Biology Models: The Great Blood Vessel Challenge–Hands-On Activity for Your Students

Materials needed for a reusable class set:
1 standard garden hose
1 soaker hose
1 discharge hose (find in pool supply stores)

This is an easy way to have students carefully consider the characteristics of blood vessels. To set it up, you will need three hoses (or lengths of hose) of three different types: a simple garden hose with fairly thick walls (red?), a soaker hose with mesh walls, and a discharge hose (blue?) such as is used to drain the water from swimming pools. The latter can be ordered from a pool supply company. It will flatten when not full of liquid.

Students use common hoses to model blood vessels

Directions:  Simply cut the hoses in lengths of 12 to 18 inches.  Each student or small group is then given one of each type of hose. They are asked to decide which best represents a capillary, vein, or artery. There is not one right answer, although some choices may seem more appropriate than others. Students must consider the properties of each type of blood vessel and make reasoned decisions regarding their choices, citing characteristics to back up their reasoning. It might be helpful to allow them to take the hoses to the sink and run water through them.

Background Information:

Arteries are thick-walled vessels that carry oxygenated blood on its journey away from the heart. (Exception: the pulmonary arteries also carry blood away from the heart, but it is deoxygenated blood on its way to the lungs where oxygen is added.) It is helpful to remember that arteries always carry blood away from the heart, Arteries Always Away. Arterial walls are composed of three tissue layers called the tunica interna, the innermost layer which includes the epithelial lining, tunica media in the middle, and tunica externa, the outer layer. The arterial walls contain more smooth muscle and elastic fibers than do the walls of the veins. This makes arterial walls thicker and more elastic, so they retain their circular shape in cross-section, even when emptied of blood on the commercially prepared slides your students may view. The walls are thicker than the walls of veins and more contractile. Blood pressure in the arteries is high and pulses as the heart beats. The greater elasticity of the walls allows them to spring back from pressure. Their greater contractility allows arteries to constrict or dilate to control blood flow to areas of the body. No valves are present.

Veins are vessels that carry deoxygenated blood on its return trip to the heart. (Exception: the pulmonary veins also carry blood back to the heart, but it is oxygenated blood returning to the heart from the lungs.) Veins are composed of three layers as are the arteries, but with less smooth muscle and elastic fibers. In a tissue sample such as those on commercially prepared slides, the emptied veins may collapse and flatten. Reduced connective tissue content in the venous walls allows the veins to lose their round shape readily when emptied. The blood in the veins is under lower pressure since it is farther removed from the pumping action of the heart. Since the blood pressure is lower and the journey through the veins is mostly against the pull of gravity, extra help comes in the form of valves present inside the veins. Contraction of skeletal muscles surrounding the veins also helps to push the blood back to the heart.

Capillaries are very thin-walled vessels with a very small diameter. Some are only 4 microns across. (Compare this to the diameter of the red blood cell: 8 microns!) They are the site of gas exchange and chemical exchange between the blood and the body’s cells. The capillary walls are only one cell thick, being composed simply of epithelium, and oxygen and carbon dioxide can pass through them readily. They make up for their small diameter by being extremely plentiful, existing in capillary beds in all tissues of the body except epithelial tissue.

Blood vessel illustration by National Cancer Institute, National Institutes of Health –, Public Domain,


Biology Models: Consider the Red Blood Cell

It was a pretty good lecture, as lectures go:  brief and to the point, with interesting subject matter– the red blood cell!  All other cells in the body depend on it to bring that life-giving substance, oxygen.  It’s tough and stream-lined to perform its function–zipping through the blood vessels with its payload, bumping into the vessel walls and other blood cells, stacking into rouleaux which reduce wear and tear.  Early on it loses its nucleus and organelles, including mitochondria, so it can transport oxygen with maximum efficiency, traveling by the bulk flow of the blood.  I described its width–8 microns–and the fact that it can fold to fit through capillaries that are only 4 microns in diameter.  A lovely little cell, admirable in every way!

And the next day the class remembered nothing!  I could almost believe we were viewing each other from alternate universes, with no sound and no meaning bridging the gap in between.  Over the summer I thought about it a lot, and finally I went shopping.  In a pet store I found a flexible rubber frisbee.  The fabric store yielded some stretchy red cotton knit and some batting to pad the edges.  Then I went home and sewed a red blood cell, a handsome bi-concave disc, flexible yet strong.

In time, I added to the one red blood cell: an ABO set plus a sickle cell.

In the new school year the day finally arrived when the lesson included blood cells.  This time I tossed the disc to a kid in the middle of the room, asking “What is this?”  They passed it around, looked at it, and came up with the answer.  “Why do you think so?”  “What characteristics do you notice?”  “How can this 8-micron-wide red blood cell fit through capillaries only 4 microns in diameter?”  “What could be the benefit of having no mitochondria?”  At this point I added five minutes worth of further information.  The next class meeting, the students could tell me a lot about red blood cells, without even checking their notes.  Over time that one red blood cell grew to a collection of four, with black and white buttons to represent blood type antigens, plus an appropriately shaped sickle cell.

