Making No Bones About It! A Lesson on Skeletal Evidence, part I: Determining Age and Sex Through Bones

Have you ever wondered how archaeologist can learn so much from studying skeletons? 

Forensic Archaeology

Determining Age with Bones

Most of the bones in humans develop from cartilage that resemble the bones they will become. As people grow, their bones get longer and thicker and the cartilage is replaced by bone. If cartilage can be seen at the ends of bones, there will be no further growth and if no cartilage is present, the person has reached full maturity.

All during life, minerals are deposited and removed from the bone. During childhood and adolescence, the deposit of mineral occurs faster than the mineral loss, and the bones grow. The average female grows until 18 years of age and males continue to grow to 20 or 21 years of age. Between the years of about 18 to 35, there is a balance of mineral deposit and loss, so bones stay a constant size. After age 35, bone loss exceed bone gain. 

In adults, the ends of the rib bones gradually change shape over the years. The sternal ends are rounded in young adults and become more cup-shaped and jagged with increasing age.

The skulls of adolescents and children are quite different than those of adults. At birth the bones of the head are not fused together as they are in adults. Instead they are separated by membranous areas called fontanelles or soft spots. These allow some movement between bones so that the skull can be compressed as it pass through the birth canal. As a child grows, the fontanelles allow the brain to also grow as the bones slowly grow together and eventually fuse in adulthood.

In youth the pelvic girdle consists of three bones: ilium, ischium and pubis, which eventually fuse to for the pelvic girdle. This pelvic girdle serves as an area of attachment for the bones and muscles of the legs.

Male or Female Bones?

Females have wider pelvises than males to make childbirth possible, so the arch is wide and the bones are lighter and smoother. The female sacrum (large, triangular bone at the base of the spine) is wider and shorter than the male's. In a female, the coccyx (or tail bone) is more movable than in a male.

 You can also tell whether a skeleton is male or female by looking at the skull. The female skull is rounder and smaller than the male's. The female forehead is longer vertically and the jaw is smaller. 

In males, expansion of the ribcage is caused by the effects of testosterone during puberty. Thus, males generally have broad shoulders and expanded chests, allowing them to inhale more air to supply their muscles with oxygen. The sternum or breastbone is a long flat bone located in the center of the chest. Male sternums are noticeably larger than female.

I gave the boys pictures of bones and had them determine whether they were adult or child bones and whether they were male or female. Can you tell which they are from looking at the pictures?

Source: Crime Scene Investigations, Real-Life Science Labs For Grades 6-12 by Pam Walker and Elaine Wood

How to Make an Edible Model of Skin (Elementary to Middle School Hands-On Project)

For this project, you will need:
Jello
Mini Marshmallows
Fruit Roll Up
Pull Apart Twizzlers
Handmade Labels, if desired

1. Dermis For the dermis, you will need to make a packet of Jello, following the directions on the package. We made cherry, but any flavor will do. Pour it into a small square dish.

2. Hypodermis Before you put the Jello in the refrigerator, fill the top of the Jello with mini marshmallows. Now, put it in the refrigerator to set properly.

This is what your Jello with marshmallows should look like when you put it in the refrigerator.

3. Epidermis with Pores When the jello is set, run the knife around to “unstick” it from the sides and plop it out onto a big enough plate.  Ours did not come out smoothly, but that is okay because it made it look more real that way. Now you can add the epidermis.

Unroll a Fruit Roll Up and poke holes in it with a skewer or toothpick. 

4. Hair Some of these holes will be pores and some will be for the hair.

Pull licorice apart and cut them into desired lengths for the hairs and stick ’em in your pre-poked holes.

You may need to enlarge some of the holes in order for the licorice to fit.

5. Labels Now you can label the different parts using handmade labels, either typed on the computer, as we did, or handwritten.

Human Biology: The Circulatory System (grades 5-8)

The Human Circulatory System

The circulatory system includes the heart, the blood and the blood vessels. The circulatory system carries blood to the cells of the body. It also carries carbon dioxide and other wastes away from all parts of the body. The circulatory system also helps carry substances throughout the body that protect the body from disease. The heart is the pump that sends the blood coursing rapidly through the network of blood vessels.

Model of the Components of  Blood

Blood is made up of plasma, red blood cells, white blood cells, and platelets. 

Blood Typing

Blood typing is an interesting topic to learn about, but can get a little confusing sometimes, so we completed a little blood typing activity that clarified things.

