Structure of the Lung
pulmonary capillary is polarized one side has a thinner barrier than the other
thinner: outer most = alveolar epithelial cell inner most = capillary endotheleum between the layers = insterstitial matrix the interstitial is a fusement of the basement membranes collagen supports the blood gas barier
on the thicker side: fibroblast visible on M.E leading to interstitial matrix
barrier is a third of a mikron (v.v. thin)
ficks law of diffusion: the volume of gas that moves across a sheet is proportional to the area of the sheet, the diffusion constant, and the difference in pressure between the twosides of the sheet. it is also inversely proportional to the thickness of the sheet
Cast of Lung Airways: the airways become more numerous, shorter, narrower and eventually end up to the alveoli
the trachea is made up of cartilogenous rings that support it (anterior) the posterior is membranous and there is invagination
clara cell- function not fully understood, releases another substance to the mucus lining layer
from bronchioles to alveoli, epithelial cell's height decreases from columnar. to cuboidial, (both cilial) and then squamous
type 1 alveoli epitheleal cell - main structure for alveoli surface. lazy cell, long protoplasmic extention type 2 - diff shape, globular. ring of microvili. holes through which it secretes material to alveoli surface surfactant reduces tension and confers stability to al surface type 2 - highly metabolic, produces surfactant
Alveolar macrophage - moves through al surface, engulfes foreign particles surfactant leaves/ turns into remnants that are engulfed by al macrophage remnats and surfactant is identifiable by their onion layer skin
airways divide dichotomically - two daughter branches up to 16 generations till alveoli called dead space bc no gas exchange then the 16th is terminal bronchiole three generations of respiratory bronchioles - alveoli bud off on the branches then 3 gens of alveolar ducts and then alveolar sacs