5 m long & 7.5 cm wide
-extends from end of small intestine (illeum) to anus
-lies distal to stomach and liver
-frames the small intestine
-has 3 parts: cecum, colon, rectum

Question 16

cecum

Answer 16

• pouch like initial parts of the large intestine
• receives materials arriving from the ileum
• attached to illeum by ileocecal valve
• has vermiform appendix

Question 17

vermiform appendix

Answer 17

slender hollow appendage 
\+/- 0.5 cm long 
-attached to cecum
-dominated by lymphoid nodules
-used to be huge in digestion but its beleived that weve evolved out of the need for it - still helps

Question 18

colon

Answer 18

largest part of the large intestine

• has larger diameter and thinner wall than small intestine (less absorbtion happens here)
• has 4 regions: ascending colon, transverse colon, descending colon, sigmoid colon, all separated by flextures (bends)

Question 19

ascending colon and descending colon are:

paritoneal or retroparitoneal?

Answer 19

retroperitoneal

Question 20

flextures of the colon (3)

Answer 20

right cholic (hepatic) flexture

• between ascending and transverse
• under inferior surface of the liver

left cholic (splenic) flexture

• between transverse and descending
• under the spleen

sigmoid flexture
-between descending and sigmoid

Question 21

rectum

Answer 21

forms last 15 cm of the digestive tract

• expandable for temporary storage of feces
• movement of fecal matter into rectum triggers urge to defecate

Question 22

anal canal

Answer 22

• last part of rectum
• lined by stratified squamous epithelium
• contains small longitudinal folds called anal columns

Question 23

anus (anal orrifice)

Answer 23

• exit of the anal canal

- has keritanized epidermis (makes tissue more firm - lots of mechanical stress in that area)

Question 24

anal sphincters

Answer 24

internal anal sphincter

• circular muscle layer of muscularis externa
• has SM cells
• involuntary control

external anal sphincter
-encircles distal portion of anal canal
-ring of skeletal muscle fibers
voluntary control

Question 25

peritoneal covering of large intestine (mesocolon)

Answer 25

- transverse and sigmoid mesocolons = complete covering - ascending and descending and rectal mesocolons = partial covering (retroparitoneal) - mesoappendix - connects appendix to ileum and cecum

Question 26

layers of the large intestinal wall (4)

Answer 26

mucosa, submucosa, muscularis and serosa

Question 27

mucosa of large intestine

Answer 27

- no plicae or vili - simple columnar epithelium (same cells as smi) - goblet cells increase towards anus to lubricate fecal matter - intestinal glands (crypts) are deeper, dominated by goblet cells and do not produce digestive enzymes - lamina propria has an accumulation of lymphatic tissue

Question 28

muscularis externa of large intestine

Answer 28

teniae coli - 3 longitudinal bands of smooth muscle (that correspond to outer longitudinal layer) - run along the outer surfaces of the colon/cecum in the anal canal the circular muscle layer thickens as the interal anal sphincter haustra - series of pouches in the wall of the colon - created by muscle tone in the teniae coli - permit expansion and elongation of the colon

Question 29

arterial blood supply of large intestine

Answer 29

from abdominal aorta: - superior mesenteric artery - cecum, ascending and transverse - inferior mesenteric - descending, sigmoid and rectum

Question 30

venous drainage of large intestine

Answer 30

- superior mesenteric vein > hepatic portal vein | - inferior mesenteric vein > splenic vein > hepatic portal vein