Histology Of Lower GI-1/8/16 Flashcards
___ are folds of the mucosa projecting into the lumen of the SI. These increase the absorptive surface of the mucosa
Villi
What are the 4 degrees of folding of the SI?
1) Plicae circulares
2) Intestinal villi
3) Intestinal glands (of Lieberkuhn)
4) Microvilli on the apical surface of enterocytes
___ are permanent folds of the mucosa and submucosa that begin in the duodenum, distinct in the jejunum, and disappear mid-ileum
Plicae circulares
____ are finger-like projection of the mucosa covering the entire surface of the SI (increase the surface area)
Villi
Villi extend deep into the mucosa to form ____ ending at the muscularis mucosae
crypts of lieberkuhn
____ are simple tubular glands that increase the intestinal surface area. They are formed by invaginations of the mucosa between adjacent intestinal villi
Crypts of Lieberkuhn
What are the cell types of the crypts?
Absorptive
Goblet
Paneth
Enteroendocrine
____ are evaginations of the apical part of the enterocytes to increase surface area. They produce a brush border on the apical border of enterocytes
Microvilli
This layer of the SI wall is responsible for segmentation and peristalsis:
Muscularis externa
This layer of the SI wall is a thin layer of loose CT covered by visceral peritoneum (mesothelium)
Serosa
This layer of SI wall is the site for the main distribution of blood and lymphatic flow:
Submucosa
This capillary plexus supplies the intestinal villus and upper part of the crypts of lieberkuhn:
Villus capillary plexus
This capillary plexus supplies the lower half of the crypts of lieberkuhn
Pericryptal capillary plexus
___ are within a villus and convey chyle (lymph containing lipids absorbed from the meal and package in chylomicrons) from the intestine to the lymphatic circulation and thereby to the thoracic duct and then to the systemic blood circulation
Lacteals
Motility of the SI is controlled by ___ through submucosal and myenteric plexi
ANS
____ innervation is received from the mucosa and muscle wall of the intestine
Intrinsic input
___ innervation is from the CNS through the parasympathetic (vagus n.) and sympathetic trunks
Extrinsic
List histological characteristics of the duodenum
BRUNNER’S GLANDS (mucous) in submucosa
Few goblet cells
Villi with a leaf-like shape
List histological characteristics of the jejunum
Well developed PLICAE CIRCULARES (characteristic feature)
Irregular villi with a finger-like shape
More goblet cells
No brunner’s glands and No peyers patches
List histological characteristics of the ileum
Peyers patches in lamina propria and subucosa
Finger-like villi (smaller than jejunum)
Most goblet cells
Location of M cells (ag-transporting cells)
What type of epithelium are villi and crypts of lieberkuhn lined by?
What are the cell types of the villi and crypts?
Simple columnar
1) absorptive cells (enterocytes) (villi)
2) goblet cells (villi)
3) paneth cells (crypt)
4) enteroendocrine cells (crypt)
___ cells have an apical domain with a prominent brush border containing about 3000 closely packed microvilli, which increase the surface luminal area 300-fold
The microvilli of these cells contain intramembranous enzymes (lactase, maltase, sucrase) for terminal digestion of carbs
Absorptive (enterocytes)
The wall of the SI includes these layers:
Mucosa
Submucosa
Muscularis
Serosa (outer)
____ are columnar mucus-secreting cells scattered among enterocytes of the intestinal epithelium. The secretory product of these cells contains glycoproteins released by exocytosis and the mucus hydrates to form a protective gel coat to shield the epithelium from mechanical abrasion and bacterial invasion
Goblet cells
___ cells secrete antimicrobial proteins to limit bacteria-enterocyte contact. Most of the proteins kill bacteria directly by enzymatic degradation of the bacterial wall or by disrupting the bacterial inner membrane
Paneth
Regarding protection from pathogens in the SI,:
A viscous gel-like blanket is produced by ___ cells
An intestinal tight-junction barrier that links adjacent ____
___ of the intestinal epithelium, participates in cell surveillance of Ags.
___, a product of plasma cells secreted by intestinal epithelium and in bile, neutralizes Ags.
Inactivation of microbial pathogens by antimicrobial proteins, products of ___ cells
Goblet Enterocytes Peyer's patches IgA Paneth
Crohn’s disease affects which part(s) of the intestine?
Terminal ileum but also observed in the LI
The initial alteration of the intestinal mucosa in IBD is by infiltration of these immune cells into the crypts of lieberkuhn:
Neutrophils
The purpose of fecal transplant is to replace good bacteria that has been killed or suppressed, usually the use of antibiotics, causing bad bacteria, specifically ___ to overpopulate the colon
Clostridium difficile
The mucosa of the LI is lined by a ____ epithelium formed by enterocytes and abundant goblet cells
simple columnar
What is a major function of enterocytes in the LI?
transport of ions and water
Numerous openings of the straight tubular glands or crypts of lieberkuhn are characteristic of the ___ of the colon
Mucosa
___ have short apical microvilli and participate in transport of ions and water in the LI
Enterocytes
In the LI, ___ cells secrete mucus to lubricate the mucosal surface and serve as a protective barrier
Goblet
In the colon, ___ contain goblet, enteroendocrine, and stem cells
Glands of lieberkuhn
___ is a characteristic feature of the LI, formed by fused bundles of the outer smooth muscle layer. Contraction of this and the inner circular smooth muscle layer produces periodic saccular structures called Haustra
Taeniae coli
What type of epithelium is found below the pectinate line?
Stratified squamous (keratinized)
Familial polyposis and colorectal tumorigenesis is determined by a defect in this protein (gene):
Adenomatous polyposis coli (APC) gene
Excess of APC activates genes leading to colorectal tumorigenesis
