GI Tract Flashcards
describe filliform papillae
- small and conical
- most numerous
- entire dorsal surface
-
involved in mechanical function
- highly keratinized stratified squamous epi.
- no taste buds
filliform papillae
filliform papillae
describe fungiform papillae
- mushroom shaped
- prominent on tip of tongue
- stratified squamous epithelium (usually non-keratinized)
- taste buds in the epithelium on dorsal surface
fungiform papillae
arrows = fungiform papillae
in between arrows = filliform papillae
describe foliate papillae
- found on the lateral edges of tongue
- parallel rows separated by deep clefts
- taste buds
- rudimentary in humans
describe circumvallate papillae
- large and dome shaped
- located anterior to sulcus terminalis
- only 8-12
- surrounded by a moat-like invagination
- receives ducts of Von Ebner’s glands
- serous secretion
- receives ducts of Von Ebner’s glands
- many taste buds in epi. of lateral surface
describe taste buds and the types of cells
- extend through entire thickness of epi.
- taste pore
- 3 types of cells:
-
neuroepithelial cells
- sensory cells
- microvilli on apical surface
- turnover ~10 days
-
supporting cells
- microvilli on apical surface
- turnover ~10 days
-
basal cells
- stem cells
-
neuroepithelial cells
name the 3 distinct layers of mucosa
- epithelium
- lamina propria
- loose CT, blood & lymph vessels, mucosal glands, gut-associated lymphatic tissue (GALT)
- muscularis mucosa
- variable, usually 2 layers
- inner circular
- outer longitudinal
- contraction produces movement of the mucosa
- boundary between mucosa and submucosa
- variable, usually 2 layers
describe the function of the mucosa
- protection: separates the external lumen from tissues and organs of the body
- absorption: movement of the digested nutrients, water and electrolytes into blood and lymph vessels
- secretion: carried out mainly by glands throughout the tube which secrete mucus, digestive enzymes, hormones and antibodies
describe the submucosa
- dense irregular CT
- large blood vessels and lymphatic vessels
- some areas contain submucosal glands
- esophagus and duodenum
describe the submucosal plexus (Meissner’s plexus)
- part of enteric nervous system
- cell bodies of postganglionic PS neurons
- innervate muscularis mucosa
- derived from neural crest cells
describe the muscularis externa
- two concentric layers of smooth muscle
- inner circular
- contracts, compresses and mixes content by constricting the lumen
- forms sphincters at specific locations
- outer longitudinal
- contractions propels content of lumen by shortening the tube
- in large intestine, thickened to form three bands called teniae coli
- inner circular
submucosal plexus
pale-staining PS ganglion cells
muscularis externa
describe the myenteric plexus (Auerbach’s plexus)
- located between the circular and longitudinal muscle layers
- derived from neural crest cells
- part of enteric nervous system
- contains postganglionic PS neurons
- innervates the muscularis externa for peristlatic movement
- slow rhythmic contraction of muscle layers
myenteric/Auerbach’s plexus
describe the serosa layer of the alimentary canal
- serous membrane
- CT lined by simple sqamous epi.
- mesothelium
- small amount of underlying loose CT
- continuous w/ mesentery and lining of abdominal cavity
describe the adventitia layer of the alimentary canal
- CT not lined by simple squamous epi.
- attaches structures to the body walls
- parts of the GI tract that do not possess a complete serosal covering
- thoracic esophagus
- 2nd, 3rd, 4th parts of duodenum
- ascending and descending colon
- rectum and anal canal
- parts of the GI tract that do not possess a complete serosal covering
describe the esophagus
- epithelium = stratified squamous non keratinized
- lamina proopria: CT containing diffuse lymphatic tissue and lymphatic nodules
-
esophageal cardiac glands are present mainly in the terminal part of esophagus
- produces neutral mucus which protects from regurgitated gastric contents
-
esophageal cardiac glands are present mainly in the terminal part of esophagus
- muscularis mucosa: single layer of longitudinal muscle that begins at the level of cricoid cartilage