Digestive System IV Flashcards
(31 cards)
Characteristics of undifferentiated crypt cells (3)
- located in basal portion of gland
- give rise to other types of epithelial cells
- intestinal epithelium replaced every few days
Characteristics of goblet cells (2)
- secrete protective mucin
- increase in numbers caudally in intestine
Characteristic of enteroendocrine cells
important in hormonal regulation of GI function
Characteristics of paneth cells (3)
- only found in base of gland
- have apical membrane bound granules
- probably control the microflora of the crypts
Characteristics of globular leukocytes (3)
- have large eosinophilic globules
- small heterochromatic nucleus
- intraepithelial as well as in lamina propria
Characteristics of M cells (3)
- located over lymphatic areas or nodules
- apical surfaces have blunt microvilli or ridges
- take up antigens by endocytosis
Characteristic of intraepithelial lymphocytes
common throughout intestine
Characteristics of enterocytes (intestinal absorptive cells) (3)
- numerous on surface of villi in small intestine, luminal surface in large intestine, and glands of both
- columnar w/ apical microvilli
- glycocalyx covering microvilli serve as anchorage site for digestive enzymes
Functions of intestinal enterocytes (5)
- active uptake of small molecules
- resynthesis of triglycerides from fatty acids that diffused into the cell
- formation of glycoprotein droplets (chylomicrons)
- (neonates) takes IgG into absorptive cells in jejunum and ileum
- protease resistant IgAs from mucosal yphatic tissue are passed into lumen to fight foreign invaders
Order of lipid absorption in enterocytes
- lipids broken down in gut lumen
- resulting glycerol, fatty acids, and monoglycerides diffuse across the plasmalemma of apical microvilli
- resynthesis of triglycerides by SER
- protein synthesis by RER
- synthesis of glyco- and lipoproteins by golgi
- assembly into chylomicrons
- exocytosis of chylomicrons at basolateral cell membrane and diffusion into capillaries
3 secretions of enterocytes
- enzymes secreted to glycocalyx
- active movement of ions at basal membrane
- chylomicrons released at lateral membrane by exocytosis
What must be intact for peristalsis to occur?
intrinsic interneurons
What does the submucosal plexus in the T. submucosa do?
- sensory to epithelium
- motor to muscularis mucosae and blood vessels
What does the myenteric plexus in the T. submucosa do?
- coordinates peristalsis
- stretch receptors
- motor to T. muscularis and blood vessels
What 3 things make up the intestinal mucosal barrier?
mucous
bicarbonate
apical junctions (seal lumen)
Characteristics of large intestines (3)
- site of microbial action
- epithelium absorbs or secretes H2O and electrolytes, secretes mucus, absorbs products of fermentation in non-ruminant herbivores
- forms fecal mass
Anorectal line
marks the separation between rectum and anal canal
epithelium changes from simple columnar to stratified squamous
Anal canal
short terminal segment of digestive tract that is lined by stratified squamous epithelium
Where does the anal canal terminate?
anus
Anal columns
longitudinal folds which alternate with sinuses
continuous with rectal columns and sinuses in ruminants but not present in horse
Anocutaneous line
point at which stratified squamous epithelium becomes keratinized
it is a mucocutaneous junction
External anal sphincter is made of what kind of muscle?
skeletal muscle
Internal anal sphincter is made of what kind of muscle?
thickening of the circular layer of the smooth muscle of the T. muscularis
Anal sacs (or perianal sinuses)
located on either side of the anal canal between the external and internal anal sphincters
ducts from the anal sacs open into the anal canal at the anocutaneous line
