L1 Intro To Renal Func Flashcards
Functions of the kidneys
Reg of water and inorganic ion balance
Reg of body fluid osmolality and vol
Excretion of metabolic waste (urea, uric acid, creatinine)
Excretion of foreign chemicals (drugs, pesticide, food additives)
Secretion of hormones (renin, erythropoietin, 1,25-dihydroxycholecalcoferol)
Reg blood bicarbonate levels
Inputs
Beverages
Food
Metabolic
Outputs
Insensible - water loss associated w skin evaporation and respiratory tract
Sweat
Fecal
Urinary
Types of balance
Sodium balance
Water balance
Potassium balance
Others
Balance equation
Total In - Total Out = Balance
Negative sodium and water balance examples
Diarrhea
Diuretic meds
Insufficient aldosterone (ie adrenal dysfunction) regs Na reabsorption in kidney to maintain blood volume
Positive sodium and water balance
Excess exogenous steroids
Congestive heart failure
Salt-retaining disease (ie hyperaldosteronism)
Kidney gross anatomy
Cortex - granular
Medulla - striated
Renal pyramid
Urine excreted from papillae into calyces
Pelvis
Calyces drain into renal pelvis
Ureter
Nephron anatomy
Basic unit of kidney
About 1 million per kidney
Tubular structure
Vascular elements
Juxtaglomerular apparatus (JGA) Include two cell types: arteriolar supply of glomerular capillary, wall of nephron
Components of nephron
Renal corpuscle
Proximal tubule
Loop of Henle
Juxtaglomerular apparatus JGA
Distal convoluted tubule
Collecting duct
Renal corpuscle
Glomerulus - tuft of specialized capillaries
Bowmans capsule
Proximal tubule
Drains bowmans capsule
60-80% of filtered solute and water reabsorbed (isosmotic)
Doesn’t concentrate urine
Also does a lot of secretion
Loop of henle
LOH
Descending and ascending loops
Generates osmotic gradients in medulla that allow kidney to concentrate the urine
Ascending - thick
Descending - thin
It itself doesn’t do the concentrating
Juxtaglomerular apparatus
JGA
Where thick ascending limb passes between afferent and efferent arteriole
Distal convoluted tubule
Early distal tubule continues process of diluting urine
Some reabsorption of ions
Fluid hyposmotic
Collecting duct
Water permeability controlled by vasopressin (ADH) anti-diuretic hormone
Site where final concentration of urine is adjusted- urine may be iso, hypo, or hyperosmotic
Cortical nephrons
Glomeruli in outer cortex
LOH short and do not extend into the inner medulla
Most common type of nephron
Juxtamedullary nephrons
Glomeruli near corticomedullary border
LOH long and extend deep into the inner medulla
Two types of nephrons
Cortical and juxtamedullary
Ability to produce concentrated urine is proportional to the number of juxtamedullary nephrons (May or May not be true)
All nephrons function in parallel
Collecting ducts shared by many nephrons
Renal corpuscle
Bowmans capsule Encompasses capillary tuft
Blood goes in through afferent arteriole and out through efferent arteriole
Capillaries within bowmans capsule have podocytes with individual projections called pedicels
Filtration barrier consists of three layers
Capillary endothelium
Glomerular basement membrane = basal lamina
Visceral epithelial cells = podocytes
Pedicels are extensions of podocytes
Slits btw podocytes constitute the path of filtrate flow into the bowmans capsule
Juxtaglomerular apparatus composed of
Macula densa
Extraglomerular mesangial cells EGM
Granular cells AK juxtaglomerular cells
JGA function
Helps control GFR
controls renin secretion (BP and volume)
Mesangial cells
Between capillary loops
Contract in response to hormone angiotensin II - compress glomerular tuft into tighter ball, decreases flow
Angiotensin II can enhance or retard GFR
Renal vasculature
Two capillary beds: glomerular and peritubular
Peritubular
Cortical division
Vasa recta division
Follow LOH of juxtamedullary nephrons
Found in medulla
Blood supply to nephrons
Cortical arteries give off afferent arterioles
One afferent arteriole per glomerulus
Fluid not filtered goes to efferent arteriole
Then to peritubular capillaries which supple blood to nephron
Two arterioles (afferent and efferent) and two capillary beds (glomerular and peritubular) in series
Vasa recta
Specialized peritubular capillaries of juxtamedullary nephrons
Long, hairpin shaped capillaries that follow LOH
Supply nutrient to medullary tissue and important for recovery of water
Renal nerves
Sympathetic only- release norepinephrine and dopamine
Alpha1 receptors on afferent and efferent arterioles but primarily afferent
Stimulation by SNS tends to reduce RBF and GFR but the simultaneous release of prostaglandins PGE2 and PGI2 oppose alpha1 mediated vasoconstrictions. Reductions in RBF and GFR are minimized
Granular cells (JGA) innervated by SNS, renin released upon stimulation of B1 receptors
Components of renal function
Glomerular function
Production of protein free filtrate
GFR is 120-125 ml/min
Tubular reabsorption
From tubular lumen to peritubular capillary
Tubular secretion
From peritubular capillary to tubular lumen
Excretion
Substance appears in urine
