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Urinary System Anatomy & Physiology

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  • Primary functions of the kidneys

    Remove urea and excess water from the blood, regulate solute concentrations, maintain acid-base balance, produce erythropoietin, activate vitamin D, and perform gluconeogenesis during fasting.

  • Anatomical position of the kidneys

    Bean-shaped organs located retroperitoneally between T12 and L3 vertebrae, with a convex lateral surface and a concave medial surface containing the renal hilum.

  • Three layers of supportive tissue around the kidney

    Renal fascia, perirenal fat capsule, and fibrous capsule.

  • Three distinct internal regions of the kidney

    Renal cortex, renal medulla (containing renal pyramids), and renal pelvis.

  • Functional unit of the kidney

    Nephron, which filters blood, reabsorbs needed substances, and secretes wastes into urine.

  • Major parts of a nephron

    Renal corpuscle (glomerulus and Bowman's capsule), proximal convoluted tubule, nephron loop (Henle's loop), and distal convoluted tubule.

  • Two classes of nephrons

    Cortical nephrons and juxtamedullary nephrons, differing in location and length of nephron loop.

  • Three processes of urine formation

    Glomerular filtration, tubular reabsorption, and tubular secretion.

  • Glomerular filtration characteristics

    Passive process where plasma-like filtrate is formed by filtering blood through fenestrated endothelium, basement membrane, and podocyte foot processes.

  • Factors affecting glomerular filtration pressure

    Outward pressures: hydrostatic pressure in glomerular capillaries and colloid osmotic pressure in capsular space; inward pressures: hydrostatic pressure in capsular space and colloid osmotic pressure in glomerular capillaries.

  • Definition of glomerular filtration rate (GFR)

    Volume of filtrate formed per minute by all nephrons combined, regulated by intrinsic and extrinsic mechanisms.

  • Tubular reabsorption

    Process of reclaiming useful substances like sodium, nutrients, water, and ions from filtrate back into the blood, via active or passive transport.

  • Tubular secretion

    Active process adding wastes, excess K+, and substances controlling blood pH from blood into the filtrate for elimination.

  • Renal clearance concept

    Measurement of kidney's ability to clear a substance from blood, calculated as \(C=\frac{UV}{P}\), where U=urine concentration, V=urine flow rate, P=plasma concentration.

  • Urine composition

    Approximately 95% water and 5% solutes including urea, uric acid, creatinine, and other nitrogenous wastes.

  • Anatomy of the urinary tract

    Includes kidneys, ureters, urinary bladder, and urethra, which transport, store, and eliminate urine.

  • Role of ureters

    Active transport of urine from kidneys to urinary bladder via peristalsis.

  • Structure and function of the urinary bladder

    Smooth, collapsible muscular sac with trigone region and detrusor muscle; stores urine and allows distension.

  • Micturition process

    Urination requiring contraction of detrusor muscle, opening of internal urethral sphincter, and voluntary relaxation of external urethral sphincter.

  • Common urinary system pathologies

    Includes pyelonephritis, hematuria, anuria, chronic renal disease, renal calculi, urinary incontinence, urinary retention, urinary tract infection, cystitis, dysuria, horseshoe kidney, hypospadias, and polycystic kidney disease.