Yesterday we talked a bit about about the human skeleton. Now let’s compare it to an insect skeleton.
Insect and other arthropods have their supporting structure on the outside of their bodies. The outside skeleton is called an “exoskeleton.” It has the same function as the vertebrate internal skeleton, that is protecting the internal organs and allowing for movement. The biggest difference is that the exoskeleton doesn’t grow and must be shed or molted for an insect to increase in size.
When you first look at an insect anatomy diagram, it might seem like the vocabulary is unusual.
It turns out, however many of the parts are named the same as in humans.
For example, the name of the segments of the insect’s legs correspond to the names of the bones in the human legs. The big bone in the thigh is the femur, the bone below the knee is the tibia, and the bones in the feet are called the tarsals and metatarsals.
A doctor of thoracic medicine specializes in the chest, particularly the lungs. A doctor might ask if you have a pain in the lower left abdomen.
The human jawbone is called a mandible, and insects with biting mouthparts have mandibles.
Insects have a membrane that helps them detect sounds called a tympanum. Humans have a tympanic membrane in the ear that helps with hearing.
Learning the vocabulary is easier once you see the similarities.
Can you find your femur? Can you see the large, jumping femur of this grasshopper?
Our post this weekend is inspired by a new book, Inside the Human Body by Dr. Aron M. Bruhn, M.D., with illustrations by Joel Ito and Kathleen Kemly.
Starting with the parts of the cell, the first two pages look like any other nonfiction book.The surprise comes when the pages fold out to a 35-inch long illustration of a human boy with many different organs labeled. The illustration is detailed and tastefully done, so that the boy looks healthy and lively. There are nine other fold out sections throughout the book.
On the following pages come the skin, nervous system, senses, and digestive system. Traveling through the excretory system, muscles, and respiratory system, Dr. Bruhn then explains bones, the immune system, hormones and ends with the reproductive system. Some of you may be wondering about the reproductive system part. It shows external drawings of a fairly realistic male and a female form overlaid with an illustration of the internal organs. The fold out for this section shows the stages of development of a fetus in the womb during pregnancy.
Inside the Human Body poses and answers some interesting questions, such as “How old is your skin?” and “Why do my veins look blue if my blood is red?” I admit, I didn’t know the answer to the first one, which is that the skin replaces itself in just over one month. You can also find out what causes a sore throat, and how to find your blind spot.
If you are doing a human biology unit with middle grade students, or have a child who is learning more about his or her own body, then this is definitely a book worth considering as a resource.
Activities to learn more about cells:
The human body is made up of building blocks called cells. Different organs are composed of different types of cells, such as muscle cells or nerve cells. Within the cells are components called organelles. Some organelles are the nucleus and the mitochondria.
Cells from the inside of your cheek are easy to obtain, and mounting them on a slide gives you practice with common laboratory techniques.
If you are going to actually look at something as small as a living cell, you will need access to a microscope. If you are not familiar with microscopes, the type you will need is called a compound microscope, preferably with about 400x capability. You will also need glass slides, slide covers, and stains, which are dyes that help darken structures so that you can see them. Two common stains are iodine and methylene blue (available at fish supply stores). Always follow all safety precautions listed in the instructions of these stains and wear old clothes.
Once you have your microscope plugged in and set up, place a few drops of water on the slide. If you are using methylene blue, it is possible to use a few drops of the stain directly on the slide without adding water first. With your mouth open, gently scrape some cells from the inside of your cheek with a toothpick or cotton swab. Swish the cells you collected into the liquid on the slide, and immediately throw the toothpick or cotton swab away.
Now position the slide cover as directed in the video, at the side of the liquid and slowly lower it. The idea is to avoid trapping air bubbles in the liquid, which interfere with viewing. If you are using iodine, place one drop of the stain to the side of the cover slip, so that it can diffuse into the water, as shown in the video.
Put the slide onto the stage of the microscope and then view at a low power. Once you have located the cells, move to a higher power to see more details.
Cheek cells are epithelial cells. You should see a cell with a nucleus that looks something like this:
Photograph from Wikimedia. (I believe the white objects outside the cell are air bubbles.) The lighter oval in the center is the nucleus. The cell is surrounded by the cell membrane and is full of cytoplasm.
Hope you have fun and let me know if you have any questions.
Inside the Human Body by Dr. Aron M. Bruhn, M.D., with illustrations by Joel Ito and Kathleen Kemly.
Inside Dinosaurs by Andra Serlin Abramson, Jason Broughham, and Carl Mehling.
Disclosures: Book was provided for review purposes. Also, I am an affiliate for Amazon. If you click through the linked titles or ads and make a purchase, I will receive a small commission at no extra charge to you. Proceeds will be used to maintain this self-hosted blog.