GI 1 Flashcards
What are the three basic processes of the GI tract?
- ingestion - occurs from mouth to stomach
- digestion, secretion, and absorption - occurs from the stomach to the ileum
- motility - this occurs throughout the entire GI tract
what are sphincters?
they are circulatory smooth muscle sections that exist on either side of digestive organs. They are tonically contracted and must relax to function –> e.g. sphincter relaxes to let food into stomach
list the sphincters from top to bottom
upper oesophagal lower oesophagal pyloric - before SI oddi - for bile and pancreatic juice ileo-cecal - between SI and LI anal
Explain the layers of the small intestine
outside -> inside
- peritoneal membrane
- serosa
- longitudinal muscle
- circulatory muscle
- submucosa
- mucosa
- villi
- microvilli
blood vessels exist near the mucosa, nerves innervate the muscles and the glands
what is the submucosal plexus and the myenteric plexus?
submucosal plexus innervates glands (submucosa)
myenteric plexus innervates longitudinal and circular muscle (muscualris externa)
explain the difference between skeletal muscle and smooth muscle in the GI tract
skeletal –> on either end of the tract, react to all or none responses.
smooth –> exists between the two ends of the tract, graded potentials –> balance between excitation and inhibition.
- they are tonically somewhat contracted and function upon relaxation
t or f, skeletal muscle and smooth muscle are multi-nucleated
false
smooth muscle is mono-nucleated
note: SM relaxes when stimulated with NO or VIP
true or false, the mucosa is essentially the barrier between your gut microbiome and your systemic area.
true
what two things is the ENS responsible for?
- regulation of motility and secretions
2. integrated sensory and motor pathways
t or f ENS provides pain signals
false
lack of sensation, poorly localised, cramping feeling is characteristic of what?
pain in the intestinal area
what detects pain in the intestine if it is not from the ENS?
dorsal root ganglia somatic neurons.
what is the extrinsic innervation of the GI tract?
- ANS
- parasympathetic (vagal)
- sympathetic - somatic sensory - dorsal root ganglia
NOT ENS - this is the intrinsic innervation
what creates the barrier between the lumen and the body?
the epithelial mucosa
what part of the SC does the SNS stimulation stem from for the GI tract?
the thoracic-lumbar section (middle)
think - vagal comes from top (PNS) so SNS gets middle
why are mucosal epithelial cells susceptible to chemotherapy?
Epithelial cells are constantly growing, maturing, dividing, and dying off. chemotherapy targets cells like this since this what cancer is like.
what kind of epithelium is the intestine?
simple columnar epithelium
what two functions to goblet cells have?
- secrete mucus
2. important for intestinal folding
what are the important layers of the mucosa?
the lamina propria + the epithelium + the muscularis mucosa
Note, the layers go epithelium lamina propria muscularis mucosa submucosa muscularis externa - splits into longitudinal and circular muscle adventitia / serosa
where are the gut immune cells located?
lamina propria right under the epithelium
what are Peyer’s patches?
lymphatic tissue of the lamina propria with immune cells
what is the mesentery?
the mesentery is the membrane that attaches the GI tract to the abdomen wall –> similar to peritoneum
what controls motility in the gut?
intrinsic innervation via the ENS through the myenteric plexus.
what conveys information to the CNS from the gut
the extrinsic innervation
e.g. the dorsal root ganglia conveys pain (somatic sensory innervation)
