Lecture 31: Upper GI Histology II

Question 1

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

Answer 1

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.

Question 2

Describe the overall structure and regions of the gastric glands

Answer 2

Cardia: mostly mucous glands

Fundus: gastric glands

Body: gastric glands similar to fundus

Pylorus: mucous glands and hormone-secreting enteroendocrine cells.

Question 3

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

Answer 3

Long tubular glands extending down to the muscularis mucosae

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

Open into gastric pits

Question 4

Identify gastric glands and parietal and chief cels on photo:

Answer 4

K

Question 5

Describe the overall structure and regions of the gastric glands

Answer 5

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.

Question 6

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

Answer 6

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.

Question 7

Identify gastric glands and parietal and chief cells in photos:

Answer 7

K

Question 8

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

Answer 8

Length of small and large intestine

Plicae circulares (valves of keckring)

Villi

Microvilli

3 orders of folding:
Plicae
Crypt-villus system
Microvilli

Question 9

Describe the histology of the crypt-villus system.

Answer 9

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 .

Question 10

Describe the fine structure of a microvillus

Answer 10

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.

Question 11

Describe the glycocalyx

Answer 11

glycocalyx contains brush border enzymes:

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