Overview
This lecture covers the gross anatomy of the kidney, including its major visible structures, blood supply, and the organization of the urinary system.
Organization of the Urinary System
- The urinary system consists of kidneys, ureters, urinary bladder, and urethra.
- The right kidney is slightly lower than the left kidney.
- Ureters carry urine from kidneys to the urinary bladder, entering at the posterior aspect.
- The urethra carries urine from the bladder to outside the body.
- The triangular area in the bladder where ureters enter is called the Trigone, which has a unique epithelium.
Gross Anatomy of the Kidney
- The kidney is divided into an outer cortex and an inner medulla.
- The cortex contains glomeruli (visible as speckles), which are capillary beds for filtration.
- The medulla contains renal (medullary) pyramids, visible as striped, candy-corn-like structures.
- Collecting ducts run through the pyramids, draining filtrate to the tips.
Urine Collection and Flow
- Filtrate exits pyramids at the renal papilla, forming the first drop of urine.
- Urine is collected by minor calyces, which merge into major calyces.
- Major calyces combine to form the renal pelvis.
- The renal pelvis drains into the ureter, which empties urine into the bladder.
Blood Supply to the Kidney
- The renal artery branches from the aorta and supplies the kidney.
- Renal artery divides into lobar arteries → segmental arteries → interlobar arteries.
- Arteries ascend renal columns and branch into arcuate arteries and then cortical radiate arteries in the cortex.
- Cortical radiate arteries supply glomeruli (tufts of capillaries).
- Blood leaves the glomerulus via efferent arterioles, then to peritubular capillaries or vasa recta.
- Blood drains via cortical radiate veins → arcuate veins → lobar veins → renal vein (no segmental veins).
Key Terms & Definitions
- Cortex — Outer portion of the kidney containing glomeruli.
- Medulla — Inner portion of the kidney, contains pyramids.
- Glomerulus — Tuft of capillaries for blood filtration.
- Renal Pyramid — Medullary structure filled with collecting ducts.
- Renal Papilla — Tip of pyramid where urine exits into minor calyx.
- Minor Calyx — Funnel-like urine collector from papilla.
- Major Calyx — Formed by merging minor calyces.
- Renal Pelvis — Central collecting region in kidney.
- Trigone — Triangular area in bladder where ureters and urethra meet.
Action Items / Next Steps
- Review the microanatomy of the glomerulus and the tubular network of the kidney in the next session.