1. You must be able to draw the structure of the lungs and alveoli

2. Lung Anatomy

3. Why and how do we breathe?

4. The need to ventilate
A ventilation system is needed to maintain concentration gradients in the alveoli
The steep concentration gradient across the respiratory surface is maintained in two ways: by blood flow on one side and by air flow on the other side. The ventilation system replaces diffuses oxygen (keeping the concentration high) and removes carbon dioxide (keeping the concentration low).
This means oxygen can always diffuse down its concentration gradient from the air to the blood, while at the same time carbon dioxide can diffuse down its concentration gradient from the blood to the air.

5. Alveoli and Pulmonary capillaries

6. Features of the alveoli
large surface area: surface area of the alveolar epithelium m2
thin: single cell layer of epithelium across which diffusion occurs
moist: gasses need to dissolve before passing membranes
rich blood supply: extensive net of capillaries for transport of gasses to and from alveoli

9. Inhalation Intercostal muscles contract. Ribs move out and ______
Diaphragm contracts and gets ____________
Inhalation
Volume _____________
Pressure ____________
Intercostal muscles contract.
Ribs move out and up
Diaphragm contracts and gets flatter
Volume increases
Pressure decreases
Air enters the lungs

10. The lungs relax here and the pressure
inside and outside the lungs goes back
to normal atmospheric pressure 760mm Hg

11. Exhalation Intercostal muscles ______. Ribs move ___ and ______
Diaphragm _______ and returns to its dome shape
Exhalation
Volume _____________
Pressure ____________
Intercostal muscles relax.
Ribs move in and down
Diaphragm relaxes and returns to its dome shape
Volume decreases
Pressure increases
Air leaves the lungs
Air _____ the lungs

12. Lowering of the diaphragm and rising of the ribs causes a drop in air pressure of 4mm Hg

13. Gas exchhange
Howstuffworks "Gas Exchange"

14. HL: Partial pressure
In summary, gases move from a region of higher partial pressure to a region of lower partial pressure.
Animations partial pressure. Keep in mind above summary.

15. Partial Pressures of O2 and CO2 in the body (resting)
Alveoli
PO2 = 100 mm Hg
PCO2 = 40 mm Hg
Alveolar capillaries
Entering the alveolar capillaries
PO2 = 40 mm Hg (relatively low because this blood has just returned from the systemic circulation & has lost much of its oxygen)
PCO2 = 45 mm Hg (relatively high because the blood returning from the systemic circulation has picked up carbon dioxide)

17. How are oxygen & carbon dioxide transported in the blood?
Oxygen is carried in blood:
1. bound to hemoglobin (98.5% of all oxygen in the blood)
2. dissolved in the plasma (1.5%)
Animation Quizzes hemoglobin

18. The graph below shows the Haemoglobin- Oxygen Association Curve
The graph below shows the Haemoglobin- Oxygen Association Curve. This shows the % of oxygen in the blood (oxyhaemoglobin) and the partial pressure of O2 in the environment. Simply put it means that oxygen joins haemoglobin and stays joined at high partial pressures of oxygen. When the level of oxygen is low (low partial pressure), the oxygen molecules dissociate (jump off) the haemoglobin molecule. The more O2 a molecule of Hb accepts, the easier it is to carry more, as it changes its shape.

20. Mammalian muscles also contain a chemical called Myoglobin
Mammalian muscles also contain a chemical called Myoglobin. It is similar, but smaller than haemoglobin. It holds onto oxygen much more tightly (higher affinity) and only dissociates at much lower partial pressures- a store of oxygen for difficult times.

21. In the developing foetus, the haemoglobin has a much higher affinity for oxygen. This means that the baby can absorb oxygen efficiently across the placenta at fairly low partial pressures.

22. The Bohr Shift: When there is lots of CO2 due to respiration, the acidity of the blood increases slightly. This causes the whole graph to shift to the right (and get steeper). This allows oxygen to unload at these places even easier.

23. High altitudes
People who live at high altitude have to cope with having less O2 available for respiration. Their body compensates by making far more haemoglobin. This increases the amount of oxygen that can be carried. However, there is a downside: when there is too much haemoglobin, blood becomes sticky and viscous and it is harder for the heart to pump the blood around the body. This happens in chronic mountain sickness.
Athletes often train at altitude- this can benefit
them when they return to run races, as they
have an improved exchange rate with more
haemoglobin

24. CO2 produced in mitochondria
Diffuses out into tissues and tissue fluid
In rbc it combines with H20 forming carbonic acid
(H2CO3) using carbonic anhydrase.
This splits (dissociates) into H ions and HCO3 ions
Haemoglobin acts as a buffer and takes the H ions to form Haemoglobonic acid (H.Hb)
The blood stays fairly neutral and can absorb lots of CO2
As the amount of HCO3 rises in the rbc, they start to diffuse out down the conc. gradient into the plasma
This cannot be balanced, as the cell stops ions like Na and K
The cells would get more and more positively charged (compared to the plasma) and prevent O2 uptake
Chloride ions are pumped in from plasma to balance it- called the chloride shift
At the lungs the oxygen is taken up by dissolved H.Hb- forming Hb.O2
H ions are released and combine with HCO3 forming carbonic acid- the CO2 then diffuses out
The HCO3 content falls, so more moves in from the plasma, so more CO2 released
The chloride shift moves ions into the plasma to maintain neutrality

25. What is asthma?
In asthma, the muscles lining the airways are very sensitive and
overreact to substances or events, known as triggers, that other
people tolerate without problem. Often pollen, dust, mould spores and smoke can cause this, but often other allergens can trigger it too.
3 things generally happen:
Tightening of the muscles lining the airways
Mucus production
Inflammation
Imagine having done 3 minutes exercise, then try to recover, but ONLY breathing through a straw!!

26. Lung volumes
Tidal volume – the amount of air breathed in or out of the lungs in a normal breath. This is about 500cm3
Inspiratory reserve volume – extra lung volume available if you breathe in as much as you can. This is about 3000cm3
Expiratory reserve volume – extra lung volume available if you breathe out as much as you can. This is about 1100cm3

27. Lung volumes
Vital capacity – this is the TV + IRV + ERV or the useable lung capacity. It is about 4500cm3
Residual air – this is the amount of air that needs to stay in your lungs to stop them collapsing. It is about 1200cm3

28. Lung capacity practical
Look at the instructions for how to use the lung volume kit.
Try to measure your own lung volume
Plan an investigation into a factor that could affect vital capacity.