1. Gas exchange involves ventilation, external respiration, and internal respiration. 2. Ventilation involves inspiration and expiration moving air in and out of the lungs. 3. External respiration is the diffusion of oxygen and carbon dioxide between the alveoli and blood. 4. Internal respiration is the diffusion of gases between blood and tissue cells.

2.  Sequence of events that results in gas
exchange.
 In terrestrial vertebrates it includes 3 steps:
1. Ventilation: Inspiration and
expiration.
2. External respiration: Gas exchange
between air (in lungs) and blood.
Blood then transport Oxygen to the
body tissue cells.
3. Internal respiration: Gas exchange
between blood and tissue fluid.
Blood then transports carbon
dioxide to the lungs.

3. Gas exhange surface
must be: Alveoli filled with air (gas) External
•Moist respiration
Carbon dioxide oxygen
•Thin
•Large in relation of
size of body
Blood – part of
circulatory system
contain red pigment
Process: Diffusion of – hemoglobin, to
gasses (oxygen and transport gasses
carbon dioxide
Internal
respination
oxygen Carbon dioxide
Body cells surrounded by tissue fluid

4.  Is the process whereby an organism uses
oxygen and food to produce energy (ATP) and
2 by products e.g. water and carbon dioxide
 Glucose + O2 ATP + H2O + CO2
Therefore gaseous exchange is necessary for
to get oxygen for cellular respiration.

5.  Consists of:
1. Nose
2. Air passages:
 Pharynx
 Trachea
 Bronchus
 Bronchioles
3. Lungs – Alveoli

6.  Nose has a nasal cavity that
leads to the pharynx.
 Nasal cavity is lined with
cilia and hairs and goblet
cells that make mucus (anti-
septic and moisten air)–
filter the air – dust, pollen
and other foreign material
sticks to it.
 3 x turbinate bones divide
the nasal cavity into 4
passages – This enlarges the
surface of the nasal cavity –
For warming, cleaning and
moisten of air.
 Several surface blood
vessels help to warm air.

7.  Pharynx – pass air
form nose to trachea
via larynx.
 Trachea:
long, straight tube
kept open by C-
shaped cartilage
rings.
 Trachea – lined with
cilia and goblet cells
(mucus production) –
traps foreign
particles

8. CILIA (SEM) TRACHEAL LINING

9.  Trachea divides in a
right and left
bronchus – consist of
C-shaped cartilage
rings and lined with Right bronchus-short
goblet cells (mucus) Branch in 3 Left bronchus –
 Bronchi branch in long, branch in 2
lung to form
bronchioles – branch
further and cartilage
rings disappears –
lead air to air sacs of
lung. Bronchiole

10.  Right lung (3 lobes -
shorter) and left lung (2
lobes – longer, narrow)
 Spongy, elastic pink
organ.
 Consists of several air
sacs called alveoli.
 Alveoli are grouped
together and form the
endings of the
bronchioles.

11.  Lined with single layer
squamous epithelial cells –
Thin easy diffusion of gas.
 Alveoli is surrounded by a
network of blood capillaries
– gasses diffuse into and
out of blood.
 Alveoli is lined with moist
layer – oxygen dissolves in
moisture and diffuses
through alveoli wall into
blood capillary.

12. Pulmonary vein
Pulmonary
(Oxygenated
artery
blood)
(Deoxygenated
blood)
Turbinate bones
Pharynx
Alveoli
Trachea
Bronchus
Bronchiole
Diaphragm
SEM TEM

13.  INSPIRATION  EXPIRATION
Air inhaled
Air exhaled
Rib cage
expands Rib cage
as rib gets
muscles smaller as
contract rib muscles
relax
When pressure in
lungs increase –
When pressure in air is pushed out
INSPIRATION
lungs decrease –
Diaphragm EXPIRATION
Diaphragm
contracts relaxes
air rush in
(moves down) (moves up)

14.  Air moves in and out of the body via the same
route.
 All terrestrial vertebrates do this except for
birds.
 The lungs are not completely emptied during
each breathing cycle.
 The air entering mixes with used air
remaining in the lungs.
 This help to conserve water, but decreases
gas-exchange efficiency

15.  A spyrometer can be used to determine how
much air enters the lungs.
 Your lungs has a volume of +/- 5 liters.
 During a normal breath, only 0.5 liters of air is
exchanged – This air is known as tidal volume.
 During forced breathing, as much as 3.5 liters
of air can be exchanged, this is known as vital
capacity. (The fitter you are, the higher your
vital capacity.)
 +/- 1.5 liters of air always remains in the lungs
– this air is known as residual air/volume.

