Urinary System Practice Exam

The renal medulla is organized into renal pyramids. Each pyramid contains loops of Henle and collecting ducts that help establish the osmotic gradient for water reabsorption.

Nephrons are the functional units that span cortex and medulla, and the sinus and pelvis are collecting spaces in the renal hilum, not medullary structures.

The juxtaglomerular apparatus is formed by juxtaglomerular (granular) cells of the afferent arteriole and the macula densa of the distal convoluted tubule. This pairing helps regulate GFR and systemic blood pressure via renin release.

The arterial inflow to the glomerulus follows:

segmental → interlobar artery → arciform artery → interlobular artery → afferent arteriole

An interlobar vein is part of the venous return, not the arterial pathway.

Urea is the most abundant organic solute in normal urine, produced from amino acid catabolism.

Uric acid and creatinine are present in much lower amounts, and glucose should be negligible in healthy individuals.

The thick ascending limb actively reabsorbs Na⁺, K⁺, and Cl^– via the NKCC2 cotransporter and is impermeable to water.

Potassium reabsorption here is not passive, and urea handling is mainly in the inner medulla/collecting duct.

The middle layer of the bladder wall is the muscular coat, which generates the force for micturition.

The submucosa lies internal to the detrusor, and a sphincter coat is not a standard histologic layer.

The micturition reflex center is in the sacral spinal cord (S2–S4). Higher control from the pontine micturition center coordinates the reflex but is not the reflex center itself.

Oliguria means “low urine output,” typically <400 mL/day in adults.

Pyuria indicates pus/WBCs in urine, enuresis is involuntary urination, and diuresis is increased urine production.

The vasa recta run alongside loops of Henle and help maintain the medullary osmotic gradient via countercurrent exchange.

The descending limb is highly permeable to water but not to solutes, so water is reabsorbed by osmosis into the increasingly hypertonic medulla.

The ejaculatory ducts empty into the prostatic urethra at the seminal colliculus (verumontanum).

The pre-prostatic segment lies within the bladder neck, the membranous segment passes through the external urethral sphincter, and the spongy (penile) segment runs through the corpus spongiosum.

Glucosuria is the presence of glucose in urine, usually when plasma glucose exceeds the renal threshold or with SGLT2 inhibitor use.

Common kidney stone components include calcium oxalate, calcium phosphate, and uric acid. Bicarbonate is not a typical stone constituent.

The DCT reabsorbs Na⁺ and Cl^– through the NCC and is also a site of Ca²⁺ reabsorption (↑ with PTH).

Bulk water and most glucose reabsorption occur in the proximal tubule, and filtration happens at the glomerulus.

ADH increases water reabsorption in the late DCT and collecting duct by inserting aquaporin-2 channels, concentrating the urine and reducing its volume.

The kidneys release erythropoietin, secrete renin, and activate vitamin D (to calcitriol). They do not synthesize or “release” vitamin E.

Each kidney contains about 1,000,000 nephrons on average.

Angiotensin II preferentially constricts the efferent arteriole, which maintains or increases glomerular capillary pressure and helps preserve GFR despite reduced renal blood flow.

Diuretics increase urinary excretion of sodium and water, reducing extracellular volume and preload, which can lead to a decrease in cardiac output.

Loop diuretics include furosemide, bumetanide, and ethacrynic acid. Chlorothiazide is a thiazide diuretic, not a loop.