Histology of the Esophagus and Stomach

Question 1

4 layers of GI tract from lumen —> superficial

Answer 1

Mucosa
Submucosa
Muscularis/muscularis externa
Serosa/adventitia

Question 2

What is the difference between serosa and adventitia?

Answer 2

Serosa = covered by peritoneum

Adventitia = retroperitoneal

Question 3

3 components of mucosal layer of GI tract

Answer 3

Lining epithelium (varies segment to segment)

Underlying lamina propria (vascularized loose CT)

Muscularis mucosae (thin layer of smooth muscle that controls mobility of mucosa/mucosal glands)

Question 4

2 major components of submucosal layer of GI tract

Answer 4

Dense irregular CT with neurovasculature and lymphatics

Glands may be present (esophagus and duodenum)

Question 5

The muscularis/muscularis externa layer of GI tract has 2 layers of smooth muscle, and inner circular layer and an outer longitudinal layer. Neurovascular plexuses reside between layers. What are the differences in function of these muscular layers?

Answer 5

Contraction of circular layer constricts lumen

Contraction of longitudinal layer shortens the tube

Question 6

The serosa/adventitia is comprised of loose CT. When digestive tube is suspended by a mesentery/peritoneal fold, the adventitia is covered by _______ forming the ______ layer

Those without mesothelium covering have an _______. Organs may have adventitia and/or serosa, depending on location

Answer 6

Mesothelium; serosa

Adventitia

Question 7

The digestive tube is innervated by what 2 major components?

Answer 7

Extrinsic = parasympathetics and sympathetics

Intrinsic = enteric component

Question 8

Important parasympathetics for GI innervation

Answer 8

Vagus nerve (until splenic flexure)

Pelvic splanchnics (splenic flexure —> inferiroly)

Fibers in vagus and pelvic splanchnics are presynaptic; ganglion and postsynaptic fibers are intermural (postganglionic)

Question 9

Important sympathetics for GI innervation

Answer 9

Branches from greater, lesser, least, and lumbar splanchnics

Synapse in prevertebral ganglia (celiac, SM, aorticorenal, and IM ganglia)

Postsynaptic nerves travel to organs via blood vessels on peri-arterial plexuses

Question 10

Intrinsic/enteric innervation involves what 2 interconnected plexuses, formed by sensory and motor neurons but linked by interneurons?

Answer 10

Submucosal plexus of Meissner (submucosa)

Myenteric plexus of Auerbach, located between inner circular and outer longitudinal layers (muscularis)

Question 11

The intrinsic/enteric innervation responds to local stimuli and input from extrinsics. They regulate and control what 2 major gut functions?

Answer 11

Peristaltic contractions of the muscularis and movements of muscularis mucosae

Secretory activities of the mucosal and submucosal glands

Question 12

_________ axons of the parasympathetics increase gut motility

________ axons of the sympathetics decrease gut motility

Answer 12

Preganglionic

Postganglionic

Question 13

Does the esophagus have serosa or adventitia?

Answer 13

Both!

Thoracic esophagus has adventitia with adipose tissue. Inferior to the diaphragm, it has serosa

Question 14

Describe the 2 major types of glands found in the esophagus

Answer 14

Cardiac esophageal glands - reside in LP (mucosa)

Submucosal glands - consist of small lobules with mucous and serous cell types, drained by a single duct

Question 15

Describe mucosal layer of esophagus

Answer 15

Stratified squamous epithelium overlying a lamina propria

Numerous folds

Muscularis mucosa only present in lower segment

Question 16

Describe submucosa of esophagus

Answer 16

Network of collagen and elastic fibers, many small blood vessels

Submucosal venous plexuses drain into both the systemic and portal venous system

Question 17

Increased pressure in the submucosa of the esophagus may lead to what condition?

Answer 17

Esophageal varices - dilation of the submucosal venous sinuses

Question 18

Describe muscularis layer of esophagus

Answer 18

Inner circular and outer longitudinal layers have segment dependent variation!

Upper third = skeletal muscle
Middle third = skeletal and smooth
Lower third = smooth muscle

Question 19

What forms the unique divider between the esophagus and stomach?

