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Urinary System
~Functions~
- Regulation of Composition of Body Fluids (water balance, electrolyte balance, and acid-base balance)
- Waste Removal (from metabolism, phagocytosis, and foreign chemicals/drugs/food additives)
- Endocrine Function (erythropoietin which stimulates red blood cell production)
- Enzyme Production (renin which helps regulate blood pressure and kidney function)
- Gluconeogenesis (during prolonged fasting)
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Urinary Organs
- Kidneys – major excretory organs of body; forms urine (water and solutes filtered from blood)
- Ureters – transport urine to storage
- Urinary Bladder – temporarily stores urine
- Urethra – carries urine to outside of body
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Kidneys – Location
Retroperitoneal in superior lumbar region
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Kidneys – External Anatomy
- Bean-shaped
- Renal Hilus: vertical cleft where blood vessels, lymphatic vessels and nerves enter renal sinus Supporting tissue
- a. Renal capsule – inner fibrous and transparent; protects kidney against infection and holds organ together
- b. Adipose capsule – middle fatty mass; attaches kidneys to posterior wall and cushions it
- c. Renal fascia - outer layer of dense fibrous connective tissue; anchors kidney and adrenal gland to surrounding structures
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Kidneys – Internal Anatomy
- Regions
- a. Renal cortex (outer dark region with extends called renal columns)
- b. Renal medulla (inner light region containing renal pyramids)
- c. Renal pelvis (flat funnel shaped tube continuous with ureter leaving hilus)
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Path of urine drainage
- Papillary duct of renal pyramid
- Minor calyx
- Major calyx
- Renal pelvis
- Ureter
- Bladder
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Blood and nerve supply
- a. Urine is a filtrate of blood
- b. Largely sympathetic nerves from renal plexus which are vasomotor fibers which regulate renal blood flow
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Nephron
Structural and functional unit of kidneys
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Nephron Parts
Renal Corpuscle = glomerulus (capillary tuft) and glomerular (Bowman's) capsule
Renal Tubule = proximal convoluted tubule (PCT), loop of Henle and distal convoluted tubule (DCT)
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Nephron Filtrate
Enters collecting ducts and then drains into:
- Papillary duct of renal pyramid
- Minor calyx
- Major calyx
- Renal pelvis
- Ureter
- Bladder
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Types of Nephrons (2)
- Cortical Nephrons
- Juxtamedullary Nephrons
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Cortical Nephrons
85%, parts almost entirely in renal corex
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Juxtamedullary Nephron
15%, with long loops of Henle that invad the medulla; important for forming concentrated urine
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