The Human Body
The human body is extremely complex, and in this paper I am going to try to explain how each part of the body works, if you already know how a certain part of the body works, you may skip over that section.
The skin of the human body is not thought of much, but it is extremely useful at what it does, and without it the body would be frail and easily damaged, or even just fall apart!
The skin is not a sheet of stuff, but it is actually 3 layers of cell sheets with neurons and hair pores, along with blood vessels that will not fit anywhere else, it is what holds the muscles and other things together.
The neurons in the skin are responsible for touch and pain, both are extremely useful senses, they work by detecting pressure or exposure to oxygen (cuts & bruises expose neurons in a lower layer to air or oxygenated blood), and these neurons send electrical signals to the brain via neural pathways.
Skin is not single, but is instead layered, and the layers are being replaced constantly to make sure that the one layer does not wear down and expose the internal parts.
The outer layer is called the Epidermis, being waterproof (so we do not soak up unwanted water!), and is the most frequently replaced layer. The Epidermis is composed of 5 sublayers, so that it is easier to shed a single layer at a time.
The middle layer is called the dermis, and it protects the body from stress and strain, many pain sensing neurons are found in this layer, it is divided into two layers.
The lower layer is called Subcutaneous Tissue, it is not a true layer of skin, and contains most of the blood vessels and neurons, it also contains most of the body fat (this layer is composed of 50% body fat), and provides insulation. This layer is thicker in children.
The muscles are the most important part of the body, and there are three types of them, being the skeletal muscle, the smooth muscle and the cardiac muscle.
The skeletal muscle is a muscle attached to the skeleton or to tendons and it is used for locomotion and movement, these muscles can be moved at will. These muscles are made of muscle fibres that are small tubes with attachment points and grapples inside, the grapples will chemically pull themselves across the tube, and make the tube shrink in length, and get “fatter”, many of these together will create a skeletal muscle.
The smooth muscle is found in the walls of organs and cannot be controlled (lungs are not a smooth muscle, and they are the only skeletal muscles in the body) these muscles are the same as a skeletal muscle but cannot be controlled.
The cardiac muscle is only found in the heart and is extremely durable and fast, it cannot be controlled and is quite strong.
The bones are what hold you together, and without them, you would be useless and vulnerable. Bones are composed of a compact and strong calcium lattice that is constantly being replaced, and inside there are blood vessels and a bone marrow, making the bone, actually an organ.
Body fat is not the greasy stuff that comes off a chicken or a steak, but in its uncooked form, is actually many cells that store fat and chemicals.
The ear is responsible for the sense of hearing, and the visible part of it is for focusing the sound into the eardrum.
The eardrum is used for converting sound waves into movements on the skeletal lever that can be retracted away from the eardrum via a small muscle in the ear that some people have learnt to control.
The skeletal lever converts the movements in the eardrum into movements in a liquid filled cavity that has many tiny hair-like sensors that send signals to the brain.
The nose is responsible for the sense of smell, it works by picking up airborne particles and using a key in lock & molecular vibration sensing method (these are theorised, it is not truly known how it distinguishes smells), and doubles as an airway to the lungs.
The tongues taste buds bind with the chemicals in the food, then they release the chemical and send a signal to the brain, the scent coming off the food passes through the nose on exhale and that means that most of the taste comes from the nose, although the tongue can sense heat and the 5 tastes (sweet, sour, bitter, salty & umami), it is also responsible for speaking, and speaking is impossible without the tongue.
The digestive system is responsible for extracting all the nutrients, proteins, fats, calories and vitamins from food that you eat. The digestive system is composed of the stomach and the small and large intestines.
The lungs collect oxygen from the air and pass it into the blood, at the same time they take the carbon dioxide and dispose of it. The lungs are connected to the mouth and the nose via a closable tube.
Kidneys & Liver
The Kidneys are used for filtering blood, and they create urine, the liver is for filtering out certain minerals & synthesising bile, digestive juices & proteins, and does biochemical reactions.
The heart is the only organ that contains cardiac muscles, and it is responsible for pumping blood around the body.
The last, but definitely not least is the brain, the brain is you, and it is composed of trillions of synapses and neurons. The brain is made of the conscious (you) and the subconscious (controls heart and other smooth muscles) and it is responsible for controlling nearly all of the body parts via neural pathways.
Note that I have missed parts of the body, and those are likely the parts i do not know about, although i hope this gave you a better general understanding of the human body