Structure of the Kidneys
π° 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 |
π§ B. Renal Drainage Pathway
Renal Papilla β Minor Calices β Major Calices β Renal Pelvis β Ureter
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Renal Lobe = Renal pyramid + overlying cortex
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Renal Hilum = Entry/exit for renal artery, vein, ureter
π§ͺ C. Nephrons (β1 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
π΄ A. Main Supply
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Renal Arteries: From abdominal aorta
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Right is longer; passes behind IVC
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Branches: Inferior suprarenal artery, anterior/posterior divisions
π³ B. Intrarenal Branching
Renal Artery β Segmental β Interlobar β Arcuate β Interlobular
π 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
π° A. Ureters
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9-inch muscular tubes
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Connect renal pelvis β bladder
π« B. Urinary Bladder
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Muscular reservoir (~500 mL capacity)
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Expands as it fills; located in pelvis
π§΅ C. Urethra
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Tube from bladder β outside world
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Sphincters regulate flow
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Internal & external (voluntary control)
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Female: short; opens into perineum
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Male: longer; passes through penis
Summary Flowchart
Nephron (glomerulus + tubules)
β
Collecting ducts β Renal papilla
β
Minor calices β Major calices
β
Renal pelvis β Ureter
β
Bladder β Urethra β Exit
References
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Cleveland Clinic. (n.d.). Renal Cortex: Function and Anatomy. Retrieved from https://my.clevelandclinic.org/health/body/23127-renal-cortex
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TeachMeAnatomy. (n.d.). Kidney β Gross Anatomy and Structure. Retrieved from https://teachmeanatomy.info/abdomen/viscera/kidney/
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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/
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Jansen, K. (2022). Kidney Anatomy. In StatPearls. StatPearls Publishing. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK482248/
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Kenhub. (n.d.). Renal Artery β Anatomy and Function. Retrieved from https://www.kenhub.com/en/library/anatomy/renal-artery
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Cleveland Clinic. (n.d.). Urinary System: Organs, Function, and Conditions. Retrieved from https://my.clevelandclinic.org/health/body/21197-urinary-system
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SEER Training. (n.d.). Urinary System β Components and Functions. Retrieved from https://training.seer.cancer.gov/anatomy/urinary/components/