Excretion

• Excretion

  Removal of metabolic waste from the organism
• Homeostasis

  Maintenance of constant internal environment in an organism even when external environment changes
• Excretion in plants

  1. During the day, plants excrete oxygen and water vapour through stomata on the underside of leaf and through lenticels on stem

  2. During night plants lose carbon through stomata and lenticels
• Role of excretory system in homeostasis

  • Regulate body temp
  • Control osmosis (salt + water balance of the body)
  • Control concentration of body fluids
  • Removing waste products of metabolism from body
• Organs of excretion

  • Lungs excrete water and carbon dioxide
  • Skin excretes water and salts (sweat)
  • Kidneys excrete water, salt and urea (urine)
• Skin

  Regulates human body temperature
• Skin

  • Consists of outer epidermis and inner dermis, beneath these layers is the adipose tissue which has fat rich cells to insulate body
• Functions of skin- protection

  • epidermis protects body from damage, barrier to prevent loss of water
  • Dermis protects internal organs
  • Melanin is a pigment in the skin, protects from uv radiation
  • Sebum is an oil produced by sebaceous gland that are alongside hair follicles. This keeps hair moist and flexible and keeps skin from drying up
• Vitamin production

  vitamin D Produced in skin from uv rays from sun, helps absorb calcium in intestines
• Food store

  • fat stored in adipose tissue
• Sense organ

  • skin contains receptors that allow it to act as a sense organs, it detects sensations of touch, pain and temp
• Excretion

  • sweat glands
• Ectotherms

  Organisms that gain or lose heat from or to their external environment e.g. reptiles
• Endotherms

  Organisms that generate their own heat from metabolic reactions e.g. mammals
• Temperature regulation - cold

  1. Erector muscles contract forming goosebumps, causing hair to stand up in a process called piloerection, trapping a layer of warm air close to skin

  2. Blood vessels in the skin contract, this is called vasoconstriction
• Temperature regulation - warm

  1. Sweat produced

  2. Blood vessels in skin expand
• Urinary system

  • 2 kidneys
  • 2 ureters
  • bladder
  • urethra
• Sphincter muscle

  Controls release of urine from bladder through urethra
• Kidneys carry out

  1. Filtration

  2. Reabsorption

  3. Secretion
• Filtration

  Filter waste from blood (happens in cortex)
• Reabsorption

  Reabsorb useful materials from filtrate (happens in cortex and medulla)
• Secretion

  Secrete some substances from blood into filtrate (happens in cortex)
• Parts of urinary system

  • Renal artery
  • Renal vein
  • Ureter
  • Cortex
  • Medulla
• Renal arteries carry blood that's high in waste products from body to each kidney
• Renal veins carry purified blood from kidney back to vena cava for circulation around the body
• Ureters carry urine formed in kidneys to bladder
• Bladder stores urine
• Urethra carries urine out of body
• Urine


  96% water, 2.5% nitrogenous waste, 1.5% salts
• Urea

  A nitrogen containing salt that's poisonous to body, made from protein, made in liver, excess amino acids are taken to the liver and broken down, enters blood at the liver, leaves blood at kidneys
• Functions of kidneys

  • Excretion of water, salts and urea
  • Osmoregulation- control water content of the blood and salt concentration of body
  • Control pH of blood
• Transverse section of kidney

  TS of kidney