Anatomy
Lungs
In humans, the left lung is smaller because the heart extends further into the left side of the thorax; the right lung has an additional lobe in its place. In Time Lords, this is of course not the case. As there is a heart on each side, both lungs are the same size. The posterior sections are significantly larger and split into superior and inferior lobes; the anterior lobes are larger at the top, and taper around the hearts (see figure 1).
Scans I have been able to do suggest that the internal structure of the lungs is the same as in humans.
Figure 1: Transverse section of the thorax (adapted from CT scan)
| 1. Right lung, posterior lobe
2. Aorta 3. Azygous vein 4. Esophagus 5. Rib 7 6. Scapula 7. Rib 6 8. Rib 5 9. Rib 4 10. Thoracic duct of the lymphatic system 11. Thymus gland 12. Sternum 13. Pericardial sac 14. Left atrium 15. Left ventricle (pumps deoxygenated blood) 16. Right ventricle (pumps oxygenated blood) 17. Right lung, anterior lobe 18. Pleural sac "T7" indicates the 7th thoracic vertebra. |
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Larynx
While the larynx appears the same as in humans, there is one significant difference at the microscopic level. There are receptors that detect the presence of liquid or poisonous gas.
Bronchi
After the trachea splits into two bronchi, these bronchi then split into four, for the anterior and posterior lung lobes. The pulmonary arteries follow the bronchi.
Physiology
Locking of the glottis
If water is about to enter the lungs, or poisonous gas is present at levels high enough to outweigh the need for oxygen, the glottis will clamp shut, preventing anything from entering the lungs. This can also be done voluntarily, and it can be released voluntary as long as the subject remains conscious. If he falls unconscious, the glottis will not open until the receptors indicate it is safe to breathe.
Respiratory bypass
The lungs are not the only means by which a Gallifreyan can take in oxygen from his environment. Oxygen is also gathered through the skin, from air or water. In the epidermis, there are highly specialized molecular channels that will pass oxygen - and only oxygen, not carbon monoxide, even though hemoglobin recognizes it - into the blood.
In the event glottal closure or other interruption of air supply (such as suffocation or strangulation), enough oxygen can be gathered to sustain life. However, if the environment is particularly low in oxygen, it is unlikely to provide enough to sustain consciousness. This means the subject can not get himself out of danger, but must wait for rescue, or for danger to go away on its own.
The presence of fetal hemoglobin is helpful in this instance, because it will absorb more of the oxygen passed through the skin than normal adult hemoglobin would. When the tissues are starved for oxygen, the fetal hemoglobin will release it to them.
Index by system
Cardiovascular - Respiratory - Genetics - Life Cycle