1. The Mechanics of Breathing

2. Breathing The mechanism by which mammals ventilate their lungs
Air will flow from a region of higher pressure to a region of lower pressure
There are two muscular structures that control air pressure inside our lungs

3. Muscles involved in breathing:
Intercostal Muscles
Diaphragm

4. Intercostal Muscles
Muscles associated with the ventral surface of the rib cage
These muscles are found between the ribs
There are two kinds

5. Intercostal Muscles Internal Intercostal Muscles
Located in the inside of the ribcase
External Intercostal Muscles
Located in the outside of the ribcase

6. Intercostal Muscles

7. X-Section of Intercostal Muscles

8. Diaphragm A muscle layer that separates
the thoracic cavity (region of the lungs) from
the abdominal cavity (region of the stomach and the liver)

9. Diaphragm Found in all mammals
Prime function: to assist in the ventilation of the lungs
Works simultaneously with intercostal muscles
To produce breathing-related movements

10. How breathing works Inhalation vs. Exhalation Lungs Diaphragm

11. HOW BREATHING WORKS- Inhalation
To inhale, the external intercostal muscles contract
Intercostal muscles expand the rib cage, lifting it up and out

12. HOW BREATHING WORKS- Inhalation
the diaphragm contracts and pulls downward in the thoracic cavity
This increases the volume of the thoracic cavity, causing the lungs to expand.
How?

13. How Lungs Expand The thoracic cavity is relatively airtight
An increase in its volume, produces a decrease in air pressure within the cavity
This decrease in pressure draws the flexible walls of the lungs outward into the thoracic cavity
Therefore, the lungs expand

14. HOW BREATHING WORKS- Inhalation
As a result of this expansion, the air pressure within the lungs is lower than the air pressure in the external environment
Recall: Air will flow from a region of higher pressure to a region of lower pressure
Therefore, air enters the lungs

15. HOW BREATHING WORKS- Exhalation
The diaphragm relaxes, returning to a dome- shaped curve

16. HOW BREATHING WORKS- Exhalation
To exhale, the external intercostal muscles relax
But the internal intercostal muscles contract to help pull the ribcage back to its original shape and position

17. HOW BREATHING WORKS- Exhalation
These changes create a higher pressure in the thoracic cavity
This causes the lungs to shrink, which results in a higher pressure in the lungs
Air then moves out through the trachea

18. Inhalation and Exhalation
Intercostal muscles contract, lifting rib cage up and out
Diaphragm contracts and pulls downward
The lungs expand, air is sucked in
Intercostal muscles relax
Diaphragm relaxes
The ribs fall downward and inward
Diaphragm back into dome shape, squeezing lungs and pushing air out

19. Exchange of Gases
Review Capillary network and gas exchange

20. Composition of inspired and expired air under normal conditions
16.49% Oxygen
4.49% Carbon Dioxide
79.02% Nitrogen and Trace gases
20.94% Oxygen
0.04% Carbon Dioxide
79.02% Nitrogen and Trace gases

21. Lung Capacity
The different volumes of air drawn in or pushed out by the lungs are distinguished

22. The volume of air inhaled and exhaled in a normal breathing movement
Tidal Volume
The volume of air inhaled and exhaled in a normal breathing movement

23. Inspiratory Reserve Volume
The additional volume of air that can be taken in, beyond a regular or tidal inhalation

24. Expiratory Reserve Volume
The additional volume that can be forced out of the lungs, beyond a regular or tidal exhalation

25. The total volume of gas that can be moved in or out of the lungs
Vital Capacity
The total volume of gas that can be moved in or out of the lungs
VC=Tidal volume+IRV+ERV

26. The residual volume never leaves the respiratory system
The amount of gas that remains in the lungs and the passageways of the respiratory system even after a full exhalation
The residual volume never leaves the respiratory system
If it did, the lungs and the respiratory passageways would collapse
It has little value for gas exchange, because it is not exchanged with air from the external environment

27. Residual Volume

28. Respiratory Efficiency
In mammals, the rate at which oxygen can be transferred into the blood stream for transport to the rest of the body
There are factors that affect the respiratory efficiency
Other animals have respiratory systems with special adaptations to help increase respiratory efficiency
One adaptation is facilitated diffusion

29. The Respiratory System in Fish
The gills of fish utilize counter-current flow
A very effective mechanism for removing the maximum amount of oxygen from the water flowing over them

30. Gills & Gas Exchange: Counter-current Flow
Oxygenated blood
Deoxygenated Blood
During counter-current flow, two types of fluids (blood and water) with different concentrations flow in opposite directions past one another

31. Counter-current Flow
These two fluids (water and blood) are separated by thin membranes

32. Counter-current Flow
Fish gills consist of a series of filaments supported by bony gill arches
Each filament is covered with thin folds of tissue called lamella
Blood flows across each lamella within a dense network of capillaries
Filament
Gill arch
Gill arch
High O2
Filament
Lamellae
Low O2

33. Counter-current Flow
Water is deflected over the lamellae in a direction opposite the flow of blood in the capillaries
Thus, the most highly oxygenated blood is brought close to the water that is just entering the gills and that has an even higher oxygen content than blood
Vein-Oxygen poor blood
Artery-Oxygen rich blood
Low Oxygen
High Oxygen
Water flow
Low Oxygen
High Oxygen
Blood flow

34. Counter-current Flow
As the water flows over the lamellae, gradually losing its oxygen to the blood, it encounters blood that is also increasingly low in oxygen
In this way, the gradient encouraging oxygen to move from the water into the blood is maintained across all the lamellae.
Vein-Oxygen poor blood
Artery-Oxygen rich blood
Low Oxygen
High Oxygen
Water flow
Low Oxygen
High Oxygen
Blood flow

35. Counter-current Flow Vein-Oxygen poor blood Artery-Oxygen rich blood
Low Oxygen
High Oxygen
Water flow
Low Oxygen
High Oxygen
Blood flow

36. Current vs. Counter-current Flow

37. Counter-current Flow
Within each lamella, Counter-current flow enhances diffusion by maintaining a concentration gradient of oxygen between the water (relatively high in oxygen) and the blood (lower in oxygen)
Countercurrent flow is so effective that some fish extract 85% of the oxygen from the water that flows over their gills.

38. Gas Exchange in Mammals
In the mammalian lung, the oxygen gradient between the respiratory medium in the lungs and the blood in the capillaries is steadily reduced as oxygen passes across the alveoli wall
The blood may take up about 50% of the oxygen in the respiratory medium entering the lungs

39. Gas Exchange in Fish
In a countercurrent exchange system, the oxygen gradient is maintained over the whole of the gill
The blood may take up as much as 80% of the oxygen carried in the respiratory medium entering the gill

40. The Respiratory System in Birds
Respiration in birds is much different than in mammals.
Birds do not have a diaphragm; instead, air is moved in and out of the respiratory system through pressure changes in the air sacs

41. Avian Respiratory System
Anterior air sacs
Inhalation:
When the bird breathes in, the air sacs expand
Most of the inhaled air passes into the posterior air sacs
Some flow from there into the lungs
At the same time, the air that was in the lungs moves into the anterior air sacs
Posterior air sacs
Anterior air sacs
Lungs

42. Avian Respiratory System
Anterior air sacs
Exhalation:
When the bird exhales, all the air sacs contract, forcing the air in the posterior air sacs into the capillary- lined tubes of the lungs
Gas exchange takes place in the lungs
Then, the air from the anterior air sacs is forced out through the trachea
Posterior air sacs
Anterior air sacs
Lungs