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Biology for Kids

The Skin

What is it?

We all have skin. It covers our entire body and keeps the good stuff in and the bad stuff out. But what exactly is skin? We'll get into the details below, but for starters the skin is an organ. Just like the heart or the brain. It's an important organ that performs many functions to enable us to live.

Integumentary System

The skin is part of an important organ system called the integumentary system. The integumentary system consists of the skin, hair, nails, and exocrine glands.

Functions of the skin

The skin is multipurpose, meaning it has a lot of functions. It's our first line of protection against the outside environment, it houses one of our five senses, it absorbs sunlight for vitamin D and heat, and regulates our internal temperature.

Protection - One of the basic functions of the skin is protection. Over the majority of your body the skin is around 2mm thick. In some areas, like your eyelids, it's thinner, while in other areas, like the soles of your feet, it's much thicker. The skin helps to keep bad stuff out of our body, like germs and dirt that can cause infection. It also keeps good stuff in, like fluids such as water and blood.

Sense of Touch - The skin also houses one of our five senses: touch. In our skin are thousands and thousands of sensors or receptor cells. These sensors send information to the brain about things we touch. They can tell the brain if it's hot, cold, rough, smooth, or painful. Different areas of our body have more receptor cells than others. Our hands, feet, and lips all have extra receptors making those areas even more sensitive. There are actually different types of receptor cells for each type of sensation.

Temperature Control - The skin plays a large role in regulating our body's temperature. When we get too hot it sweats to help cool us off. It can also widen the skin's blood vessels to get more blood near the skin where it can cool off. At the same time the skin can narrow the blood vessels to help us warm up. By controlling blood flow and sweat, the skin regulates our body's temperature.

Layers of the skin

The skin has three primary layers. Each one has its own function.

Epidermis - The epidermis is the outer layer of skin. Its main function is protection. The cells on the very outer layer of the epidermis are constantly dying and getting replaced by new cells.
Dermis - The dermis is thicker than the epidermis. The dermis houses blood cells, hair follicles, and sweat glands.
Hypodermis - The hypodermis lies under the dermis and connects the skin to muscles and bone.

See the picture below for more detailed parts of the skin:

A. Epidermis
B. Dermis
C. Hypodermis
D. Blood Vessels
E. Stratum Germinativum

1.Hair Shaft
2.Stratum Corneum
3.Pigment Layer
4.Stratum Spinosum
5.Stratum Basale
6.Arrector Pili Muscle
7.Sebaceous Gland
8.Hair Follicle
9.Papilla of Hair
10.Nerve Fiber
11.Sweat Gland
12.Pacinian Corpuscle
13.Artery
14.Vein
15.Sensory Nerve ending (for touch)
16.Dermal Papillary
17.Sweat Pore

Experiment:
Skin Temperature - How does our skin lower or raise our temperature?

Activities

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