Why are women’s voices higher than men’s and why do we sneeze?

Why are women’s voices higher than men’s?

The larynx, or voice box, in the throat has a mucous membrane that forms two pairs of folds: an upper pair (the “false” vocal cords) and a lower pair (the “true” vocal cords). The false vocal cords hold the breath against pressure from beneath – say, when you strain to lift a heavy object. They do not produce sound.

The true vocal cords do produce sound. Under the folds are bands of elastic ligaments stretched between pieces of rigid cartilage like the strings on a guitar, with muscles attached to both the cartilage and the true vocal cords.

When the muscles contract, they pull the elastic ligaments tight, stretching the vocal cords out into the air passageway; this narrows the space between them. Air directed against the vocal cords makes them vibrate, creating sound waves in the air in the throat, nose and mouth. The greater the air pressure, the louder the sound.

Pitch is controlled by the tension of the true vocal cords. If they are pulled taut they vibrate more rapidly, creating a higher-pitched sound. Male sex hormones mean the vocal cords are usually thicker and longer in men than women; they therefore vibrate more slowly, giving men a generally lower range of pitch than women.

How does the retina work?

The retina, at the back of the eye, is a complex structure which has a deep layer of light-sensitive cells called rods and cones, a middle layer of bipolar neurones and a surface layer of ganglion (nerve) cells. The neurones connect the rods and cones with the ganglion cells, fibres which join to form the optic nerve.

This means that the front surface of the retina, which is about the size of a postage stamp, is not the light-sensitive part, because it is covered with blood vessels and nerve cells. But the brain ignores these obstructions; we do not see them as part of our image of the world. Instead, the back is the light-sensitive part, and the surface acts as a projection screen. The rods and cones capture the light, which is transmitted to the brain via the optic nerve.

We cannot see an object whose image falls on the retina at the point where the optic nerve leaves the eye. It contains no receptor cells, and so any light striking this small area is not picked up. This is why we call it the blind spot. 

Is it true that the eye provides evidence of ‘intelligent design’?

If anything, it suggests the opposite. It seems unlikely that a higher being would have designed a retina that is, in effect, back to front, with incoming light having to penetrate a tangled mass of nerves before it reaches the light-sensitive cells at the base. But the eye does suggest how blind natural selection works on random mutations within existing structures.

How and why do we sneeze?

We sneeze to clear irritating material from our upper air passages. This can be dust, pollen or snuff, or excess mucus blocking the nose when we have a cold or hay fever. Sneezing is a reflex action that blasts air out at up to 103mph to clear the air passages. Pain receptors in the cells lining the upper respiratory tract are triggered by the dust or mucus and instruct the medulla (the base of your brain) to make you sneeze.

The sneeze itself is just a very powerful out-breath. The vocal cords are kept shut till the pressure in the chest has risen, and then the air is suddenly allowed to escape upwards, being directed into the back of the nose by the soft palate. But the 103mph of a sneeze is nothing compared to the 600mph that a cough gets up to.