GI 2 continued Flashcards
What is the mucosa of small intestines?
- involved in digestion and absorption of food.
- Lined by simple columnar epthelium for absorptive function.
How is the surface area increased in the small intestine?
The pilicae circularis increase surface area by increasing transverse folds of the mucosa.
- TThe lamina propria and its underlying epithelium create flattened productions into the lumen known as villi.
- The surface of the absorptive cells contains many microvilli for absorption of food stuff
What are crypts of lieberkuhn?
Intestinal glands and theyre located in the mucosa
What cell types are found in the epithelium of the small intestines?
- Absorptive cells.
- Goblet cells
What are absorptive cells?
The predominant cells in the epithelium.
- Simple columnar with distinct pattern or polerization
- Nucleus is always basal and apical surface is covered by aproximatly 3000 microvilli.
What compromises striate or brush border?
The microvilli in absorptive cells
What covers the striate (brush) border?
Glycocalyx which encloses disaccharidases and dipeptidases which are important digestive enzymes.
What are lacteals?
lipid catabolisim products that are generated from absorptive sells then passed to lymphatics.
What are goblet cells?
Interspersed between absorptive cells. They gradually increase in number from the duodenum to the ileum. they secrete protective mucus high in proteoglycans onto the surface epithelium
What are the cell types in intestinal glands?
- Enteroendocrine cells
- Paneth cells
- M Cells
- Undefferentiated cells.
describe enteroendocrine cells in small intestine?
Interesperesed between absorptive and goblet cells. They secrete many products including:
-Secretin, cholecystokinin, gastic inhibiroty peptide and motlin into the lamina propria
Describe paneth cells in S.I
Found in the bas of each intestinal gland in SI. Known to secrete lyzozyme which plays a role in controlling intestinal bacteria
describe the roll of M cells
M stands for membranous epithelial cells which are flattened and located over lymphoid nodules in the mucosa and lamina propria. Their apical surface have small folds instead of microvillus. Endocytose antigens from lumen then pass them to lymphoid cels in the underlying nodule to initiate immune response.
Describe Undefferentiated cells in the SI
The lower 1/3 to 1/2 of intestinal glands undergo continual mitosis. Differentiate into all cell types in the epithelium, New paneth cells move to the base but other cells move to the tip of glands. Oldest cells are found on the tips of microvilli except for paneth cells. Entire epithelium renews every 3-7 days
Describe the lamina propria of SI
Lacteals (Lymph vessels) are present as well as prominent muscularis mucosae. many lymphoid nodules are projecting from mucosa and lamina propria.
What are prevalent lymphoid nodules found in SI?
Peyer’s patches
Describe the submucosa of SI
Brunner’s glands is another name for SI submucosal glands. In duodenum they produce alkaline mucus to offset the acidity of the food entering from the pylorus.
Describe the muscularis externa of SI
inner circular and outer longtitudinal muscle layers.
Describe the serosa of SI
Visceral peritoneum covering small intestines; consists of connective tissue with a single layer of simple squamous epithelium.
What is the major function of the mucosa of Large intestine?
Water absorption electrolytes and adding mucus to undigested material from SI.
How does water absorption occurs in large intestines?
Passively across the apical surface of simple columnar cells due to the gradient produced by active transport of sodium ions into the extracellular space.
Are you able to see villi in large intestines as well as brush border on the surface of columnar absorptive cells?
Nah
Describe the mucosa of L.I
- two cell types dominate; goblet and simple columnar cells.
- Lamina propria and lymphoid nodules are present.
Describe the submucosa of L.I
-Composed of blood vesseles, nerves and lymphatics
describe serosa of L.I
The large intestine covered by visceral peritoneum or serosa
What are the gut associated lymphoid tissues (GALT)
- 1/4 of mucosa consists of lymphoid tissue in form of lymphoid nodules, lymphocyes, macrophages, eosinophiles and plasma cells in lamina propria
- The M cells overlying peyer’s patches and other lymphoid nodules also transport antigens from the lument to surrounding lamina propria. This can simulates lymphocytes and plasma cells activity.
