Excretory system

• homeostasis


  the ability of an organism to maintain a constant internal environment
• Ectotherm


  an organism that gains heat from or loses heat to their external environment
• Endotherm


  organisms that generate its own heat from metabolic reactions
• Lungs, skin, and kidneys are all excretory organs
• 1. lungs excrete carbon dioxide by exhaling
  2. skin excretes water and salts by sweating
  3. kidneys excrete urine by urinating
• the skin has two layer which are the outer epidermis and the inner dermis

  Below this layer is the adipose tissue which has fat rich cells
• The epidermis

  outer layer of skin

  New cells produced by mitosis in Malpighian layer

  the new cells become cornified with a protein called keratin

  cells in the Malpighian layer produce pigment called melanin
• Melanin


  Produced in Malpighian layer

  this pigment gives colour to our skin, eyes & hair

  protects us from uv radiation

  production of melanin increases when we are exposed to the sun
• The dermis 


  located: beneath the outer epidermis

  consist of: Collagen, connective tissue

  within dermis: Sweat glands, hair follicles, sebaceous glands, blood vessels, nerve receptors
• Function of the skin

  Protection

  Vitamin D production

  Food store

  sense organ

  excretion

  Temperature regulation
• Protection

  epidermis: acts as a barrier preventing water loss & pathogens entering

  dermis: protects internal organs from damage due to bangs

  melanin: protects skin from UV lights

  Sebum: keeps our hair moist & flexible, prevents skin from cracking
• Sebum is oil produced by sebaceous glands
• Vitamin D production

  produced by skin after exposed to UV RADIATION

  Vit D helps absorb calcium
• Food store

  fat is stored in the adipose tissue
• Sense organ


  receptors in the skin sense touch, temperature and pain
• excretion


  sweat contains water and salts
• Temperature regulation- in cold conditions

  Piloerection: warm air is trapped close to skin reducing heat loss

  Vasoconstriction: reduces heat loss

  shivering: produces heat raising body temperature

  fat stores: adipose tissue helps insulate the body
• piloerection- erector muscles in skin contract causing goosebumps and hair to stand up
• vasoconstriction- blood vessels in the skin contract reducing heat loss through skin
• Shivering- rapid contraction and relaxation of the muscles in the body
• temperature regulations- warm conditions


  sweat: as water evaporates it lowers the body temperature

  vasodilation: noticed after exercise in the face, increases heat loss and lowers body temperature
• Vasodilation is the expansion of the blood vessels in the skin when we are too hot
• kidney is the main excretory organ
• kidneys excrete urea, water and salts
• kidneys control the amount of water and salt excreted
• the sphincter controls the release of urine
• kidney

  shape: bean shaped, fist sized

  location: below the diaphragm
• kidney structure

  cortex

  renal pelvis

  medulla

  renal artery

  renal vein

  ureter
• processes of the kidney

  filtration

  reabsorption

  secretion
• urine is composed of water, urea and salts
• urea is formed in the liver
• deamination is the breakdown of amino acids with the production of urea
• urine is collected in the pelvis
• ureter transports urine to the bladder
• urine is stored in the bladder
• functions of the kidneys

  excretion

  osmoregulation

  pH control
• excretion

  kidney removes waste from blood & converts it to urine

  urine is excreted through urethra
• osmoregulation water content

  kidney controls water levels in the body by varying the amount of water in the urine
• osmoregulation salt concentration

  kidneys control salt levels in the body by varying the amount of salt in the urine

  by controlling the water and salts, kidney ensures blood plasma levels are the correct concentration

  this minimises cells losing/gaining fluids due to osmosis
• kidneys are known as the osmoregulators of the body