Cardiovascular System/Circulatory System

A cell is the basic unit of structure and function in our bodies.

William Harvey was the first one to discover that the heart pumps blood around our bodies. His early research laid the foundation for modern understanding of the circulatory system.

3 main parts of cardiovascular system: (cardio = heart, vascular = vessels)

1. Heart 2. Blood 3. Blood vessels

3 functions of the cardiovascular system:

It pumps blood to the body so it can:

1. transport oxygen and nutrients to cells 2. carry waste products away (carbon dioxide and ammonia) from the cells 3. blood contains cells that fight disease

I. Heart

A. Structure

1. Fist sized organ located between lungs, behind sternum, enclosed in rib cage for protection

2. Cardiac muscle is special because it never gets tired

3. Has 4 chambers: right and left ventricle, right and left atrium

4. Has 2 sides: septum separates the two sides

B. Function: How it works

1. 2-way pump system that circulates blood because the blood needs to stop at the lungs to pick up oxygen.

2. Loop 1 – to the lungs and back to the heart.

3. Loop 2 – to the body and back to the heart.

4. One-way valves (flaps of tissue) ensure that blood only goes in one direction. The sound ‘lub-dup’ is what we hear during the pumping phase when the valves close.

5. Pacemaker - A group of heart cells that send out signals that make the heart muscle contract. It receives messages about how much oxygen your body needs and adjusts the heart rate accordingly. Some people need artificial pacemakers.

(Draw a flow chart in spiral instead of writing all this information below, but use the information to teach them as they construct the flow chart). The right side receives blood returning from the rest of the body that is oxygen-poor, or de-oxygenated. It appears ‘blue’ in pictures. (It is not actually blue but instead a deep red.) This blood goes from right atrium to right ventricle. Then right ventricle pumps blood to lungs so it can pick up oxygen. Blood comes back from lungs with oxygen and goes from left atrium to left ventricle (which is the largest chamber of the heart.) The left ventricle pumps the blood through the aorta and out to the rest of the body.

Right atrium – right ventricle - to the lungs – left atrium - left ventricle - out the aorta and to the body ……then back to the right atrium again!

II. Blood Vessels

A. 3 kinds of blood vessels:

1. Arteries - carry oxygen-rich blood away from the heart to all cells of the body. (A – Away!) The oxygen is what makes the blood look bright red.

a) The aorta is the largest artery in your body, located at the top of the heart.

2. Capillaries - arteries become smaller and smaller then they become capillaries. Capillaries are very tiny, narrow vessels. Capillary walls are only one cell thick! Therefore, materials can easily pass through them. They exchange substances between the blood and body cells. Oxygen and nutrients are delivered and waste products (such as carbon dioxide and ammonia) are picked up. This process is called diffusion: molecules move from an area of high concentration to lower concentration.

3. Veins -From the capillaries, blood flows into veins. Veins carry oxygen-poor blood back to the heart. Because they don’t have as much oxygen, they are not as bright red in color and are colored blue on models and diagrams. The loop starts all over again. It takes about 1 minute for a drop of blood to loop around your body. (Students will cut, paste, and color Flow Chart of Blood Flow#2 into spiral.)

4. Fun Facts:

a) Your brain receives about 20% of your body’s blood flow because it needs a LOT of oxygen! b) Your body has about 60,000 miles of blood vessels (adults 99,400 miles)

B. Pulse - is the rise and fall of an artery in your wrist. You can count the number of heart beats a minute (heart rate) by counting the number of times your artery pulses.

C. Pressure – the force of blood against the walls of the vessels, caused by the force of the heart ventricles contracting. Pressure is greatest near the heart. Pressure decreases as blood moves away from the heart. 1. Sphygmomanometer – an instrument used to measure blood

2. It is important to know if you have high blood pressure because it can be a sign that your heart is working too hard to pump blood.

IV. Role of the liver and spleen in the circulatory system

A. Liver

1. Largest and heaviest organ in body It has LOTS of jobs, including helping the circulatory system!

2. Liver is a filter which breaks down many substances, storing them, and releasing them from the blood as needed. (For example, it changes ammonia into urea, a less toxic substance. The liver then sends urea to the kidneys for excretion as urine.)

3. Liver can also remove other toxic substances like alcohol, some drugs, and hormones.

4. You cannot live without a liver! There is also no way to hook up to a machine to do the liver’s job (like dialysis when kidneys fail).

5. The liver is the only organ of the body that can regenerate itself!

B. Spleen

1. Acts as a filter for bacteria and viruses that are in the blood.

2. Red blood cells are also disposed of here

3. Makes antibodies (that destroy bacteria and viruses)