We began our human anatomy today with the Integumentary System – the organ system consisting of the skin, hair, nails, and exocrine glands. The skin is only a few millimeters thick yet is by far the largest organ in the body.
Skin forms the body’s outer covering and forms a barrier to protect the body from chemicals, disease, UV light, and physical damage. Hair and nails extend from the skin to reinforce the skin and protect it from environmental damage. The exocrine glands of the integumentary system produce sweat (sudoriferous glands), oil (sebaceous glands), and wax (ceruminous glands) to cool, protect, and moisturize the skin’s surface.
Hair, Skin, & Exocrine Glands
We began our session with three short demonstration activities to familiarize ourselves with the organs of the integumentary system. We first observed hair under the microscope and differentiated between dog, cat, rabbit, and human hair.
Secondly, we explored our fingerprints or the images made by the tiny ridges that cover our skin on the tips of our fingers. We collected the fingerprints from each person in class and then made careful observations under a magnifying lens. I then distributed to the class a mystery print and allowed time to identify to whom it belonged.
Lastly, we talked about how our skin works to help keep our body at a constant temperature with the help of our sudoriferous or sweat glands. These glands are located deep in our skin and produce a salty liquid we call sweat. To demonstrate how these glands work, we first blew on the inside of our forearm when it was dry and then again when it was wet. As sweat reaches the surface of our skin, it evaporates or dries. As it does so, the area feels cooler as warmth is drawn away from the skin.
Somatosensation Inquiry Lab
Somatosensation, or your sense of touch, is controlled by tiny receptor cells in your skin. Because your skin is the largest organ in your body, you have millions of these receptor cells scattered throughout your body. Somatosensative cells respond to four separate sensations: pleasure, pressure, pain, or temperature.
We did an experiment to see which parts of our skin are most sensitive: fingertip, back of hand, palm, forearm, and back of neck. With the testing device pictured here, the kids partnered up and gently placed the two ends of the toothpicks on one of the five areas of their partner’s body. Their partner then stated whether they could feel both toothpicks or only one.
They first made a guess as to which body part would be the most sensitive (their hypothesis), numbering them in order of sensitivity. They then took turns testing one another. Their data was recorded on a table in their notebooks.
When we had completed the data collection period, we gathered together to discuss the following questions:
- Which part of the body seems to have the least sensitivity?
- Which part of the body seems to have the most sensitivity? Why do you think that part of the body is the most sensitive?
- Your skin is designed to help protect you from harm. Describe at least two situations in which your skin helped protect you or was trying to protect you.
- You’ve probably noticed that when you sit for a long period you have to shift your weight from one part of your rear to the other. You simply become uncomfortable and must move a bit. Why do you think this happens? Why do sensory cells in that part of your skin indicate too much pressure exists?
- What do you think people who are paralyzed from the waist down (paraplegics) must do every 20 to 30 minutes, whether they can feel anything or not? Why?
For homework, I encouraged students to continue this lab again with other family members. Alternatively, I suggested they examine other sensations, such as temperature, and design alternative methods to map out skin sensitivity levels.
Models of Skin
Additionally, I asked students to use materials they found around their house to create a model of skin (as shown in the picture at top). They were asked to label the following structures and to orally describe the function of each:
- fatty layer
- hair follicles
- oil glands
- sweat glands / pore
- blood vessels
We used the models to discuss skin pigmentation. We noted that under the top layer of skin, with its varying amounts of melanin, we are the same.
It was a great start to our anatomy cycle. Next week we will explore the nervous system in depth. The kids are very excited as we will be dissecting a bovine eye! Come join us!