Lecture 11 - Microscopic structure of gas exchange Flashcards
what is the smallest unit in which gas exchange occurs?
alveoli
where are alveoli scattered?
within the walls of respiratory bronchi
where are alveoli continuous? what do they lead to?
in walls of alveolar ducts which lead to terminal alveolar
what are the two cell types of the alveoli epithelial cells
type 1 alveolar epithelial cells
type 2 alveolar epithelial cells
describe the shape and function of type 1 alveolar cells, can they divide?
- very flattened cells, sit on basement membrane
- terminally differentiated (cannot divide)
- allow gas diffusion across cytoplasm
describe the shape and function of type 2 alveolar cells
- cuboidal
- cytoplasmic granules contain surfactant (surface tension)
- divide to replace type I and II cells
other than type I and II epithelial cells, what else can be found within the alveoli?
macrophages
how are alveolar seperated? what do they contain
by inter alveolar septa: contain fibroblasts, mast cells and macrophages
what are alveolar pores?
holes in septa between adjacent alveoli, allow passage of air between alveoli
blood - air barrier
oxygen must diffuse across;
- alveolar fluid
- alveolar epithelium
- basement membrane of alveolar epithelium
- basement membrane of capillary cell
- capillary endothelial cell
how thick is the blood - air barrier
0.2 - 2 micron thick
what are pulmonary macrophages, where are they present?
present in 3 locations
1. intravascular: associated with endothelium
2. interstitial
3. alveolar: function to clear alveolar surface - removed via trachea
can proliferate locally
what does the interlobar septa contain?
collagen and elastic fibres
blood vessels
what is partial pressure?
pressure exerted by a given gas in a mixture of gases
alveolar air
water vapour added to air in inspiration --> changes in partial pressure o2 = 146 CO2 = 0.27 N2 = 556 H20 = 47
