Lecture 31: Upper GI Histology II Flashcards

1
Q

Describe the specialization of the esophagus, including the transition zone btw the esophageal and stomach epithelium

A

Function: digestion and addition of mucous to food bolus

Specializations:
Mucosa=stratified squamous nonkeratinized epithelium.
Muscularis externa: undergoes transition from skeletal muscle in the upper 1/3 to a mixture of skeletal and smooth in the middle third to smooth muscle only in the lower third.

Transition btw esophagus and stomach: transitions btw stratified squamous epi. Of esophagus and simple columnar epi. Of stomach is a frequent CA site.

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2
Q

Describe the overall structure and regions of the gastric glands

A

Cardia: mostly mucous glands

Fundus: gastric glands

Body: gastric glands similar to fundus

Pylorus: mucous glands and hormone-secreting enteroendocrine cells.

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3
Q

Describe the histology and function of the major cell types found in the gastric glands, especially the parietal and chief cells.

A

Long tubular glands extending down to the muscularis mucosae

Composed of mucous neck cells, parietal, chief, stem, and enteroendocrine cells.

Open into gastric pits

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4
Q

Identify gastric glands and parietal and chief cels on photo:

A

K

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5
Q

Describe the overall structure and regions of the gastric glands

A

Simple branched tubular glands, narrow isthmus opens into bottom of gastric pit. Fundus =base; goes into lamina propria.

  • Mucous neck cells: soluble mucous
  • chief cells(zymogenic): pepsinogen
  • parietal cells(oxyntic): HCl [stomach]
  • enteroendocrine cells(APUD cells): diffuse neuroendocrine cells that secrete hormones.
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6
Q

Describe the histology and function of the major cell types found in the gastric glands, especially the parietal and chief cells

A

Pit=narrowin from surface
Neck=btw pit and body.
Body=base-gastric glands

Chief cells: pepsinogen.

Parietal cells: HCl, unique to gastric gains. Pyramidal shaped. EOSINOPHILIC, produces gastric intrinsic factor: necessary for Vit B12 absorption. Prominent intercellular canaliculi lined by microvilli.

Enteroendocrine cells=secretory vesicles POLARIZED toward basal surface close to vessels…to enter blood stream-peptide hormones and serotonin.

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7
Q

Identify gastric glands and parietal and chief cells in photos:

A

K

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8
Q

List the major structural features that increase SA for absorption in the GI tract

A

Length of small and large intestine

Plicae circulares (valves of keckring)

Villi

Microvilli

3 orders of folding:
Plicae
Crypt-villus system
Microvilli

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9
Q

Describe the histology of the crypt-villus system.

A

vilus= contain core of lamina proporia.
Crypts extend down btw the VIII and biases of villi.

Crypts and villi constitute glands of small intestine. Simple columnar. Contains capillary plexus and lacteal .

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10
Q

Describe the fine structure of a microvillus

A

Covered w/ glycoprotein and glycocalyx.
Contains BRUSH-BORDER enzymes in glycocalyx.
Bundles of actin filaments w/in microvillus is covered by a formin cap.

Supported by core of actin microfilaments. Bound to plasma membrane. Contains myosin, calmodulin, and crosslinked by vimbrin and fimbrin.

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11
Q

Describe the glycocalyx

A

glycocalyx contains brush border enzymes:

-Maltase, sucrase,isomaltase, lactase, etc. produced by small intestine epithelial cells.

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