Exam #5: Intro to GI Flashcards
What is the UES? What two anatomical structures does this sphincter separate?
UES= Upper Esophageal Sphincter
This is the sphincter that segregates the mouth from the esophagus
What is the LES? What two anatomical structures does this sphincter separate?
LES= Lower Esophageal Sphincter
This is the sphincter the segregates the esophagus from the stomach
What is the pyloric sphincter? What two anatomical structures does this sphincter separate?
The pyloric sphincter is the sphincter between the stomach & small intestine i.e. pylorus of stomach & duodenum
What is the ileocecal sphincter? What two anatomical structures does this sphincter separate?
This is the sphincter muscle also known as the “ileocecal valve” between the ileum & cecum (small & large intestine)
What is the IAS? What two anatomical structures does this sphincter separate?
IAS= Internal Anal Sphincter
What is the EAS? What two anatomical structures does this sphincter separate?
EAS= External Anal Sphincter
What are the four layers of the GI tract?
1) Serosa= outer, connective tissue & squamous epithelium
2) Muscularis= longituindal & circular smooth muscle
- Neurons that innervate regulate peristalsis
3) Subumucsa= large blood vessels, glands, and connective tissue
4) Mucusa= inner & can be divided into:
- Lamina propria= capillaries, neurons, and immune cells
- Lamina muscularis muscoa= smooth muscle to coordinate GI motility
What are the three modes of cell communication in the GI system?
1) Endocrine= utilizes blood
2) Paracrine= localized
3) Neurocrine= neurons innervating endocrine, vascular, or muscle cells
Define the relationship between the parasympathetic, sympathetic, and enteric branches nervous systems.
The SNS, PNS & enteric nervous system (ENS) are all parts of the autonomic nervous system:
- ENS communicates with the SNS & PNS
- Enteric= intrinsic
- SNS & PNS= extrinsic
*****Note that the GI tract can function INDEPENDENTLY of the CNS b/c of ENS, but if works better with the SNS & PNS input
What is the function of PNS in GI tract?
Generally, think STIMULATION i.e. parasympathetic innervation:
- Stimulates motility
- Increases blood flow via vasodilation
- Increases release of GI secretions
What is the function of the SNS in GI tract?
Generally, think INHIBITION i.e. sympathetic innervation:
- Inhibits motility
- Causes a reduction in blood flow via vasoconstriction
- Inhibits release of GI secretion
- **Note direct vs. indirect effects:
- Indirect= ENS inputs
- Direct= input directly on GI
What is the function of the enetric NS in GI tract?
Generally, the ENS is an independent nervous system entirely for the GI tract that is contained in the tissue layers of the GI tract; it is modulated by SNS & PNS input. Functions:
1) Motor neurons stimulate or inhibit smooth muscle contraction
2) Promotion of vasodilation & increased blood flow
3) Regulation of water, electrolyte, and hormone secretion
4) Sensory neurons relay stretch, pain, and chemical to extrinsic fibers
Associative= interneuron
Intestinofugal= regulate sympathetic ganglia
What is the function of associative neurons in the ENS?
These are interneurons that communicate between ENS neurons
What is the function of intestinogufal neurons in the ENS?
These neurons leave the GI tract and termination on sympathetic ganglia; they regulate sympathetic input to the GI tract
What the effect of ACh on GI function?
Generally excitatory
- Vasodilation
- Increase secretions
- Smooth muscle contraction
*****This may be done indirectly via the ENS
What the effect of NE on GI function?
Generally inhibitory
- Vasoconstrictive
- Decrease secretion
- Inhibit smooth muscle contraction
What the effect of DA on GI function?
Generally inhibitory
- Vasoconstrictive
- Decrease secretion
- Inhibit smooth muscle contraction
*****Note that DA also inhibits ENS neuronal firing by interacting with pre-synaptic D2 receptors
