L29. Alimentary Canal

Question 1

Describe the tubular portion of the GI tract

Answer 1

mucosa
muscularis mucosae
submucosa
muscularis externa
adventitia

Question 2

Describe the mucosa layer

Answer 2

• endodermally derived

- loose CT with lymphoid nodes

Question 3

Describe the musclaris mucosae

Answer 3

contains smooth muscle

Question 4

Describe the submucosa layer

Answer 4

dense irregular CT

Meissner nerve plexus (autonomic ganglia)

Question 5

Describe the Muscularis Externa

Answer 5

• regulates peristalsis
• has an inner circular and outer longitudinal layer
• smooth muscle : has a thickening at the eosphogal/cardiac and duodenal/pyloric opening : sphinctors that control the flow of lumen

Question 6

Describe the adventitia layer

Answer 6

• thinlayer of CT
• simple squamous epithelial covering
• may or may not attach to abdominal wall and contains blood vessels and nerves

Question 7

Describe the esophagus

Answer 7

• conduit that links the pharynx with the stomach

- does not participate in absorption or secretion

Question 8

Describe the different layers of the esophagus

Answer 8

Mucosal: stratified squamous epithelial (non-keratinized), protective
Lamina propria: loose CT
Submucosal: dense irregular CT, secrete seromucous (to lubricate and has anti-bacterial properties)
Adventitia:skeleal muscles needed for swallowing(top portion) lower portion: involuntary required for peristalsis

Question 9

Describe the mucosal layer of the stomach

Answer 9

• apically secretes acids,enzymes and mucous
• basally secretes paracrine release factors
• simple columnar epithelium with depressions =gastric glands
• has rugae(transient gastric mucosal folds) that flatten when stomach is full

Question 10

What is Barette’s Syndrome

Answer 10

when your cardiac sphincter muscles doesn’t work, loads of acid reflux causes the tissues in the esophagus to be changed to stomach tissue

Question 11

Describe the gastro-esophageal junction

Answer 11

abrupt transition from stratified squamous to columnar epithelium
separated by cardiac sphinctor

Question 12

name the different types of stomach cells

Answer 12

1. stomach lining cells
2. regenerative cells
3. mucous neck cells
4. oxyntic parietal cells
5. zymogenic chief cells
6. enteroendocrine cells (DNES/APUD)

Question 13

What is the function of stomach lining cell

Answer 13

produce some protective mucus

Question 14

What is the function of regenerative cell

Answer 14

contains stem cells has proliferative ability

Question 15

What is the function of mucous neck cells

Answer 15

like goblet cells produce a lot of protective mucus

Question 16

What is the function of oxyntic parietal cells

Answer 16

secretes acid /HCL (synthesis of acids similar to RBC)

Question 17

What is the function of zymogenic chief cells

Answer 17

secretes pepsinogen apically
pepsinogen is inactive and will be activated by acid in the stomach
lots of RER

Question 18

What is the function of enteroendocrine cells

Answer 18

secretes peptides basally acts as paracrine or endocrine factors (paracrine:gastrin and endocrine:VIP)

Question 19

What is the function of VIP endocrine factor

Answer 19

VIP (vasoactive intestinal pepide) increases peristalsis of intestine

Question 20

What is the function of the gastrin paracrine factor

Answer 20

increases parietal cell acid secretion and relaxes pyloric sphinctor muscle
release of chyme into the duodenum

Question 21

Describe the gastro-duodenal junction

Answer 21

thickening of the smooth muscles of the muscularis externa =pyloric sphinctor

Question 22

Describe the small intestine

Answer 22

1. has digestive function: facilitated by enzymes secreted from the pancrease
2. absorptive function: increased surface area for absorption through mucosal projections (villi) and depressions (crypts)

Question 23

Describe the epithelium of the small intestine

Answer 23

1. contains goblet cells that secrete mucous
2. absorptive cells : enterocytes
3. anti-bacterial cells: paneth cells
4. simple columnar cells

Question 24

Describe the lamina propria of the small intestine

Answer 24

1. loose connective tissue
2. prominent MALT
3. many vascular capillaries and lacteals

Question 25

Describe the Paneth cells

Answer 25

1. eosinophilic secretory vesicles
2. released apically, contains anti-bacterial lysosyme
3. can become antigen presenting cells , founds deep within the crypts at their base

Question 26

Describe the submucosa of the small intestine

Answer 26

1. contains Brunner gland
2. Brunner gland is an exocrine gland that secretes alkaline mucous that protects and neutralize acid entering small intestine

Question 27

Describe the large intestine

Answer 27

1. highly absorptive for water and ions

2. contains enterocytes and goblet cells

Question 28

Describe the mucosa layer of the large intestine

Answer 28

1. Absorptive

2. crypts and glands are present but have no vili

Question 29

Describe the epithelium layer of the large intestine

Answer 29

simple columnar, has enterocytes with goblet cells

Question 30

Describe the submucosa layer of the large intestine

Answer 30

dense irregular connective tissue no Brunner gland

Question 31

Describe the m. externa of the large intestine

Answer 31

external - skeletal muscles
internal - smooth muscles
terminal thickening: anal sphincters

Question 32

Describe the epithelial transition at the recto-anal junction

Answer 32

-metaplastic can change from simple columnar to stratified squamous at the divison

Question 33

What is the pectinate line at the recto-anal junction

Answer 33

congenital malformations can occur: site where the epithelium from the endoderm and ectoderm fuse

Question 34

Describe the 2 anal sphincters at the recto-anal junction

Answer 34

• superior internal sphincter: smooth muscle

- external sphincter: skeletal muscle : voluntary control

Question 35

Describe hemorrhoidal veins in the recto-anal junction

Answer 35

-at the mucosal and submucosal CT there are large diameter hemorrhoidal veins

Question 36

What happens to the hemorrhoidal veins when a person has hemorrhoids

Answer 36

veins are swollen and bulge in the recto-anal canal ( due to poor venous return to the hepatic portal vein; worsens due to hypertension)