17.  Normal breathing rate for adults: 12 – 20
ventilations per minute.
 Respiratory Center in the Medulla Oblongata
of the brain controls breathing.
 The respiratory center send impulses through
the phrenic nerve to the diaphragm and
through the intercostal nerve to the
intercostal muscles to either contract or
relax. (Contract during inspiration and relax
during expiration)

18. Brain
Respiratory center
automatically regulates
breathing
Intercostal nerves
stimulate the
intercostal muscles
Intercostal muscles
Pheric nerve stimulates
the diaphragm
Diaphragm

19.  Gas exchange between  Gas exchange between
air in lungs and blood blood and tissue fluid
 Movement driven by  Movement driven by
diffusion gradient. ( [] to diffusion gradient. ( []
[]) to [])
 Gasses exerts
 Gasses exerts
pressure, the amount
pressure, the amount of of pressure each gas
pressure each gas exerts exerts is called –
is called – partial partial pressure (PO2
pressure (PO2 and PCO2) and PCO2)
EXTERNAL RESPIRATION INTERNAL RESPIRATION

20.  If PO2 differs across a membrane – oxygen will
diffuse from a high to a low pressure.
 If PCO2 differs across a membrane – carbon
dioxide will diffuse from a high to a low
pressure.
 During inspiration the alveoli fills with air –
higher PO2 and lower PCO2 than blood.
 Oxygen diffuse from alveoli into blood and
carbon dioxide diffuse from blood into
alveoli.

21.  When blood reaches the tissue, cellular
respiration in cells causes the tissue fluid to
have a lower PO2 and a higher PCO2 than the
blood.
 Thus oxygen diffuse from a high pressure in
the blood to a low pressure in the tissue fluid
and eventually in the tissue cells.
 Carbon dioxide diffuse from a high pressure
in the tissue fluid to a low pressure in the
blood.

23.  Most oxygen is transported by hemoglobin
(red pigment protein in erythrocytes).
 Oxygen combines with hemoglobin to form
oxyhemoglobin.
Hb + O2 = HbO2
Hemoglobin Oxygen Oxyhemoglobin
 A small amount of oxygen is transported in
solution in the blood plasma.

24.  Consist of 4
polypeptide chains
(protein – 2 alpha and
2 beta).
 Each chain is
associated with a heme
group.
 Each heme group
contains an iron atom.
 Iron binds with
oxygen.
Each red blood cell carries 250
million Hb molecules = 1 Billion
Oxygen molecules

25.  Most CO2 is transported as bicarbonate ions
(HCO3-)
HOW?
FIRST CO2 binds with water to form carbonic
acid (H2CO3)
CO2 + H2O = H2CO3
Then carbonic acid dissosiates to form
hydrogen and bicarbonate ions.
H2CO3 = H+ + HCO3-

26.  A small amount of carbon dioxide is
transported by the Hemoglobin molecules in
the form of carbaminohemoglobin (HbCO2).
CO2 + Hb = HbCO2
 The higher the amount of hydrogen ions in
the blood the lower the pH. Therefor
hydrogen ions bond with the globin part of
Hb to keep the pH normal in the blood.

27.  The following lower respiratory tract
disorders are caused by exposure to
infectious pathogens and / or polluted
air, including tobacco smoke.
 Pneumonia
 Pulmonary Fibrosis
 Pulmonary Tuberculosis
 Emphysema
 Bronchitis
 Asthma

28.  Alveoli fill with pus and
fluid making gas
exchange difficult
X-ray of a
patient with
pneumonia
Bacteria streptococcus
can cause pneumonia

29.  Fibrous connective
tissue builds up in
lungs, reducing their
elasticity and Oxygen
diffusion.

30.  Caused by a bacillus
bacterium

31.  Alveoli burst and fuse
into enlarged air
spaces. – Surface area
for gas exchange is
reduced.

32.  Airways are inflamed
due to infection (acute)
or due to an irritant
(Chronic). Coughing
brings up mucus and
pus.

33.  Airways are inflamed
due to irritation and
bronchioles constrict
due to muscle spasms

34.  Smoking causes almost 90% of all lung
cancers and is also a major cause of
emphysema.
Healthy normal Lung of a
lung of a non- smoker
smoker

35. Lung with large
tumors causing
lung cancer