Human Skin

The skin is the largest organ of the human body and covers and protects muscles, bones, organs, and all other parts of the body. Without the skin, the body parts may fall out onto the floor. Besides protecting the body, the skin helps the body maintain its temperature, and allows a person to have a sense of touch.

There are three main layers of human skin and each has its own function and parts. The epidermis layer is the outmost layer of skin and is the part that can be seen. Its main function is for protection. Deep inside the epidermis layer, there are growing cells, and, on the outside, there are flat, dead skin cells that easily flake off the body. In fact, every minute of the day, a person loses about 30,000 to 40,000 dead skin cells or about 9 pounds every year. When new skin cells come to the surface, they contain keratin, which makes the skin waterproof and tough. Other cells of the epidermis produce a pigment called melanin which darkens the skin and protects it from strong sunlight. Most of the cells in the epidermis, about 95%, work to make new skin cells and the other 5% make the melanin.

The layer beneath the epidermis is the dermis, which is a thicker and more elastic layer compared to the epidermis. This layer is home to glands, hair follicles, nerves, and blood vessels. The two types of glands include sebaceous, which produce sebum, a type of oil that helps keep the skin soft and waterproof, meaning water cannot get inside the body. The second type are sweat glands which make sweat and when the body gets too hot, the moisture is sent through the pores or tiny holes of the skin to help cool a person.

The hair follicles are where the hair on the body is made. They look like tiny bulbs, and most of the hair on the body is short and fine. The only places where there is no hair is the lips, palms of the hands, and the soles of the feet. There are about 100,000 hair follicles on a typical person's head.

The nerves in the dermis layer are the sensors for the body that send messages to your brain. They tell the temperature, cause one to feel pain, lets a person feel the smoothness or roughness of things, and tell how hard skin is being pressed. Finally, the blood vessels in the dermis layer are part of the body's circulatory system and carry oxygen and nutrients to the cells in the body and carry away waste.

The final layer, located beneath the dermis, which is also called the subcutaneous layer, is the hypodermis layer of skin. It is mostly made of fat and helps keep the body warm and absorbs shocks. It holds all the skin to the tissues beneath it, and the start of hair follicles take place in this layer and is the location of the hairs' roots. Glands in this layer connected to each hair follicle coat the hair with oil giving it a shine plus a small amount of waterproofing. The fat cells in the hypodermis layer keep the body warm, and the more body fat a person has the more a person will sweat.

The skin is responsible for other functions as well including temperature control. The typical temperature of a person's body is 98.6°F which is needed to keep the body and cells healthy. The skin responds to messages sent to it by the brain's inner thermometer called the hypothalamus.

When the body is cold, the blood vessels help keep the body warm by keeping blood away from the skin's surface. This is when goosebumps appear, the scientific name for them is the pilomotor reflex. This reflex makes special tiny muscles called the erector pili which pull on the hairs, so they stand up straight causing the goosebumps.

There are different thicknesses and forms of skin on the body too. The skin on most of your body is about 2 millimeters thick, but it is thicker on the soles of feet because it gets rubbed a lot when a person is moving around. The skin on the eyelids is only about 0.5 mm thick.

In addition, the skin on your knees and elbows is more elastic and looser because it must do a lot of stretching when a person moves. Finally, the skin on the palms of the hands is much firmer than the skin on the back of the hand. This makes it easier for the hands to grasp things.

The largest organ of the human body, skin, is a fascinating part of the body that protects, maintains body temperature, allows the sense of touch, and much more. Everyone has different shades of skin color but deep down, all skin is the same, and it is the inside of a person that is unique and special.

A: Keratin
B: Melanin
C: Sebum
D: Follicles

A: Nerves
B: Blood vessels
C: Both A and B
D: None of the above

A: Hypothalamus
B: Hypodermis
C: Pilomotor reflex
D: Subcutaneous

A: Subcutaneous
B: Hypodermis
C: Dermis
D: Epidermis

A: Pilomotor reflex
B: Follicles
C: Sebum
D: Hypothalamus

A: Palms of hands
B: Knees and elbows
C: Soles of feet
D: Lips

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