My conclusion:  an object to hold in the hand, to observe, to bend, and even toss around the room, made quite a positive difference in kids’ receptiveness and retention!  Probably any teacher reading this has already reached this conclusion for her/himself, and I knew this too, even before the red blood cell epiphany.  However, after that I devised even more biology models, and I used them in a more determined and systematic way.  Using them in an introductory lecture, then having students explain key concepts using them, and finally, bringing them out for review prior to tests–this is a powerful strategy to enhance student understanding and recall.

So when and how could a teacher use manipulatives?

  1.   Introduce a topic:   Bring out your biology models to lead into a lecture.
    Question the students:  What do you observe?  What do you suppose it represents?  What is its function?  Comment on the surface area-to-volume ratio– is surface area increased by the way the object is shaped?  How would that affect its function?  How might it interact with what you studied before?
  2.  In your lecture:  Manipulate the biology model yourself as you discuss it.
  3.   Pose a mystery:  Hand out the model and have students examine it to find an answer.    Ex:  How does this red blood cell, 8 microns in diameter, pass through a capillary that’s only 4 microns wide?
  4.   Have students use the object to explain its function to the class.
  5.   For a powerful review:  Put your biology models out in stations with question cards for the students to use, answering  together as they move around the room.
  6. Comply with NGSS:  NGSS calls for use of models.  When there isn’t time for students to create their own, then bring out biology models you have made or purchased, and watch your students get engaged.


Six Cool Ideas to Help Teach, Learn, and Review

Are you seeking active learning strategies that will engage your students?  Do you want your students to have fun with life science?  Here are six great ideas, for teachers by teachers, for using our educational tools in teaching, learning, and review!

In Combination

Put several kits on the board at the same time and let the class figure out how they’re connected.  Different kit combinations that can be useful include:

  •  Macromolecules/Digestive and Respiratory/Enzymes (see the image below)
  •  Macromolecules/Enzymes/Protein Synthesis
  •  Cells/Cell Membrane/Photosynthesis
  •  Photosynthesis/Cellular Respiration
Pieces from several board kits are displayed at once to challenge the students. Change the enzyme name to lipase or amylase. Ask students to match the enzyme to its substrate and location.

Repeat to Remember

Leave a kit up for awhile so the kids can just handle the pieces and put them together over and over.  Handling and assembling the kits repeatedly can help students remember structures and understand processes in biology and life science.

Review/Use Stations to Engage Students

To review for a test, set up stations with our life science kits and have the kids work their way through the stations, assembling and explaining them to each other.  They’ll be more engaged in the review if it feels less like a lecture, and as they handle the pieces they will remember what they learned initially.  And you can also use our magnetic life science models as assessment tools in teaching life science and biology.

Emergent Properties Intro

The Levels of Organization Kit makes a particularly effective tool for student discovery and engagement.  Students will have some prior knowledge on this topic, and as they attempt to place the levels in order and match them to the pictures, those who are watching will be drawn in to help arrive at the correct sequence.  This makes a powerful introduction for a lecture on emergent properties and even for an overview of your course!

Not Enough Magnet-Receptive Board Space?

Improve your classroom setup with more board space!  Drop by a paint or hardware store and pick up magnetic paint.  This is water-based paint that is full of iron filings.  Two coats on a wall or cupboard doors will provide extra display space.  The paint can be given a top coat in a color of your choice.

The Coolest Idea of All!

Speak Easies kits save you time by helping to organize your lecture, by providing a quick review of your topic in the background information sheets (Board Kits), with suggestions for use, and with built-in activities in the Desk Kits.  Wouldn’t you like a little spare time?



Waterborne Disease/ Poop Chronicles, Part Two

Waterborne Disease/ Poop Chronicles, Part Two


stopepidemicscreenshotThe cholera epidemic in London in 1854 was raging on, and Queen Victoria had called Dr. John Snow and commanded him to stop the epidemic.  But this seemed impossible, since no one at the time understood the germ theory of disease or how diseases spread.

Some strange ideas about how to avoid disease were floating around, as seen in this somewhat exaggerated newspaper cartoon.  We can all imagine how scary it must have been to be surrounded by an epidemic and not know how to protect yourself.screenshotstayinghealthy

But Dr. Snow did something unprecedented—he went into the area of the city where the epidemic was in progress, the neighborhoods around Broad Street, and he interviewed the survivors of the disease as well as the families of the deceased, to gather information about how the victims had lived, looking for clues.  [The students can be supplied with this map of London at the time.  Discuss with them the symbols on the map, being certain to discuss the pumps that were in use.  The picture at the end of this article may be helpful, since not many students have ever used such a pump, but if you show it before the class tries to figure out how to stop the epidemic, it’s a tip-off.]