The Heart and Blood Flow

James' (age 14) notebook page

The circulatory system delivers oxygen to all parts of the body. It takes two different routes. One route, the systemic circulation, carries oxygen-rich blood through arteries to all parts of the body. The same system returns the blood, now containing carbon dioxide, through veins to the heart for more oxygen. The other route, the pulmonary circulation, carries blood from the right side of the heart, travels only to the lungs to pick up oxygen, then returns the blood to the left side of the heart where it is sent on to the systemic circulation.

Quentin's (age 10) notebook page

Veins, Arteries and Capillaries

We read about the difference between arteries and veins. Arteries are blood vessels that carry blood away from the heart and veins are blood vessels that carry blood back to the heart. We also learned that capillaries are tiny, thin-walled vessels that allow the exchange of gases and nutrients between the blood and cells. We then played the Circulation Game. As it says on the website in which I downloaded the free game, "this game is about some of the important jobs your blood does as it circulates throughout your body. In this game, you will help the blood pick up oxygen from the lungs, and food from the intestines and deliver them to the individual cells of the body. The blood will also pick up carbon dioxide and other wastes produced by the cells and get rid of them by taking them to the lungs or the kidneys.

The object of the game is to get oxygen and food to the cells, then get rid of the waste products produced by the cells. The cells will use the oxygen to burn the sugar and release energy. In this burning process, which is surprisingly similar to how a car engine works, carbon dioxide is produced as a waste product. The proteins are the ingredients your cells need in order to make repairs and build new cells. The cards marked "waste" represent the waste products made by the cells as they use up the proteins."

Blood Typing Activity for Elementary and Middle School Aged Kids

Blood typing is an interesting topic to learn about, but can get a little confusing sometimes. 

Blood typing illustration from Exploring Creation with Human Anatomy and Physiology

First we read about blood typing from our text. Exploring Creation with Human Anatomy and Physiology does a nice job of explaining blood type antigens or markers as like flags on a ship, which declare for all to see where the ship came from. If an antigen that isn't yours is found on a red blood cell, your body will destroy whatever cells are "flying the foreign flag."

After getting the background information, we completed this easy demonstration that clearly shows which blood types are compatible and to whom. For this demonstration, you will need four clear plastic cups, some way to mark the cups (we used a Sharpie, but you could also use some Post-Its or the like), some red and blue food coloring and a way of being able to mix the two. I had an eyedropper and a glass slide on hand, but those are not necessary. You could just use another empty clear plastic cup to mix in, rinsing between additions. 

First mark your cups, "O", "A", "B" and "AB". Next put a few drops of red food coloring in the cup marked "A", a few drops of blue food coloring in the cup marked "B" and a few drops of each blue and red in the cup marked "AB". Do not put any food coloring in the cup marked "O". Fill cups about half-way with water.

Next we got a little of the receiver's blood type in a dropper and put a few drops on the slide. We then rinsed out the dropper with a little clear water. Lastly, we got a few drops of the donor's blood type in the dropper and added it to the blood type on the slide.

If the "blood" (colored water) on the slide does not change color when you add the "blood" (colored water) from the donor then that blood type receiver can receive the blood type from that donor. For example, if I put a little purple water from the blood type "AB" cup on the slide as the receiver and then add a little of the red water from the blood type "A" cup on the slide as the donor, the water stays purple. That means that "AB" blood can accept type "A" blood.

We filled out a chart as we went along, recording the compatibility results. 

This demonstration clearly shows that...

O can receive only O blood.

A can receive both A and O blood

B can receive both B and O blood

AB can receive all blood types and is the universal receiver.

O can donate to all blood types and is the universal donor as it can give to any blood type.

Older kids can reason it out once they see the colored cups of water, but may actually want to do the mixing anyway. Younger students may need to do the entire process.

Note: this experiment does not deal with positive and negative blood types but is meant only as an introduction to blood types.

Sources and Resources:

• Blood Type Science Experiment at Learnin' & Earnin' Adventures in Homeschooling
• Blood Types Activities for Kids at Adventures in Mommydom
• Blood Type Activity at Highhill Homeschool

Model of the Components of Blood

The Components of Blood

Model of the Components of Blood

To make a model of the components of blood, you will need 1 cup of white corn syrup, some yellow food coloring, some red candies such as red hots (we used Cherry Sour Balls), a white jelly bean and 1 teaspoon of round cake sprinkles.

 Plasma is the liquid that makes up a little over half of the blood. It is over 90% water. The other 10% is proteins, dissolved gases, salts, vitamins, nutrients, hormones and waste products that come from protein breakdown. Pour a cup of white corn syrup into a bowl to represent the plasma.

