The document summarizes respiration in the human body. It describes how: During inhalation, the internal intercostal muscles relax and external intercostal muscles contract, expanding the rib cage and increasing the thoracic cavity volume. The diaphragm also contracts, lowering pressure in the alveoli and causing air to move in. During exhalation, the actions reverse, decreasing thoracic cavity volume and raising alveolar pressure to push air out. Oxygen diffuses into the blood in the alveoli due to higher partial pressure, while carbon dioxide diffuses out of the blood into the alveoli due to lower partial pressure. Oxygen is transported through the blood bound to hemoglobin

3. • Internal intercostal muscle
• External intercostal muscle
• Rib cage
• Diaphragm
• Volume of thoracic cavity
• Air pressure in alveoli
• Air moves in @ out

4. Internal intercostal muscle relaxed
External intercostal muscle contract
Rib cage moves upwards & outwards
Diaphragm contracts & flattens
Volume of thorax cavity increase
Pressure in alveoli decrease
Air moves in

5. Internal intercostal muscle contract
External intercostal muscle relaxed
Rib cage moves downwards & inwards
Diaphragm relaxes
Volume of thorax cavity decrease
Pressure in alveoli increase
Air moves out

7. 1. Gaseous Exchange Across
Surfaces of Alveolus and Blood
Capillaries
- The greater the
gradient of
concentration across
respiratory surface, the
greater the rate of
diffusion
- Diffusion of gas
depends on the
differences in partial
pressure between two
regions

8. 1. Gaseous Exchange Across
Surfaces of Alveolus and Blood
Capillaries
• Partial pressure of 𝑂2 in
alveoli is HIGHER than
partial pressure of 𝑂2 in
blood capillaries
• Therefore, 𝑂2 diffuse
across the surface of
alveolus and blood
capillaries into the blood

9. • Partial pressure of 𝐶𝑂2
is LOWER in the air of
alveoli compared to
blood capillaries
• Therefore, 𝐶𝑂2 diffuse
out of the blood
capillaries into the
alveoli.

10. • Gug
summary

11. 2. Transport of respiratory gases
in humans

12. OXYGEN
• After gaseous exchange take place, 𝑂2 in blood is transported
to body cells for cellular respiration
• In blood, 𝑂2 combines loosely with the respiratory pigment
called haemoglobin
• 𝑂2 is carried in the form of oxyhaemoglobin to all parts of
the body
Haemoglobin + Oxygen Oxyhaemoglobin
not stable
!

13. HAEMOGLOBIN

15. CARBON DIOXIDE
• 𝐶𝑂2 released by respiring cells can be transported in three ways:
• Most of the bicarbonate ions are carried in the blood plasma to the
lungs and diffuse from blood plasma to red blood cells & form
carbonic acid again later on breaks down into 𝐶𝑂2

17. 3. Gaseous Exchange Between
Blood and Body Cells
• In tissue capillaries: partial pressure of oxygen in
blood is higher
• In cells: partial pressure of oxygen is lower (due to
cellular respiration)
• Hence, oxyhaemoglobin breaks down & release
oxygen, which then diffuse through capillary walls
into the cell

18. 4. Composition of Inhale and
Exhale Air