urinary system

• kidney functions

  • regulates composition and volume of extracellular fluid
  • removes metabolic waste from blood and combines w/ excess water to form urine
• kidney functions

  • secretes erythropoietin hormone for RBS production
  • secretes renin enzyme to maintain blood volume + blood pressure
• kidney function

  • processes 180 L of filtrate daily
  • filters entire plasma volume > 60x a day
  • ~ 22 minutes
  • only <1% of fluid leaves the body as urine
• structure

  • hilum: concave part of kidney, entrance/exit for blood vessels, nerves, lymphatic vessels, ureter
• renal sinus: hollow chamber within kidney

  • renal pelvis: tunnel to ureter
  • major calyx: large passage for urine
  • minor calyx: smaller passage for urine
• Renal Medulla

  • renal pyramids: striated conical tissue (~ 8 lobes)
  • renal papillae: small projections
  • parallel bundles of urine collecting tubes
• Renal cortex: granular shell around renal pyramids

  • renal columns: cortex tissue that separates medulla
  • nephrons: functional unit of the kidneys
• Renal Corpuscle

  • glomerulus: tangles cluster of blood capillaries, "glom" = ball of yarn
  • glomerular capsule: surrounds glomerulus (bowman's capsule)
• Renal Tubule

  • proximal convoluted tubule
  • loop of henle, 1. descending limb of nephron loop, 2. ascending lib of nephron loop
  • distal convoluted tubule
• urine formation

  • glomerular filtration: glomerular capillaries filter blood plasma
• 1. Afferent (incoming) arteriole is larger than the efferent (outgoing) arteriole
  2. BP greater for blood in glomerulus
  3. blood plasma filtered in glomerular capsule
  4. filtration rate affected by constriction/dilation of blood vessels and plasma colloid pressure
  5. only molecules smaller than 3mm pass freely through
• molecules smaller than 3nm that pass freely through

  1. water, glucose, amino acids, nitrogenous waste
  2. blood cells or protein in urine indicate pathology
• tubular reabsorption: renal tubules return dissolves material back to peritubular capillaries

  1. sodium ions moved back by active transport
  2. water diffuses passively by osmosis
  3. almost all water and sodium is reabsorbed
  4. other chemicals reabsorbed: glucose, creatine, amino acids, urea, bicarbonate, potassium etc.
• tubular secretion: peritiubular capillaries allow material to be transported to renal tubules

  • drugs, histamine, hydrogen ion, ammonia, pottasium, urea, creatine, hormones, etc.
• regulation of blood pressure/volume

  • Aldosterone: stimulates distal convoluted tubule to reabsorb sodium
  • Angiotensin II: stimulates secretion of aldosterone
  • Antidiuretic hormone: increase water reabsorption by distal convoluted tubule
• diabetes: continuous high blood sugar over time

  1. kidneys reach threshold of glucose reabsorption, excess glucose in nephron tubule
  2. high osmosis pressure in nephron tubule inhibits water reabsorption
  3. increased urine output, dehydration, thirst, fruity odor
• diuretic: enhances urine output

  • alcohol: inhibits release of aldosterone
  • caffeine: inhibits Na^+ reabsorption, increases glomerular filtration
• chemical compound

  • water: 95%
  • urea: breakdown of amino acids
  • uric acid: breakdown of nucleic acids
  • creatinine: breakdown of creatine used by skeletal muscle
• Color

  • urobilin (urochroms): yellow pigment from breakdown of heme
  • abnormal: cloudy (bacteria), food pigments (beets), blood, bile pigments
• Urine elimination

  • ureter: lined w/ smooth muscle to move urine by peristalsis to urinary bladder
• urethra: to be from urinary bladder to outside body
• urinary bladder: hollow organ that stores urine

  trigone: flow of urinary bladder

  3 openings

  • 2x ureter
  • 1x urethra
• detrusor muscle: smooth muscle of the bladder

  1. bladder wall
  2. internal urethral sphincter
  3. involuntary
• micturition: process that expels urine from bladder

  1. stretch receptors stimulated as bladder fills, triggering micturition reflex
  2. detrusor muscle contracts rhythmically, causing sense of urgency
  3. urge begins as bladder fills to 150ml, but max is 600ml
  4. passing 300 ml, sensation intensifies and contractions are more powerful
  5. once contractions are strong enough, internal urethral sphincter is forced open
  6. external urethral sphincter (voluntary) relaxes and bladder empties