1. Anatomy & Blood Supply The upper urinary tract has two retroperitoneal, bean-shaped kidneys (T12–L3) and 2 ureters. The lower tract comprises the bladder and urethra. Each kidney is shielded by a fibrous capsule and cushioned by fat. The functional unit is the nephron (~1 million), consisting of a glomerulus, Bowman's capsule, and tubule system (PCT, loop of Henle, DCT, and collecting ducts). Blood flow is ~1200 mL/min (20-25% of cardiac output) via the renal artery, which divides into afferent arterioles.

2. Physiology of Urine Formation Urine is formed through filtration, reabsorption, secretion, and excretion.

• Glomerular Filtration: Hydrostatic pressure filters blood across a porous, semipermeable membrane into Bowman’s capsule, yielding a filtrate lacking cells and lar ...