1B Anatomy of the GI Tract Wall Flashcards
T/F The GI tract is continuous w/ the external environment
T
What is one of the most common problems with GI tracts in the US?
Peptic ulcer disease (PUD)
What is PUD?
Gastric juice penetrates the gastric mucosal barrier, injuring the gastric wall w/ its acidic and enzymatic contents
What is acute pancreatitis?
Pancreatic juice escapes the pancreas and/or duodenum. Pathology usually involves an obstructed pancreatic duct at its entrance into the duodenum
What happens during a ruptured appendix?
The colon wall tears open, allowing intestinal bacteria to escape to the abdominal and pelvic cavities, causing peritonitis or even death
What are the four layers of the GI tract wall?
Mucosa, submucosa, muscularis externa, and serosa
What are smooth muscle pacemaker cells?
Smooth muscle cells that display rhythmic, spontaneous variations in membrane potential
What is the prominent type of self-induced electrical activity in digestive smooth muscle called?
Slow-wave potential
What is the slow-wave potential also referred to as?
Basal electrical rhythm (BER) or pacemaker potential
What is the enteric nervous system?
The neurons of the submucosal and myenteric plexuses. AKA intrinsic nerve plexus
What are extrinsic nerves and how do they differ from the intrinsic nerves?
Extrinsic nerves originate outside the GI tract and innervate the various GI organs. Intrinsic nerves are inside the walls of the GI tract
T/F The extrinsic nerves have both paraSNS and SNS
T
What part of the GI tract does the Vagus nerve innervate?
The upper GI tract - esophagus, stomach, small intestine, and ascending colon
What percentage of the vagus nerves are afferent vs. efferent?
75% are afferent
25% are efferent
What pelvic nerves innervate the lower GI tract?
S2, S3, and S4
What are pelvic nerves also known as?
Pelvic splanchnic
What parts are included in the lower GI tract that are innervated by the paraSNS of the pelvic nerves?
Transverse, descending, and sigmoid colons.
Anal canal
The majority of ParaSNS pos-ganglionic neurons servicing the GI system are what type? What are the other ones?
Cholinergic.
Some are peptidergic (VIP, enkephalins, neuropeptide Y, and substance P)
What three sympathetic ganglia serve the GI tract?
Celiac, superior mesenteric, and inferior mesenteric
What kind of fibers do these post-ganglionic fibers have?
Adrenergic
What percentage of the SNS fibers are afferent vs efferent?
about 50% each
How do the autonomic nerves (extrinsic nerves) influence GI tract motility and secretion?
By modifying ongoing activity in the enteric nervous system.
Altering the level of GI hormone secretion.
Acting directly on smooth muscle and glands.
GI (gut) hormones get secreted from which cells?
Endocrine cells in the mucosa of certain regions of the GI tract
How are GI hormones carried to other areas of the GI tract or accessory GI structures?
Thru blood
What type of influences do GI hormones exert and where do they exert them?
Excitatory/inhibitory influences on smooth muscle and exocrine cells
What part of the large intestine is innervated by the vagus nerve? What part by the pelvic splanchnic nerves?
Ascending colon is innervated by the vagus nerve.
Pelvic splanchnic nerves innervate the rest of the large intestine - transverse, descending, and sigmoid colons
What effect does the SNS have on the GI tract?
Inhibitory - Slows things down - slows down motility, secretion, digestion
When we eat, which nervous system activity is high, paraSNS or SNS?
ParaSNS
Which layer of the gut has lymph nodes?
Mucosa
Which layer of the gut has lots of glands?
Submucosa
What are the two layers of the muscularis externa layer of the gut?
Circular muscle and longitudinal muscle
Which muscle layer of the muscularis externa is responsible for segmentation? For Peristalsis?
Circular muscle for segmentation.
Longitudinal muscle for peristalsis
