Excertory

• Homeostasis


  The regulation of a stable internal environment, no matter where we are or what we're doing
• Our organ systems have some hand in maintaining homeostasis
• Excretory system


  The urinary system, which includes the kidneys, the ureters, the bladder, and the urethra, is the star quarterback of the homeostasis team
• Osmoregulation


  The process of maintaining the right levels of water and dissolved substances in the body
• Ammonia is a toxic byproduct of metabolizing food
• Urea


  A compound made from combining ammonia and carbon dioxide, it has very low toxicity
• Uric acid


  Can be excreted as a paste, so not a lot of water is needed
• How the excretory system works in humans

  1. Kidneys filter fluid and dissolved materials from blood

  2. 99% of the filtered fluid is reabsorbed

  3. Remaining 1% becomes urine
• Nephrons


  • Tiny filtering structures in the kidneys, each kidney has about a million of them
  • If unravelled, all the nephrons would stretch over 80 kilometers
• Filtration and reabsorption in the nephron

  1. Blood enters the glomerulus, where fluid and small molecules are filtered out

  2. Filtered fluid (filtrate) enters the proximal convoluted tubule, where important substances are reabsorbed

  3. Filtrate enters the Loop of Henle, where water and salts are reabsorbed

  4. Filtrate enters the distal convoluted tubule, where more regulation of ions occurs

  5. Remaining fluid becomes urine and is collected in ducts
• Anti-diuretic hormone


  Regulates the permeability of the collecting ducts, telling them to reabsorb more water
• Alcohol interferes with anti-diuretic hormone, leading to excessive urination and dehydration
• Urine production and excretion

  1. Urine flows from the kidneys to the bladder through the ureters

  2. Urine is stored in the bladder until it is released through the urethra
• Some body systems are more familiar and well-known than others, such as the circulatory system, nervous system, and digestive system
• The excretory system is a body system that many people are not as sure about what it includes, nor do they realize how incredible it is
• Osmotic balance


  Maintaining the balance of water and solutes in the body
• Metabolic wastes


  Substances like carbon dioxide and nitrogenous wastes that need to be excreted
• Organs and structures involved in the excretory system

  • Skin
  • Liver
  • Lungs
  • Kidneys
• Urinary system


  The system focused on the kidneys, bladder, ureters, and urethra
• Nephron


  • The functional unit of the kidney
  • Processes waste products from the blood to create urine
• Glomerulus


  A specialized mass of capillaries surrounded by the Bowman's capsule
• Filtrate


  The fluid that enters the Bowman's capsule from the glomerulus, containing water, glucose, amino acids, salts, ions, and urea
• Filtration and reabsorption in the nephron

  1. Filtrate enters Bowman's capsule

  2. Substances reabsorbed in proximal tubule

  3. Water and solutes reabsorbed in loop of Henle

  4. Substances secreted or reabsorbed in distal convoluted tubule

  5. Water and solutes reabsorbed in collecting duct
• Diffusion and facilitated diffusion


  Transport processes that don't require ATP and move substances down their concentration gradient
• Active transport


  Transport process that requires ATP to move substances against their concentration gradient
• Not all substances are 100% reabsorbed, so some remain in the filtrate
• The proximal tubule and distal convoluted tubule are important for pH regulation
• The permeability of the collecting duct to water is controlled by hormones
• Urea is reabsorbed and secreted at different points in the nephron
• Urine produced by the nephrons travels down the ureters to the bladder before being expelled from the body
• The complex processes in the nephron are influenced by hormonal control and the surrounding osmotic balance
• Diuretics


  Medications that increase the amount of water in the filtrate, leading to more water in the urine
• Dialysis


  A process that filters the blood and assists with osmoregulation for people with severely compromised kidney function
• Ureters


  Tubes connecting the kidneys to the bladder
• Urinary Bladder


  The place that holds your urine until it is released
• Renal cortex


  The outer layer of the kidney. It includes the bowman's capsule, proximal and distal tube.
• Nephrons


  Little structure that is located inside the kidney, which filters and reabsorbs substances.
• Excretory


  The system that removes waste and excess water from the body
• There are two fist sized beans in your body. They are called kidneys.
• 4 steps your kidneys do

  • Glomerulus filtration
  • Tubular reabsorption
  • Tubular secretion
  • Water reabsorption