Lungs

lungs

Human gaseous exchange system

human gaseous exchange system

Nasal cavity

  • large SA with good blood supply - warms air to body temp

  • hairy lining which secretes mucus to trap dust and bacteria - protects delicate lung tissue from irritation and infection

  • moist surfaces increase humidity of incoming air so reduces evaporation from exchange surfaces

Bronchus

  • trachea divides to form left and right bronchi

  • similar structure to trachea but with smaller supporting rings of cartilage

Trachea

  • ciliated epithelium

    • tissue

    • cilia waft to move mucus up to the throat where it is swallowed

    • stomach acid and enzymes kill any bacteria

  • goblet cells

    • release mucus to trap dirt and bacteria and protect the epithelium

  • trachea

Bronchioles

  • bronchi divide to form many small bronchioles

  • no cartilage rings

  • walls contain smooth muscle

  • smooth muscle contracts and bronchioles constrict (and vice versa) meaning amount of air that can reach the lungs is controlled

  • lined with a thin layer of flattened epithelium making some gaseous exchange possible

Alveoli

  • main exchange surface of the body

  • layers of thin flattened epithelium cells

  • collagen and elastic fibres

  • elastic tissues allow alveoli to stretch as air draws in. when return to resting they help squeeze air out - elastic recoil

  • thin layers

  • good blood supply

  • good ventilation

  • inner surface covered in thin layer of solution of water, salts, and lung surfactant

    • makes it possible for alveoli to remain inflated

  • alveoli