O: You will be able to explain the difference between blood vessels. Do Now: What transports the blood and oxygen around our body?

The circulatory system The heart, lungs, and blood vessels work together to form the circulatory system. They form a a circle of blood around the body.

Blood Vessels A blood vessel is a hollow structures for carrying blood that are located throughout your body. There are three main types of blood vessels. Arteries Capillaries Veins

Arteries Arteries carry blood AWAY from the heart. One main artery carries the oxygen rich blood out of the heart but then divides into smaller arteries that transport the blood all over your body. The arteries transport the “renewed blood” to the body.

About the Artery The artery has muscles in it. It works with the heart to expand and contract to pump your blood. When you touch an artery you can take your pulse.

Veins Veins transport the blood back to the heart and lungs. The blood flow is not as strong in the veins as it is in the arteries. The veins bring the blood with carbon dioxide and the muscle waste back to the lungs and heart.

Veins continued Once the carbon dioxide or “waste rich” blood reaches the lungs the carbon dioxide is released and the oxygen is reabsorbed. The blood is then pumped back out through the artery. Veins have special valves so that the blood only pumps in one direction.

Home work 1. What is the difference between veins and arteries? 2. Why is it important that the blood in veins can only flow n one direction? 3.Why do you think it is called the circulatory system?

O: You will be able to explain the role of capillaries. Do Now: What would happen if you only had arteries?

Capillaries The capillaries are the blood vessels that connect arteries and veins. They are like little webs that pass all through the body’s tissue and connect the veins and arteries. The capillaries are so thin that the blood has to go through single file.

It is in the capillaries that the exchange of oxygen for carbon dioxide happens. The blood releases the oxygen and takes the carbon dioxide from the tissue and the tissue releases the carbon dioxide and takes the oxygen. Capillaries are very thin and fragile.

Capillaries are also involved in the body's release of excess heat. During exercise, for example, your body and blood temperature rises. To help release this excess heat, the blood delivers the heat to the capillaries which then rapidly release it to the tissue. The result is that your skin takes on a flushed, red appearance. If you hold your hand, for example, under hot water, your hand will quickly turn red for the same reason. Your arm, however, is not likely to change color because it is not actually feeling an increase in temperature.

Fun Facts If you took all of the blood vessels out of an average child, and laid them out in one line, the line would be over 60,000 miles long! An adult's vessels would be closer to 100,000 miles long! You have 5 liters of blood that circulates around your body.

Homework 1. What is the main job of capillaries? 2. What do you think is the most important blood vessel? Why do you think that? 3. What would happen if you broke all of your capillaries?