Structure + Fnc of Upper GI Flashcards
In the stomach, food is churned in the presence of digestive juices to generate a semi-fluid mass of partially digested food called chyme which leaves the stomach via the_____ and enters the duodenum
pylorus
Chyme leaves the stomach via the pylorus and enters the duodenum where it encounters
pancreatic digestive enzymes and bile from the liver
is completed in the small intestine, and digestive products are absorbed.
Digestion
The liquid residue enters the _____ where water is absorbed. As water is absorbed, the residue becomes solid generating fecal material that is collected in the rectum.
large intestine
• Initially _______ muscle action in the oral cavity and upper 1/3rd of the esophagus moves food into the alimentary canal.
voluntary
_______muscle action (peristalsis) takes over after the upper 1/3 of the esophagus to propel the food and products of digestion through the remainder of the GI tract.
Involuntary
• Four tunics define separate functional layers in the GI system:
• Mucosa • Submucosa • Muscularis externa • Adventitia / Serosa
The mucosa consists of three distinct tissue layers.
epithelium lamina propria muscularis mucosae
major site of mucosal function, varies in type depending upon function; stratified squamous or simple columnar
epithelium (part of mucosa)
loose connective tissue that supports the epithelium, which is rich in lymphatic and blood capillaries and contains lymphocytes and plasma cells
Lamina propria (part of mucosa)
- thin layer of smooth muscle required for local movements of the mucosa and folding of the mucosa
Muscularis mucosae (MM)
Layer of loose collagenous and adipose tissue that supports the mucosa. Contains large blood vessels and lymphatic vessels
Submucosa
What is present in the submucosa?
Mucous-secreting glands present in SM of esophagus and duodenum Nervous tissue; submucosal (Meissner’s) plexis (PG, parasympathetic ganglia) Control muscularis mucosae movement, blood flow and gland secreation
mixes luminal contents and propels contents along GI tract
Muscularis externa
Muscularis externa (ME) surrounds the submucosa with a thick layer of smooth muscle except in the
esophagus and anal sphincter, which also contain skeletal muscle
How is the muscularis externa arranged?
as an inner circular layer and outer longitudinal layer; responsible for peristalsis.
What kind of nervous tissue resides in the muscularis externa?
Myenteric (Auerbach’s) plexus resides between the muscle layers, and it controls peristalsis.
What protects the GI tract?
adventitia/serosa; outermost covering of GI tract
– loose connective tissue layer surrounding the GI tract located outside of the peritoneal cavity.
Adventitia
simple squamous epithelium (mesothelium) along with connective tissue covers the GI tract within the peritoneal cavity
Serosa
What is the purpose of the epithelial component in the adventitia/serosa?
secretes serous fluid to lubricate the interface between the visceral and parietal peritoneum allowing movement of the GI tract organs
Enteric nervous system - “the second brain” is composed of _______ neurons and is a division of the ______ system but can operate independent of the brain and spinal cord
~ 100 x 10 to the 6th neurons autonomic nervous system
What can regulate the enteric NS besides the brain and sp cd?
hormones secreted by enteroendocrine cells
Enteric neurons mediate their action through the standard repertoire of neurotransmitters and neuromodulators found in the brain including
acetylcholine, norepinephrine, and serotonin.
_________ system stimulates secretion and peristalsis.
Parasympathetic
________ represses peristalsis and activates activity of sphincters.
Sympathetic
Be able to identify layers of GI
Note layers in GI
Controls mucosal movement, secretory activity and blood flow
Submucosal (Meissners Plexus)
Controls peristaltic gut movements
Myenteric (Auerbach’s) plexus
Mucosal types vary throughout the G.I.
Tract depending on
function
Function of stratified squamous epithelium mainly found in the _upper G.I. and anus. _
Protective
Function of the mucosa: found in the stomach, this mucosa contains an abundance of tubular glands.
Secretory
Function of the mucosa is folded into villi to maximize surface area; found throughout
the small intestine.
Absorptive
Function of mucosa that lines the large intestine; produces mucin to help fecal movement
and absorbs water.
Absorptive/protective
What is included in the Mucosa of the esophagus?
• Epithelium (E): stratified nonkeratinized
squamous epithelium with Langerhans cells (antigen presenting cells)
• Lamina propria: narrow with lymphoid aggregates (Ly)
narrow with lymphoid aggregates (Ly)
lamina propria in the mucosal layer of the esophagus
Epithelium (E): stratified________
squamous epithelium with _________cells (antigen presenting cells)
nonkeratinized
Langerhans
clusters of mucosal glands that
secrete mucous to help propel food =
Location?
esophageal cardiac glands
can be
difficult to identify because it consists
of a single layer of smooth muscle
cells; more substantial near stomach
Muscularis mucosae (MM)
(layer in mucosa of esophagus)
What does the submucosa of the esophagus contain?
Esophageal glands arragned as acini. Has two cell types; mucous cells and serous cells that secreate pepsinogen and lysoxyme.
- Submucosa:
Esophageal glands (G) are abundant in
the submucosa. Only the______ and
_______contain glands in their
submucosal layers.
esophagus
duodenum
Esophageal glands contain what two cell types?
Where are their nucleus’s located?
They contain two cell types - mucous
cells that have a basally located nucleus
and the less abundant serous cells that
have a centrally located nucleus.
Major secretory products of serous
cells are____ and______ that
are deposited via ducts into the lumen.
pepsinogen
lysozyme
What is included in the muscularis externa in the esophagus?
— inner layer of circular smooth
muscle (CM) and an outer layer of
longitudinal smooth muscle (LM)
upper the 1/3rd of the esophagus
has _______ interspersed
with the smooth muscle. Initial
swallowing is under_____ control
and so utilizes skeletal muscle
skeletal muscle (Sk)
voluntary
Prior to reaching the diaphragm, the
esophagus is encased with an
_______. Once it traverses the
diaphragm, it is covered with a_____.
adventitia
serosa
