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GI Midterm > Histology of the Esophagus and Stomach > Flashcards

Histology of the Esophagus and Stomach Flashcards

1
Q

4 layers of GI tract from lumen —> superficial

A

Mucosa
Submucosa
Muscularis/muscularis externa
Serosa/adventitia

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2
Q

What is the difference between serosa and adventitia?

A

Serosa = covered by peritoneum

Adventitia = retroperitoneal

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3
Q

3 components of mucosal layer of GI tract

A

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)

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4
Q

2 major components of submucosal layer of GI tract

A

Dense irregular CT with neurovasculature and lymphatics

Glands may be present (esophagus and duodenum)

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5
Q

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?

A

Contraction of circular layer constricts lumen

Contraction of longitudinal layer shortens the tube

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6
Q

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

A

Mesothelium; serosa

Adventitia

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7
Q

The digestive tube is innervated by what 2 major components?

A

Extrinsic = parasympathetics and sympathetics

Intrinsic = enteric component

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8
Q

Important parasympathetics for GI innervation

A

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)

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9
Q

Important sympathetics for GI innervation

A

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

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10
Q

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

A

Submucosal plexus of Meissner (submucosa)

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

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11
Q

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

A

Peristaltic contractions of the muscularis and movements of muscularis mucosae

Secretory activities of the mucosal and submucosal glands

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12
Q

_________ axons of the parasympathetics increase gut motility

________ axons of the sympathetics decrease gut motility

A

Preganglionic

Postganglionic

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13
Q

Does the esophagus have serosa or adventitia?

A

Both!

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

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14
Q

Describe the 2 major types of glands found in the esophagus

A

Cardiac esophageal glands - reside in LP (mucosa)

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

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15
Q

Describe mucosal layer of esophagus

A

Stratified squamous epithelium overlying a lamina propria

Numerous folds

Muscularis mucosa only present in lower segment

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16
Q

Describe submucosa of esophagus

A

Network of collagen and elastic fibers, many small blood vessels

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

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17
Q

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

A

Esophageal varices - dilation of the submucosal venous sinuses

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18
Q

Describe muscularis layer of esophagus

A

Inner circular and outer longitudinal layers have segment dependent variation!

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

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19
Q

What forms the unique divider between the esophagus and stomach?

A

Gastroesophageal junction

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20
Q

Describe the epithelial transition that occurs at the gastroesophageal junction

A

Stratified squamous nonkeratinized epithelium —> simple columnar

Epithelium in the stomach is glandular with pits and glands

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21
Q

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

A

Upper esophageal sphincter (UES) - anatomical, swallowing reflex

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

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22
Q

What is GERD

A

Gastroesophageal reflux disease

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

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23
Q

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

A

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!

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24
Q

4 regions of the stomach

A

Cardia (2-3cm, near esophageal opening)

Fundus (projects to left of cardia)

Body (extensive central region)

Pyloric antrum (ends at gastroduodenal orifice)

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25
Q

2 areas of stomach based on motility characteristics

A

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

26
Q

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

A

Rugae; pits

27
Q

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

A

Secretory simple columnar; glands

Reticular; collagen; muscularis

28
Q

Describe the submucosal layer of the stomach

A

Dense irregular CT with collagen and elastic fibers

Arterioles, venous plexuses, and lymphatics

Meissner’s plexus

29
Q

Describe muscularis/muscularis externa layer of stomach

A

3 layers of smooth muscle: oblique, circular, and longitudinal (poorly defined)

Circular muscle layer thickens in pyloric region, forming pyloric sphincter

30
Q

Does the stomach have adventitia or serosa?

A

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

31
Q

Describe cardiac glands found in the stomach

A

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

32
Q

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

A

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

33
Q

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

A

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

34
Q

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

A

Surface mucous cells

35
Q

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

A

Mucous neck cells

36
Q

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

A

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

37
Q

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

A

Chief cells and enteroendocrine cells

Some parietal cells

38
Q

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

A

Mucins

Alkaline

39
Q

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

A

Menetrier’s disease

40
Q

What 2 things do parietal cells produce?

A

HCl of gastric juice

Intrinsic factor (glycoprotein that binds vitamin B12)

41
Q

3 distinctive features of parietal cells

A

Abundant mitochondria

Secretory/intracellular canaliculus

H/K dependent ATPase rich tubulovesicular system

42
Q

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

A

Produce ATP to pump H+ into secretory canaliculus

43
Q

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

A

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

44
Q

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

A

RER; zymogen

45
Q

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?

A

Pepsinogen

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

46
Q

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

A

Somatostatin
Gastrin
Ghrelin

47
Q

What cells produce gastrin and what is its function?

A

Produced by G cells in pyloric antrum

Stimulates production of HCl by parietal cells

48
Q

What cells produce somatostatin and what is its function?

A

Produced by D cells

Inhibits gastrin action

49
Q

Where is ghrelin produced and what is its function?

A

Produced in gastric fundus

Binds its receptor in pituitary and stimulates GH secretion

50
Q

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

A

Ghrelin

51
Q

Describe appearance of pyloric glands

A

Simple tubular and branched at distal end

52
Q

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

A

Gastric pits are deeper, they extend halfway through the depth of the mucosa

Pyloric glands have larger lumen and are highly branched

53
Q

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

A

Lysozyme

54
Q

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)

A

True

55
Q

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)?

A

Autoimmune gastritis

56
Q

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

A

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

57
Q

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

A

Helicobacter pylori

58
Q

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

A

Peptic ulcers

Adenocarcinoma

59
Q

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

A
  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
60
Q

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

A

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

GI Midterm (14 decks)

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