Lecture 31: Upper GI Histology II Flashcards
Describe the specialization of the esophagus, including the transition zone btw the esophageal and stomach epithelium
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.
Describe the overall structure and regions of the gastric glands
Cardia: mostly mucous glands
Fundus: gastric glands
Body: gastric glands similar to fundus
Pylorus: mucous glands and hormone-secreting enteroendocrine cells.
Describe the histology and function of the major cell types found in the gastric glands, especially the parietal and chief cells.
Long tubular glands extending down to the muscularis mucosae
Composed of mucous neck cells, parietal, chief, stem, and enteroendocrine cells.
Open into gastric pits
Identify gastric glands and parietal and chief cels on photo:
K
Describe the overall structure and regions of the gastric glands
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.
Describe the histology and function of the major cell types found in the gastric glands, especially the parietal and chief cells
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.
Identify gastric glands and parietal and chief cells in photos:
K
List the major structural features that increase SA for absorption in the GI tract
Length of small and large intestine
Plicae circulares (valves of keckring)
Villi
Microvilli
3 orders of folding:
Plicae
Crypt-villus system
Microvilli
Describe the histology of the crypt-villus system.
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 .
Describe the fine structure of a microvillus
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.
Describe the glycocalyx
glycocalyx contains brush border enzymes:
-Maltase, sucrase,isomaltase, lactase, etc. produced by small intestine epithelial cells.