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Urinary System

Urinary System. Urinary System Basic Anatomy. Kidneys -filter blood of toxins, regulate water, pH, salt content of blood (also helps regulate blood pressure, produces erythropoietin) Ureters - carry urine to bladder Bladder - stores urine Urethra - allows urine to pass out of body.

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Urinary System

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  1. Urinary System

  2. Urinary System Basic Anatomy • Kidneys -filter blood of toxins, regulate water, pH, salt content of blood (also helps regulate blood pressure, produces erythropoietin) • Ureters - carry urine to bladder • Bladder - stores urine • Urethra - allows urine to pass out of body

  3. Kidneys • Are located posterior to digestive organs in a retroperitoneal position (behind peritoneal membrane) • Covered by transparent membrane called the renal capsule

  4. Renal Blood Supply • Renal artery carries blood from aorta into kidneys at the hilus (see diagram) • Renal vein carries blood from kidneys to inferior vena cava • Blood vessels branch into tiny capillaries inside the kidneys

  5. Cross-section of Kidney • Cortex (outer portion of kidney) • Medulla (inner portion of kidney)

  6. The Nephron

  7. Nephron Functional unit of kidney (1 million per kidney): Composed of: • Glomerulus: ball of capillaries involved in filtration of blood- keeps large particles (blood cells, large proteins) out of the filtrate (filtrate becomes urine) • Renal tubules: involved in reabsorption - (putting needed substances back into the blood) and secretion (moving wastes from blood to the filtrate to be excreted in urine) Components of a nephron

  8. Areas of the Nephron Bowman’s capsule 1) Glomerulus (surrounded by Bowman’s capsule) - filtration 2) Proximal convoluted tubule (PCT) - reabsorption 3) Loop of Henle (descending and ascending limbs) 4) Distal convoluted tubule (DCT) - secretion * The filtrate drains into the collecting duct (not part of the nephron) and is carried out of the kidneys to the ureters 1 2 4 Collecting duct 3 3 A Nephron

  9. The Nephron

  10. Concentration of Urine • ADH (antidiuretic hormone - released from pituitary gland) enhances the reabsorption of water in the collecting ducts • Triggered when blood pressure and volume are low • Makes urine very concentrated • Urine is dilute when ADH is not present No ADH With ADH

  11. ADH vs. No ADH ADH present No ADH

  12. Renin-Angiotensin System • Renin – enzyme secreted by juxtaglomerular cells in the kidneys in response to low blood pressure/volume • Leads to a cascade of reactions that results in production of angiotensin II, a vasoconstrictor • Angiotensin II stimulates aldosterone production from adrenal glands • Blood pressure increases

  13. Aldosterone • Released from the adrenal glands on top of the kidneys • Leads to conservation of sodium (and sometimes water) and the excretion of potassium • Raises blood pressure by increasing blood volume

  14. Bladder • Holds urine (made of smooth muscle) • Stretch receptors in wall of bladder trigger urge to urinate (occurs after about 200ml of urine collect) - maximum capacity is about 800-1000ml • Micturition (urination) occurs when it is “convenient” to go (see animation) Micturition Reflex

  15. Urinary Tract Infections (UTIs) • Infection of the urinary tract (most commonly urethra) by bacteria (usually E.coli from digestive tract) • More common in women (shorter urethra and proximity of urethra to anus) • Infections could spread to bladder (cystitis) or kidney (pyelonephritis) if not treated • Risk increases if urine flow is obstructed or if catheters are used frequently

  16. Kidney Stones

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