[At this point, the class can be supplied with information about the victims, in addition to the map, and asked to figure out how to stop the epidemic.  This activity is from Project Wet, a wonderful resource for many water-related lessons, and can be found at  When students have figured out how to stop the disease and have discussed the additional question at the Rivanna Stormwater site, continue with the Poop Chronicles lecture.]

After figuring out that the disease was spread through the contaminated well water in the Broad Street pump, Dr. Snow told the authorities how to stop the epidemic:  “Remove the pump handle.”  Eventually the suggestion was carried out and the epidemic stopped.  It was found that “Patient 0”, the source of the disease, lived in a tenement house close to the Broad Street pump, and effluent from the tenement’s privy was leaking into the ground water and contaminating it.

Subsequently the Queen called in Sir Edwin Chadwick, who made some recommendations to improve the health of the people living in London.  He designed a house, intended for a single family to live in, which removed their pump at the greatest possible distance from their privy and also supplied more room as well as air circulation and natural light.

screenshotlondonsewersAnd eventually this plan was submitted to the Queen.  What does it show?  Sewer lines!  Even  so, when the sewers were put in, they simply drained the sewage to the river.  Sewage treatment plants did not come about till later.



[A good extension of this activity would be to investigate some other waterborne diseases (for example, polio virus, giardia, Salmonella typhus),  along with a few other contagious diseases.  Students could be given pictures of the pathogens that cause the diseases and asked to investigate the symptoms, causes and cures, in addition to prevention.  The students could also be given a picture of the body showing different organs and asked to match the pathogens to the organs they infect.  And finally, they could sort the pathogens according to which taxonomic kingdom each belongs to.

To emphasize the environmental aspects of waterborne disease, you might show students the form below, which shows a data table for a number of tests that, taken together, comprise a water quality index.  Note that one of the tests checks for the presence of coliform bacteria, a family of bacteria always found in sewage.]screenshotWQI




Waterborne Disease/Poop Chronicles, Part One

Students are interested in disease, especially the diseases with a high yuck factor! Waterborne diseases fill the bill. It’s easy to engage kids with this, but it’s also a very sound idea because this encompasses lots of important topics: sanitation, hygiene, the digestive system, water treatment, microbiology, etc. You can even look at history and warfare from a perspective of disease. So here are some pictures and a mini-lecture to get started.  (I also mentioned one or two diseases that are not waterborne, just because their mode of transmission is interesting!)

In ancient history, before settlements were established, the world’s human population lived in small tribal groups that were nomadic. They hunted and gathered in one area till game ran low, then they moved on. And as they moved they left their wastes behind. A good idea, since human wastes can harbor disease!

But about 10,000 years ago people started planting seeds and domesticating livestock. This was a huge change that we call the first agricultural revolution, and it allowed humans to settle in one place.  In time farmers became successful enough that they had excess grain that could be stored, encouraging the presence of rodents, which in turn carried diseases such as smallpox that could then make the jump into humans.

poop chron screen shot ag with irrigationpoop chron screen shot mice

Isolated settlements sprang up, and they were usually located on a river or stream so people had plenty of water for drinking and for irrigation.  And rivers were also used as handy places to dispose of wastes.

Over time the settlements grew into teeming cities and wastes built up, harboring microbes that caused outbreaks of epidemics.  Merchants plied their trades, moving from marketplace to marketplace, bringing diseases with them.

As the human population grew, settlements sprang up in the empty spaces between cities.  At the point in time when settlements began to be located about two weeks’ walk apart, smallpox, which had an incubation period of fourteen days, spread in epidemics.

Centuries passed, till finally a phenomenal change occurred in human history, a change in which machines were developed that could do the work of humans.  This, of course, was the Industrial Revolution.  Threshing machines and other inventions could do the work previously requiring many human hands, and the out-of-work farm workers moved into the cities, where newly-built factories needed laborers.

poop chron screen shot working conditions

Working conditions there were often miserable:  long hours (dawn to dark), dusty, dark factories that were unsafe and closed in, no vacation, no sick-leave.  Child labor was common, even in the mines.

Living conditions for the poor were crowded and unhealthy, with several families living in one room of a tenement building.  The air of the cities was dark with smoke and soot and the streets were filled with trash and garbage.  Slaughter houses with blood, dung and flies were built in the cities, sometimes located next to schools.  Rivers carried chemicals and raw sewage floating on the surface.  Drinking water was accessed in public wells and was also taken directly from the river, bottled and sold untreated.

