Medical Physiology Block 6 Week 1 Flashcards
Identify the different segments of the gastrointestinal tract, their locations, and the sphincters that regulate movement of chyme through it.
- oropharynx (sphincter = upper esophageal; glands: parotid and salivary); 2. esophagus (lower esophageal sphincter); 3. stomach (pyloric sphincter); 4. Small intestine- duodenum, jejunum, and ileum (iliocecal; glands: pancreas); 5. Large intestine- ascending colon, transverse colon, descending colon, anus (internal anal sphincter and external anal sphincter
Digestion requires enzymes secreted from where in the body?
mouth (salivary glands), stomach, pancreas, and small intestine
What organs are derived from the foregut of the primitive gut tube? what artery supplies this division and what is the origination of parasympathetic innervation?
esophagus, stomach, parts of the duodenum, liver, pancreas, gall bladder, pharynges, lungs, thyroid, and spleen; celiac artery and vagus nerve
What organs are derived from the midgut? what artery supplies this division and what is the origination of parasympathetic innervation?
parts of the duodenum, jejunum, ileum, cecum, appendix, ascending colon, and parts of the transverse colon; superior mesenteric artery and vagus nerve
What organs are derived from the hindgut? what artery supplies this division and what is the origination of parasympathetic innervation?
parts of the transverse colon, descending colon, and rectum; inferior mesenteric artery and pelvic splanchnic nerves
Do the foregut rotate during development? midgut? hindgut?
Yes, 90 degree rotation to the right; yes, a further 180 degree rotation; No
Define a peritoneal organ; retroperitoneal organ
has a mesentery and is almost completely enclosed in peritoneum (is mobile); partially covered with peritoneum and is immobile (covered only anteriorly)
What is peritoneum comparable to in other parts of the body? what are mesenteries?
pleural cavity: visceral and parietal layers (parietal layer lines the abdominal cavity and visceral layer forms the serosa of abdominal organs); portions of the peritoneum that suspend the gut and its derivatives and provide path for blood vessels and nerves to viscera
The greater omentum is formed from? how many layers is it?
double layer of dorsal mesentery; four
What are the major peritoneal organs?
stomach, liver, spleen, jejunum, ileum, appendix, and transverse colon
What are the major retroperitoneal organs?
thoracic esophagus, kidneys, adrenals, ureter, aorta, inferior vena cava, anus
Which organs lost a mesentery during development (secondary retroperitoneal; dorsal mesentery joined with body wall)?
parts of duodenum, majority of pancreas, ascending colon, descending colon, and parts of rectum
When the stomach rotates 90 degrees clockwise, what happens to the right vagus nerve?
becomes posterior vagal trunk
What attaches to the greater curvature of the stomach?
dorsal mesentery; it is considered the greater curvature becomes the dorsal portion of the stomach proliferates faster than the ventral portion
What is the ventral mesentery attached to?
liver (from behind); develops into lesser omentum
The appendix is appended to which organ? what quadrant is it located in?
cecum; lower right
Describe the arterial, venous, and lymph flow of the GI tract
arteries along the muscular layer branch into arterioles at submucosa (form a plexus), which branch into capillaries in the mucosal villi; Venules emerging from the villi and mucosal and muscularis layers converge into veins (exit the intestinal wall, paralleling the arterial supply); lipophilic nutrients are taken up by lacteals, which merge with lymphatics and drain into thoracic duct
What does the majority of the blood flow to the liver come from? What are the consequence of portal hypertension?
portal vein which carries blood away from the other GI tract organs; ascities (liver cirhossis and collateral blood pools such as caput medusae, varices, and hemorrhoids)
Describe postprandial (after a meal) hyperemia.
CNS anticipatory increase in blood flow during cephalic phase; production of vasodilator metabolites; local increases in blood osmolarity; CCK and other hormones may increase intestinal blood flow (BLOOD FLOW INCREASES SEQUENTIALLY DOWN THE GI TRACT); contractions decrease blood flow
In regards to the enteric nervous system, what stimulates vasoconstriction of splanchnic vessel? vasodilation?
alpha adrenergic innervation; vagal nerve stimulation indirectly increases blood flow
What is the result of sustained splachnic vasoconstriction following a severe hemorrhage?
the ischemic mucosal epithelia slough off (susceptible due to countercurrent flow); endotoxic shock (bacteria and toxins escape from lumen; normally detoxified by liver)
Which sphincter has the highest resting pressure?
upper esophageal sphincter
What happens to the pressure in the esophagus after swallowing? What happens to the glottis and how is breathing affected? Can pressure be below zero, and if so why?
After a dry swallow (UES relaxes), the pressure wave of primary peristalsis (contraction/relaxation) moves sequentially down the esophagus; glottis is closed and breathing is inhibited; yes and this is reflective of thoracic pressure (and work of respiratory muscles)
What is a method for measuring pleural pressure?
inflating a balloon in the esophagus