GI Overview, Esophagus, and Stomach

Question 1

Principal layers in GI tract

Answer 1

. Mucosa
. Submucosa
. Muscularis externa
. Adventitia/serosa

Question 2

Mucosa

Answer 2

. Formed by epithelial lining, underlying lamina propria and musculari mucosae

Question 3

Epithelial lining functions

Answer 3

. Formation of selective permeable barrier btw contents of GI tract and tissues in body
. Facilitation is transport/digestion of food
. Promotion of digestion and absorption of food
. Production of hormones
. Protection of epithelial lining by mucous production

Question 4

Lamina propria

Answer 4

. Loose CT w/ blood and lymph vessels

. Lymphoid tissue in diffuse and modular form

Question 5

Gut-assoc.-lymphoid-tissue

Answer 5

. GALT

. Provides immunological barrier protecting against invasion of microbial pathogens

Question 6

Muscularis mucosae

Answer 6

. Smooth muscle
. Inner circular and outer longitudinal
. Permits movement of mucosa independent of other movements in GI tract

Question 7

Submucosa

Answer 7

. Dense CT
. Blood and lymph vessels, glands, and lymphoid tissue
. Contains scatter parasympathetic ganglia (submucosal/Meissner’s nerve plexus) as part of enteric system

Question 8

Muscularis externa

Answer 8

. layers of smooth muscle (inner, outer, stomach has added oblique)
. Parasympathetic nerve cells form ganglia of myenteric (Auerbach’s) nerve plexus located btw inner and outer layers of smooth muscle
. Interstitial cells of Cajal (ICC) form network located btw neurons of myenteric plexus that serves as gastroenteric pacemaker system
. ICCs essential in maintenance of motility of GI tract

Question 9

Adventitia/serosa of GI tract

Answer 9

. Outer layer of loose CT
. Adventitia if organ is surrounded by CT and there is no clear outer demarcation
. Where gut lies w/in abdominal cavity the outer CT layer is covered by mesothelium and outer CT layer is called serosa

Question 10

Esophagus

Answer 10

Long (25 cm), straight. Muscular tube that transmits food from oropharynx to the stomach

Question 11

Esophagus mucosa

Answer 11

. SSNK epithelium (can be keratinized if abrasion)
. Lamina propria: loose CT, contains esophageal cardiac glands in proximal and distal ends of esophagus
. Muscularis mucosae: longitudinally arranged smooth muscle, not present in upper portion of esophagus

Question 12

Esophagus submucosa

Answer 12

. Dense irregular CT w/ collagen and elastic fibers

. Esophageal proper glands (compound tubuloalveolar mucus glands) scattered throughout length of esophagus

Question 13

Esophagus muscularis externa

Answer 13

. Upper 1/3 contains only skeletal muscle continuous w/ skeletal muscles of pharynx
. Middles 1/3: smooth muscles internal to skeletal muscle
. Distal 1/3: only smooth muscle
. Auerbach myenteric plexus btw outer and inner muscle layers along whole esophagus

Question 14

Lower esophageal sphincter

Answer 14

. Specialized zone of circular smooth muscle surrounding esophagus and it’s transit through diaphragm and short course in abdomen

Question 15

Esophagus adventitia

Answer 15

Loose CT

Question 16

GERD

Answer 16

. Incompetent barrier at gastroesophageal junction
. Inflammation of esophagus and damage to epithelial lining lead to erosion of esophageal mucosa
. Can lead to metaplasia if untreated (SSNK to simple columnar)

Question 17

Stomach

Answer 17

. Mixed endocrine-exocrine organ stores and digests food and secretes hormones
. Food acidified and transformed into chyme
. Protein digestion is initiated w/ enzyme pepsin
. Triglyceride digestion initiated by lipase
. Regions: cardia, fundus and body, and the pylorus
. Mucosa and. Submucosa of empty stomach lie in longitudinally directed folds called rugae (disappear when stomach distendeD)

