Micturition and Colonic Function Flashcards
what is the posterior urethra?
funnel shaped extension of the body of the bladder that connects to the urethra. includes the internal sphincter
what lies on the posterior wall of the bladder between the ureters? what happens to it during bladder emptying?
the smooth trigone area
relaxes during bladder emptying
what is the body of the bladder composed of?
the detrusor muscle
describe the bladder emptying reflex.
stretch receptors from the posterior urethra usually trigger micturition
response is inhibited and control of this reflex is learned
what structure in the CNS control the detrusor muscle and urinary sphincters? what controls this center?
pontine micturition center
it is controlled by suprapontine centers
what does the PNS control in micturition? what inhibits it?
control the detrusor muscle contraction and internal sphincter relaxation
inhibited by efferent impulses from the brain
what nerve innervates the external sphincter?
the pudendal nerve
describe the SNS control over micturition
beta adrenergic receptors inhibit detrusor contraction
alpha adrenergic receptors promote contraction of the internal sphincter
what are the abnormalities of micturition?
atonic bladder and incontinence by sensory destruction
automatic bladder by suprasacral spinal injury
neurogenic bladder by lask of inhibitory signals from brain
what are the functions of the large intestine?
move material from SI to rectum
eliminate fecal matter through anus
extract water, electrolytes and nutrients
what does the colon secrete and what is its function?
mucus to bind feces, aid fecal movement and protect the colonic mucosa
what is the gastroileal reflex?
intensifies peristalsis in the ilem to empty its contents into the cecum
what are the comparative dwell times and functions of the large intestine?
ascending colon- absorption, short dwell time
transverse colon- absorption, long dwell time (24 hrs)
descending colon- stool storage
what are the two types of diarrhea?
osmotic- non absorbable solutes in lumen
secretory- excess secretion of fluids by crypt cells due to bacteria
what delays ileal emptying into the colon? how is this mediated?
distension, pressure or irritiation of the cecum
mediated by myenteric plexus and SNS
what are the symptoms of appendicitis? what is the cause?
symptoms: gastric pain, vomiting and fever. if not removed- peritonitis and septicemia
cause is obstruction of appendix by calcified fecal matter
what immune tissue is in the colon?
lymphatic nodules (no pyer’s patches)
what is absorbned and secreted by the colon?
absorbs Na, Cl and water (follows solutes)
secretes K and bicarbonate
what apical transporters are in the colon mucosa?
Na/H and Cl/HCO3 antiporters (electroneutral) and active K secretion
what stimulates K secretion into the lumen of the colon?
aldosterone, cAMP and cholera
how is electrical conduction in the large intestine similar to the small intestine?
there are slow waves that are pace makers
no action potentials unless there are triggers from the PNS, SNS, chemical or stretch
what are haustrations?
large circular muscle constrictions that allow slow segmental propulsion and mixing- time for fluid and electrolyte reabsorption
what are mass movements?
large peristaltic movements that force feces towards the rectum. haustrations disappear. signal the urge to defecate
what is the gastrocolic reflex?
reflexive mass movement after a meal
