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What is a ureter?
Connects kidneys to the bladder (to move urine)
What is a urethra?
Connects bladder to the genitals (to move urine)
What percentage does each kidney receive of cardiac output?
10% TO EACH KIDNEY-- So total 20%
What is primary function of the kidneys?
To filter the blood and remove wastes, control body fluid balance and regulate balance electrolytes. (All the blood in our bodies passes thru the kidneys several times a day).
As the kidneys filter blood, they create urine. Urine flows -> ureters -> bladder ->urethras
Each kidney contains around a million units called nephrons, each of which is a microscopic filter for blood.
What is a nephron?
basic structural and functional unit of the kidney.
Chief function: to regulate concentration of H2O & soluble substances (ie sodium salts) by filtering the blood, reabsorbing what is needed and excreting the rest as urine.
1= Bowmans Capsule (around glomerulus)
2= proximal convoluted tubule (tube before loop)
3= loop of henle
4= distal convoluted tubule (tube after loop)
5= Collecting tubule (which goes to renal pelvis filled with waste, aka urine)
Kidneys recieve what percentage of cardiac output?
What are the three basic processes of nephron filtration?
- glomerular filtration
- tubular reabsorption
- tubular secreation
filtration = when something transfers from glomerulus to bowmans capsule
reabsorption = taken back into the blood (leaving tube)
- secretion = pushed from blood into tubes
- THINK OF IT AS POV FROM BLOOD VESSELS
What can pass through?
- everything EXCEPT
What is driving forces (or what pushes) glomerular filtration?
If BP goes down... what effect does it have on kidneys? (or urine output) And what happens when BP goes up?
- BP goes down, then kidneys slow down, less urine output
- BP goes up, then kidneys speed up and increase urine output (b/c glomerular rate increases)
What is the normal glomerular filtration rate?
120 (or 125) mL / min
this equates to 180L/day
During filtration, out of the 125mL/min..... How much is reabsorbed by the body?
In filtration, how much of glucose gets reabsorbed?
In filtration, how much of sodium gets reabsorbed?
What increases sodium reabsorption?
Aldosterone increases sodium reabsorption
What follows sodium around? What then follows that?
Water then follows, by osmosis! How much? 99%
In glomerular filtration, what can pass through?
- EVERYTHING EXCEPT:
What pushes glomerular filtration?
Which hormone increases sodium?
Renin is released by the kidneys. Renin leads to the secretion of aldosterone (comes out of adrenal cortex).
- The kidneys can also secrete erythropoietin when the blood doesn't have the capacity to
- carry oxygen. Erythropoietin stimulates red blood cell production.
Vitamin D from the skin is also activated with help from the kidneys. Calcium (Ca+) absorption from the digestive tract is promoted by vitamin D.
Which hormone increases water reabsorption?
ADH -- anti diuretic hormone (makes water reabsorb = a dark concentrated urine)
fyi: alcohol inhibits ADH, thus making you pee more since water isn't being reabsorbed by body
Can the kidney's make bicarbonate?
How much bicarbonate gets reabsorbed (under healthy circumstances)?
Under normal circumstances, the kidney is able to completely reabsorb all the filtered bicarbonate.
To completely reabsorb bicarbonate,the kidney must secrete 4320 meq/day of H+ (in addition to the amount required) to excrete the daily acid load.
This is vitally important, since any loss of bicarbonate in the urine would disturb acid base balance
How do kidneys control blood pH?
The kidneys help maintain the blood pH mainly by excreting hydrogen ions and reabsorbing bicarbonate ions as needed.
What part of the kidney secretes H+ ions?
the collecting duct
- if body thinks blood is too acidic= more H+ secreted = acidic urine (low pH)
if body thinks blood is too basic/alkaline= more bicarbonate secreted= alkaline urine (high pH)
What contracts/ reflexes for the bladder to work?
When the bladder fills with urine (about half full), stretch receptors send nerve impulses to the spinal cord, which then sends a reflex nerve impulse back to the sphincter at the neck of the bladder, causing it to relax and allow the flow of urine into the urethra.
The Internal urethral sphincter is involuntary.
sympathetic (fight!) = inhibits bladder
parasympathetic (normal) = bladder contracts
what sphincters control what
-Internal urethral sphintor = involuntary/autonomic (made of smooth muscle)
-External urethral sphinctor = voluntary/ somatic nervous (made of skeletal muscle)
For successful urination
pressure in bladder reaches threshold (signaled from stretch sensors) THEN bladder contracts AND sphincter relaxation