Renal Lecture 1 Flashcards
What three things do the kidneys regulate?
- Body fluid osmolality and volumes
- Electrolyte balance
- Acid-base balance
What other function does the kidney have?
Excretion of metabolic products and foreign substances and production and secretion of hormones.
What inorganic substances do the kidneys regulate?
Na+, K+, Cl-, HCO3-, H+, Ca2+ and Pi (inorganic phosphate)
These are electrolytes.
How do kidneys regulate pH and why?
The pH is maintained by buffers within the body fluids and coordinates it along with lungs and liver. Since many metabolic functions of the body are sensitive to pH, the pH must be maintained within narrow limits.
What waste products to the kidneys excrete?
Urea, uric acid, creatine, end products of hemoglobin metabolism and metabolites of hormones. Thus, also plays a role in hormonal concentrations.
How are the kidneys important endocrine organs?
Produce and secrete renin, calctriol and erthropoietin
What does renin do?
Activates the renin-angiotensin-aldosterone system, which helps regulate blood pressure and Na+ K+ balance.
What does calcitriol do?
It is a metabolite of vitamin D3 and is necessary for the normal absorption of calcium by the GI tract and for its deposition in bone.
What does erythropoietin do?
It stimulates RBC formation by the bone marrow.
What is GFR?
Glomerular filtration rate
What is ESRD?
End-stage renal disease
Point at which ureter, renal artery, and renal vein meet
Hilium
Glomerulus
a cluster of capillaries around the end of a kidney tubule, where waste products are filtered from the blood.
Peritubular capillary
tiny blood vessels that travel alongside nephrons allowing reabsorption and secretion between blood and the inner lumen of the nephron.
Vasa recta
are a series of straight capillaries in the medulla, parallel to loop of henle
Renal corpuscle
Glomerulus + Bowman’s capsule
Bowman’s capsule
a capsule-shaped membranous structure surrounding the glomerulus of each nephron in the kidneys of mammals that extracts wastes, excess salts, and water from the blood.
What is the first step in urine formation?
Ultrafiltration of plasma by glomerulus - plasma is cell-parts and protein free after being filtered
Components of the filtration barrier
Fenestrated capilary endothelium, basement membrane, slit diaphragm
What types of species are best filtered?
Small, positively charged species/
What happens to filtration if negative charge on glomeral wall is reduced?
Filtered based on size (small=better) alone; not charge.
Heparin Sulfate
HS is the molecular source of the negative charge on the glomerular basement membrane
Glomerular capillary starling forces
Drive fluid from the lumen of glomerular capillaries across the filtration barrier into Bowman’s space.
Pnet=(glomerular capillary pressure + oncotic pressure of Bowman’s space) - (pressure of Bowman’s space + oncotic pressure of glomerular capillary)
Glomerular filtration rate
GFR=(Kf) * Pnet
Kf=ultrafiltration coefficient
Can substitute in Starling forces equation for Pnet
Constriction of afferent arteriole before glomerulus
Decreased Pgc, decreased GFR, decreased RBF (renal blood flow)
Constriction of efferent arteriole after glomerulus
Increased Pgc, increased GFR, decreased RBF
Dilation of efferent arteriole
Decreased Pgc, Decreased GFR, Increased RBF
Dilation of afferent arteriole
Increased Pgc, Increased GFR, Increased RBF
Increased GFR can be from…
Vasodilators on afferent arteriole: -prostaglandins -kinins -low dose dopamine -ANP -NO Vasoconstrictors on efferent arteriole -Angiotensin II (low dose)
Decreased GFR can be from…
Vasodilators on efferent arteriole -Angio II blockade Vasoconstrictors on afferent arteriole -Angio II (high dose) -Noradrenaline (SNS) -Endothelin -Adenosina -Vasopressin -IPG blockade
Describe myogenic response of afferent arterioles
- An increase in BP stretches the smooth muscles of the afferent arteriolar wall
- Stretch sensitive Ca2+ channels are opened,, leading to Ca2+ influx and muscle contraction
- Vasoconstriction minimized increase in Pgc
- A decrease in BP reduces the tonic level of afferent arteriolar smooth muscle contraction
- Vasodilation will sustain Pgc
What cells make up the juxtaglomerular apparatus
Macula densa cells and granular cells
Describe tubuloglomerular feedback
GFR increase -> flow through tubule increase -> flow past macula densa increase and so NaCl content increase -> paracrine from macula densa to afferent arterial -> afferent arteriole constricts -> resistance in afferent arteriole increase -> hydrostatic pressure in glomerulus decrease, GFR decrease
Principle of Renal Clearance
Amount filtered = amount excreted
(clearance of solute) x (plasma concentration of solute) = (urine concentration of solute) x urine flow rate
or, Cx[Px]=[Ux]V
Clearance of inulin
Equivalent to glomerular filtration rate (GFR), the volume of plasma filtered in one minute
Does inulin get more absorbed or more secreted?
Neither! Inulin goes into the afferent arteriole, is filtered through the glomerulus, travels down tubular system and is excreted with urine. Filtered inulin = excreted inulin.
Describe the stages of kidney disease in terms of creatine clearance and plasma creatine levels.
Normal GFR is high (normal) and plasma creatine level normal (low).
Mild kidney disease GFR drops slightly and plasma creatine level increases slightly.
Moderate kidney disease creatine clearance declines further and plasma creatine begins to grow expoentially.
Severe kidney disease creatine clearance very low and creatine levels spike through the roof.
Clearance approach to measure GFR
Clearance=[U]*V/[P]
Creatine-based estimation of GFR
creatine clearance = [140-age]*weight[lbs]/[serum creatine]
