I’ve been overwhelmed in recent times with the realization that I don’t really know my body as well as I thought I did. So I’ve been feeling a need to understand the human body with much more depth than the superficial understanding and collection of facts that I have. What do I know so far? Where to begin? Let’s use a single human life as an example.
So the parents of a human-to-be typically have sexual intercourse, where the father ejaculates semen into the mother’s vagina, and the sperm goes along the canal where it meets an egg that has been released from the ovary. The egg gets fertilized and the fertilized egg “plants” itself into the wall of the uterus, where it then begins to grow. The fertilized egg undergoes some sort of cellular division process, where one cell becomes 2, 4, 8, 16.
At some point along this process (apparently usually 9 weeks), the rudimentary systems of the body begin to take shape and the embryo (latin: to-swell) becomes a fetus (latin: to-bear, suckle)– a circulatory system with the heart and veins, a respiratory system with the nose, mouth, windpipe, lungs, a nervous system with the brain, spinal cord, etc, a muscular system, bones, tendons, a digestive system with oesophagus, stomach, intestines, anus, a urinary system with kidneys and bladder.
And there’s all this other stuff you don’t hear so much about– a liver, adrenal glands, pitutary, lymph nodes, appendix, testicles for men, ovaries for women. Oh, and of course, you have the senses– eyes, nose, mouth, ears, skin. (And interesting things like proprioception, which tell you where your body parts are respective to one another without you necessarily having to see them.)
The violent, messy miracle of pregnancy and childbirth happen, which I’m not too concerned about right now. How do placentas even work, etc. (This will obviously change if/when I ever become a father. For now I’m trying to figure out how to understand my own body first.)
Child is born, typically drinks mother’s milk, sleeps and cries a lot, learns to function in this suddenly difficult, harsh, volatile environment (relative to the womb). Has to learn to communicate with other humans. Grows a lot, very quickly. Grows taller, grows teeth, loses baby teeth, grows adult teeth. Has to learn to urinate and defecate in socially appropriate contexts. Has to learn to eat and drink. (May or may not develop an understanding of what food is and how it works. Took me really long to do this.)
Child learns to play, socialize. Read, write. And then comes puberty.