Upper GI

Question 1

What are the 4 layers of the GI tube?

Answer 1

1. Mucosa
2. Submucosa
3. Muscularis externa
4. Adventitia or serosa

Question 2

What is the basic structure of the mucosa of the GI tube?

Answer 2

1. Epithelium - rests on basal lamina
2. Lamina propria - contains CT, glands, blood vessels, lymphatic tissue
3. Muscularis mucosae - inner circular and outer longitudinal layers of smooth muscle, contraction produces local movement of mucosa to facilitate absorption and secretion

Question 3

What is the basic structure of submucosa in the Gut tube?

Answer 3

Dense irregular CT

Blood and lymphatic vessles

Submucosal nerve plexus

Glands present in only esophagus and duodenum

Question 4

What is the basic structure of the muscularis externa of the GI tube?

Answer 4

Inner circular and outer longitudinal smooth muscle layers - stomach has extra layer

Contraction results in peristalsis

Myenteric nerve plexus between inner and outer muscular layers

Question 5

What is the basic structure of the adventitia of a standard GI tube?

Answer 5

Adventitia - CT only, present in extraperitoneal portion of GI tube (rectum and esophagus)

Serosa - CT covered by simple squamous epithelium, present in peritoneal cavity

Question 6

What is part of the enteric nervous system?

Answer 6

Autonomics:
Parasympathetic preganglionic axons and postglanglionic neurons
Sympathetic postganglionic axons

Visceral afferent dendrites

Plexuses:
Myenteric plexus
Submucosal plexus

Question 7

What is the myenteric plexus and where is it located?

Answer 7

Between inner and outer layers of the muscularis externa

Controls peristalsis

Question 8

What is the submucosal plexus?

Answer 8

Regulates glandular secretion in mucosa and submucosa, blood flow, and muscularis mucosae

Visceral afferents monitors chemistry of gut contents and mechanical stimulation of mucosa

Question 9

What is achalasia?

Answer 9

Dysfunction of myenteric plexus causes constriction of the lower esophageal sphincter

Question 10

What is Hirschsprung’s Disease?

Answer 10

Cognenital megacolon

Absence of enteric nerves in portion of bowel

Question 11

What is the function of the esophagus? How does that connect to its lining?

Answer 11

Transport masticated food to stomach

Epithelial lining must resist abrasion

Question 12

What layers does the esophagus contain?

Answer 12

Mucosa

Submucosa

Muscularis externa

Adventitia

Serosa

Question 13

What is in the mucosa of the esophagus?

Answer 13

Nonkeratinized stratified squamous - protects from abrasion

Lamina propria - cardiac glands concentrated proximally and distally. Glands secrete mucus for lubrication and neutralization of stomach acid

Muscularis mucosae contains only longitudinal fibers

Question 14

What is the submucosa of the esophagus?

Answer 14

Contains esophageal glands proper (seromucous) - serous and mucous secretions

Also secretes pepsinogen and lysozyme

Question 15

What is in the muscularis externa of the esophagus?

Answer 15

Transition from striated to smooth muscle

Question 16

What is in the adventitia and serosa of the esophagus?

Answer 16

Thoracic esophagus - adventitia

Abdominal esophagus - serosa

Question 17

What is the gastroesophageal junction?

Answer 17

Transition in function from transportation to digestion

Transition from stratified squamous epithelium to secretory gastric epithelium

see “z-line” in gross anatomy

Question 18

What is barrett’s esophagus?

Answer 18

Metaplastic columnar epithelium with goblet cells in distal esophagus, usually near gastroesophageal junction

Due to chronic insult from gastric secretions (stomach acid) - GERD or frequent vomiting

Increased risk of adenocarcinoma

Question 19

What are the regions of the stomach?

Answer 19

Cardia - region around gastroesophageal junction

Fundus - makes up bulk of stomach

Pylorus - region around pyloric sphincter and gastroduodenal junction

Question 20

What are the rugae of the stomach?

Answer 20

Longitudinal folds that allow for distension

Formed by muscosa and submucosa

Question 21

What are the functions of the stomach?

Answer 21

Temporary storage

Secretion of gastric juice

Formation of chyme - product of gastric churning and chemical digestion

Question 22

What layers does the stomach have?

Answer 22

Mucosa

Submucosa

Muscularis Exzterna

Question 23

What is in the mucosa of the stomach?

Answer 23

Epithelium - simple columnar that are surface mucous cells and form pits

Question 24

What are gastric pits?

Answer 24

Formed by invagination of surface epithelium into the lamina propria

Lined by simple columnar epithelium and surface mucous cells that secrete bicarbonate rich protective mucus

Question 25

What are the gastric glands? What types of cells do they contain?

Answer 25

Empty into the gastric pits

Contains 3 regions:
1. Isthmus - contains regenerative stem cells

2. Neck - contains mucous neck cells that secrete lubricating mucus that lubricates chyme. Also parietal cells that secrete HCL and gastric intrinsic factor, which binds to B12 for absorption by ileum
3. Base - Contains chief cells that secrete pepsinogen and converts to pepsin when mixes with acid. Also contains enteroendocrine cells that secrete hormones

Question 26

What are cardiac glands?

Answer 26

In cardia region of stomach

Shallow pits and long, coiled glands

Predominantly surface mucous cells

Question 27

What are pyloric glands?

Answer 27

In pyloric region

Deep pits and short glands

Mainly mucous neck cells that secrete lysozyme

Question 28

What are the protective mechanisms of the gastric epithelium?

Answer 28

1. Rapid turnover of surface epithelial cells ensures damaged cells replaced with healthy ones
2. Epithelial cells secrete mucous that is bicarbonate rich to raise pH of surface cells and protect them from acid
3. Mucous neck cells secrete mucous that lubricates chyme to prevent abrasion in peristalsis and gastric churning

**If these break down, erosion or ulceration of gastric mucosa can occur

Question 29

What is the gastroduodenal junction?

Answer 29

Transition in mucosa from secretory to absorptive

Pyloric sphincter - thickening of middle circular layer of muscularis externa

Duodenal glands (Brunner’s glands) - in submucosa of duodenum and secrete bicarbonate mucus