1. 6.4
Gas
Exchange
IB
Biology
12

2. Assessment
Statements
Obj.
6.4.1
Dis0nguish
between
ven;la;on,
respira;on
and
gas
exchange.
2
6.4.2
Explain
the
need
for
a
ven;la;on
system.
3
6.4.3
Describe
the
features
of
alveoli
that
adapt
them
to
gas
exchange.
2
6.4.4
Draw
and
label
a
diagram
of
the
ven;la;on
system,
including
trachea,
lungs,
bronchi,
bronchioles
and
alveoli.
1
6.4.5
Explain
the
mechanism
of
ven;la;on
of
the
lungs,
in
terms
of
volume
and
pressure
changes
caused
by
the
internal
and
external
intercostal
muscles,
the
diaphragm
and
abdominal
muscles.
3
Assessment
statements
from:
Online
IB
Biology
Subject
Guide

3. Respira;on
-­‐
3
Major
Stages
• Ven;la;on
– Movement
of
air
into
and
out
of
the
lungs
in
two
stages:
inspira;on
and
expira;on
– Controlled
by
movement
of
the
diaphragm
and
ribcage

4. Respira;on
-­‐
3
Major
Stages
• Gas
Exchange
– Exchange
(diffusion)
of
oxygen
and
carbon
dioxide
to
and
from
the
blood
at
the
alveoli
and
the
respiring
;ssues
– Controlled
by
movement
of
the
diaphragm
and
ribcage

5. Respira;on
-­‐
3
Major
Stages
• Cellular
Respira;on
– Produc;on
of
ATP
at
the
cellular
level
– Aerobic
respira;on:
using
oxygen
– Anaerobic
restora;on:
no
oxygen
• SO4
2-­‐,
NO3
-­‐,
S
or
fumurate

6. Respira;on
-­‐
3
Major
Stages
• Ven;la;on
• Gas
Exchange
• Cellular
Respira;on
Respira0on
is
the
transport
of
oxygen
from
the
outside
air
to
the
cells
within
6ssues,
and
the
transport
of
carbon
dioxide
in
the
opposite
direc6on

7. Why
do
we
need
a
ven;la;on
system?

8. Ven;la;on
System
• Smaller
organisms,
like
pro;sts
and
bacteria
– exchange
gases
directly
by
diffusion
• Larger
organisms,
like
fish
and
mammals
– ul;mately
use
diffusion
BUT
– require
habitat-­‐dependent
adap;ons
to
exchange
gases

9. Ven;la;on
System

10. Why
do
we
need
ven;la;on
systems?
• We
are
large
organisms
– Oxygen
cannot
diffuse
into
all
our
cells
directly
from
the
air
– Waste
products
cannot
be
removed
directly
from
the
body
– Specialized
organ
systems
require
delivery
of
nutrients
and
removal
of
waste

11. Why
do
we
need
a
ven;la;on
system?
• We
are
land-­‐borne
– Gases
need
moist
surfaces
in
order
to
diffuse
• Membranes
– Our
moist
membranes
are
the
lungs

12. Why
do
we
need
a
ven;la;on
system?
• The
ven;la;on
system
maintains
a
large
concentra0on
gradient
between
the
alveoli
and
the
blood

13. Why
do
we
need
a
ven;la;on
system?
1) Large
organisms
2) Land-­‐borne
3) Concentra;on
gradient

15. Image
from
ibguides.com

16. Parts
of
the
Ven;la;on
System
• lungs
–
• trachea
–
• bronchi
–
• bronchioles
–
• alveoli
–
• diaphragm
–

17. Parts
of
the
Ven;la;on
System
• lungs
–
major
respira;on
organ
• trachea
–
the
windpipe
• bronchi
–
passages
of
airways
• bronchioles
–
smaller
branches
of
bronchi
• alveoli
–
“li_le
cavity”,
gas-­‐exchange
surface
• diaphragm
–
sheet
of
skeletal
muscle
that
seperates
the
thoracic
cavity
from
the
abdominal
cavity;
major
role
in
respira;on