Lecture 20: Respiratory Mechanics Flashcards
what are alveoli
single layer of cells surrounded by capillaries across which oxygen and CO2 exchange occurs
What are type I alveoli cells
epithelial cells forming exchange surface w/ the capillaries
what are type II alveolar cells
-scattered among type I
-make surfactant that coats alveoli to reduce surface tension
what do alveolar pores do
connect adjacent alveoli and equalize air pressure
what do alveolar macrophages (dust cells) do
they are phagocytic cells that consume microbes and dust particles
what helps prevent mammalian lungs from collapsing
surfactant - the fluid lining the inner surface of the alveoli, reduces surface tension so that less pressure is needed to inflate the lungs
why is the pleural space between the visceral and parietal pleura important
it reduced friction, allowing the pleurae to slide against eachother
- also acts to glue the lung to the chest wall
how does the pressure inside the pleural cavity help keep lungs expanded
pressure inside pleural cavity is negative in respect to the atmospheric pressure which keeps the lung slightly expanded
If P alveoli is < P atmosphere, then air (enters/exists) lung
enters
If P alveoli is > P atmosphere, then air (enters/exists) lung
exits
the active process of inhalation in mammals occurs when
motor neurons in the phrenic nerve stimulate the diaphragm to contract
- increases size of thoracic cavity
- the pressure in pleural cavity becomes more (-), and Palv > Ppleural cavity so the alveoli expand
- adhesion of pleural membranes assists in expansion of lungs
air moves into the alveoli unit until..
the air pressure in alveoli equals atmospheric pressure
when Palv=Patm…
there is no movement of air b/c there is no pressure gradient to act as a driving force
what causes exhalation to occur
the phrenic nerve stops firing –> inspiratory muscles relax
-elasticity of thorax and lung decrease the size of alveoli, increasing Palv
what is residual volume (RV)
the air left in lungs after a forced exhalation
