The human respiratory system consists of the nose, trachea, bronchi, bronchioles and alveoli. Air enters through the nose and is warmed and filtered before reaching the lungs. In the lungs, oxygen diffuses into the blood in the alveoli and carbon dioxide diffuses out. Oxygen is carried through the bloodstream bound to hemoglobin and is released to tissues where it is used for cellular respiration. Carbon dioxide moves from tissues back to the lungs to be exhaled.

2. 1.1 The Human Respiratory System
By the end of this section, you will be able to:
(a)Identify the structure of the human respiratory system
(b)Identify the structure of the lung
(c)Describe the process of inhalation and exhalation
(d)Relate the changes of air pressure in the thoracic cavity
to inhalation and exhalation
(e)Describe the breathing mechanism

3. The Human Respiratory SystemThe Human Respiratory System
1) The human respiratory system provides an area for
gas exchange between the blood and the
environment.
2) The gas exchange in lungs is called breathing.This
exchange involves the taking in and letting out of air.
3) The human respiratory system consists of:
a) Breathing organ (nose and trachea)
b) Intercostal muscles
c) Ribs
d) diaphragm

5. Air enter the respiratory system through the nasal cavity.
As air passes the nasal cavity, it is warmed and moistened. Dust is trapped by
the hairs.
After the air leaves the nasal cavity, it enters the trachea.
The trachea branches into two bronchi (singular:bronchus)
Each bronchus branches into smaller tubes called bronchioles.
The bronchioles end in millions of tiny air sacs called alveoli (singular:alveolus)
4) How does it occur???
*** Each alveolus has a very thin wall which is moist and
contains a network of blood capillaries.

6. Pathways of the inhale air:
Nose trachea bronchus
bronchiole alveolus

7. 5) The lungs are made up of alveoli, bronchioles
and blood capillaries, bronchus.
6) The lungs are located in a space called the
thoracic cavity.
7) The lungs are protected by the rib cage which
consists of ribs and intercostal muscles.
8) A sheet of muscle called the diaphragm
separates the thoracic cavity from the abdomen.

10. Inhalation Differences Exhalation
Move upwards
and outwards
Rib cage Move
downwards and
inwards
Move
downwards,
contract, flatten
Diaphragm Upwards,
relaxes, curve
bigger Volume of
thoracic cavity
smaller
Decrease/lower Air pressure in
the lungs
Increase/higher
Comparison between inhalation and exhalation mechanism.

11. PARTS OF THE
MODEL
PARTS OF THE
RESPIRATORY
SYSTEM
Bell jar
Y-shaped glass
tube
Balloons
Rubber sheets

13. Rubber
sheet
Changes in
the balloons
Breathing
process
Pulled down
Pushed up

14. 1.2 Transport of Oxygen in the Human Body
By the end of this section, you will be able
to:
(a) Describe the diffusion of oxygen from the
alveoli into the blood capillaries
(b) Describe the transport of oxygen by
blood
(c) Describe the diffusion of oxygen from
blood capillaries into the cells.

15. 1) The movement of oxygen from the alveolus into
the blood capillaries is diffusion.
2) Diffusion is the movement of molecules from a
region of higher concentration of the molecules
to a region of lower concentration of the
molecules.
Higher concentration  lower concentration
3) In the blood, the oxygen will combine with
haemoglobin in the red blood cells to form
oxyhaemoglobin.
Oxygen + Haemoglobin  oxyhaemoglobin

16. 4) The blood containing oxyhaemoglobin is
transported from the lungs to other parts of our
body.
5) The oxyhaemoglobin breaks down and releases
its oxygen at places where the oxygen
concentartion is lower.
6) The oxygen then diffuses through the blood
capillaries into the cells.
7) Then the oxygen is used by the cell for
respiration.
Glucose + oxygencarbon dioxide + water+ energy
8) The carbon dioxide produced is carried by
deoxygenated blood (blood without oxygen) to the
lungs to be eliminated.

17. 9) Adaptation of the alveoli for efficient gas exchange
a) Large surface area
#The lungs have millions of alveoli to provide
a large surface area for gas exchange.
b) Very thin walls
#The wall of each alveolus is one-cell thick to
provide a very short distance for the diffusion
of gases.

18. c) Moist inner surface
#The inner surface of each alveolus is moist so
that oxygen can dissolve in the moisture before
diffusing across the alveolar wall.
d) Surrounded by numerous blood capillaries
#The blood capillaries help to transport gases
to and from the alveoli quickly.