The Making of You by Katharina Vestre

Author:Katharina Vestre
Language: eng
Format: epub
Publisher: Profile
Published: 2019-02-06T16:00:00+00:00

Secret Preparations

YOUR CELLS MIGHT BE HAVING a busy time in the womb, but it’s a spa-hotel compared to what’s in store after you are born. The heat and the cold outside are things your cells don’t have to worry about – your mother keeps things at a comfortable, and stable, temperature of thirty-seven degrees. And thanks to the placenta being full of nice warm blood, your cells never need worry about whether there is enough air or food. Later in life, however, your cells will face a heap of new challenges: baking-hot sun, running, forgotten water bottles and salty crisp crumbs. So, be glad that you acquired a pair of kidneys when you had the chance.

The kidneys and urinary tract are made at the same time as the genitals, and originate from the same cell vesicles. Like so many other parts of the body, they are made in a wonderfully convoluted way, and one of the clearest examples of how haunted we are by our ocean-dwelling past. The cells build things, remove things, change things round and change their minds. It took three attempts before they managed to make the kidneys sitting inside you right now.

What happened to the abandoned drafts? The first were a collection of small tubes that formed right by your neck during the third week. Unfortunately, these primitive kidneys were useless and quickly disappeared. A little later, a new pair appeared further down your back. These sausage-shaped kidneys looked quite similar to the ones found in fish and amphibians, and you actually used them in the womb for a short while. (In girls this pair also disappear, but in boys some of the cells stay behind and become part of the genitals.) Then, in week five, construction of the final kidneys began. However, just to make it extra difficult, they popped up in the wrong place, meaning that they had to go on a journey before they could settle down. First they moved down towards your pelvis and attached themselves to your bladder, later they turned round and moved upwards. Eventually, they arrived at their final position: on each side of your spinal column, at roughly the same height as your lowest ribs.

The finished kidneys are a reddish-brown colour, bean-shaped, each one the size of a clenched fist. Their normal working day looks something like this: receive blood, clean it, pass it on, repeat 399 times – Phew! Each kidney is composed of many small channels that are connected to coils of blood vessels. The fluid is extracted from the blood, and then flows through the channels, where the kidney filters away what you don’t need and returns the rest. Just as the potato peelings and discarded packaging accumulate when you make dinner, a certain amount of rubbish is also created and needs disposing of when your cells are at work. For example, you need to remove the ammonia formed when you break down proteins. If ammonia builds up in your body it is extremely toxic.

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