The bones in the human body make up the Skeletal System. Bones serve several purposes. In addition to giving the body structure, they protect important body parts. For example, the skull protects the brain. The tissue inside bones, the bone marrow, makes blood cells and stores fat. Also, bones house nerves and work with the muscles to help us move.
We likely all know what a bone looks like from the outside. But what do they look like on the inside? For this lab, I thought something new and fun would be to dissect a bone.
From a local butcher, I obtained a bovine leg cut down the center to see the bone interior lengthwise. With a class of students, I would also suggest about 15 discs or cross-sections (about 1″ thick) for students to dissect and observe under the dissecting microscope. I, sadly, neglected to do this.
I had the students identify the following structures:
Femur shaft, head, and trochanter
Red and yellow marrow
We were also able to locate and identify skeletal muscle, tendon, and blood vessels.
Anatomy of Bones
Bones are complex structures and they differ from species to species and by location in the body. The differences are mostly in the function of the bone, but there are some things that most bones have in common.
We often think that a bone is a solid structure. However, some parts of the bone are hard while other parts are very soft. Parts will look very different when examined closely – with a magnifying lens or microscope.
The bones in your legs, and in the legs of a cow, are made of both compact bone and spongy bone. The exteriors are walls of calcium and other minerals. This compact bone runs the length of the bone and is designed to bear loads and protect organs. The larger the animal, the thicker the compact bone. There are small channels running through the calcium to carry blood and nerves to and from the marrow, but in general, the compact bone is not very porous.
The marrows of bones are complex yet can be broadly divided in two categories, red spongy marrow and yellow marrow. At the ends of bones, you find highly porous marrow, also called red spongy marrow. Spongy marrow serves as a home to stem cells that produce blood cells. Red spongy marrow is the hard honeycomb marrow that you have likely seen in some cuts of steak because the bones are often cut open by a bandsaw. Yellow marrow is the type you find in the center of femurs and other leg bones. It is mostly fat but is edible.
The entire bone is covered by a thin covering called the periosteum, which contains blood vessels, nerves, and bone-forming cells.
Each end of the bone is covered with a cap made of cartilage. The cartilage covers the part of the bone where there is a joint or place where two or more bones come together. The cartilage is white in color, is slippery and smooth, and enables bones to move without rubbing together.
Bring it Home
The “activity menu” I described last week for homework seemed to have worked really well. While those who completed only the one required activity made the same choice, there were a few who did additional (bonus) activities. They were all able to share what they learned and as a result the group was able to make connections as well as review the material. We will most assuredly be using this approach again.
Menu Choices (choose at least one):
Memorize the 29 major bones in the body using the handout as a guide (available to newsletter subscribers)
Research the myth of the Achilles tendon. How did the tendon get its name?
Research Andreas Vesalius. Why is he called the ‘father of anatomy’?
Some of the main types of joints in the body are ball-and-socket, saddle, hinge, pivot, and gliding. On a chart, describe each joint and list an example of each. Make a display of real-life objects that resemble these joints.
Obtain some X-rays of broken bones from a hospital or clinic. You may also find some X-ray images online. Identify the bones in the X-ray. How do doctors treat broken bones?
Try the Bendable Bones activity in the handout (available to newsletter subscribers).
Create a board game using facts about bones and muscles.
Write and present a skit that teaches about good care of your bones and muscles.
Research and present an oral report on Scoliosis.
Next week, we will explore the Muscular System in depth. My kids loved creating a fun skit to demonstrate what they learned. You won’t want to miss it.
This week, I introduced the Nervous System which consists of the brain, spinal cord, sensory organs (skin, eyes, ears, nose, and tongue), and all of the nerves that connect these organs with the rest of the body. Together, these organs are responsible for the control of the body and communication among its parts.
The brain and spinal cord form the control center known as the central nervous system (CNS), where information is evaluated and decisions made. The sensory nerves and sense organs of the peripheral nervous system (PNS) monitor conditions inside and outside of the body and send this information to the CNS. Efferent nerves in the PNS carry signals from the control center to the muscles, glands, and organs to regulate their functions.
As the nervous system includes all our sensory organs, our focus activity was dissection of a cow eye. A cow eye is very similar to the eye of a human. By dissecting and examining the anatomy of a preserved cow eye, we can learn how our own eye forms images of the world around us and sends these images to our brain.
Cow Eye Dissection
Distributed around the table were dissection tools and one cow eye per pair of students. I then walked them through the steps of the dissection process elaborating upon the function of each structure as we went along.
