Overview of Renal Phys Flashcards
Describe in 1 sentence the role of kidney in total body homeostasis
1) maintenance of composition and volume of ECF
State volume of each major body compartment in healthy 70kg male
1) intracell fluid (circ volume of blood cells and non-circulating cell volume)
2) extracell fluid (interstitial fluid and plasma)
1) 27 L (3L and 24L)
2) 15L (12L and 3L)
Major components of daily water intake
Inputs
1) ingestion (food and drink) = 2.0L
2) metabolic processes (hydrolysis reactions = 0.5L
Major components of daily water output
1) sweat and feces = 0.1 L
2) insensible losses (respiration) = 0.9 L
3) Urine = 1.5 L
Process of water intake; What happens if you ingest too much water?
significance for the kidney?
1) take in too much water
2) urinate more –> urine matches input
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kidney relies on excess ingested fluids and components to return body to proper volumes and excrete the rest
ECF remains constant by regulating urinary output
how does ECF volume remain constant despite taking in more fluids?
kidney makes urine to match the input
Regulated ECF values
1) volume
2) osmolarity
3) electrolyte composition = Na+, K+, Ca2+
4) acid/base balance- H+ via HCO3-
5) metabolic wastes = urea, nonvoltaile acids, drugs, liver catabolites
Functional components of nephron (2)
Parts of blood supply
1) epithelial tube = tubule
2) blood supply
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Blood supply= 2 capill beds in series = glomerular and peritubular capillaries
parts of tubule and functions
1) glomerular capillary –> non-specific filtration of plasma into tubule (F)
2) tubule = selective + variable reabsorption of regulated substances (R)
3) excretion of excess regulated substances (E)
Examples of things secreted from peritubular capillaries and not glomerular capillary
beta lactam antibiotics (penicillin)
K+
Describe glomerular filtration process
Functions of filtration
1) blood enters glomerulus via afferent arteriole
2) filtered into initial part of tubule
3) exits via efferent arteriole
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Functions (1) allows water and electrolytes into tubule but retains large solutes in blood
Describe tubular reabsorption process
1) in tubule, kidney recaptures filtrates using transporters selective in kidney epithelium to maintain homeostasis (electrolytes, glucose)
Describe tubular secretion
Describe excretion
some ECF parts regulated by kidney are secreted from blood into tubule directly
some secreted and reabsorbed both
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excess regulated elements in ECF above ECF balance pass through tubule and excrete into urine
For a normal person, calculate magnitude of renal blood flow, renal plasma flow, GFR, Filtration fraction and urine flow rate
RBF = CO x % of CO = 5.2 x 0.25 = 1.3 L/min
RPF (RBF without cellular) = RBF x Hct = 1.3 L/min x 0.5 = 0.65 L.min
Filtration fraction = proportion fo plasma filtered in glomerulus~ 0.2
GFR = plasma flow from blood filtered = RPF x Filtration Fraction
Urine flow rate ~ 1.5 L/day
How much of filtered content is reabsorbed
GFR = 5.2 L/min x 0.25 (RBF) x 0.5 (HCT) x 1440 min per day = 190 L/day
99% of filtered is reabsorbed
Describe RAA axis in response to decr blood pressure
1) decr blood pressure
2) carotid baroreceptors –> kidney
3) incr renin secretion
4) renin cleave angiotensinogen (inactive prohormone) –> angiotensin I –> ACE in lungs –> angiotensin II
5) AGII causes arteriolar smooth muscle constrction, incr vascular resistance –> incr MAP
