Digestive 1 Flashcards
Why can we say that the GIT is extremely efficient?
It can absorb 99% of carbohydrates, 95% of fats and 92% of proteins
T or F
The GIT is an extracellular structure.
True, it communicates with the external environment on both ends
What as important physiologically if the GIT is an extracellular structure?
There are going to be important barrier components
How long is the GIT in the living adult?
4.5m
Which surface is larger and how much larger? internal or external? Why?
The internal surface is about 600x larger bc there are folds (increases absorption surface area)
What are the 4 main layers of the GIT? (out to in)
Serosa (thin, tough layer of connective tissue)
Muscularis externa
Submucosa
Mucosa
What are the layers within the muscularis externa layer?
longitudinal fibers
circular fibers
What is particular about the neural control of the muscularis externa throughout the GIT?
The striated portions (upper 1/3 and anus) are not under the same neural control as the smooth portions
What are the 3 layers within the mucosa?
Muscularis mucosae (smooth)
Lamina propria (loose connective)
Epithelial layer (with glandular cells)
What nervous system is responsible for the GIT? How is it different?
Enteric nervous system
It is an independent and integrated nervous system
What are the two plexuses of the ENS and where are they?
The submucosal plexus is in the submucosa
The Myenteric plexus is between the two muscularis externa layers
What is important in the workings of the ENS?
They create reflex arcs
What are the NT and receptors of the excitatory and inhibitory neurons of the ENS?
E: ACh onto muscarinic (can be blocked by atropine)
I: release NANC transmitters like NO
The system independent of the CNS and embedded in the gut is called the
short reflexes
What are the various things ENS ganglions can synapse with? (3)
smooth muscle
Endocrine and exocrine cells
T or F
The ANS cannot have input onto the ENS (explain)
False, the ANS can input via ENS neurons ONLY
What do ANS neurons (pre or post) secrete onto ENS neurons and what is the intended action (excitatory or inhibitory) of each the PANS and SANS
PANS: PREganglionic releases ACh onto nicotinic receptors to excite the ENS (and increase blood flow)
SANS: POSTganglionic releases NA onto muscarinic receptors to inhibit the ENS (and reduce blood flow)
What are the parasympathetic nerves that innerve the ENS?
vagus nerve and the pelvic nerves
The circuit involving both the ENS and the ANS is called the
long reflexes
