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• Respiratory system


  Provides gas exchange between the blood and the environment, allowing oxygen to be taken in and carbon dioxide to be expelled
• Gas exchange in lungs

  Internal respiration, taking in and letting out of gases
• Structure of the human respiratory system

  1. Air enters through nostrils

  2. Passes through nasal cavity, warmed and moistened

  3. Enters trachea

  4. Trachea branches into bronchi

  5. Bronchi branch into bronchioles

  6. Bronchioles end in alveolar sacs
• Trachea


  • Contains C-shaped rings of cartilage for support and flexibility
• Branching of the trachea

  1. Trachea branches into two bronchi

  2. One bronchus goes to the right lung, the other to the left lung

  3. Bronchi branch further into bronchioles
• Bronchioles


  • End in alveolar sacs, the site of gas exchange
• Lungs


  • Housed in the thoracic cavity
  • Protected by the rib cage
  • Separated from the abdomen by the diaphragm
• Mechanism of human breathing

  1. Lungs expand to inhale air

  2. Lungs return to normal size to exhale air

  3. Movements of the ribs and diaphragm bring about breathing
• Inhalation


  Air flows into the lungs
• Exhalation


  Air flows out of the lungs
• Breathing is the process of taking in and letting out air
• Sclera


  Strong layer that maintains the shape of the eye and protects it
• Choroid


  Black layer that contains blood vessels that supply oxygen and nutrients to the eye
• Cornea


  Transparent layer which refracts and focuses light onto the retina
• Pupil


  Opening in the centre of the iris which controls the quantity of light entering the eye
• Aqueous humour


  Transparent fluid which maintains the shape of the eyeball and focuses light into the eye
• Retina


  Layer containing photoreceptors which detect light and produce nerve impulses
• Yellow spot


  Part of the retina which is most sensitive to light as it has many photoreceptors
• Optic nerve


  Nerve fibres which carry nerve impulses from the retina to the brain
• Blind spot


  Part of the retina which is not sensitive to light as there are no photoreceptors and an exit point for all optic nerve fibres
• Vitreous humour


  Transparent jelly-like substance which maintains the shape of the eyeball and focuses light onto the retina
• Ciliary muscle contractions and relaxations change the shape of the lens to focus light onto the retina
• Suspensory ligaments hold the eye lens in position
• The iris controls the size of the pupil to regulate the amount of light entering the eye
• Light rays pass through the cornea, lens, and vitreous humour before reaching the retina
• Nerve impulses from the retina are transmitted through the optic nerve to the brain for interpretation
• berlakunya kemajuan indu


  Enactment of industrial progress
• yawan perlombongan bi


  Mining industry
• For a person with normal vision


  1. Thickness of the lenses is changed

  2. Images of distant and near objects are focused exactly on the retina

  3. Image produced is sharp and clear
• For a person with defective vision

  1. Light rays are not focused exactly on the retina

  2. Images formed on the retina are blurred
• Most common defects of vision

  • Short-sightedness
  • Long-sightedness
• These defects usually occur because watching television or the computer screen too close, bacterial infection and aging process
• Short-sightedness (myopia)


  Sees near objects clearly but distant objects are blurred
• Long-sightedness (hypermetropia)


  Sees distant objects clearly but near objects are blurred
• Cause of short-sightedness and long-sightedness


  • Condition of the lens and shape of eyeball
• For short-sightedness


  Light is focused in front of the retina
• For long-sightedness


  Light is focused behind the retina
• Laser treatment (LASIK) can also be used to correct vision defects