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What are the functions of the urinary system? (5) (4 are regulatory)
- Plasma ionic composition
- Plasma vol
- Plasma osmolarity
- Plasma pH
- Remove metabolic waste and foreign substances from plasma
Secondary functions of kidneys include secretion of ___ and ____, activation of ___, and ____ (involved in metabolism).
- erythropoietin, renin
- Vit D3 to calcitriol
Kidneys: ___ urine
Ureters: ___ urine from ___ to ____
Bladder: ___ urine
Urethra: ___ urine from ___ to ___
- transport; kidneys to bladder
- excrete; bladder to outside body
Smallest functional unit of kidney
___ allows us to conserve water
Loop of henle
4 steps of renal processes
- 1. Glomerular filtration: from glomerulus to Bowman's capsule
- 2. Reabsorption: from tubules to peritubular capillaries
- 3. Secretion: from peritubular capillaries to tubules
- 4. Excretion: from tubules out of body
What are the two parts of the renal corpuscle?
Bowman's capsule and glomerulus
Does the portion of cardiac output the kidneys
receive match the portion of body weight the kidneys represent?
No, kidneys are less than 1% body weight, but receive 20% of cardiac output at rest
Cortical nephron is located primarily in ___ but a juxtaglomerular nephron is located in both cortex and medulla (b/c loop of Henle dips deep in medulla)
Mvmt of protein-free plasma from glomerulus to Bowman's capsule
Volume of plasma filtered per unit of time. What is normal?
- Glomerular filtration rate (GFR)
- 180 L/dy (or 125 mL/min)
Epithelial cell of Bowman's capsule
Why is GFR highly regulated?
B/c if mean arterial pressure gets too low (such as lots bleeding or lots sweating...ie fluid loss), so does filtration pressure and thus the GFR. Also decrease in MAP increases symp nerve activity, causing arterioles to constrict, which decreases blood flow to glomerulus, which decreases filtration pressure, which decreases GFR
Between what blood pressures can we keep GFR constant?
80-180 mm Hg
Small increase in ____ causes large increase in fluid filtered and excreted
GFR (glomular filtration rate)
Selective transport of molecs from inside renal tubules to interstitial fluid, which then move into bloodstream via peritubular capillaries
Just be aware that most solutes with the
exception of urea are mostly reabsorbed.
During reabsorption, solutes move from inside renal tubules to ____, then to ___.
interstitial fluid, then into bloodstream via peritubular capillaries
Where does most solute reabsorption occur?
Proximal convoluted tubule (but some in distal as well)
What are the 2 barriers for reabsorption in kidneys?
- Epithelial cells of renal tubules
- Endothelial cells of capillary
What is the difference between active and passive reabsorption?
- Active: solutes move against their concentration gradient (this causes water to passively move towards the direction of higher solute concentration)
- Passive: solutes diffuse down their concentration gradient
How does solute reabsorption affect water
During active solute reabsorption, solutes move against their concentration gradient, and this causes water to passively move towards the direction of higher solute concentration
Point at which a certain plasma concentration of a solute is totally saturated by carrier proteins, and some of it "spillsover" into the urine
What does renal threshold mean for a solute
like glucose that needs a carrier molecule to be reabsorbed?
It will show up in the urine, such as is the case with a diabetic. Also increases urine volume b/c glucose is considered a solute, and when glucose is in the tubules, water stays there also instead of being reabsorbed.
Where do we have unregulated reabsorption?
- Unregulated: proximal tubule
- Regulated: distal tubule/collecting duct
glucose is actively reabsorbed by cotransport of sodium across the ______, followed by facilitated diffusion across the ____
- Apical membrane
- Basolateral membrane
What is the loop of Henle’s job?
Establishes conditions necessary to concentrate urine, which minimizes water loss
When a solute, such as ___ or ___, moves from peritubular capillaries into tubules. Same barriers and transport mechanisms as reabsorption but opposite direction
K+ or H+
When a solute and water are eliminated from body in form of urine
Amount of a substance excreted =
Amt filtered + Amt secreted - Amt reabsorbed
Amt of a substance that is excreted depends on: (3)
- Filtered load
- Secretion rate
- Reabsorption rate
If amt of solute excreted per min was less than filtered load --> solute was ____.
If amt of solute excreted per min was more than filtered load---> solute was ___.
Where does urine go from the end of the renal
Drains into renal pelvis and into ureter, which lead to bladder