Crash course kidney videos

• The liver plays a tremendous role in directing dead cells and leftover chemicals to the digestive and urinary systems
• The liver can't actually escort waste out of your person
• The lungs can lend a hand, exhaling carbon dioxide, and the colon will eventually poop out unusable stuff and old cell-parts
• Much of your chemical waste still needs to be sorted and disposed of, so the urinary system steps in to bat clean-up
• Urinary system


  Regulates your water volume, ion salt concentrations, and pH levels, and influences your red blood cell production and blood pressure
• Urinary system's main purpose

  Filters toxic leftovers from your blood and ferries it out of the body
• Most of what's in your blood is totally removed by the kidneys, then your body pulls back what it wants to hold onto, before the rest is sent to the bladder
• Metabolizing nutrients, especially protein, makes a mess by producing ammonia, which is toxic
• Liver


  Converts ammonia into less-toxic urea, which the kidneys filter out into your pee
• Urea can degrade back into ammonia, which is why dirty, pee-soaked toilets and cat litter boxes smell like ammonia
• Kidneys


  • A pair of dark red, fist-sized, bean-shaped organs that sit on each side of your spine against the posterior body wall
  • Retroperitoneal, meaning they lie between the dorsal wall and the peritoneum rather than inside the abdominal cavity
• Kidney layers


  • Outermost cortex
  • Medulla, a set of cone-shaped masses of tissue that secrete urine into tiny sac-like tubules
  • Innermost renal pelvis, a funnel-shaped tube surrounded by smooth muscle that uses peristalsis to move urine out of the kidney, into the ureter, and into the bladder
• Kidneys filter about 120 to 140 liters of blood every day
• Nephrons


  • The microscopic filtering units in the kidneys, where the real business of blood-processing and pee-making begins
  • Consist of a renal corpuscle and a long, winding renal tubule
• Nephron filtration, reabsorption, and secretion

  1. Filtration: Fluid, waste products, ions, glucose, and amino acids pass from the blood into the glomerular capsule

  2. Reabsorption: Useful substances like ions and glucose are reabsorbed back into the blood from the renal tubule

  3. Secretion: Remaining waste products are secreted into the urine
• Parts of the renal tubule

  • Proximal convoluted tubule (PCT): Reabsorbs useful substances
  • Loop of Henle: Creates a salt concentration gradient to drive water reabsorption
  • Distal convoluted tubule (DCT): Final processing of urine
• Urea is used by the kidneys to ramp up the concentration gradient in the medulla, making it more effective at drawing water out of the collecting duct
• Tubular secretion


  Selectively transports extra waste like hydrogen, potassium, and certain organic acids and bases out of the blood and into the urine
• The kidneys clean up the mess left over from metabolizing food
• Urine


  • Filled countless diapers
  • Caused discomfort for airline passengers
  • Ruined the Dude's rug
• Micturition


  The scientific term for urination
• All mammals, and most animals urinate to remove toxins and to help maintain water-volume homeostasis, or blood pressure
• Some animals spray urine around to attract mates or mark territory, or deter predators
• Humans are the only animals that actually study pee
• Early Sumerian and Babylonian physicians were making urine-related observations


  Thousands of years ago
• Doctors diagnosed diseases based on smelling, inspecting, or even tasting urine samples

  Medieval times
• Urological tests can help detect a lot of ailments based on the color, smell, clarity, and chemical composition of a urine sample
• Freshly peed urine


  95% water, slightly acidic (pH around 6), a little aromatic, and usually somewhere between clear and dark yellow in color
• Urine contains over 3000 different chemical compounds, and their varying levels of concentration can tell us a lot about what's going on in the body
• Urine conditions that can be detected

  • Cloudy with white blood cells = urinary tract infection
  • Sweet smell and high glucose = diabetes
  • Pink color = internal bleeding
  • High protein = pregnancy, overexertion, high blood pressure, or heart failure
• The process of producing, storing, and eliminating pee is complex, involving the circulatory, nervous, and endocrine systems
• Regulation of urine production

  1. Glomerular filtration

  2. Glomerular filtration rate regulation

  3. Hormonal regulation by antidiuretic hormone (ADH)
• Glomerular filtration rate


  The constant rate of blood flow through the glomeruli in the kidneys
• Autoregulation


  The kidneys' intrinsic ability to regulate the glomerular filtration rate despite changes in blood pressure
• Antidiuretic hormone (ADH)


  A hormone secreted by the posterior pituitary gland that helps the body retain water
• Caffeine and alcohol


  Inhibit the release of antidiuretic hormone (ADH)
• Aquaporins


  Protein channels in cell membranes that allow water to move easily
• Movement of urine from kidneys to bladder

  1. Ureters use peristalsis to move urine

  2. Bladder stores urine temporarily
• Bladder


  • Collapsible sac that can hold up to 1 liter of urine
  • Has an inner mucosal layer, a thick muscular layer, and a fibrous outer membrane
• Urination


  1. Stretch receptors in bladder wall send impulses to spinal cord and brain

  2. Parasympathetic neurons are excited, sympathetic neurons inhibited

  3. Detrusor muscle contracts, internal urethral sphincter opens, external urethral sphincter relaxes