science

• Kidneys


  Bean-shaped organs that work as fine-tuned internal sensors, balancing the amount of fluid in the body, detecting waste in the blood, and releasing vitamins, minerals, and hormones
• Main role of kidneys

  • Dispose of waste products and turn them into urine
• The body's 8 liters of blood pass through the kidneys between 20 and 25 times each day, meaning that, together, these organs filter about 180 liters every 24 hours
• Blood filtration in kidneys

  1. Blood enters each kidney through arteries

  2. Arteries branch into tiny vessels that entwine with nephrons

  3. Nephrons use glomeruli and tubules to filter blood

  4. Useful ingredients are reabsorbed

  5. Waste products are redirected as urine

  6. Urine is discharged through ureters and bladder
• Tubule


  Long, stringy, straw-like vessel that detects whether filtered ingredients are needed and reabsorbs them
• Nephron


  Internal module in the kidney that contains a glomerulus and tubule to filter blood
• Each kidney contains 1 million nephrons
• When the kidney detects too much water in the blood


  It sends the extra liquid to the bladder to be removed
• When the kidney detects low water levels in the blood


  It releases some water back into the blood stream, meaning less water makes it into the urine
• Urine color


  Appears yellower when you're less hydrated
• Other functions of kidneys

  • Activate vitamin D
  • Secrete hormones like renin and erythropoietin
• Without the kidneys, our bodily fluids would spiral out of control and we'd expire
• Levels of body organisation

  • Organelles
  • Cells
  • Tissues
  • Organs
  • Organ Systems
  • Organisms
• Organelles


  Specialized structures within a cell that perform specific functions
• Cells


  The basic structural and functional units of life
• Cells vary in size, shape, and function, but all carry out essential processes necessary for the organism's survival, such as metabolism, growth, and reproduction
• Tissues


  Groups of similar cells that work together to perform a specific function
• Types of tissues in multicellular organisms

  • Epithelial tissue
  • Connective tissue
  • Muscle tissue
  • Nervous tissue
• Organs


  Structures composed of two or more types of tissues that work together to perform a particular function or set of functions
• Examples of organs


  • Heart
  • Lungs
  • Liver
  • Brain
  • Stomach
• Organ Systems


  Groups of organs that work together to perform coordinated functions and maintain homeostasis within the organism
• Organisms


  Complete living beings made up of multiple organ systems working together
• Organisms can be unicellular (consisting of a single cell) or multicellular (consisting of many cells)
• Organisms exhibit characteristics of life, such as growth, reproduction, response to stimuli, and metabolism
• Body systems


  • Respiratory
  • Digestive
  • Circulatory
  • Nervous
  • Excretory
• Respiratory system


  Takes in oxygen and releases carbon dioxide
• Digestive system


  Breaks down food into nutrients the body can absorb
• Circulatory system


  Transports blood throughout the body
• Nervous system


  Controls the body's activities and allows us to respond to stimuli
• Excretory system


  Removes waste products from the body
• Characteristics of life (MRS GREN)

  • Movement
  • Respiration
  • Sensitivity
  • Growth
  • Reproduction
  • Excretion
  • Nutrition
• Parts of the excretory system

  • Kidneys
  • Ureters
  • Bladder
  • Urethra
• Kidneys


  Filter waste products, excess ions, and water from the blood to form urine
• Ureters


  Carry urine from the kidneys to the bladder
• Bladder


  Stores urine until it is ready to be excreted from the body
• Urethra


  Tube through which urine passes from the bladder out of the body
• Skin


  Excretes sweat, which contains water, salts, and some waste products
• Lungs


  Remove carbon dioxide, a waste product of cellular respiration, from the body through exhalation
• Urea


  Produced in the liver when proteins are broken down and released into the bloodstream
• Urea excretion


  1. Travels to the kidneys

  2. Filtered out along with other waste products to form urine

  3. Purified blood leaves the kidneys through the renal vein and returns to the heart

  4. Waste collected in the nephrons passes through the ureters to the urinary bladder

  5. Urine is expelled from the body through the urethra during urination