Glomerular Filtration and Renal Clearance - Ch 16 Flashcards
What hormones does the kidney produce / convert?
Erythropoietin
Renin
1,25-dihydroxyvitamin D (convert to active form)
What can the kidney produce during starvation and how?
Glucose (via gluconeogenesis)
What percent of the cardiac output enters the kidney? What volume of blood is this?
20% (1 L / min)
What is the ratio of cortical (superficial) to juxtamedullary (deep) nephrons?
85% Cortical - 15% Juxtamedullary
What do the efferent arterioles associated with the cortical and juxtaglomerular nephrons lead to, respectively?
Cortical - peritubular capillaries (collect material reabsorbed from nephrons)
Juxtaglomerular - vasa recta (collect material reabsorbed from medullary tubules)
What is the juxtaglomerular apparatus?
Specialized site where the macula densa is in contact with the distal convoluted tube and afferent arteriole
What do the macula densa cells regulate?
Glomerular filtration rate (GFR)
Renin release
What are the consequences of damage to the glomerular basement membrane?
Reduce the negative charge and allow large proteins (ie albumin) to be filtered
What is the consequence of mesangial matrix deposition?
Decrease area of filtration and reduced renal function
What are the symptoms of acute glomerulonephritis?
Edema Low urine volume Headaches Nausea Joint pain
How do you calculate renal plasma flow?
RPF = RBF x (1 - HCT)
What is used to determine effective renal plasma flow (ERPF)
Para-aminohippurate (PAH)
What is the effective pore size of the glomerulus?
30 A
How do you calculate net filtration pressure?
(HP gc - HP bs) - pi gc
What is a normal GFR?
100-125 mL/min
130 ml/min (Rao)
What is the filtration fraction and how do you calculate it?
The proportion of the RPF that becomes glomerular filtrate
FF = GFR / RPF
What is filtered load and how do you calculate it?
Amount of a specific substance filtered per unit time
FLx = Px x GFR
What is urinary excretion and how do you calculate it?
The urine concentration of the substance times the volume of urine produced per unit time
Ex = Ux x V
How do you calculate reabsorption rate?
Rx = FLx - Ex
How do you calculate secretion rate?
Sx = Ex - FLx
What is renal clearance and how do you calculate it?
Volume of plasma cleared of a substance per unit time
Cx = (Ux x V) / Px
When does clearance equal GFR?
When a substance is freely filtered, but not reabsorbed or secreted
What is the relationship between plasma creatinine and GFR?
Proportional to 1 / mg% Pcr
ie 1 = 100%, 2 = 50%, etc
What is the mechanism by which arteries and arterioles respond directly to increases in systemic blood pressure?
Mycogenic mechanism
What mechanism involves the juxtaglomerular apparatus?
Tubuloglomerular feedback (TGF)
What triggers the TGF?
Decrease in flow and tubular sodium leads to decreased arteriolar resistance and increased GFR and vice versa
How is the renin-angiotensin-aldosterone system (RAAS) activated?
Low renal vascular flow
What is angiotensin II and what does it do?
It is a vasoconstrictor that acts on the renal arteries (decreases GFR)
What is atrial natriuretic peptide (ANP) and what does it do?
It is released from the right cardiac atrial myocytes in response to stretch (high blood volume) and increases GFR by dilating the afferent arteriole and constricting the efferent arteriole
What stimulates sympathetic nerves and catecholamine secretion and what do they do?
Reductions in systemic blood pressure cause vasoconstriction of the renal arteries and arterioles
Name 2 intrarenal prostaglandins and their actions
PGE2 and PGI2 (prostacyclin) are vasodilators
*Note NSAIDS restrict compensatory renal vasodilation
