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The Urinary System Urinary System Contribution to Homeostasis Regulates body water levels Excess water taken in is excreted Output varies from 2-1/2 liter/day to 1 liter/hour Regulates nitrogenous and other solute waste Nitrogen from amino acids are made into urea in liver and transported to kidney as waste Other solutes Sodium, chloride, potassium, calcium, hydrogen ions, creatinine Urinary System Cortex Kidney Renal artery Renal vein Nephrons Aorta Inferior vena cava Cortex Renal pelvis Medulla Ureter Bladder Medulla Collecting duct Ureter Urethra a) The components of the urinary system. b) Internal structure of the kidney. c) The cortex and medulla of the kidney are composed of numerous nephrons. Organs of the Urinary System Kidneys Principle organ Cortex - outer Medulla - inner Urinary System Cortex Kidney Renal artery Renal vein Nephrons Aorta Inferior vena cava Cortex Renal pelvis Medulla Ureter Bladder Medulla Collecting duct Ureter Urethra a) The components of the urinary system. b) Internal structure of the kidney. c) The cortex and medulla of the kidney are composed of numerous nephrons. Organs of the Urinary System Ureters Transport urine to bladder Urinary bladder Stores urine (600–1000 ml) Urethra Carries urine from body Two sphincters Males about 20 cm, females about 4 cm Organs of the Urinary System Urinary bladder Rectum Prostate gland Internal urethral sphincter Uterus Vagina Penis External urethral sphincter Rectum Urethra Testis a) The male b) The female Tubular and Vascular Nephron Components Nephrons: Produce Urine Tubules Function Filter fluid and reabsorb needed substances Structures Proximal tubule Loop of Henle Distal tubule Collecting duct Nephrons: Produce Urine Blood vessels associated with tubules Arterioles Afferent Efferent Capillaries Glomerular Peritubular Vasa recta Formation of Urine Formation of Urine: Glomerular Filtration Glomerular filtration Filters fluid from capillaries into glomerular capsule Rate of filtration Resting rate under local chemical control Stress causes sympathetic nervous system to reduce blood flow to kidneys Formation of Urine: Tubular Reabsorption Tubular reabsorption returns water and needed solutes to blood capillaries Sodium moved by active transport from tubule cells to interstitial fluid and diffuses to capillaries Chloride passively accompanies sodium (balanced charge) Water reabsorbed with salts Movement of sodium creates energy to transport glucose and amino acids into renal tubule then diffuses to the interstitial fluid Tubular Secretion Tubular secretion removes other substances from blood Purpose Regulation of chemical levels in body Excretion of harmful chemicals Substances secreted Penicillin, cocaine, marijuana, pesticides, preservatives, hydrogen ions, ammonium, potassium Concentration or Dilution of Urine: ADH (antidiuretic hormone) Formation of Dilute urine (see next slide for diagram) Excreting excess water Mechanism Cycling of NaCl and urea create a concentration gradient in the medulla that allows water to diffuse from the renal tubules into the interstitial fluid and then into the blood capillaries Formation of Dilute Urine Concentration or Dilution of Urine: ADH Formation of concentrated urine (see next slide) Conserving water Mechanism Countercurrent exchange Increased ADH causes increased permeability to the collecting tubules and increased conservation of water Formation of Concentrated Urine Urination Micturition reflex Internal urethral sphincter Smooth muscle External urethral sphincter Skeletal muscle Kidney’s Role in Homeostasis Maintains water balance Adjusts blood volume and blood pressure Aldosterone, renin, ANH help maintain salt balance in order to control blood volume Maintains acid–base balance and blood pH Regulates red blood cell production via erythropoietin Activates an inactive form of vitamin D Kidney’s Role in Homeostasis Kidney’s Role in Homeostasis