Plasma is actually straw-colored so stir a bit of yellow food coloring into the white corn syrup.

Red blood cells are so plentiful, they color the blood. Their job is to deliver oxygen and pick up carbon dioxide as they go through the bloodstream. The red blood cells make a protein called hemoglobin which contains iron atoms. Oxygen is attracted to the iron atoms, and gets pulled along with the hemoglobin through the bloodstream.

For every 700 red blood cells, there will be one white blood cell. We represented this with one white jelly bean. White blood cells are generally larger than the red blood cells. The white blood cells fight infections and clean up the debris and dying cells.

The last component of blood is the platelets, which are fragments of cells. These can be represented by about 1 teaspoon of sprinkles. Platelets aid in the process of coagulation, a chemical mechanism which clots blood when a blood vessel is broken, which keeps us from bleeding to death when we are cut.

from Bones and the Skeletal System

These fragments, if not used to form a clot, circulate in the bloodstream for about ten days before they are removed by special cells called phagocytes, which carry the fragments to the liver in order for the iron to be returned to bones via the liver.

Red blood cells are short-lived and so are being continually being replaced by the bone marrow.

Science Notebook Page, (left) James', age 14 (right) Quentin's, age 11

When your students are finished making the model, they can make a sketch in their science journals and label the components of blood.

Sources and Resources:

• Exploring Creation with General Science, Jay Wile
• Exploring Creation with Human Anatomy and Physiology, Jeannie Fulbright and Brooke Ryan

Human Biology: The Respiratory System (grades 5-8)

The respiratory system has the job of providing the body with the oxygen it needs to function. 

Lungs and Blood Oxygenation

Your lungs hold air so that your blood can be oxygenated. This demonstration helps determine about how much air your lungs hold.

The Respiratory System

The Respiratory system includes the trachea, larynx, lungs, bronchial tubes and diaphragm.

Make a Edible Model of the Respiratory System

Draw a diagram of the respiratory system and label arrows to show what happens when we breathe.

Make a working model of the lungs

Vocal Cords

A good example of how your vocal chords work is to make a simple musical instrument by putting rubber bands over a cardboard box with an opening. Similarly to how this musical instrument works, your vocal chords are stretched tight and air passes over them, making them vibrate and therefore a humming sound.

Other Circulation and Respiration Systems

There are many types of circulatory and respiratory systems in nature. Sponges, for example, we have learned, have mobile cells that travel throughout their bodies, exchanging oxygen for cell waste, as well as other jobs as needed.

Fish extract oxygen from water, using gills instead of lungs.

Even plants have a circulatory system, of sorts. Tubes called xylem run throughout the plant, transporting water up from the roots to the rest of the plant, and other tubes, called phloem, carry food from the leaves down to the rest of the plant.

The Capacity of Your Lungs

This is a really fun demonstration to show the amazing amount of air your lungs can hold.

For this simple demonstration, you will need some flexible aquarium tubing (we used about 3' of it), a plastic one gallon jug with lid, a sink with a plug and a measuring cup.

Fill the sink about half-way with water and plug it so that it stays in the sink. Fill the jug completely with water, and tap it to get the air bubbles out.

Put the lid on the jug and invert the jug so that the opening of the jug is under the water at all times.

Take the lid off the jug, and keeping the jug completely inverted and the opening of the jug under the water at all times, insert one end of the tubing so that it goes into the jug through the opening. The tube should just be inside the jug, not too high into the jug.

Take a deep breath and blow into the other end of the tubing in one continuous breath (without pausing to breathe again). Try to empty your lungs as much as you can.

When you have finished blowing all you can, put the lid back on the jug while it is still under the water.

Now you can remove the jug from the water and turn it upright.

Take the cap off and pour what water is left into a measuring cup. Keeping track of the amount of water you have measured, keep pouring out and measuring the water until the jug is empty.

There are 16 cups in a gallon. Subtract the number of cups of water that were in the jug from 16, and that will roughly tell you how many cups of air your lungs can hold. 

When James blew into the jug, there were about 5 cups of water remaining, which meant that his lungs can hold approximately 11 cups of air. When Quentin blew into the jug, there were a little more than 8 cups of water remaining, which meant that his lungs can hold a little less than 8 cups of air.

How many cups of air can your lungs hold?

Sources and Resources:

• Exploring Creation with General Science, Jay Wile