1. Gas Exchange

2. 6.4.1 Distinguish between ventilation, gas exchange and cell respiration

3. Ventilation maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries

4. Breathing is NOT respiration!
Ventilation
Movement of air into and out of the lungs in two stages: inspiration & expiration. Controlled by diaphragm & ribcage.
Gas Exchange
The exchange (diffusion) of oxygen and carbon dioxide to and from the blood at the alveoli and the respiring tissues
Cell Respiration
This is production of ATP at the cellular level (mitochondria). Aerobic respiration uses oxygen, whereas anaerobic does not.

5. Ventilation Movement of gases
1st , in the lungs where oxygen moves from the air into the bloodstream
2nd, in a capillary bed elsewhere in the body where the opposite gas exchange occurs, (O2 & CO2)

6. 6.4.2 Explain the need for a ventilation system

7. Why do we need a ventilation system?
We are large organisms. Oxygen cannot diffuse into all our cells directly from the air, nor can waste products be directly ejected from the body. The ventilation system ensures the blood can be the medium for this.

8. Why a ventilation system?
We are land-borne.
Gases need moist surfaces in order to diffuse
Lungs are moist membranes
Vent. System maintains a large concentration gradients
The constant flow of blood past the alveoli brings blood with a high CO2 concentration and low O2 concentration
Exhaling keeps the CO2 concentration in the alveoli low, so it diffuses out.

9. Ventilation System
High concentration gradients must be maintained in the alveoli.
Breathing in increases the concentration gradient of oxygen between the alveoli & blood (diffuse in)
Breathing out removes (CO2) increasing the concentration gradient of CO2 between blood and alveolus – CO2 diffuses out

10. Gas Exchange
If the alveoli were not ventilated, equilibrium would be reached and no gas could be exchanged.

11. Respiratory Basics

12. 6.4.3 Describe the features of alveoli that adapt them to gas exchange

13. Alveoli are well adapted to gas exchange
Alveoli increase the surface area for gas exchange.
Millions in number (300), each with their own network of capillaries
Rich blood supply maintains a high concentration gradient of O2 and CO2
Surfaces are wet

14. Alveoli Membranes are very thin Diffusion path is short
Both of the alveoli and the capillaries
Diffusion path is short
Composed of single layer of cell (2 different types of cells)

15. 2 Types of Pneumocytes Type 1 pneumocytes Type 2 pneumocytes Very thin
Large membrane surface area
Great for diffusion
If damaged – no mitosis
Cuboidal in shape
Little membrane surface area
Produce & secrete a solution that acts as a surfactant
Prevents the sides of the alveoli from sticking to each other
Damaged – stil mitosis

16. Which process(es) of membrane transport are being used in gas exchange at the membranes of the alveoli?

17. How many membranes must an oxygen molecule pass through in order to enter an erythrocyte?

18. Draw and label a diagram of the ventilation system, including trachea, lungs, bronchi, bronchioles and alveoli.

20. Explain the mechanism of ventilation of the lungs in terms of volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm and abdominal muscles.

21. Gas Exchange

22. Gas exchange

24. Antagonistic Muscles Muscles only work when they contract
Opposite state is relaxation
Inspiration
Expiration
diaphragm
Moves downward & flattens
Moves upward and becomes more domed
ribcage
Moves upwards and outwards
Moves downwards and inwards

25. Mechanisms of inspiration
The diaphragm contracts & at the same time the abdominal muscles and intercostal muscles help to raise the rib cage. All of these help increase the volume of the thoracic cavity.
Because of the increase in volume, the pressure inside the cavity decreases. Leads to less pressure “pushing on” the passive lung tissue

26. Mechanism of inspiration
The lung tissue increases its volume because there is less pressure exerted on it.
This leads to a decrease in pressure inside of the lungs, also known as a partial vacuum
Air comes in through your open mouth or nasal passages to counter the partial vacuum within the lungs

27. Mechanism of Expiration
Previous steps reversed.

28. Emphysema Alveoli are progressively destroyed Main cause smoking
COPD(chronic obstructive pulmonary disease)
Turns healthy alveoli into large, irregularly shaped structures with gaping holes

29. Nature of Science: Epidemiology
Epidemiology is the study of the incidence and causes of disease
Most studies are observational rather than experimental
Survey data is collected

30. Epidemiology
Correlation between a risk factor and a disease does not prove that the factor causes the disease.
Example:
Association between leanness and increase risk of lung cancer
Yet among smokers leanness is not significantly associated with risk
So what’s up with this?

31. Lung Cancer Cancerous growth beginning in lungs
Prone to spreading (metastisizing)
Lung becomes dysfunctional
May cause internal bleeding in the lungs
Caused by carcinogens

32. Lung Cancer Most common cancer in the world
Cases and death
Smoking causes about 87% of cases
Risk increase by number of cigarettes smoked per day & number of years
Passive smoking causes about 3%
Decreasing with ban of smoking indoors

33. Lung Cancer Air pollution causes about 5%
Diesel exhaust fumes, nitrogen oxides, smoke from burning coal, wood, etc
Radon gas causes significant number of cases in some parts of the world
Radioactive gas that leaks out of certain rocks (granite)

34. Lung Cancer Asbestos Silica and some other solids
Dust or other particles inhaled
Construction sites, quarries, mines, factories