Respiratory Tree Functional Anatomy

Trachea

10-12cm long and 2cm wide hollow tube, passes through mediastinum, supported and kept open always by incomplete c shaped hyaline cartilage rings

What completes trachea cartilage rings

Completed at the back by elastic connective tissue and smooth muscle - trachealis muscle, protects the oesophagus posterior to trachea and allow it expand during swallowing

Carina

Last tracheal cartilage ring covering with mucous membrane with a large number of sensory receptors, located where trachea branches into two primary bronchi, irritation of receptors triggers violent cough reflex which prevents entry of unwanted particles into the lungs

Layers of the trachea

Mucosa = respiratory epithelium and lamina propria, submucosa, hyaline cartilage, circumferential smooth muscle, adventitia

Respiratory bronchioles

Diameter smaller than .5mm, start the respiratory zone, branches into two or more alveolar ducts, leads to alveoli

Alveoli

90 percent lined with type one alveolar cells/pneumocytes, 5-10 percent has type two alveolar cells, large surface area for gas exchange, in close proximity to pulmonary capillaries - forms thin respiratory membrane, squamous epithelia of alveoli and capillaries

Type one alveolar cells

Thin simple squamous epithelia for diffusion

Type two alveolar cells

Simple cuboidal cells that secrete surfactant to reduce surface tension and prevent alveolar collapse

Alveolar macrophages

Final defence against debris and microorganisms