Answer 19

Gastroesophageal junction

Question 20

Describe the epithelial transition that occurs at the gastroesophageal junction

Answer 20

Stratified squamous nonkeratinized epithelium —> simple columnar

Epithelium in the stomach is glandular with pits and glands

Question 21

The esophagus has 2 sphincters, what are their specific functions?

Answer 21

Upper esophageal sphincter (UES) - anatomical, swallowing reflex

Lower esophageal sphincter (LES) - functional, prevents reflux of gastric contents

Question 22

What is GERD

Answer 22

Gastroesophageal reflux disease

Causes chronic inflammation, ulceration, and difficulty swallowing (dysphagia) due to reflux of gastric contents

Question 23

What happens to the stratified squamous epithelium of the gastroesophageal junction transition zone if GERD is a chronic issue?

Answer 23

It may be replaced at the lower end by a columnar mucus-secreting/glandular form, Barrett’s esophagus/metaplasia

Metaplastic epithelium is at high risk of developing dysplasia or carcinoma!

Question 24

4 regions of the stomach

Answer 24

Cardia (2-3cm, near esophageal opening)

Fundus (projects to left of cardia)

Body (extensive central region)

Pyloric antrum (ends at gastroduodenal orifice)

Question 25

2 areas of stomach based on motility characteristics

Answer 25

Orad area = fundus and upper part of body, relaxes during swallowing Caudad area = lower portion of body and antrum, participates in regulation of gastric emptying

Question 26

The stomach contains gastric mucosal folds called ______, which are covered by gastric _____. A gastric mucosal barrier protects the mucosal surface

Answer 26

Rugae; pits

Question 27

The mucosa of the stomach is lined with _____ epithelium. The lamina propria contains cardiac, gastric, and pyloric _______. _____ and _____ fibers predominate, and the ______ mucosae facilitates release of gastric gland secretions

Answer 27

Secretory simple columnar; glands Reticular; collagen; muscularis

Question 28

Describe the submucosal layer of the stomach

Answer 28

Dense irregular CT with collagen and elastic fibers Arterioles, venous plexuses, and lymphatics Meissner’s plexus

Question 29

Describe muscularis/muscularis externa layer of stomach

Answer 29

3 layers of smooth muscle: oblique, circular, and longitudinal (poorly defined) Circular muscle layer thickens in pyloric region, forming pyloric sphincter

Question 30

Does the stomach have adventitia or serosa?

Answer 30

Serosa - with loose CT and blood vessels (bc stomach is intraperitoneal)

Question 31

Describe cardiac glands found in the stomach

Answer 31

Glands are tubular with coiled end (appear similar to sweat glands) Opening is continuous with gastric pits Extend only a few centimeters from gastroesophageal junction Lined with mucus-secreting cells similar to those in esophagus

Question 32

The major contributors of gastric juice in the stomach are the glands of the fundus/body. Describe these glands

Answer 32

Straight tubular with 2-7 opening into single gastric pit (bc many shared connection/exit points)

Question 33

3 major regions of glands found in fundus/body of stomach

Answer 33

Pit (foveolar), lined by surface mucous cells Neck, lined by mucous neck cells, stem cells, and parietal cells Body, upper andlower portions contain different proportions of cells

Question 34

What type of cell predominates in the pit of glands of fundus/body of stomach?

Answer 34

Surface mucous cells

Question 35

What type of cell predominates in the neck of glands of fundus/body of stomach?

Answer 35

Mucous neck cells

Question 36

What type of cell predominates in the upper portion of the body of glands of fundus/body of stomach?

Answer 36

Parietal cells (some chief cells and stem cells as well, but these don’t predominate until lower portion of body)

Question 37

What type of cell predominates in the lower portion of the body of glands of fundus/body of stomach?

Answer 37

Chief cells and enteroendocrine cells | Some parietal cells

Question 38

Both surface mucous cells and mucous neck cells produce _____ (glycoproteins) A mucous layer containing this substance forms and insoluble gel that attaches to surface of mucosa, neutralizing the microenvironment to an ________ pH

Answer 38

Mucins Alkaline

Question 39

Condition associated with TGF-alpha induced hyperplasia of surface mucous cells leading to nausea, vomiting, epigastric pain, GI bleeding, and diarrhea

Answer 39

Menetrier’s disease

Question 40

What 2 things do parietal cells produce?

