1. The respiratory system
Structure

2. Gas exchange
All processes carried out in the body require energy. This energy is obtained from food but before it can by used by cell in needs to be broken down thanks to the process of respiration.
Aerobic respiration need oxygen and produces CO2 as a waste product. The oxygen needed comes from the air we breath in. This oxygen is dissolved in the blood and carried where needed by the circulatory system.

3. Respiratory surfaces Large surface area.
Distance across which diffusion has to tale place in small.
Good blood supply.
Difference of concentrations of the gas at two points.

4. Organs of the respiratory system
Larynx
Trachea
Rib cage
Bronchus
Mediastinum
Lung
Diaphragm

5. Section through the head
Nasal cavity
Palate
Teeth
Tongue
Pharynx
Epiglottis
Hyoid bone
Vocal cords
Larynx
Esophagus
The Miles Kelly Art library, Wellcome Images

6. The mucous lining
The nasal cavity and upper airways have a mucous lining.
The epithelial lining contains goblet cells which secrete a clear, sticky mucus.
The function of mucus is to trap dirt particles and microbes before they enter the lungs.

7. The nose (nasal cavity)
Air enters and leaves the body through the nose.
Here it is cleaned, warmed and moistened before entering the body.
The nasal secretions contain an anti-bacterial enzyme – lysozyme.

8. A section through the nasal cavity
Sinus
NASAL CAVITY
Hard palate
Soft palate
Nostril
The Miles Kelly Art library, Wellcome Images

9. The larynx (Adam’s apple or voice box)
The larynx is a box-like structure constructed from nine cartilages and is the entrance to the trachea and lungs.
The larynx houses the vocal folds or vocal cords.
The entrance to the larynx is protected by the epiglottis.
Gray’s Anatomy

10. The bronchial tree Alveoli Larynx Trachea Bronchus (Bronchi)
Mass of little, thin-walled air sacs.
Larynx
350 million with a total surface area of 90m2
Trachea
Bronchus (Bronchi)
Bronchiole
0.2 mm in diameter
The Sourcebook of Medical Illustration (The Parthenon Publishing Group, P. Cull, ed., 1989)

11. Trachea & bronchi
The trachea & bronchi are reinforced with C-shaped rings of cartilage (these prevent the tubes collapsing during inhalation).

12. The bronchi Cartilage rings Muscular wall Mucous lining
The Miles Kelly Art library, Wellcome Images

13. The upper airways are lined with a ciliated mucous membrane
The sticky mucus traps dirt & microbes
The cilia sweep the dirty mucus up the trachea and into the throat.

14. The ciliated lining tissue
Mucus-secreting goblet cells
Cilia
G. Meyer, ANHB-UWA,

15. EM of ciliated epithelium & goblet cells
D Gregory & D Marshall, Wellcome Images

16. Alveoli
Alveoli
G. Meyer, ANHB-UWA
The bronchioles terminate in microscopic clusters of air sacs – the alveoli.
Gas exchange takes place in the alveoli.
The tree cluster shape allows for a high number of alveoli which means higher surface area.

17. The alveoli (air sacs)
The Miles Kelly Art library, Wellcome Images

18. Section through a lung showing alveoli and blood supply
M I Walker, Wellcome Images

19. The respiratory system
Gas exchange

20. Exchange surfaces Like all exchange surfaces, the alveoli:
are very thin
have a large surface area
are moist
have a rich blood supply

22. Breathing
Breathing (sometimes referred to as ventilation) is the process of moving air into and out of the lungs.
The purpose of breathing is to exchange oxygen and carbon dioxide between the lungs and the air .

23. Capacity Total volume when lungs fully inflated is 5 litres.
When at rest, exchange is around 500 cm3.
During exercise we can take in and expel an extra 3 litres.
There is a residual volume of 1.5 litres that can never be exhaled.
At rest you inhale/exhale 12 times per minute.
During exercise you inhale7exhale over 20 times per minute.

24. This can be stated mathematically as: PV = k
Boyle's law
Boyle's law states that: for a fixed amount of gas kept at a fixed temperature, pressure (P) and volume (V) are inversely proportional (while one increases, the other decreases).
This can be stated mathematically as: PV = k
where: P is the pressure, V is the volume & k is a constant value representative of the pressure and volume of the system.

25. Respiration
Respiration is the transport of oxygen from the air to the tissues and the transport of carbon dioxide in the opposite direction. [not to be confused with the process of cellular respiration discussed earlier]

26. External respiration and Internal respiration
External respiration is the movement of O2 and CO2 between the lungs and the bloodstream.
Internal respiration is the exchange of O2 and CO2 between the blood and the tissues.

27. External respiration Partial pressure (mmHg) Oxygen 100 40
Alveolar air
Deoxygenated blood
Oxygenated blood
Oxygen
100 40
Carbon Dioxide 44
Breathing maintains the correct concentration of gases in the lungs
Concentration gradient

28. Breathing – inhaling (remember P1V1 = P2V2)
Anatomical changes V P1
P1:P2
Result
Rib cage raised
Diaphragm flattens
Increases
Decreases
P1<P2
Air drawn into lungs
V = volume of thoracic cavity
P1 = pressure in thoracic cavity
P2 = air pressure

29. Thoracic volume Rib cage relaxes Diaphragm domed Rib cage raised
Diaphragm flattens

30. A bicycle pump works in much the same way as the lungs
P1V1 = P2V2

31. The lungs work in much the same way as a bicycle pump
If you increase the volume of the chamber air is sucked in
If you decrease the volume of the chamber air is forced out

32. Breathing – exhaling (remember P1V1 = P2V2)
Anatomical changes V P1
P1:P2
Result
Rib cage relaxes
Diaphragm domed
Decreases
Increases
P1>P2
Air forced out of lungs
V = volume of thoracic cavity
P1 = pressure in thoracic cavity
P2 = air pressure

33. Thoracic volume decreased Thoracic pressure > air pressure
INHALE
EXHALE
Thoracic volume decreased Thoracic pressure > air pressure
Thoracic volume increased Thoracic pressure < air pressure
Ribcage raised
Ribcage lowered
Diaphragm flattened
Diaphragm domed
The Miles Kelly Art library, Wellcome Images

34. Why breathe?
Fresh air passing through the lungs delivers oxygen to the red blood cells. At the same time, waste carbon dioxide is removed from the blood. This can only occur if fresh air is constantly circulating through the lungs.
Carbon dioxide
Oxygen
Wellcome Photo Library

35. Oxygen transport
Oxygen combines with haemoglobin in RBCs to form oxyhaemoglobin.

36. Carbon dioxide transport
Most CO2 is transported in the plasma as dissolved bicarbonate ions. -

37. Oxygen saturation

38. Diseased lung tissue healthy lung tissue Smoker’s lung Emphysema B A
CDC C
Photo by Pöllö
healthy lung tissue
Smoker’s lung
Emphysema