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29 Cards in this Set
- Front
- Back
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functions of the kidneys?
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Maintain fluid and electrolyte balance
Disposal of water‐soluble wastes Secondary functions o Erythropoetin (EPO) production o Vitamin D activation |
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afferent arterioles bring blood
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to the kidneys
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efferent arterioles bring blood
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out of the kidneys (exit = efferent)
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what is normal GFR?
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125ml/min
(with a normal hematocrit (percentage of RBCs) of 45%) |
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how much absorption occurs in the proximal tubule?
what is absorbed there? |
60%
most of the Na, Cl, HCO3, K, glucose, urea, and water |
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how much absorption occurs in the Loop of Henle
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30% occurs
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how much absorption occurs in the distal tubule?
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7%
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what percentage of the original filtrate enters the collecting ducts?
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3%
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what is the goal of GFR?
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to generate enough pressure for urine formation
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how does Systemic blood volume affect GFR
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↑Systemic BP~↑GFR
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what is the driving force for filtration?
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hydrostatic pressure in golmerular capillaries
Colloid osmotic/oncotic pressure: proteins are negatively charged, attract + ions which then attract water. THUS, oncotic pressure opposes filtration by holding water, ions in capillaries |
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what gets filtered?
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Water, electrolytes (H+, K+), solutes (Creatinine, urea,
glucose, AAs), organic acids, phosphates |
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what does not get filtered?
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Negatively charged particles (i.e., protein) or particles too
large to pass (RBCs, WBCs, platelets) |
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what structures allow each individual nephron to regulate GFR?
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juxtaglomerular apparatus
macula densa |
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where is the macula densa located?
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in the distal convoluted tubule
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what does the macula densa do?
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sensse changes in NaCl delivery
When NaCl increases, signal is sent to slow GFR |
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what is the juxtaglomerular apparatus, and what does it do?
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An endocrine gland. JG cells are modified smooth muscle
cells of afferent/efferent arterioles. JG cells are also baroreceptors. Synthesize, store, and release Renin |
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the juxtaglomerular apparatus is composed of what four things?
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the macula densa cells of the distal tubule
the afferent and efferent arterioles the glomerulus the renin-secreting juxtaglomerular cells |
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what is the role of the macula densa in GFR?
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they sense changes in the volume delivered to the distal tubule, probably by sensing the NaCl delivery. High NaCl in the distal tubule means that GFR is too high and the macula densa sends signals to the glomerulus to reduce GFR. Low NaCl levels cause the macula densa to send signals to increase GFR.
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explain how the JG cells regulate GFR
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in response to low GFR, the JG cells secrete the enzyme renin. Renin causes conversion of Angiotensin to Angiotensin II (lungs) which leads to potent vasoconstriction of efferent arterioles, which increases GFR
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what is the best indicator of how well the lungs are excreting metabolic wastes?
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Partial pressure of arterial CO2 (PaCO2)
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what is the best indicator of how well the kidneys are excreting metabolic wastes?
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HCO3- in blood
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how does the kidney excrete metabolic wastes?
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H+, NH3+, K+: too much not good. Homeostasis is driven by pH. When pH drops, H+ ↑. The
kidney can compensate for the excess H+ by creating HCO3‐, which binds to H+ to make H2CO3…carbonic acid, which can be excreted by the lungs! |
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what is the significance of NH4 and HPO4
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they are buffers - Excess H+ can also be excreted in urine with ammonia as a buffer: NH4
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Describe the Renin-Angiotensin-aldosterone System (RAAS)
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renal hypoperfusion (from low blood pressure), decreased Na+ deliver and sympathetic activation stimulates the release of the enzyme renin from the juxtaglomerular cell sin the kidney. Renin acts on circulating angiotensinogen to produce antiotensin I. Angiotensin-converting enzyme (ACE), found primarily in the vasculature of the lungs, converts angiotensin I to angiotensin II, a very potent vasoconstrictor. Angiotensin II also stimulates the release of aldosterone from the adrenal cortex, which promotes sodium and water retention by the Kidneys, which increases blood volume. The result of the vasoconstriction and increase blood volume is increase blood pressure. The increased blood pressure then signals the cessation of renin release.
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where is aldosterone secreted from?
what does it do? |
adrenal cortex
promotes the retention of Na and water by the kidneys, there by increasing blood volume, which aids in increasing blood pressure |
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renin is released when what three things happen
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blood flow to kidney
2. serum Na+ (osmolality) 3. Activation of SNS nerves |
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where is ADH secreted from
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from the posterior pituitary
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describe how ADH (vasopressin) affects blood volume
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osmoreceptors in the hypothalamus detect increased osmolality in extracellular fluid. This hormone controls the reabsorption of molecules in the tubules of the kidneys by affecting the tissue's permeability. It also increases peripheral vascular resistance, which in turn increases arterial blood pressure
So when blood volume is low (high osmolality/highly concentrated) ADH causes increased H2O reabsorption. When osmolality is low, a signal is sent to inhibit ADH |
