29/30: GI Tract I & II - Canby

Question 1

four main layers of GI tract from internal to external

Answer 1

mucosa
submucosa
muscularis externa
serosa

Question 2

most of the GI tract epithelium is…

Answer 2

simple columnar

the proximal and distal segments are stratified squamous

Question 3

layers of mucosa

Answer 3

epithelium resting on basal lamina

lamina propria

muscularis mucosae

Question 4

2 segments of GI that contain glands

Answer 4

esophagus

duodenum

Question 5

submucosal vs. myenteric plexuses

Answer 5

,Submucosal (Meissner’s) plexus – parasympathetic postganglionic neurons and their processes and sympathetic postganglionic fibers; regulates the activity of the muscularis mucosae and the secretory activity of glands (contractile activity, blood flow, secretions)

Myenteric (Auerbach’s) plexus – parasympathetic postganglionic neurons and sympathetic postganglionic fibers; regulates the activity of the muscularis externa (between the different layers of muscle) (peristalsis)

Question 6

epithelium of mucosa of esophagus

Answer 6

stratified squamous non keratinized - protects against coarse-textured foods

esophageal cardiac glands are found in the lamina propria

Question 7

muscularis externa of espophagus

proximal v. middle. distal

Answer 7

skeletal m.
mixture
smooth muscle

Question 8

describe esophageal varices

Answer 8

hepatic portal hypertension due to cirrhosis

Question 9

desribe barrett’s esophagus

Answer 9

change from stratified squamous epithelium to simple columnar with mucus producing cells/goblet cells

metaplasia due to acid reflux

can progress into adenocarcinoma of esophagus

Question 10

lymph flow in the _____ is usually upward, whereas lymph flow in lower 2/3 is _______.

Answer 10

of the esophagus

upward
downward

1. Incidence of lymphatic metastasis is low if the carcinoma is limited to the mucosa. If the carcinoma spreads into the submucosa, the incidence of metastasis increases to 60%.
2. Cancer in the superior 2/3 may spread to the internal jugular, paratracheal nodes, subcarina, and paraesophageal nodes.
3. Cancer in the inferior 1/3 tends to spread to the celiac and cardiac nodes

Question 11

Gastric pits are formed by

Answer 11

the invagination of the surface epithelium into the lamina propria

Question 12

muscularis externa layers of stomach

Answer 12

i. Inner oblique layer of smooth muscle (this is the added layer – most only have other two)
ii. Middle circular layer of smooth muscle - thickened at the pylorus
iii. Outer longitudinal layer of smooth muscle

Question 13

describe the cardia of stomach

Answer 13

Short gastric pits
Long glands in the lamina propria
Simple or branched tubular glands
Surface lining, mucous, regenerative, and DNES cells
Few parietal cells

Question 14

describe the fundus and body of stomach

Answer 14

Gastric pits become slightly longer
Gastric glands are still long
Branched tubular glands fill the lamina propria

Question 15

isthmus vs.
neck vs.
base region of glands

Answer 15

Isthmus region of gland (stem cell niche of stomach)

• • Surface lining cells - secrete mucus
• • Parietal (oxyntic) cells - secrete HCl and intrinsic factor
• • Regenerative cells - replace other cell types as they die off

Neck region of the gland

• • Mucous neck cells
• • Parietal cells (secrete HCl and intrinsic factor)

Base region of the gland

• • Contains many chief (zymogenic) cells - pepsinogen
• • Enteroendocrine (DNES) cells - hormone secreting cells
• • Some mucous cells
• • Few parietal cells

Question 16

describe the pylorus

Answer 16

Deep gastric pits
Short glands
Branched tubular glands
Surface lining, mucous, regenerative cells; a few parietal cells
Enteroendocrine cells (hormone secreting cells) (G cells – gastrin)

Question 17

structures that increase SA for absorption in small intestine

Answer 17

plicae circulares – (valves of Kerckring) - Circular folds of submucosa and mucosa (increase 3 fold, increase chyme reabsorption)

intestinal villi – Highly vascular processes of mucosa (increase 10 fold) simple columnar cells

microvilli – increase surface 20-fold (on apical domain of columnar cells)

Question 18

goblet cells in the duodenum ____ in number as ileum is approached

Answer 18

Increase in number as the ileum is approached

Question 19

paneth cells

Answer 19

baceteriostatic cells found in intestinal glands (crypts of lieberkuhn)

Question 20

Peyer’s patches (aggregates of lymphoid nodules extending into lamina propia) indicate what part of intestine?

