Airways and Lungs



The respiratory system

The respiratory system is divided into a conducting section and a respiratory section.

The conducting section consists of the:

and is responsible for conducting air to the lungs.

The respiratory section consists of the:

and is responsible for gaseous exchange

The conducting section

The respiratory section

General histology of the lungs

Lung lobules are pyramid shaped, with an apex (towards the hilum) and a basis (towards the surface of the lungs).

The branches of the pulmonary artery follows the branching of the bronchi and bronchioles. In the interalveolar septae these blood vessels become capillaries that merge to form interlobular veins.

The pleura covers the lungs. It has two layers, parietal and visceral. Both membranes are composed of mesothelial cells resting on a fine connective tissue layer with collagen and elastic fibres. These two layers define a cavity lined entirely with mesothelial cells which is filled with a thin layer of fluid.

Medical fact: The walls of the pleural cavity are very permeable to water and other substances, and therefore fluid accumulation (pleural effusion) occurs frequently.

© februarie 2005 marius loots