We first observed the external parts that were visible: the cornea, slera, optic nerve, as well as the fat and muscle tissue surrounding the eye.
In the cow eye, we observed four muscles that allow for the eye to move up and down and side to side. As we learned, humans have these same muscles. Humans also have ocular muscles, which allow for involuntary and voluntary eye movements that contribute to our overall vision.
We then began to look at the internal structures of the eye: vitreous humor, lens, iris, iris, ciliary body or suspensory ligaments, and tapetum.
One of the structures the kids found the most interesting was the lens. As the lens ages, it becomes more rigid and the ability to accommodate reduces. This is why as people get older; they wear bifocals or reading glasses. This condition is called presbyopia and results in difficulty seeing objects that are near.
We also observed the retina whichcomposes the inner layer of the wall of the eye. The retina contains the photoreceptors: rods for black- and-white vision and cones for color vision. The neuron fibers coalesce at the optic disc, where they form the optic nerve exiting the posterior side (or back side) of the eye and carries impulses to the brain. The optic disc is known as the blind spot since it has no receptors.
Bring it Home
At the conclusion of our lab, I gave each of the students a handout that expanded upon our discussion and included questions for review. It included a diagram of an eye to label, a couple of activities to discover one’s blind spot, and a list of vocabulary words. Subscribers to my newsletter will receive these in the November newsletter that will be sent next week.
I also provided a “menu” of activity choices for homework. Students are required to choose one but may do as many as they feel inclined.
Design an experiment to test the fact that different parts of the tongue are able to sense only one of four basic tastes: sweet, salty, sour, or bitter.
Tasting food involves more than just the taste receptors on your tongue. Smell, texture, temperature ,and look of food all contribute to how you perceive its taste. The olfactory nerve in either side of your nose sends smell information as impulses to your brain. Design an experiment to test how ones sense of smell affects their ability to taste.
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:
sweat glands / pore
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!
As many of you know, I teach a science class for local area homeschool students that I have come to call STEM Club. Our focus this cycle is human anatomy or human body systems.
Each week, I will be sharing with you the hands-on activities and inquiry based labs that I use with my students. If you follow along with me and do the suggested extension activities, the material covered will be equivalent to a full semester course.
Getting Started – Printables
The biological levels of organization of living things arranged from the simplest to most complex are: organelle, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystem, and biosphere.
To review this with my STEM Club students, I created a levels of organization printable chart and asked that they complete it as homework in advance of our first class.
The purpose of this unit is to understand that there are different systems within the body and that they work independently and together to form a functioning human body. At the middle school level, students should begin to view the body as a system, in which parts do things for other parts and for the organism as a whole.
To assess the students’ prior knowledge, I distributed a black outline master of the human body and asked them to draw and label the parts of the body that they knew.
I also created an accordion style mini-book of the body systems that we will use throughout the unit. Students were asked to print it and secure it in their notebooks for easy reference and note taking throughout the course.
Lastly, they were asked to complete the vocabulary worksheet.
Integumentary System – the organ system that protects the body from various kinds of damage, such as loss of water or abrasion from outside. Major organs include skin (epidermis, dermis, hypodermis), hair, nails, and exocrine glands.
Nervous System – consists of the brain, spinal cord, sensory organs, and all of the nerves that connect these organs with the rest of the body. Together, these organs are responsible for the control of the body and communication among its parts.
Endrocrine System – includes all of the glands of the body and the hormones produced by those glands. The glands are controlled directly by stimulation from the nervous system as well as by chemical receptors in the blood and hormones produced by other glands.
The endocrine system works alongside of the nervous system to form the control systems of the body. The nervous system provides a very fast and narrowly targeted system to turn on specific glands and muscles throughout the body. The endocrine system, on the other hand, is much slower acting, but has very widespread, long lasting, and powerful effects.
Head to Toe Science by Jim Wiese is a collection of demonstrations that illustrate scientific principles about the human body. The projects are geared to 9-12 year olds and arranged by system (nervous, digestive, respiratory, circulatory, muscular, skeletal, reproductive, and integumentary).
Each project includes an introduction, a list of materials, procedural guidelines, and an explanation of the science involved. It is a great resources for hands-on activities and demonstrations. The instructions are easy to follow and include fun facts to keep kids interested.
It is definitely worth buying, even though the activities are not inquiry based, as it provides background information and vocabulary. Some of the activities in the book are too simple for even junior high but most are perfect for middle school age learners.
