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Mr. Brown's Science Labs

The Circulatory System
Middle School Life Science

Heart, Blood Vessels & Blood Flow

Estimated time: 35 minutes

Score: 0 / 6

Words

Definitions

Right now, inside your chest, your heart is beating about 70–100 times every minute. Each heartbeat pushes blood through a network of tubes called blood vessels. Together, your heart, your blood, and your blood vessels make up the circulatory system. The job of this system is to deliver oxygen and nutrients to every cell in your body and to carry away waste products like carbon dioxide.

The heart is a muscle about the size of your fist. It is divided into four chambers. The two upper chambers are called atria (one atrium on each side). The two lower chambers are called ventricles. The right side of the heart pumps blood to the lungs, where the blood picks up oxygen. The left side of the heart pumps oxygen-rich blood out to the rest of your body.

Blood travels through three main types of vessels. Arteries carry blood away from the heart. They have thick, strong walls because the blood inside them is moving at high pressure. Veins carry blood back to the heart. They have thinner walls and small valves that keep blood from flowing backward. Capillaries are the smallest vessels — so thin that red blood cells must squeeze through one at a time. This is where oxygen and nutrients leave the blood and enter your cells.

Blood itself is a mixture of several parts. Red blood cells carry oxygen. White blood cells fight germs and keep you healthy. Platelets help your blood clot when you get a cut. All of these float in a yellowish liquid called plasma.

Your circulatory system also responds to what your body is doing. When you exercise, your muscles need more oxygen, so your heart beats faster to deliver oxygen quickly. When you rest, your heart slows down. You can feel this by checking your pulse — the small thump you can feel on your wrist or neck every time the heart beats.

Part A: Complete the Sentence

Use a word from the bank to fill the blank.

Question 1
two four six
The heart has _____ chambers called atria and ventricles.
Question 2
arteries veins capillaries
_____ are tiny blood vessels where oxygen passes from the blood into your cells.
Question 3
platelets red blood cells white blood cells
_____ are the part of blood that carries oxygen to your cells.

Part B: Sentence Builder

Tap a word, then tap a slot to place it in order. Words turn green when in the correct spot.

Part C: Expand the Sentence

Take the short sentence and make it more detailed by answering the prompts.

Question 7
Short sentence: The heart pumps blood.
Question 8
Short sentence: Red blood cells carry oxygen.
Question 9
Short sentence: Your heart beats faster.

Reading: One Complete Trip Through the Heart

Blood travels through your heart in a very specific order. Let's follow one drop of blood on a complete loop.

First, blood that has already delivered its oxygen to the body returns to the heart. It enters the right atrium, the upper-right chamber that catches the incoming blood. From there, the blood drops down into the right ventricle, the lower-right chamber.

The right ventricle then squeezes and pushes the blood out to the lungs. In the lungs, the blood drops off carbon dioxide (a waste gas) and picks up fresh oxygen.

The newly oxygen-rich blood returns from the lungs and enters the left atrium, the upper-left chamber. Just like on the right side, the blood drops down into the left ventricle, the lower-left chamber.

Finally, the left ventricle squeezes the hardest of all four chambers and pumps the oxygen-rich blood out to the rest of your body. The whole loop then starts over — more than 100,000 times every day.

Heart Diagram

Right Atrium Left Atrium Right Ventricle Left Ventricle From body From lungs

Order the Steps

Click a step in the pool, then click the slot you want to place it in. Correct placements turn green. Completing this activity = 4 points.

Steps (Pool)

Pathway Order

Place all 6 steps in the correct order.

How This Works

You can't safely run laps in class, so this lab simulates what your real heart would do during three activities. You will tap the heart pad at the correct speed for each activity. The lab counts your taps in 15 seconds and multiplies by 4 to get BPM (beats per minute).

Follow these steps:

  1. Pick an activity from the dropdown (start with At Rest).
  2. Watch the gray Pacer — it pulses at the speed your heart would beat during that activity.
  3. Press Start 15s Timer, then tap the red heart in time with the pacer for the full 15 seconds.
  4. When time runs out, your beats are auto-recorded in the data table below.
  5. Repeat for the other two activities.

Step 1 — Simulate Your Pulse

Target BPM range: 60–80
Pacer (match this speed)
Tap me!
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0 beats
Time left: 15s

Step 2 — Record Your Data

Enter the BPM you measured for each activity. Filling all three rows = 4 points.

ActivityBeats in 15 secBPM (× 4)
At Rest
After Walking
After Jumping Jacks

Step 3 — Your Bar Graph

Question 10
Which activity gave the highest heart rate?
Question 11
Why does your heart rate go up when you exercise?

Final Grade
0%
0 / 28 points

Score Breakdown