Transcript Gas Exchange in Mammals - Miss Jan`s Science Wikispace

Gas exchange in
Mammals
Gas Exchange in Mammals

Delivery of O2 to
gas exchange
surface (alveoli)
and removal of
CO2 from
capillaries and
out of the body
(ventilation).
In Larger Organisms
Diffusion alone cannot meet the needs of
the inner-most cells of larger organisms.
They have a higher demand for O2 and
removal of CO2.
 Larger organisms must have some form of
internal transport system for gases.

Pathway
Air (outside)  nasal passages (or mouth)  pharynx
 larynx  trachea  bronchus  bronchiole 
alveoli  bloodstream
Nasal passages
- Air is warmed and moistened. Dust and bacteria
removed by mucous and nasal hairs (cilia).
Cilia - creates wave-like movement to sweep
mucous upwards to be expeled at the
mouth/nose (along with trapped debris)
Cilia animation

http://www.bioscope.org/taste/cd1/a0255
a.htm
Trachea
Hollow tube held open by ‘C’ shaped bands of
cartilage.
 It branches into the two bronchi (one:
bronchus) which also have cartilaginous rings.

Alveolus
Bronchus then branch into
smaller tubes called
bronchioles which lead
into grape-like clusters of
thin-walled air sacs called
alveoli (one: alveolus)
which are surrounded by
blood capillaries.
Oxygen diffuses
across the moist
lining of the alveoli
into the capillaries.
 CO2 diffuses out of
the capillary and into
the air in the alveoli.

Surfactant
Lipoprotein
produced by
alveolar cells
 Reduced surface
tension (if no

surfactant – lung
cannot inflate
normally)
Pigment
Oxygen is picked up by a red pigment called
haemogoblin (in red blood cells) and is carried
around the body in the circulatory system .
 As the blood carrying the oxygen (oxygenated
blood) passes through the body the
haemoglobin releases oxygen which diffuses
into the cells.

Other bits
 Diaphragm is a sheet
of muscle at bottom of
these cavities
 Pleural membrane
lines each cavity and
covers each lung, and
encloses pleural space
(which contains fluid
to help membranes
slide past each other
during breathing)
www.tcnj.edu/~mckinney
Breathing/Ventilation
Inhalation – Breathing In
Diaphragm contracts
(lowered), intercostal
muscles contract lifts ribs up and out.
 Increases volume of
chest cavity  cause
the air from outside
to rush in and fill up
the increased space.

Exhalation – Breathing out
Diaphragm and
intercostal muscles
relaxes
 Diaphragm moves up
and the ribs down
 Air is forced out as
the volume in the
chest cavity returns to
normal.


The breathing action (diaphragm etc.)
uses considerable energy but allows the
animal to change the rate of gas exchange
quickly to suit activity/environment
requirements.
Increased Surface Area for Gas Exchange
Alveoli ↑’s surface
area exposed for
diffusion of O2 into
capillaries and CO2
out into alveoli.
 300 million alveoli
creates 40x the
surface area of the
body.

Moist Surfaces

Moist surface within nasal passages, alveoli
and capillaries help O2 in air to dissolve into
the watery substance for diffusion into
capillaries.
Thin Exchange Surface

Thin surface of alveoli and capillaries ↓’s barrier for
diffusion of O2 into capillaries and CO2 out.
A more specialised system is required for the increased
size of the animal to deal with:
→ the inefficiency of diffusion over longer distances
→ higher demand for O2 and removal of CO2.
Internal lungs are well protected from:
→ physical damage
→ drying out in a dry environment. Enables mammals
to have a wider range of habitats e.g. dry, wet, water
on land.
Lungs have a higher surface area to maximise rate of
diffusion of O2 into capillaries and removal of CO2.
Then the O2 and CO2 is transported around the body in
the bloodstream of the circulation system.
Blood vessels in the lung
Some more interesting info/pictures
Warning – some pictures are a bit gory –
so stop here if you are sensitive to blood
and gore.
Cross-section of the lung and heart
Figure 23–8
Cilia can be immobilized by smoking
Smoker’s lung tissue
Normal lung tissue
www.orangeusd.k12.ca.us/date/
Cystic fibrosis
Faulty chloride channel leads to thick mucus 
difficult to clear  blockage and infection
Normal lung tissue
Lung tissue from cystic
fibrosis patient
www.orangeusd.k12.ca.us/date/
www.pathguy.com/lectures
Black lung disease
An electron micrograph scan of coal dust (marked by dark
patches) in lung tissue infected with black lung disease. A disease
found primarily in older coal workers, black lung is characterized
by thickening and scarring of lung tissue.
Pneumothorax
: air trapped in
the chest
cavity.
(Tension pneumothorax: lifethreatening)