Answer 20

ileum

Question 21

4 signature histological features of celiac sprue

Answer 21

4 signature histologic features (enterocytes disarrayed, villus atrophy, crypt hyperplasia, inflammation of lamina propria)

Question 22

LARGE vs. small intestine

Answer 22

Mucosa

• • No folds (plicae circulares) except for the rectum and anal canal)
• • Absence of villi
• • Intestinal glands are more numerous and longer, more goblet cells, more mucus
• • Intestinal glands contain fewer Paneth cells
• • Columnar cells have short, irregular microvilli: this presents an ill-defined striated (brush) border
• • Goblet cells are more numerous

Muscularis externa

• • Outer longitudinal layer of smooth muscle does not completely surround the large intestine
• • Instead, three longitudinal bands of smooth muscle are found: these are the teniae coli

Question 23

describe the folds found in rectum

Answer 23

Longitudinal folds (temporary) - folds of submucosa and mucosa)

Plicae transversales recti (transverse rectal folds; aka folds or valves of Houston) - folds of circular muscle of muscularis externa (some folds also have longitudinal muscle), submucosa, and mucosa

Question 24

describe the anal columns

Answer 24

Anal columns (columns of Morgagni) - longitudinal folds of submucosa and mucosa. Most distended areas are anal cushions – where internal hemmorhoids form)

Question 25

before and after the white line of hilton

Answer 25

Pectinate/Dentate line to white line of Hilton

Stratified squamous, nonkeratinized epithelium

Stratified squamous, keratinized epithelium inferior to white line of Hilton - sebaceous glands are present

Question 26

internal vs. external anal sphincter

Answer 26

Internal anal sphincter
Formed by the inner circular smooth muscle layer of the muscularis externa
Does become thickened

External anal sphincter (skeletal muscle)

Question 27

what are diverticula?

Answer 27

Outpocketings of the colonic wall are diverticula. A true diverticulum involves all wall layers; whereas, a pseudo-diverticulum only involves the mucosa and submucosa. If it doesn’t have all the layers it is false (acquired) true are more genetic

Question 28

corners of hepatic lobules =

central of hepatic lobule =

Answer 28

portal triads (portal v. hepatic a bile duct) 
central v.

Question 29

Subendothelial space between the endothelial cells of the sinusoids and the hepatocytes

Answer 29

Space of Disse/perisinusoidal space

Microvilli of hepatocytes extend into this space
			c.	Reticular fibers
			d.	Perisinusoidal cells (Ito cells)
1.	Accumulate vitamin A 
Contain lipid droplets
2.	Synthesize and secrete growth factors

Question 30

Hepatic Acinus Zones: 1, 2, and 3 central vein in the middle, forms a diamond shape

Answer 30

Blood to zone 1 closest to blood source

			1. Increased oxygen
			2. Decreased carbon dioxide
			3. Decreased metabolic waste products
			4. Increased nutrients

Blood to zone 3 closest to central vein

			1. Decreased oxygen
			2. Increased carbon dioxide
			3. Increased metabolic waste products
			4. Decreased nutrients
			5. Main site of drug and alcohol detoxification *damage too
			6. More susceptible to damage
				a) Decreased nutrients, particularly during states of 							malnutrition 											b)	Hypoxic damage

Question 31

functions of hepatocyte

Answer 31

a. Detoxification via enzymes on SER
b. Glycogen metabolism
c. Blood protein synthesis and secretion (e.g., fibrinogen, factor III, prothrombin, complement, albumin, α-globulin, β-globulin, and lipoproteins)
d. Bile synthesis and secretion – sends to bile duct
bilirubin secretion (broken down blood)

Question 32

clinical relevance of no submucosa in gall bladder

Answer 32

Absence of submucosa and serosa on the hepatic surface of the GB facilitates the spread of GB cancer to the liver.

Presence of serosa on peritoneal surface of GB limits the spread of cancer to some extent.