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."

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

How to Make a Working Model of Your Lungs

To make a working model of your lungs, you need an empty 2-liter bottle, a large balloon and a plastic storage bag or two large balloons and some tape.

• Cut a plastic bottle across the middle to remove the bottom. We used a 2-liter, but any size will do. 
  
• Cut the narrow part off of a second balloon or cut the zipper off a plastic storage bag and stretch it over the bottom of the bottle. The balloon works better for smaller bottles and the storage bag works better if you are using a 2-liter bottle. If you are using a balloon, it should fit over the opening pretty tightly. If you are using the storage bag, it should fully surround the bottom of the bottle but has plenty of slack in it. Tape to secure it to the bottle. Make sure there is a good seal. If you are using the storage bag, push the bag's slack into the bottle.
  

• Blow up a balloon and let the air out a few times to stretch the balloon a bit. Place a balloon in the neck of the bottle, and stretch the opening of the balloon over the opening of the bottle, putting the balloon upside-down in the top opening of the bottle.
  
• The balloon at the bottom or the plastic bag represents your diaphragm. The balloon inside represents your lungs.
  
• When you breathe in, the diaphragm contracts. To simulate this, pull the diaphragm bag/balloon down. This lowers the air pressure in the chest cavity, because there's more room, and air fills the lungs.
  
• When you exhale, the diaphragm relaxes. To simulate this, release the bag/balloon, and push the slack up. The air pressure in the chest cavity increases and air flows out of the lungs.

Sources and Resources:

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

How to Make an Edible Model of the Respiratory System

To make an edible model of the Respiratory System, you will need:

• Laffy Taffy or similar malleable candy
• Lifesavers Gummies
• Licorice (red), such as Twizzlers or Red Vine
• Licorice Laces, (optional)
• a batch of Rice Krispy Treats (recipe below)
• red food dye (optional)
• parchment paper on a flat surface

First, make your trachea with the rings of cartilage with the licorice and about 8 Gummy Lifesavers. We used filled licorice, which is quite thick, so we only used one strand of it. If you use regular licorice, I would recommend putting two pieces of licorice together and threading them through the Gummy Lifesavers. This will make it a bit easier when you make the bronchi branch off to the two lungs. Leave space at both the top and bottom, so that you have a inch or two of the licorice sticking out at the top and several inches at the bottom.

Lay your trachea model on the parchment paper and take the top end of the trachea and mold a larynx out of Laffy Taffy and attach it to the licorice at the top of the model. It should cover the licorice that sticking out of the top of the model.

source

Using the trachea as a point of reference, sketch out the size of the lungs on the parchment paper. You can look at the diagram to get a rough lung shape. They will need to be about 8 inches tall and about 4 inches wide to match the scale of the rest of the model. You can mold the lungs freehand, without drawing it first on the parchment paper, but my students found it easier to sketch out the area in advance to give them an idea of the the relative size of the lungs to the trachea before adding the Rice Krispy Treats.

Next, make a batch of Rice Krispy Treats. I know you probably already know how to make these, but I have included the recipe, in case you need it.

Rice Krispy Treats

(source)

3 tablespoons butter or margarine
1 package (10 oz., about 40) Marshmallows OR 4 cups Miniature Marshmallows
6 cups Rice Krispies cereal or the like 

In large saucepan melt butter over low heat. Add marshmallows and stir until completely melted. Remove from heat. Add cereal. Stir until well coated. 

For this project, we used 8 oz. strawberry marshmallows and 2 oz. of plain marshmallows, which gave the lungs a nice pink-peach color. If you don't want to use the pink marshmallows, you can add a few drops of red food coloring or just leave it tan. (Note: If you use the dye, your hands may turn red as  you work with the treats.)

While your Rice Krispy Treats are still warm and malleable, put in in the areas you sketched for your lungs, molding it into the shape of the two lungs. With the leftover treats, mold little lumpy balls to represent the alveoli. 

Cut the bottom end of the licorice in half and arrange them on the lungs so that they look like they are branching off the bronchi. These represent the bronchioles. You can cut the Licorice into quarters to make even smaller bronchioles, or you can use Licorice Laces to make the bronchioles branch off. That was my original plan, but we couldn't find any Licorice Laces at the store.

