Lab 6: Histology and Dissection Flashcards
Describe the histology of the duodenum?
- The duodenum contains the same wall layers seen in the previous portions of the GI tract: mucosa, submucosa, and muscularis externa.
- The epithelia and lamina propria of the mucosal layer are thrown into villi.
- Especially notable are the Brunner’s glands in the submucosa. These glands are unique to the duodenum.
- Muscularis externa is a tad thicker
Why does the Brunner’s gland stain pale in a H&E stain?
Pale as its secretory
Secretes mucus
Name these parts of the histological image of the duodenum
Describe the epithelium of the duodenum?
Lined by a simple columnar epithelium which consists primarily of absorptive cells (enterocytes), with scattered goblet cells and occasional enteroendocrine cells. In crypts, the epithelium also includes Paneth cells and stem cells
Exocrine glands secrete into ____
Ducts
Endocrine glands secrete into ____
directly into blood
Ductless
Describe the Crypts of Lieberkuhn
- Also known as intestinal glands
- Located in the small intestine
- The epithelia of the villi extend down into the lamina propria where they form crypts. Many important cells reside in the crypts e.g. Paneth cells.
- In addition, stem cells that replenish the epithelial cells further up the villi are also found in the crypts.
Which hormones do the enteroendocrine cells of the epithelium secrete?
Secretin, cholecystokinin (CCK), gastric inhibitory protein (GIP), motilin
What role does the gastric intrinsic factor play int he digestive process?
It is necessary for the absorpton of vitamin B12 from the small intestine
The crypts of lieberkuhn contain which cells
Paneth cells (at the base of the crypts) - they have a defensive function, and stain intensely eosinophilic, due to secretory granules of antimicrobial peptides called defensins, as well as lysozyme and phospholipase A.
Endocrine cells, (also eosinophilic) which produce secretin, somatostatin, enteroglucagon and serotonin.
Stem cells, found at the base of the crypts, which divide continuously to replace enterocytes (every 2-3 days), goblet cells, paneth cells and neuroendocrine cells.
Describe the histological image of the spleen
The majority of the spleen consists of well-vascularized red pulp (pale-stained due to lower cell density) with white pulp (lymphoid aggregations) scattered throughout.
Describe the closed circulation of the spleen
blood empties from the vessels of the white pulp into sheathed capillaries of the red pulp and then directly into the sinuses
Describe the open circulation of the spleen
blood empties from the sheathed capillaries into the splenic cords and then enters the sinuses through slits in the wall.
Describe the splenic artery
Branch from the celiac artery
Follows a course superior to the pancreas
Very tortuous (wavy)
What is the physiological reason for the splenic artery to be tortuous
Allows it to lengthen when the stomach wall expands
