renal anatomy
What is the functional unit of the kidney?
nephron
What are the four main steps in urine formation?
Filtration, reabsorption, secretion, excretion
What does GFR stand for?
Glomerular Filtration Rate
What hormone do the kidneys release to raise blood pressure?
renin
What glomerulus layer stops the passage of large plasma protein?
Basement membrane
Which inner region of the kidney contains renal pyramids?
renal medulla
Which pressure promotes filtration in the glomerulus?
Glomerular blood hydrostatic pressure (GBHP)
What molecule is used to estimate GFR?
Inulin
What system is activated by renin to regulate blood pressure?
Renin-angiotensin-aldosterone system (RAAS)
Does the afferent constrict or dilates to increase GFR?
Dilates
What are the three connective tissue layers surrounding the kidney?
Renal fascia, perinephric fat capsule, renal capsule
What three layers make up the glomerular filtration membrane?
Capillary endothelium, basement membrane, podocytes
What is the formula for renal clearance?
C = (U × V) / P
What hormone causes sodium reabsorption in the distal tubule?
Aldosterone
What cells monitor concentrations of CL- and NA+ in filtrate?
Macula densa cells
What structures carry urine to the bladder and prevent backflow?
ureters
What is the formula for Net Filtration Pressure (NFP)?
NFP = GBHP - (CHP + BCOP)
What do macula densa cells monitor in the filtrate?
Sodium (Na⁺) and chloride (Cl⁻) concentration
What hormone increases water reabsorption in the collecting duct?
Vasopressin (ADH)
True or False
Epithelium transitions to stratified cubical epithelium near the urethras opening to the outside
False
Which blood vessels enter through the renal hilum and branch into cortical radiate arteries?
Renal artery → segmental → interlobar → arcuate → cortical radiate arteries
What part of the nephron reabsorbs glucose and amino acids using secondary active transport?
Proximal convoluted tubule (PCT)
What happens to GFR if blood pressure drops significantly?
GFR decreases due to lower net filtration pressure
What structure detects low blood pressure and releases renin?
Granular (juxtaglomerular) cells in the afferent arteriole
Describe how the countercurrent multiplier system in the nephron establishes the medullary osmotic gradient and explain why this is essential for urine concentration.
The countercurrent multiplier occurs in the loop of Henle, where filtrate flows in opposite directions in descending and ascending limbs. The descending limb is permeable to water but not solutes, allowing water to leave. The ascending limb is impermeable to water but actively transports Na⁺ and Cl⁻ out, increasing interstitial osmolarity. This creates a gradient that draws more water out of the descending limb, concentrating the medulla. This gradient is essential for the collecting duct to reabsorb water under the influence of ADH, allowing the body to concentrate urine and conserve water.