Urinary System Notes PDF

CHAPTER 15 The Urinary System Urinary System: Ridding the body of waste Filters wastes from the blood: urine is what has been filtered from the blood Excretes water, nitrogenous and other solute wastes. Amino acid  ammonia (protein metabolism)  urea (liver), filtered out by kidne...

CHAPTER 15 The Urinary System Urinary System: Ridding the body of waste Filters wastes from the blood: urine is what has been filtered from the blood Excretes water, nitrogenous and other solute wastes. Amino acid  ammonia (protein metabolism)  urea (liver), filtered out by kidneys to urine Uric acid from breakdown of nucleic acids Excess water Others: excess sodium, chloride, potassium, calcium, hydrogen ions (kidneys help regulate body’s pH), excess water soluble vitamins (like vitamin C).  Organs of the Urinary System Kidneys: cortex, medulla (urine formed in nephrons), renal pelvis (collects urine after formation) Ureters: transports urine from renal pelvis to bladder. Urinary bladder: stores urine (up to 600-1000 ml., men can store more than women: no uterus) Urethra: carries urine from body, two sphincters to control flow one is smooth muscle, the other skeletal. Women with shorter urethra  more bladder infections. Urinary System  Nephrons Overall, 180 liters of blood fluid enters nephrons daily: 2.5 times your body weight! Glomerular capsule  proximal tubule  loop of Henle  distal tubule  collecting duct  renal pelvis  ureter  bladder  urethra  toilet (or bushes…) Figure 15.4 Slide 15.3A What occurs at the the nephron Step 1: filtration Blood to be filtered enters the kidneys via the renal artery. Renal artery branches into many afferent arterioles, each of which has one glomerulus.  What occurs at the the nephron Step 1: filtration Blood pressure at the glomerulus is very high. The glomerulus are blood capillaries with numerous, small pores. Blood fluid is squeezed out of the glomerulus, into the glomerular capsule (the start of the nephron). Large items in the blood (red blood cells, white blood cells, large proteins) are not squeezed out of the glomerulus.  What occurs at the nephron Step 2: reabsorption Many things that were squeezed out at the glomerulus are then reabsorbed by the peritubular capillaries: All: amino acids, glucose, bicarbonate ions 99% of: water, sodium, chloride ions 93% of: potassium ion  How does tubular reabsorption occur? Tubular reabsorption: returns water and needed solutes that were squeezed out of glomerulus back to blood 1. Sodium: active transport from tubule cells to interstitial fluid, then diffuses to peritubular capillaries (this creates low sodium concentration in tubule cells  sodium diffuses in) 2. Sodium movement provides energy for glucose / amino acid transport to tubule cell, diffuses to capillary 3. Chloride passively accompanies sodium (balanced charge) 4. Water diffuses by osmosis  Note that increased sodium in the blood (due to a high sodium diet) would lead to more 2 1 water being reabsorbed back into the peritubular capillaries. Greater retention of water in blood vessels 3  higher blood pressure. 4 High sodium diets  high blood pressure.  What occurs at the nephrons Step 3: tubular secretion Certain substances actively or passively move from the peritubular capillaries back into the nephron Including: penicillin, some pesticides, some preservatives, hydrogen ions, urea, ammonium, potassium ions, cocaine, marijuana Note that hydrogen ion is secreted, and the kidneys play a key role in regulating the body’s pH The filtered blood leaves via the renal vein Blood circulation in kidney  Formation of Urine 1) Fluid from glomerulus to glomerular capsule. High blood pressure, very porous (pores of small size). Fluid and small molecules squeezed out, blood cells / large proteins remain. 2) Reabsorption of fluids and solutes by peritubular capillaries 3) Secretion of some materials from peritubular capillaries back into urine  Concentration or Dilution of Urine: ADH Urine can be dilute or concentrated to excrete excess water or retain more water. Antidiuretic hormone (ADH) influences permeability of the collecting duct and distal tubule. High blood solute concentration (= low water concentration) detected by hypothalamus in brain, ADH released and your mouth becomes dry (less saliva) and you feel thirsty More ADH  permeable collecting duct / distal tubule  more water retained by kidneys  concentrated urine Less ADH  impermeable collecting duct / distal tubule  more water lost from kidneys  dilute urine A high sodium diet can lead to high blood pressure: Increased sodium  high blood solute concentration (detected by hypothalamus)  more ADH  increased water reabsorption Increased water reabsorption leads to increased blood volume and increased blood pressure Diuretics Alcohol: interferes with ADH secretion  more water loss Caffeine: interferes with sodium reabsorption  more water loss Diuretics promote water loss (through urination), and may be useful in treating high blood pressure Urination After formation, urine from renal pelvis  ureter  bladder  urethra Internal urethral sphincter: smooth muscle. High amounts of urine: stretch receptors relax this sphincter involuntarily, and contracts the smooth muscle of the urinary bladder. External urethral sphincter: skeletal muscle under our conscious control (luckily) Urinary System  Disorders of the Urinary System Kidney stones Excess minerals (Uric acid, calcium, magnesium) crystallize in renal pelvis and may block ureters, (flow blocked, which may damage nephrons). Extreme pain as kidney stones are passed through urethra, particularly for men. Drinking plenty of water may prevent kidney stones. Treatments: Past = surgery. Present = ultrasound lithotripsy, sound waves shatter stones into sand-size particles, passed with very little pain Large kidney stone, and ultrasound lithotripsy  Disorders of the Urinary System Kidney (renal) failure: not enough nephrons working Commonly due to: high blood pressure, diabetes. Rarely due to: kidney stones, urinary tract infection, blood supply to kidneys interrupted due to accidents / surgery, other reasons. Therapies: Dialysis: wastes leave blood into surrounding fluids, either within body cavity (several times / day) or outside with machine (4 hours / 3 times / week) Kidney transplant (organ donation saves lives, and you only need one kidney to live) Dialysis Disorders of the Urinary System Urinary tract infections Bacteria enters urethra, and can extend up the urinary tract up to the kidneys. Take antibiotics, also drinking acidic juices help Women have shorter urethras, and are more vulnerable to urinary tract infections. www.hkah.org.hk www.afud.org/conditions/ksbefore.html http://www.ivy-rose.co.uk/Topics/Urinary/Kidney_Dialysis_cIvyRose.jpg