As shown in this fantastical newspaper cartoon of the 1800’s, people were starting to be disgusted by the appearance of the water, though they didn’t connect disease to the organisms that they could see in it with their microscopes that were then popular as toys or curiosities.

poop chron screen shot shocking water

Outdoor privies were used for human wastes and the matter collected in storage holes called cesspools, which were sometimes lined with brick or stone, but were sometimes just bare dirt.

It is estimated that by the 1850’s the city of London had 20,000 outdoor privies.  In the home, for convenience, people used chamber pots.  In the mornings, housewives tidied up by emptying the contents out the windows of the upper stories.  Look out below!

poop chron screen shot priviespoop chron screen shot chamber pots

These were the conditions when a cholera epidemic swept through the city of London in 1854.  Cholera was, and still is, a fearsome disease.  A victim can be healthy in the morning and dead by noon!  It is characterized by nausea and vomiting, cramps, and severe diarrhea.  Cholera sometimes breaks out, even today, where people are crowded together in conditions such as are found in many refugee camps, after a war or severe flooding or other natural disasters.  Medical workers in these places often put the patients on cots such as the ones pictured, with buckets under the holes to facilitate clean-up of the diarrhea.  So much fluid is lost from the body that vital minerals, needed for the heart to function, are carried away with the fluid, and the victims die of heart failure.  In recent years it has been discovered that clean water mixed with a little sugar and table salt, given by mouth or intravenously, can spell the difference between life and death!

poop chron screen shot cholera cots

This brings us to London and the cholera epidemic of 1854.  In one area of the city hundreds of people were infected and as many as 50% of the patients died.  Queen Victoria summoned Dr. John Snow,  a famous person in epidemiology even now, and directed that he stop the epidemic.  This was a tall order since the cause of cholera and the means of transmission weren’t known then.  In fact there was little understanding of diseases and germs at that time.poop chron screen shot the queen

Watch for Poop Chronicles, Part Two, coming next week, for the rest of the story, and for a fascinating activity modeling London’s cholera epidemic and asking students to figure out how to stop its spread.



No infringement of  copyright is intended with the use of these pictures.  Owners of copyrights can request removal and we will comply promptly.


Exciting Cell Projects for Your Students

Cells and Cell Projects
To introduce the cell or for review, you can’t beat manipulatives! Pictures of organelles that can be placed on a picture of an “empty” cell, (just the membrane or membrane and cell wall with cytoplasm and maybe ribosomes) can be a very effective strategy to engage students.
Have students try these:

  • Assemble and compare the plant cell and the animal cell.
  • Pass out the organelles.  Call out the name of an organelle and have the student who holds it bring it to the board and explain its function before adding it to the cell.
  • Have students choose the relevant organelles and use them to explain and enact an overview of protein synthesis.

Cell Projects                                                                                                                                                             Cell models made of cake, cookies, Jello, legos, styrofoam, cardboard, cloth.     One student, a dedicated skater, even made his model using bits of hardware from an old skateboard, housed inside a small metal box that originally held skateboard bearings!  The key to the organelles was pasted inside the lid.  I ran into him in a cafe 15 years later, and he told me he still remembered that model!
So it seems that these projects are time well spent. But after retiring, I wondered. If the high school students have made cell models in middle school and a brief review is sufficient to bring it all back, or if you want to present your class with more of a challenge, then maybe it’s time to up the ante.
How about going beyond the generic cell model and asking /assigning students to create a model of a specific kind of cell? Many cells are fascinating in their own right. With around 200 cell types in the human body, there’s such a rich assortment to choose from! But some students might prefer some type of plant cell or even a single-celled organism. You’ll see some ideas on the next page.

Cell Project—High School Level                                                                                                                        Make a choice from the lists below for research and a presentation. Make a poster to help as you present. Differentiated Cells These cells are specialized cell types that perform special functions. General requirements and questions to consider: Compare and contrast the specific cell(s) you chose to the generic plant or animal cell studied in class. What important function does your cell perform for the organism it is part of? How does the structure of your cell relate to its function? Are any of your cell’s organelles absent or present in extremely large numbers? To what effect? How does your cell function to help maintain homeostasis? Explain. Give special attention to any interactions between cell pairs. Do the cell pairs act together to achieve balance for the organism they are part of? What might happen if the cells’ interaction gets out of balance? Do the cells help each other in some way?                                                                                                                                           Cell Choices:

  • a cardiac muscle cell
  • a striated muscle cell
  • osteocyte/osteoblast/osteoclast
  • neuron and glial cell
  • sperm cell and Sertoli cell
  • red blood cell and platelet
  • vessel element
  • sieve tube member/companion cell

Cell & Protein Choices:

  • adipose (fat) cell and leptin
  • plasma cell and antibodies
  • chief cell and pepsin
  • red blood cell and hemoglobin
  • alpha cell of the pancreas and glucagon
  • beta cell of the pancreas and insulin