Question

D. Describe the characteristics and function(s) of a bundle of alveoli.

E. How does the diaphragm contribute to the mechanism of ventilation?

Answer 1

D. Characteristics

Alveoli are the center of respiratory system’s gas exchange. At the end of each bronchiole, there is alveolar duct which connects to a cluster of thousands of structures called alveoli. They are tiny balloon shaped structures and organized as bunches called alveolar sac. The total thickness of alveoli is less than a millimeter. The diffusion membrane is made up of 3 layers.

1. Thin squamous epithelium
2. Endothelium of alveolar capillaries
3. Basement substance between them

Functions

Alveoli are the workhorses of respiratory system which allow the Oxygen and Carbon di oxide to move between the lungs and bloodstream. Diffusion of Oxygen from alveoli to tissues and Carbon di oxide from tissues to alveoli. The alveoli are just one cell thick and this helps in the rapid exchange of gases.

E. Diaphragm helps in the generation of pressure gradients which is needed for ventilation. Inspiration starts by the contraction of diaphragm results in the increase in thoracic chamber’s volume (pulmonary volume). Thus reduction in intra-pulmonary pressure than the atmospheric pressure which forces the air from outside to move into the lungs.

Relaxation of diaphragm to their normal positions reduce the thoracic volume and thereby the pulmonary volume. This increases the pulmonary pressure and expiration (Expulsion of air from the lungs to outside) occurs.

(Please note that along with diaphragm, a set of specialized muscles also help in ventilation).