You can now attach the alveoli balls you made earlier to the ends of the bronchioles, and your model is complete!

Air travels from the mouth or nose into the trachea, passes through the trachea and into the bronchus. These two primary tubes branch into smaller and smaller bronchial tubes. At the end of the smallest bronchial tubes, called bronchioles are sacs called alveoli. 

The alveoli are covered with capillaries. The deoxygenated blood has come into the lung through the arteries, flows through these capillaries, getting red of carbon dioxide and accepting oxygen from the air that has been brought into the alveoli by the bronchioles. The carbon dioxide travels back out of the alveoli, through the bronchioles, into the bronchial tube system, and out the trachea each time one exhales.

• Have your student tell you the parts of the respiratory system, using the model as a visual. 
• Have your student tell you the process the respiratory system goes through, using the appropriate terms.
• Have your student take a picture of the model or make a sketch of it and include it in his science journal. You can have him label the model with sticky notes before he takes the picture, or your student can label it after he includes it in his science journal.
• Since everything is edible, when you are finished with the study, you can enjoy a snack!

Resources:

• Exploring Creation with General Studies, Wile
• Exploring Creation with Human Anatomy and Physiology, Fulbright and Ryan

The Human Digestive System (Grades 5-8)

We talked this week about what happens to food as it passes through each part of the digestive system. We had already reviewed our study of the digestive system and how food gets ground into small bits and mixes with saliva in the mouth and becomes a soft lump called bolus, 

The Digestive System

The muscles in the pharynx contract, squeezing the food so that it moves into the esophagus. The muscles of the esophagus contract and relax to bush the bolus along and into the stomach.

James' (age 14) science notebook page

Stomach Acid and Antacids

In the stomach, the bolus is mixed with gastric juices, which is a mixture of liquids, but one of the most important of these is hydrocloric acid. I wanted to show the boys how antacids work. In order to do this, we made up some red cabbage indicator like we have used before to experiment with acids and bases. Once it was cool, we poured it into a clear mason jar. 

We put 1 teaspoon of toilet bowl cleaner in a glass measuring cup. Not unexpectedly, the solution turns pink/red, indicating that the solution is acidic.

Then we added an antacid tablet. The tablet began bubbling and fizzing as it dissolves. Because the antacid is made up of calcium carbonate and magnesium hydroxide, both bases, it turns purple. It could also have turned blue.

All of the acid has been neutralized. Our stomach holds a lot more acid than this glass held, so if you ingest an antacid tablet because you have extra acid in your stomach, the antacid should neutralize just the extra acid, leaving plenty behind to digest food.

You can then add another teaspoon of toilet bowl cleaner, which turns the solution back to red/blue, because the solution is now acidic again. This can be done back and forth repeatedly with the same results.

Smooth muscles in the stomach relax and contract, churning the bolus with the gastric juice until it is turned into a liquid mush called chyme. Chyme passes into the small intestine.

source

The Pancreas and The Effect of Sodium Bicarbonate on Stomach Acid

The pancreas makes several digestive juices which are squirted into the small intestine as the chyme passes through the pyloric sphincter. It also produces a base called sodium bicarbonate. 

To demonstrate this, as before, we mixed together toilet bowl cleaner and red cabbage indicator, turning the indicator a red/pink. This represents our chyme as it enters the small intestine.

Next we scooped some baking soda out and added it to the solution in the glass and very quickly the solution turned purple/blue.

One of the products of this neutralization is carbon dioxide, which bubbles up in the glass, and which, if we get too much of it in our system, comes out of us as a burp. Essentially the same thing happens in your small intestine when the chyme, which contains hydrocloric acid, mixes with the sodium bicarbonate from the pancreas.

After that, the digested food continues through the intestine and, along the way, the blood absorbs the digested food so that it can used in different parts of the body. That is why the small intestine is so long. By the time the chyme has passed through the entire small intestine and moves into the large intestine, it is mostly composed of indigestible material. The large intestine's job is to make it so that it easily passes the waste out of the body. In the large intestine are bacteria which digest some of the chyme, consolidating the waste. Vitamin K, folic acid and biotin are also produced by bacteria which live in both the large and small intestine.

Any waste products that make it to this point are now called feces and are expelled out of the body through the anus via the rectum.

Sources and Resources:

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