Question 18

Cardia stomach

Answer 18

. 1.5-3 cm wide transition zone btw esophagus an stomach

. Glands primarily produce mucus

Question 19

Stomach fundus and body

Answer 19

. Histologically identical

. Gastric glands release acidic gastric juice

Question 20

Pylorus

Answer 20

. Funnel-shaped region that opens into small intestine

. Glands primarily produce mucus

Question 21

Stomach epithelium

Answer 21

. Simple columnar surface mucous cells
. Secrete alkaline mucus forming protective coat on the epithelial surface
. Mucus protects surface of stomach from acids and enzymes produced by the stomach
. Adds in lubrication
. Turnover rate for surface epithelium is high
. Epithelium invaginates at regular intervals into lamina propria forming gastric pits

Question 22

Gastric pits

Answer 22

. Lead into tubular glands that project into the lamina propria
. 1-7 glands open into the bottom of each gastric pit

Question 23

stomach Lamina propria

Answer 23

. Loose CT, contains lymph tissue and blood vessel

. Gastric glands here

Question 24

Stomach muscularis mucosae

Answer 24

. Inner circular and outer longitudinal smooth muscle layers

Question 25

Cardiac glands

Answer 25

. Shortest and least numerous

Question 26

Gastric glands

Answer 26

. In stomach, largest and most numerous in body and fundus

Question 27

T/F Pyloric glands resemble cardiac glands

Answer 27

T

Question 28

Isthmus of the gland

Answer 28

. Upper portion of gland at junction of gastric pit and gland

Question 29

Neck of the gland

Answer 29

. Below isthmus

Question 30

Base of the gland in stomach

Answer 30

. Lower portion of gland

Question 31

Undifferentiated stem cells in stomach

Answer 31

. Inside isthmus and neck regions . Low columnar w/ nasally located oval nucleus . Highly proliferation and are source of new surface mucous cels and all other cells of gland

Question 32

Mucous neck cells

Answer 32

. Shorter than surface mucous cells . Round nucleus and apical secretory granules . Include progenitor and immature surface mucous cells . Mucus produced is more soluble than mucous from surface mucous cells

Question 33

Parietal (oxyntic) cells

Answer 33

. Numerous in neck and upper segment of glands . Large spherical cells w/ extremely eosinophilic cytoplasm and centrally located nucleus . Produce hydrochloric acid absorption of B12 .

Question 34

Chief (peptic/zymogenic) cells

Answer 34

. Found in lower third of glands . Cytoplasm is strongly basophilic granular . Nucleus basally located . Produce pepsinogen and lipase

Question 35

Pepsinogen converted to ____ upon release into acid

Answer 35

Pepsin

Question 36

Enteroendocrine cells in stomach

Answer 36

. Base of glands . Contain granules in basal area of cytoplasm w/ serotonin, gastrin, and somatostatin . Part of neuroendocrine system

Question 37

Stomach submucosa

Answer 37

. Dense CT | . Blood and lymph vessels, lymphoid cells including mast cells and macrophages

Question 38

Stomach Muscularis externa

Answer 38

. Smooth muscle layers oriented in 3 directions . Inner oblique, middle circular (enlarges to form pyloric sphincter), and outer longitudinal layer . Strong contractions of muscle wall create churning action that mechanically breaks down ingested matter

Question 39

Stomach serosa

Answer 39

. Loose CT covered by mesothelium

Question 40

Cardiac region morphological appearance

Answer 40

``` . Simple or branched tubular glands . Coiled w/ large lumens . Depth of pit to depth of the gland ratio (1:2-1:3) . Most cells produce mucus and lysozyme . Some parietal cells may be present ```

Question 41

Body/fundus morphological differences

Answer 41

. Mucosa has glands that produce acid-pepsin gastric juices and some mucus . 3 7-branched gastric glands open into each pit . Pits shallow in comparison to depth of gastric glands . Pit: gland ratio is 1:4

Question 42

Pyloric morphological appearance

Answer 42

. Glands simple or branched tubular, often coiled . Secrete mucus, lysozyme, and gastrin . Pit:gland ratio is 1:1 . Longer pits than cardia

Question 43

H pylori

Answer 43

Present in chronic duodenal ulcers and gastric ulcers