3.2 Respiratory System

Main Parts and Functions

  • Nose: Filters, warms, moistens air; smell.
  • Pharynx (Throat): Passageway for air and food.
  • Larynx (Voice Box): Contains vocal cords; sound production.
  • Trachea (Windpipe): Carries air to bronchi; C-shaped rings prevent collapse.
  • Bronchi: Trachea divides into two, leading to lungs; branch into bronchioles.
  • Lungs: Primary organs; gas exchange in alveoli.

Respiration vs. Breathing

Feature Respiration Breathing
Process Biochemical (cellular level) Physical (mechanical)
Energy Releases energy from food Involves intake/expulsion of air
Location Inside cells (mitochondria) Lungs and respiratory passages
Enzymes Involves many enzymes No enzymes involved

Mechanism of Breathing

  • Inhalation (Breathing In):

    • Diaphragm: Contracts, moves downwards.
    • Ribs: Intercostal muscles contract, pull ribs up/out.
    • Effect: Chest cavity volume increases, pressure inside lungs decreases; air rushes in.

  • Exhalation (Breathing Out):

    • Diaphragm: Relaxes, moves upwards.
    • Ribs: Intercostal muscles relax, ribs move down/in.
    • Effect: Chest cavity volume decreases, pressure inside lungs increases; air is forced out.

Common Respiratory Diseases

  • Asthma: Chronic inflammation of airways; difficulty breathing, wheezing.
  • Bronchitis: Inflammation of bronchial tubes; cough with mucus.
  • Pneumonia: Lung infection; air sacs fill with fluid/pus; cough, fever, difficulty breathing.
  • Tuberculosis (T.B.): Serious bacterial infection, mainly affects lungs.