Skeletal System – includes all of the bones and joints in the body. Each bone is a complex living organ that is made up of many cells, protein fibers, and minerals. The skeleton acts as a scaffold by providing support and protection for the soft tissues that make up the rest of the body.
Muscular System – responsible for the movement of the human body. Attached to the bones of the skeletal system are about 700 named muscles that make up roughly half of a person’s body weight. Each of these muscles is a discrete organ constructed of skeletal muscle tissue, blood vessels, tendons, and nerves.
Digestive System– a group of organs working together to convert food into energy and basic nutrients to feed the entire body. Food passes through a long tube inside the body known as the alimentary canal or the gastrointestinal tract (GI tract). The alimentary canal is made up of the oral cavity, pharynx, esophagus, stomach, small intestines, and large intestines.
I highly recommend Human Anatomy Coloring Book by Margaret Matt (geared for ages 13-16). I know what you are thinking. “A color book? Really?! ”
Yes, really. Each detailed illustration in the Human Anatomy Coloring Book is accompanied by concise, informative text and suggestions for coloring. Numerous views, cross-sections, and other diagrams are included for each of the body’s organs and major systems.
Combine inquiry based activities and demonstrations that illustrate scientific principle, the memorization of vocabulary, and daily practice tracing the organ systems with the aide of this book and will discover your students will not only understand how their body works but will be able to illustrate the organs as they share what they know.
For younger students (ages 3 to 11), I recommend the alternative, My First Human Body Book by Donald Silver and Patricia Wynne. It includes 28 fun and instructive, ready-to-color illustrations that explore the human body systems. The illustrations are detailed and yet simple enough to not be overwhelming.
Excretory / Urinary System – consists of the kidneys, ureters, urinary bladder, and urethra. The kidneys filter the blood to remove wastes and produce urine. The ureters, urinary bladder, and urethra together form the urinary tract, which acts as a plumbing system to drain urine from the kidneys, store it, and then release it during urination. Besides filtering and eliminating wastes from the body, the urinary system also maintains the homeostasis of water, ions, pH, blood pressure, calcium, and red blood cells.
Respiratory System – provides oxygen to the body’s cells while removing carbon dioxide, a waste product that can be lethal if allowed to accumulate. There are 3 major parts of the respiratory system: the airway, the lungs, and the muscles of respiration. The airway, which includes the nose, mouth, pharynx, larynx, trachea, bronchi, and bronchioles, carries air between the lungs and the body’s exterior.
Cardiovascular / Circulatory System – consists of the heart, blood vessels, and the approximately 5 liters of blood that the blood vessels transport. Responsible for transporting oxygen, nutrients, hormones, and cellular waste products throughout the body, the cardiovascular system is powered by the body’s hardest-working organ — the heart.
Blood and Gutsby Linda Allison is written for the middle school aged student and is organized well. The author devotes a chapter to each of the following topics: skin, bones, teeth, muscles, heart, lungs, cells, digestion, kidneys, eyes, ears, balance, brain and nervous system, and reproduction. She provides a basic but informative narrative for each as well as illustrations.
Numerous hands-on activities and demonstrations are described for students to try. Most are relatively simple but some are difficult and require adult supervision; others require materials that may be difficult to find.
The book uses cartoon illustrations (as shown on the cover). I would suggest supplementing with models, more accurate drawings (the Dover Publication mentioned above, for example), and photos.
Lymphatic / Immune System – our body’s defense system against infectious pathogenic viruses, bacteria, and fungi as well as parasitic animals and protists. The immune system works to keep these harmful agents out of the body and attacks those that manage to enter. The lymphatic system is a system of capillaries, vessels, nodes and other organs that transport a fluid called lymph from the tissues as it returns to the bloodstream. The lymphatic tissue of these organs filters and cleans the lymph of any debris, abnormal cells, or pathogens. The lymphatic system also transports fatty acids from the intestines to the circulatory system.
Reproductive System – The female reproductive system includes the ovaries, fallopian tubes, uterus, vagina, vulva, mammary glands and breasts. These organs are involved in the production and transportation of gametes and the production of sex hormones. The female reproductive system also facilitates the fertilization of ova by sperm and supports the development of offspring during pregnancy and infancy.
The male reproductive system includes the scrotum, testes, spermatic ducts, sex glands, and penis. These organs work together to produce sperm, the male gamete, and the other components of semen. These organs also work together to deliver semen out of the body and into the vagina where it can fertilize egg cells to produce offspring.
Next week we will explorethe integumentary systemin depth. I will share a few demonstration activities as well as an inquiry science activity that tests our sense of touch, or somatosensation. You won’t want to miss it!