RS. gas pressure Flashcards
what is the point of breathing?
maintain blood gas homeostasis
how do gases move in alveoli and capillaries?
down conc gradients by diffusion
what is the partial pressure of co2 and o2 in the alveolar sacs?
co2 = 40
o2 = 102
what is the partial pressure of co2 and o2 in the trachea?
co2 = 0
o2 = 150
what is the partial pressure of co2 and o2 in the in the capillaries coming into the lungs?
co2 = 40
o2 = 102
what is partial pressure?
pressure that gas exerts in particular enviroments
what is the partial pressure of gas equal to? (pGas)
fraction of gas (Fgas) in gas mixture X barometric pressure
what do you have to take into account while working out the partial pressure?
in airways air warmed and humidified become saturated with water
what is the partial pressure of water vapour?
47mmHg
what happens as you go down divisions in the reparatory tract?
airways brach into small more numerous bronchioles until terminating to a group of alveoli
what do bronchi contain?
contain cartilage and non-respiratory bronchioles
how much of breath will always be in conducting airways?
150ml
30%
what does not participate in gas exchange?
conducting airways (top)
what is the respiratory airways?
bronchioles with alveoli where gas exchange occurs (from terminal bronchioles to alveoli)
what is a reparatory unit/ gas exchanging unit?
basic physiological unit of the lung consisting of respiratory bronchioles, alveolar ducts and alveoli.
how many alveolar sacs in a healthy adult?
300-400 million
what is the shape of alveoli?
polygonal
250um in diameter
what type of epithelial cells are alveoli composed of?
type 1 and 2
in images what colour are the arteries and veins?
veins red
arteries blue
what are conducting airways?
anatomic dead space not involved in gas exchange
what are type 1 epithelial cells?
primary site of gas exchange
97% of surface area of alveoli
what are type 2 epithelial cells?
septal cells
3% of surface area
produce pulmonary surfactant (reduces surface tension)
what is a big problem in premature babies born at around 22 weeks?
no type 2 epithelial cells
therefor unable to expand lungs
what do alveolar macrophages do?
remove debris
what characteristics of alveoli make it good for gas exchange?
thin walls
large surface area 100m2
good diffusion characteristics
what does the pulmonary circulation of the lung do?
brings deoxygenated blood from heart to lung and oxygenated blood from lung to heart then rest of body
what does the bronchial circulation of the lung do?
bring oxygenated blood from lung to parenchyma
what does the lymphatics system do?
defence and removal of lymph fluid
how much of the total blood is in pulmonary circulation?
500ml
10%
how do the arteries in pulmonary circulation compare to systemic circulation?
pulmonary
- thin walls
- highly compliant
- large diameter
- low resistance
where does gas exchange occur in capillaries and alveoli?
through dense mesh like networks
how fast do red blood cells pass through capillaries?
what happens in this time?
less than 1 second
(sufficient time for co2 and o2 gas exchange)
what happens in the pulmonary circuit and the systemic circuit?
pulmonary: o2 enters blood and co2 leaves
systemic: o2 leaves blood and co2 enters
is co2 or o2 more diffusible?
co2
does pulmonary circulation have high or low pressure?
low pressure
where does co2 and o2 move from?
co2 = from capillary to alveoli
o2 = from alveoli to capillary