Answer 40

HCl of gastric juice Intrinsic factor (glycoprotein that binds vitamin B12)

Question 41

3 distinctive features of parietal cells

Answer 41

Abundant mitochondria Secretory/intracellular canaliculus H/K dependent ATPase rich tubulovesicular system

Question 42

What is the significance of abundant mitochondria found in parietal cells?

Answer 42

Produce ATP to pump H+ into secretory canaliculus

Question 43

Chief cells predominate in the lower 1/3 of gastric glands, EXCEPT in which areas of the stomach?

Answer 43

Chief cells are not present in cardiac glands and are seldom found in the pyloric antrum

Question 44

The basal region of chief cell cytoplasm contains extensive ______. Numerous _______ granules (secretory) are located in the apical region.

Answer 44

RER; zymogen

Question 45

Numerous zymogen granules are located in the apical region of chief cell cytoplasm. What proenzyme is stored in these zymogen granules? What is its significance?

Answer 45

Pepsinogen Released into the lumen of the gland via exocytosis (stimulated by feeding) and converted to pepsin by acidic environment; pepsin digests most proteins

Question 46

Enteroendocrine cells release what 3 major peptide hormones that regulate GI tract?

Answer 46

Somatostatin Gastrin Ghrelin

Question 47

What cells produce gastrin and what is its function?

Answer 47

Produced by G cells in pyloric antrum Stimulates production of HCl by parietal cells

Question 48

What cells produce somatostatin and what is its function?

Answer 48

Produced by D cells Inhibits gastrin action

Question 49

Where is ghrelin produced and what is its function?

Answer 49

Produced in gastric fundus Binds its receptor in pituitary and stimulates GH secretion

Question 50

An increase in plasma levels of what hormone during fasting trigger hunger?

Answer 50

Ghrelin

Question 51

Describe appearance of pyloric glands

Answer 51

Simple tubular and branched at distal end

Question 52

How are the gastric pits of pyloric glands different from gastric pits in cardia or fundus region of the stomach?

Answer 52

Gastric pits are deeper, they extend halfway through the depth of the mucosa Pyloric glands have larger lumen and are highly branched

Question 53

Pyloric glands are lined by mucus-secreting cells (resemble mucous neck cells) which contain large and pale secretory mucus, as well as secretory granules containing _______, a bacterial lytic enzyme

Answer 53

Lysozyme

Question 54

T/F: Enteroendocrine cells and gastrin-secreting G cells are abundant in pyloric antrum, and lymphoid nodules can be seen in the lamina propria (GALT)

Answer 54

True

Question 55

What condition occurs when body produces autoantibodies specific to H, K-dependent ATPase, a parietal cell antigen, and intrinsic factor (all produced by parietal cells)?

Answer 55

Autoimmune gastritis

Question 56

Autoimmune gastritis causes destruction of parietal cells. What does this destruction result in?

Answer 56

A marked decrease in HCl in gastric juice = achlorhydria Without synthesis of intrinsic factor, patient develops vitamin B12 deficiency which disrupts RBC formation in the bone marrow, leading to pernicious anemia

Question 57

Flagellated bacterium that resides in mucus layer lining the gastric epithelium (especially pyloric antrum), despite hostile environment

Answer 57

Helicobacter pylori

Question 58

H pylori survives and replicates in the gastric lumen and is mainly associated with what 2 conditions?

Answer 58

Peptic ulcers | Adenocarcinoma

Question 59

What are the 3 phases of pathogenesis of H pylori infection?

Answer 59

1. Active phase = motile bacteria increase gastric pH by producing ammonia 2. Stationary phase = bacterial attachment to receptors on mucous surface cells of pyloric region; production of cytotoxic proteases for nutrient supply and attraction of leukocytes; production of ammonia and cytotoxic proteases leads to peptic ulcer formation 3. Colonization phase = detach from epithelium, replicate within mucus blanket and remain attached to glycoproteins

Question 60

Most people infected with H pylori do not have symptoms. What are the symptoms when they do occur?

Answer 60

Intense, sudden, persistent stomach pain; hematemesis and/or melena