Renal 2- The Urinary System Functional Anatomy and Urine Formation by the Kidneys Flashcards
what are the renal functions
- regulation of water and electrolyte balance
- regulation of arterial pressure
- regulation of solute concentrations (osmolarity)
- excretion of metabolic waste products and foreign chemicals
- erythropoiesis via erythropoietin
- regulation of acid- base balance
- regulation of active vitamin D (calcitriol) production
- gluconeogenesis
what metabolic waste products and foreign chemicals are the kidneys responsible for regulating
- urea, uric acid, creatinine, bilirubin
- drugs, pesticides, food additives
kidney will increase or decrease excretion rate of a substance to match ____
input
___ period of time between disturbance and balance
small
describe the position of the kidneys in the body cavity
retroperitoneal
what is the medulla of the kidneys composed of
-renal pyramids
- renal columns
what do renal pyramids contain
- nephrons
-border of cortex/medulla
-papilla
what is the functional unit of the kidney and what does it do
-nephron: produces urine
what is the pathway of urine
minor calyx -> major calyx -> renal pelvis -> ureter -> urinary bladder -> micturition reflex
what do the walls of the ureters contain
smooth muscle
describe peristalsis in the ureters
-calyces stretched by urine
- initiates peristaltic wave that flows through pelvis, along ureter to bladder
what type of nerves alter peristalsis
autonomic
what does the PNS do to peristalsis? SNS?
- PNS: increases it
- SNS: decreases it
what do the ureters enter the bladder through
the detrusor muscle
what does the muscle tone of the detrusor muscle do to the ureter
compresses ureter and prevents back flow of urine during micturition
what does the peristaltic wave do to the ureter
increase pressure within the ureter, opening ureter lumen, allowing urine to flow into bladder
what is the vesicoureteral reflux
-backflow of urine into ureter
- enlargement of ureters
-increase pressure and damage to renal pevlis
what type of innervation do the ureters have
rich pain innervation
what is the ureterorenal reflex
-ureters blocked (ex: stone)
- reflex to reduce RBF and urine formation
-protective
what type of muscle is the detrusor muscle and what junctions does it contain for cell communication
-smooth muscle
- gap junctions conduct APs
what type of muscle is the internal sphincter and what does it do
- smooth muscle and elastic tissue
- intrinsic tone
- prevents bladder emptying under pressure increases to threshold
what type of muscle is the external urethral sphincter
voluntary
what do visceral sensory neurons in the pelvic nerves detect
degree of bladder stretch
what do parasympathetic neurons in the pelvic nerves do
stimulate contraction of detrusor muscle and relaxation of internal sphincter
what is the pudendal nerve and what does it do
somatic motor neurons controlling external sphincter
what do sympathetic neurons in the pelvic nerves do
control bladder blood vessels
describe the micturition reflex (stimulus, reflex receptor, afferent, integrating center, efferent, effector, effector response, feedback type)
-stimulus: bladder stretch
- reflex receptor: stretch receptors in the bladder wall
- afferent: visceral sensory
- IC: spinal cord (spinal reflex)
- efferent: parasympathetic
-effector: detrusor smooth muscle
- effector response: local- contractions. systemic= stretch
- feedback: positive
describe the pattern of the micturition reflex
-after time reflex fatigues and ceases and bladder relaxes
- if bladder not emptied, reflex goes away then occurs again
- frequency and power of contractions increases as bladder fills
- once powerful enough, inhibits pudendal nerve to override voluntary control, allows urine to flow
what happens in voluntary urination
- contract abdominal muscles
- increases bladder pressure
- activates micturition reflex with voluntary relaxation of external urethral sphincter
what percentage of CO goes to the kidney
20%
what does the renal artery branch off of
aorta
where does the renal artery enter the kidney
at the hilum
describe the renal microcirculation in general
two arterioles and two capillary beds
describe glomerular microcirculation
- high pressure for filtration
- afferent and efferent arteriolar resistance can be altered to alter Pc in glomerular capillaries
describe peritubular microcirculation
-low pressure
-secretion and reabsorption
what is the pathway of microcirculation
-afferent arteriole -> glomerular capillaries -> efferent arteriole -> peritubular capillaries -> venules
what is the order of flow through the nephron
-glomerulus
- bowmans space
-PCT
-Proximal straight tubule (PST)
- descending loop of henle
- thin ascending loop of henle
- thick ascending loop of henle
- distal convoluted tubule (DCT)
-cortical collecting duct
- medullary collecting duct
each collecting duct collects fluid from about _____ nephrons
4000
____collecting ducts per kidney
250
_____ nephrons per kidney
1,000,000
what are the two classes of nephrons and what is the percentage of both
-cortical (70-80%)
- juxtamedullary (20-30%)
describe cortical nephrons
-glomerulus in outer cortex
- short loops of henle
-peritubular capillaries
describe juxtamedullary nephrons
- glomerulus near cortex/medulla border
-long loop of henle (extends deep into medulla) - vasa recta
what is the role of juxtamedullary nephrons
concentrates urine
where and how does filtration occur
- in glomerular capillaries
- occurs via bulk flow
how goes glomerular filtrate differ to plasma
exact same except glomerular filtrate has no proteins
what is GFR
rate of filtrate production
what is reabsorption and where does it occur
removes wanted substances from glomerular filtrate and puts it back into blood in peritubular capillaries
-passive and active transport processes across nephron epithelium
what is secretion and where does it occur
- removal of unwanted substances still in plasma and secrete it into glomerular filtrate in nephron
- passive and active transport processes across nephron epithelium
what is excretion and where does it occur
-removal of metabolic waste
-urine exits collecting duct into minor calyx
what is the amount of sodium filtered, reabsorbed and excreted per day
- filtered: 25,560
- reabsorption: 25, 410
- excreted: 150
why do we filter so much and then expend so much energy to return greater than 99% back to the ECF
we filter because we want to get rid of unwanted substances and return all the good stuff
