Small Intestine, Pancreas, Gallbladder Histology Flashcards
What are the functions of the small intestine?
- Complete digestion of food
- Absorb final products of digestion
Layers of small intestine wall?
- Serosa
- Adventitia
- Supporting wall
- Submucosa
- Mucosa
What is a main feature of the small intestine?
Plicae circulares (valves of Kerckring)
What are the Plicae circulares?
- Prominent circular folds in duodenum and upper jejunum
- Disappear in ileum
- May increase surface area by a factor of 3
- Folds of submucosa lined by mucosa
What are the four main layers of the small intestine?
- Mucosa
- Submucosa
- Muscularis externa
- Serosa
What makes up the small intestine mucosa?
- Villi
- Distinct muscularis mucosae
- Plicae circulares: mucosal folds with a submucosal core
What makes up the small intestine submucosa?
- Forms core of plicae circulares
- Larger blood vessels and lymph vessels
- Submucosa nerve poleax with post-ganglionic cell bodies
What makes up the small intestine muscularis extern?
Two layers of smooth muscle:
- Inner circular layer
- Outer longitudinal layer
What makes up the small intestine serosa?
Connective tissue covered by mesothelium
-Except in regions that are retroperitoneal (parts of duodenum have adventitia)
What are the two types of epithelium in the mucosa of the small intestine?
- Villus
- Crypt
What is Villus epithelium?
Simple columnar
- Absorptive columnar cells (aka enterocyte)
- Goblet cells
- Enteroendocrine cells
What is Crypt epithelium?
Simple columnar
- Absorptive columnar cells
- Goblet cells
- Enteroendocrine cells
- Paneth cells (bacterocidal/bacterolytic)
- Undifferentiated cells (stem cells, mitotic)
What does the Lamina propria of the small intestine contain?
- Forms c.t. core of each villus
- Contains a central lymphatic vessel (lacteal)
- Capillaries and venules present
- Very cellular connective tissue: Lymphocytes, eosinophils, plasma cells, macrophages, fibroblasts, mast cells, smooth muscle cells, etc.
What does the Muscularis mucosae of the small intestine contain?
- Smooth muscle cells in lamina propria reach down into muscularis mucosae
- Delineates separation of mucosa from submucosa
What are the properties of the Intestinal villi of the small intestine?
- Project into lumen of small intestine
- Core of lamina propria
- Muscularis mucosae does NOT extend into villus
- Increases surface area for digestion and absorption
What are the Crypts of Lieberkuhn (intestinal glands)?
- Open at base of villi
- Extend to muscularis mucosae
- Paneth cells at base of crypts
- Many mitotic cells present
- -Cell turnover every 3-6 days
- –Cells migrate to tips of villi where they are shed
What are the different cells of the small intestine?
- Absorptive columnar cells
- Goblet cells
- Enteroendocrine cells
- Paneth cells
- Undifferentiated (stem) cells
What is the main histologic feature of the duodenum?
Brunner’s glands
What do Brunner’s glands do?
- Secrete an alkaline mucus (pH 8.1-9.3) into lumen of duodenum; neutralizes acid chyme arriving from stomach
- Glands are located in submucosa and lamina propria
What are other features of the duodenum?
- Brunner’s glands
- Many plicae circulares
- Adventitia present
What is the main histologic feature of the ileum?
Peyer’s Patches
Plicae =
Folds of submucosa
Villi =
Lined with all mucosal layer
What are the histologic features of the ileum?
- Peyer’s patches
- Plicae very sparse or absent
- Goblet cells are increasing in numbers
