The skin is the outside covering of the body tissue, which protects inner cells and organs from the outside environment. The skin is the largest organ of the body and its cells are continuously replaced as they are lost to normal wear and tear. The skin has between 12 to 20 square feet in area and accounts for 12% of body weight.
It is composed of 3 layers the epidermis, the dermis, and the sub cutis.
The thickness of the epidermis and the dermis varies over different parts of the body. It is thicker on the palms of our hands and feet, and thinner on our eyelids which have to be light or our eyes would always be closed.
The dermis, or known as the true skin, is thick, sturdy, and contains lots of nerves, blood vessels, and sweat glands. It protects and repairs injured tissue.
This layer holds more collagen, which comes from cells called fibroblasts and is one of the strongest proteins found in nature. It gives skin durability and resilience.
The subcutis, joined to the dermis, is the deepest layer of the skin. It contains lipocytes, which produce lipids for the subcutaneous tissue to make a fatty layer which helps muscles, bones, and inner organs against shocks.
The facial nerve is the seventh cranial nerve. It begins in parts of the brain stem and branches into the face, neck, salivary glands, and the outer ear.
The facial nerve performs both motor and sensory functions. Branching up from the brain stem, it divides into smaller nerves that reach into the face, neck, salivary glands, and outer ear.
These branches control the muscles of the forehead. They also stimulate secretions of the lower jaw and those salivary glands which are in the front of the mouth.
Along with this, they send taste sensations from the front two-thirds of the tongue and carry sensations from the outer ear.
Although a grin and smile both use lip...