Lesson Plan - Get It!
Would you like to have scales like a fish, or feathers, or fur? That wouldn't work very well; that's why you were created with human skin to hold your insides in!
Your skin is a tough barrier to protect your internal systems from the outside world.
It has the same function as fish scales, but uses a different structure to achieve the goal of protecting you. Fish scales are tiled on top of one another, while skin cells create a thick layer of disposable cells.
- Download and print the Science Reading Guide Worksheet from Downloadable Resources in the right-hand sidebar.
- As you read through this lesson, capture your thoughts and learning in the Science Reading Guide Worksheet. You will use this document to complete the Go! section of this lesson.
Before you continue on, if you missed or need to review the three previous lessons in this Human Body Cells series, check them out under Related Lessons in the right-hand sidebar.
Did you know that your skin is an organ? It is the largest organ in your body, working as the protective barrier from the world around you. Skin also helps regulate temperature and provides us with the ability to feel and touch our environment.
Your skin has different layers made up of skin cells. These cells are constantly dividing and replacing old cells. The epidermis is the outer layer of your skin, the part that you can see when it becomes dry and flaky. The epidermis determines our skin tone and serves as the first protective barrier for the body. This is also the layer that sends messages to the brain about the objects we touch in our environment. Neurons send messages from the cells to the brain about the texture, temperature, and softness of materials we encounter.
Under the epidermis is the dermis layer, where hair follicles and sebaceous, or sweat, glands are found. Between these two layers is the basement layer that keeps the epidermis attached to the dermis. In this thin area, skin cells are produced rapidly through cell division. These new skin cells replace damaged skin cells in the epidermis.
When the sebaceous glands become clogged, you end up with a pimple! Pimples are small areas of inflammation on the skin. They increase during puberty because the glands are very active due to changing hormones in the adolescent body. Acne, an excess of pimples, has many treatments, including medications and keeping the skin clean.
The subcutaneous layer is the deepest layer and is made up of connective tissues and fat. It is what makes your skin feel flexible.
Not all skin cells are the same; there are actually three types of skin cells that make up the epidermis layer: keratinocytes, melanocytes, and Langerhans cells. Each cell type has a specific job that helps the skin protect our internal structures.
- Keratinocytes move upwards through the epidermis until they are eventually lost as dead skin cells on the surface. They occupy most of the area of the epidermis, providing the thick protective outer layer that most of us call our skin.
- Melanocytes are the cells responsible for your skin color or tone. They produce melanin, a special pigment that provides skin with color. When you lay in the sun, your melanin is stimulated, causing changes to your skin tone.
- Langerhans cells are also found in the epidermis, but in lower numbers than keratinocytes. They are immune cells responsible for helping the body identify invaders or pathogens. These cells help the skin combat immune system attacks at the first point of contact. Notice the purple cell embedded in the epidermis? That's the Langerhans cell; it uses branch-like appendages to respond quickly to invaders.
All three types of skin cells work together to promote healthy bodies. You lose skin cells each minute, every time you rub up against a surface or take a jacket off. These skin cells must be replaced in order to keep your protective barrier strong and effective. The average human loses up to 40,000 skin cells each day! That adds up to nine pounds of skin cells lost each year!
While skin cells are organized into layers, they have specific jobs that allow them to respond to threats and changes in the environment.
- What do you think would happen without Langerhans cells?
- Why do you think we have melanocytes in our skin?
Discuss these reflection questions with a parent or teacher before moving to the Got It? section, where you will learn more about why we have skin pigment.