gas exchange in humans Flashcards
where does the air enter as you breathe in
the trachea
what does the trachea split into
two bronchi
what does each bronchus split into
smaller tubes called bronchioles
what is at the end of each bronchiole
small air sacs called alveoli
what happens at the alveoli
gas exchange
what 3 structures work together to move air in/out
ribcage
intercoastal muscles
diaphragm
what is inspiration
breathing in
what happens during inspiration
external intercoastal muscles + diaphragm muscles contract
ribcage moves up + out
diaphragm flattens
volume in thoracic cavity increases
pressure decreases
air moves from area of higher to lower pressure
so air moves down trachea into lungs
what type of process is inspiration
active
what is expiration
breathing out
what happens during expiration
external interacoastal muscles + diaphragm muscles relax
ribcages moves down + in
diaphragm curved again
volume of thoracic cavity decreases
pressure increases
air forced down pressure gradient out of lungs
what type of process is expiration
passive
what happens during forced expiration
external intercoastal muscles relax
internal intercoastal muscles contract
pulling ribcage further down + in
antagonistic movement
what does a large number of alveoli provide
large surface area
what are alveoli surrounded by
a network of capillaries
how does oxygen move from alveoli to blood
o2 diffuses out alveoli across alveolar epithelium into haemoglobin into blood down a diffusion gradient
how does co2 leave the blood
co2 diffuses into alveoli from blood
is breathed out
what features do alveoli have that speed up rate of diffusion
thin exchange surface - short diffusion pathway
large surface area - larger area for gas exchange
s
teep conc gradient between alveoli + capillaries
what is the steep conc gradient maintained by
flow of blood
ventilation
