The Human
Gas Exchange
System
Objectives:
1.Recall the parts and functions of the respiratory
system
2. Describe the gas exchange process in the
respiratory system
Our respiratory
system is responsible
for bringing air into the
body, from which we
can get oxygen.
oxygen
Gas exchange
Gas exchange – YouTube
It also moves air back
out of the body—the
exhaled air contains
more of our waste gas,
carbon dioxide.
carbon
dioxide
But how do we get oxygen from the air to our
body cells and get carbon dioxide out?
air
Let’s follow the journey
of a breath of air,
starting with the
moment you inhale.
nasal cavity
oral cavity
pharynx
larynx
Air enters the body
through the nose and
mouth, where it is
filtered and warmed.
trachea
primary
bronchi
Air then passes through
the trachea and the two
primary bronchi.
These structures are held
open by rings of cartilage.
bronchiole
alveoli
Each bronchus then
branches many times into
bronchioles, terminating at
tiny air-filled sacs called
alveoli.
Oxygen and carbon dioxide are
exchanged at the alveoli.
The process involved in the
exchange of these gases is
called diffusion.
air moving in and out of the alveolus
How does
diffusion occur?
Carbon dioxide—a
waste gas—moves
from the blood into
the alveoli to be
exhaled.
capillary
red blood cell
carbon
dioxide
air moving in and out of the alveolus
Oxygen then moves
from inside the alveoli
across the walls and
into the blood.
This oxygen is used for
respiration by the
body’s cells.
capillary
red blood
cell
oxygen
They are covered in a
network of tiny
capillaries, ensuring
enough blood supply.
Their surfaces are moist,
allowing the gases to
dissolve.
How are the
alveoli adapted
for gas exchange?
Their walls are only one
cell thick, providing a
short diffusion distance.
Their lobed-shape gives
them a huge surface
area.
If given a chance, how would you
improve the design of alveoli?
To Recap
The human respiratory system moves fresh air into the body
while removing waste gases.
Oxygen and carbon dioxide are exchanged at the alveoli.
The alveoli are well-adapted to carry out their job by having
a thin, moist and large surface area.