Gi - 14

Question 1

Small Intsetine

Answer 1

-3m in length
-2.5cm diameter
-duodenum 25cm
-jejunum 100cm
-ileum 200cm

Question 2

Small Intestine Arterial Blood supply

Answer 2

slide 5 label
superior mesenteric artery supplies entire small intestine

Question 3

Small Intestine Venous Drainage

Answer 3

Slide 7
-superior mesenteric vein to hepatic portal vein and liver

Question 4

Small Intestine Specialized Layer Features

Answer 4

Mucosa:
-plicae circularis (looser than stomach rugae)
-villi
-microvilli
-all increase SA for digestion and absorption

Question 5

Small Intestine Specialized Layer Features Cont..

Answer 5

-cuboidal epithelium lining mucosa
-goblet cells - secrete mucous for protection and no friction
-blood capillaries
-lacteal (lymph projections) absorb fat
-intestinal juice pH 7.6, water, bicarb, enzymes

Question 6

Muscularis Fed and Fasted Patern

Answer 6

fasted: cirucular pinching seen in stool, chemical and mechanical digestion

fed: longitdunal muscle, peristalic wave, move waste and prevent bacterial overgrowth

Question 7

The Duodenum

Answer 7

-25 cm
-curved around pancreas head
-secretions enter from hepatopancreatic ampulla
-only site of Ca and Fe absorption
-most dense plicae circularis
-has submucosal glands (in first 10cm of duodenum) that secrete bicarb rich mucous

Question 8

The Jejunum

Answer 8

-1m long
-less dense plicae circularis (wrinkled sock) than duodenum
-long vasa recta (arterial supply)
-mostly glucose, amino acid and water absorption

Question 9

Ileum

Answer 9

-60% intestinal length
-plicae circularis and lumen taper out
-short vase recta
-fat absorption
-B12 aborption for DNA synthesis
-has lympoid nodules at terminal end (t and be cells waiting to attack)

Question 10

Neural and Hormonal Signals

Answer 10

-vagus nerve stimulates release on pacnreatic juice
-chyme entering duodenum causes enteroendocrine cells to release secretin and CCK
-secretin and CCK enter bloodstream, once they get to pancreas, CCK –> enzymes, secretin –> bicarb

Question 11

Digestive Enzymes

Answer 11

carbs: amylase, lactase, maltase, sucrase (oligosaccharides to galactose, glucose and frutose monosaccharides)

proteins: pepsin, tyrpsin, chymotrypsin, carboyxypeptidase (as amino acids)

fats: bile salts (liver), lipase (fatty acids and glyerol)

Nucleis acids: nucleases

Question 12

Monosaccharide Absorption

Answer 12

1. glucose absorbed by symport with Na into intestinal epithelial cells
2. symport is driven by sodium gradiant in a Na/K pump
3. glucose moves out of the intestinal epithelial cells by facilitated diffusion
4. glucose enters capillaries of the intestinal villi and is carried through hepatic portal vein to liver

Question 13

Amino Acid Absorption

Answer 13

-absorbed by symport into intestinal epithelial cells
-symport driven by sodium gradient in Na/K pump
-amino acids move out of intestinal epithelial cells via diffusion
-amino acids enter the capillaries of the intestinal villi and are carried through hepatic portal vein to liver

Question 14

Lipid Absorption

Answer 14

1. bile salts surrounded by fatty acids and monoglycerides to form micelles
   (micelles diffuse into intestinal epithelial cell, turn into chylomicron, chylomicron exocytosis into lacteal)
2. micelles attach to plasma membranes of intestinal epithelial cells, and fatty acids and monoglycerides pass by simple diffusion into the intestinal epithelial cells
3. within intestinal epithelial cells, fatty acids and monoglycerides are converted to triglycerides; proteins coat the triglycerids to from chlyomicrons which move out of the intestinal epithelial cells y exocytosis
4. the chylomicrons enter the lacteals of intestinal villi and are carried through lymphatic system to geeral circulation

Question 15

Large Intestine/Colon

Answer 15

slide 29

Question 15

Large Intestine Arterial Blood Supply

Answer 15

slide 30

Question 16

Large Intestine Specialized Layer features

Answer 16

-very small (triangle shaped) mucosa
-thin circular muscle layer (muscularis) of 3 bands (triangle) - teniae coli

Question 16

Large Intestine Venous Drainage

Answer 16

slide 31
-inferior mesenteric feeds into hepatic portal vein via splenic vein

Question 17

Large Intestine Cells

Answer 17

goblet cells - mucous
-absorptive cells
(no enzymes secreted)
-most water absorption
-acidosis/alkalosis can lead to diarhea or constipation

Question 18

Large Intestine Chemical Digestion

Answer 18

-undigested carbs (gas)
-amino acids (smell)
-bilirubin (colour)
-bacteria synthesize vit B and K

Question 19

Mechanical Digestion in Colon

Answer 19

gastrocolic reflex: peristalsis begins when food enters stomach –> 3-12 contractions/minute (slow)

gastroileal reflex: gastrin relaxes ileocecal sphincter when stomach is full

haustral chruning: every 30 min (slow) haustra rearrange (waffle shape)

mass peristalsis: strong peristalic waves from transverse colon pushes to rectum

defecation reflex: push to poo

feces: dead epithelial cells, undigested food (cellulose), live and dead bacteria

Question 20

Defecation Reflex

Answer 20

1. mass movement of feces (gastrocolic reflex) stretches rectal wall (afferent signal to spinal cord)
2. initiates parasympathetic reflex: contract colon and rectum but relax internal canal sphincter
3. if age appropriate, defecate, relax external anal sphincter

Question 21

Payers patches

Answer 21

b and t cells waiting to attack in ileum (most concentatrated at distal ileum closer to colon

Question 22

Hepatopancreatic ampulla

Answer 22

confluence of the common bile duct and pancreatic duct, marking the entry point of bile into the second portion of the duodenum