In the human lung, inhaled air is conducted through a branched system of airways until it reaches structures called alveoli. Here, the air gets in close proximity to deoxygenated blood coming from the heart and gas exchange takes place. The diffusion of CO2 and O2 out of and into the blood respectively is a passive process driven by pressure gradients.
The structure of an alveolus is designed to optimize efficiency of diffusion: It provides a large surface area in combination with an extremely thin tissue barrier between air space and blood. The blood is passing this tissue through a tight net of small capillaries with a diameter that is comparable to the size of an erythrocyte - leading to a deceleration of blood flow and increased contact time between air and blood.
We are using modern technologies like the open source software blender to virtually reconstruct this tissue in its three-dimensional arrangement. The goal is to be able to use this in silico model for investigation of the tight relationship between structure and function of the human alveolus.
On the left you see an example of a blender model. It shows two substantial components of the alveolar wall that are in close contact with each other: A tightly woven net of small capillaries and a thin type I alveolar epithelial cell.