2.2 Structure of mammalian gas exchange system

Respiratory system order

Nose/mouth → Trachea → Bronchi (one for each lung) →Bronchioles → Alveoli (GE)

Trachea

• Carries air towards the lungs. C-shaped rings of cartilage prevent it from collapsing

• The c-shape prevents any friction from rubbing with the oesophagus located close behind + providing increased flexibility when food is being swallowed

• layer of mucus covering the lining of the trachea → helps to trap dust and pathogens

  • Tiny hairs called cilia are also found on the lining of the airways, where they waft mucus towards the top of the trachea, removing any trapped particles and pathogens from the airways

Bronchi

• Carry air into each lung. Irregular cartilage patterns supports their walls.

• Thinner walls and a smaller diameter than trachea

Bronchioles

• Smaller branching airways that distribute air throughout the lungs. Smooth muscle can alter their diameter

• The larger bronchioles possess elastic fibres and smooth muscle that enable adjustment of the size of the airway to increase or decrease airflow

Alveoli

• Tiny air sacs where oxygen and carbon dioxide are exchanged by diffusion

• Groups of alveoli are located at the ends of the bronchioles

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Diaphragm

Muscle that contracts during inhalation, helping increase thoracic volume

Intercoastal muscles

Move the ribcage during ventilation

Pleural membranes

Surround the lungs; pleural fluid reduces friction as the lungs move