Histo of Small and Large Intestines Flashcards
Main portions of the small intestine?
Duodenum
Jejunum
Ileum
Principal site for digestion of food and absorption of digested products?
Small intestines
What are the transverse folds in the intestines called and what are layers are they made of?
Plicae Circularae
- Submucosal and Mucosal layers
What project off of the Plicae Circulares?
Villi
Intestinal villi project off of the folds of plicae circularae, what type of epithelium are they?
Simple columnar epithelium
What type of cells make up the simple columnar epithelium on the intestinal villi?
Enterocytes and scattered goblet cells
Each intestinal villi also contains a white core, what is that called?
Lacteal
What is the function of enterocytes?
Produce enzymes for digestion and absorption
What is the function of goblet cells?
Produce mucus coating for protection from abrasion
What is located on individual cells of the intestinal villi to increase absorption?
Microvilli
On what cell are microvilli located?
Enterocytes of the villi of the plicae circulares
What is the innervation of the small and large intestines?
Submucosal plexus of Meissner AND
Myenteric plexus of Auerbach
Where will you find the myenteric plexus of auerbach?
Between the inner circular layer and outer longitudinal layer of the muscularis externa
What type of epithelium are intestinal glands?
Simple columnar
What are the cell types found in intestinal glands?
Paneth cells
M cells
Intestinal stem cells
Enteroendocrine cells
Another word for the intestinal gland?
Crypt
Describe paneth cells
Found at base of intestinal gland
- Will stain eosinophilic in cytoplasm
- Functions in innate immunity
Describe intestinal stem cells
Found in niches at base of intestinal gland
- Differentiate into different cell types such as goblet cells or enteroendocrine cells or enterocytes
Main function of M cells?
Highly specific antigen transporting cells
Where will you find M cells?
Overlying Peyer’s Patches
Main function of Enteroendocrine cells?
Secrete hormones that aid in digestive function
2 types of Enteroendocrine cells?
Closed - not open to lumen
Open - apical end contacts lumen
Epithelial type found in the small intestines?
Simple columnar
Defining features of the Duodenum?
Simple columnar epithelium with scattered goblet cells
- DUODENAL GLANDS FOUND IN SUBMUCOSA
Defining features of the Jejunum mucosal and submucosal layers?
NONE
- simple columnar epithelium with scattered goblet cells, long villi and lymphoid nodules (mucosa)
- NO submucosal glands
Defining features of the Ileum?
Simple columnar epithelium with scattered goblet cells,
PEYER’S PATCHES, Paneth cells at base of glands
- NO submucosal glands
Describe the duodenum mucosal layer
Simple columnar epithelium with scattered goblet cells
Describe the duodenum submucosal layer
DUODENAL GLANDS! - neutralize acidic chyme
Describe the jejunum mucosal layer
Simple columnar epithelium with scattered goblet cells, long villi, long lacteal and lymphoid nodules
Describe the jejunum submucosal layer
NO SUBMUCOSAL GLANDS
Describe the ileum mucosal layer
Simple columnar epithelium with scattered goblet cells, PEYER’S PATCHES, Paneth cells at base of glands
What are peyer’s patches?
Lymphoid nodules found in the ileum mucosal layer
Describe the ileum submucosal layer
NO SUBMUCOSAL GLANDS
How can you tell you are at the Gastroduodenal junction?
Noticeable presence of duodenal submucosal glands deep to the muscularis mucosase
What makes up the large intestine?
Cecum Ascending colon Transverse colon Descending colon Sigmoid colon Rectum Anal canal
Main function of large intestine?
Absorb water, vitamins, minerals, sedatives, anesthetics, steroids
Does the large intestine have villi?
NO
What are the main hallmarks of the large intestine?
NO villi, lots of goblet cells making up the intestinal glands of simple columnar epithelium with colonocytes
Describe the mucosal layer of the large intestine
Simple columnar epithelium with colonocytes and lots of goblet cells
- lamina propria and muscularis mucosae are also present
Describe the submucosal layer of the large intestine
Dense irregular CT, well vascularized
What is different about the outer longitudinal layer of the muscularis externa in the large intestine?
Organized into taeniae coli that will form the haustra of the large intestine
What is the haustra of the large intestine?
It’s segmented appearance
Hirschsprung’s Disease
Aganglionosis in the distal colon
= portion of distal colon is not innervated by a plexus!
What gene mutation causes Hirschsprung’s Disease?
RET gene mutation that causes insufficient migration of NCC
Most common site of Hirschsprung’s Disease?
Short-segment disease - confined to rectosigmoid region
Symptoms of Hirschsprung’s Disease?
Constipation, poor feeding, progressive abdominal distention
What 3 things will you find in the anal canal?
Anal columns
Anal sinuses
Anal glands
What are anal columns?
Mucosal folds
What are anal sinuses?
Depressions between the anal columns
What are circumanal glands?
Apocrine glands surrounding the anal orifice
What are the 3 anal canal zones on a histo image?
Colorectal zone
Anal transition zone
Squamous zone
What epithelium is in the colorectal zone?
Simple columnar
What happens at the anal transition zone?
Simple columnar transitions into stratified squamous epithelium
What type of epithelium is at the squamous zone?
Stratified squamous
