Structure of the Kidneys
🏰 A. Three Main Layers
| Layer | Description |
|---|---|
| Renal Capsule | Outer fibrous protective covering |
| Renal Cortex | Contains nephrons (filters); brown-red + grainy |
| Renal Medulla | Contains renal pyramids; smooth texture |
🧊 B. Renal Drainage Pathway
Renal Papilla → Minor Calices → Major Calices → Renal Pelvis → Ureter
Renal Lobe = Renal pyramid + overlying cortex
Renal Hilum = Entry/exit for renal artery, vein, ureter
🧪 C. Nephrons (≈1 million/kidney)
| Structure | Function |
|---|---|
| Glomerulus | Filtration via capillary network |
| Bowman’s Capsule | Encloses glomerulus |
| Podocytes | Specialised cells for selective filtration |
| Tubules | Reabsorption and secretion |
| Loop of Henle | In medulla; concentrates urine |
| Collecting Ducts | Final urine concentration |
Renal Blood Supply
🔴 A. Main Supply
Renal Arteries: From abdominal aorta
Right is longer; passes behind IVC
Branches: Inferior suprarenal artery, anterior/posterior divisions
🌳 B. Intrarenal Branching
Renal Artery → Segmental → Interlobar → Arcuate → Interlobular
💉 C. Microcirculation
| Vessel | Role |
|---|---|
| Afferent arteriole | Brings blood to glomerulus |
| Efferent arteriole | Exits glomerulus |
| Peritubular Capillaries | Surround cortical tubules (reabsorption) |
| Vasa Recta | Surround Loop of Henle; maintain medullary gradient |
Urine Flow Pathway
🚰 A. Ureters
9-inch muscular tubes
Connect renal pelvis → bladder
🫙 B. Urinary Bladder
Muscular reservoir (~500 mL capacity)
Expands as it fills; located in pelvis
🧵 C. Urethra
Tube from bladder → outside world
Sphincters regulate flow
Internal & external (voluntary control)
Female: short; opens into perineum
Male: longer; passes through penis
Summary Flowchart
Nephron (glomerulus + tubules)
↓
Collecting ducts → Renal papilla
↓
Minor calices → Major calices
↓
Renal pelvis → Ureter
↓
Bladder → Urethra → Exit
References
Cleveland Clinic. (n.d.). Renal Cortex: Function and Anatomy. Retrieved from https://my.clevelandclinic.org/health/body/23127-renal-cortex
TeachMeAnatomy. (n.d.). Kidney – Gross Anatomy and Structure. Retrieved from https://teachmeanatomy.info/abdomen/viscera/kidney/
Yu, J., & McMahon, A. P. (2007). Kidney development and the origins of renal cortex and medulla. In Kidney Development [Figure]. In Kidney Development in the Mouse. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK27080/figure/mousekidneydevelopment.F1/
Jansen, K. (2022). Kidney Anatomy. In StatPearls. StatPearls Publishing. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK482248/
Kenhub. (n.d.). Renal Artery – Anatomy and Function. Retrieved from https://www.kenhub.com/en/library/anatomy/renal-artery
Cleveland Clinic. (n.d.). Urinary System: Organs, Function, and Conditions. Retrieved from https://my.clevelandclinic.org/health/body/21197-urinary-system
SEER Training. (n.d.). Urinary System – Components and Functions. Retrieved from https://training.seer.cancer.gov/anatomy/urinary/components/