Lecture 8: Histology of Small and Large Intestines Flashcards
What are the parts of the small intestine
Duodenum
Jejunum
Ileum
What is the name of the transverse folds found in the mucosal layer of the SI that has submucosal core to increase the surface area of the small intestine
Plicae Circulares
What are the cells found in the villi of the small SI
Simple columnar epithelium of Enterocytes and goblet cells
What are the structural features of the SI
The surface of the SI consist of villi (mucosal folds that project into lumen). These villi are covered with microvilli to increase absorptive surface area of SI
What is the name of the structure found in the core of the intestinal villi of the SI
Lacteal
What type of epithelium is found in the mucosa layer of the SI
Simple columnar epithelium
Small Intestine:
What is found in the submucosa layer
Dense irregular CT, Neurovascular, lymphatics and glands may be present
Small Intestine:
What is the Muscularis layer comprised of
Inner circular & outer longitudinal layers
Small Intestine:
Serosa or Adventitia present?
Serosa
What is the innervation of the SI & LI
- Submucosal plexus of Meissner
- Myenteric plexus of Auerbach (btw inner circular & outer longitudinal layers of muscularis externa)
Where are the intestinal glands of the SI located
In between the intestinal villi and are continuous with the simple columnar epithelium of enterocytes and goblet cells
List the cells that can be found in the intestinal glands of the SI
- Paneth cells
- M (microfold) cells
- Intestinal stem cells
- Enteroendocrine cells
What is the function of Paneth cells and where are they found?
Function: Innate immunity & regulate normal bacterial flora
Location: Found at base of intestinal glands
What is the function of Intestinal Stem cells (ISCs) and where are they found?
Function: Repopulate epithelial lining
Location: Base of glands, near Paneth cells
What is the function of M (Microfold) Cells and where are they found?
Function: Highly specialized antigen-transporting cells
Location: Mucosa of Ileum overlying Peyer patches
Where is the function of Enteroendocrine Cells and where are they located
Function: Secrete hormones for digestive role
Located: Mucosa layer
What type of cells are Enteroendocrine Cells and what system are the considered a part of
Most are Amine precursor uptake & decarboxylation (APUD_ cells - process amines
Diffuse neuroendocrine system (DNES)
What are the two kinds of Enteroendocrine Cells
- Closed type - cellular apex is covered by neighboring epithelial cells and is not exposed to GI lumen
- Open type - Apical end of the cell contacts the lumen and has chemoreceptors that sample limical contents
How can you distinguish the Duodenum from other areas of the SI
Presence of duodenal/Brunner’s glands in the submucosa. Other parts of the SI don’t have this
How can you distinguish the Ileum from other parts of the SI
- Presence of Peyer’s patches (MALT) in the mucosa layer
- Villi is typically smaller than in jejunum
- Paneth cells found at base of intestinal glands
How can you distinguish the Jejunum from other parts of the SI
- Lacks features that the duodenum and ilieum have (duodenal glands in submucosa & Peyer’s patches in Mucosa respectively)
- Has longer Villi than Illeum
What is the gastroduodenal junction and how can you identify it?
Region where the pyloric region of the stomach meets the small intestine.
Can be identified by the appearance of submucosal glands in the duodenum and presence of a pyloric sphincter
What are the hallmarks of the large intestine
- No intestinal villi
- Large amounts of goblet cells
- Tubular intestinal glands are opened to lumen
