Why Does Our Heart beat To pump blood

Why Does Our Heart beat? • To pump blood around the body.

Why do we need to pump blood around the body? • To get oxygen to all the organs and tissues in our bodies.

What happens when we run out of oxygen? • We need to get more

How do we get more? • The blood is pumped back to our lungs. • Where it is oxygenated again.

Where does it go from here? • Back to the heart.

Where does it go from here? • To the rest of the body.

Double circulatory system The heart pumps both oxygenated and deoxygenated blood at the same time. lungs body’s cells

This is often shown in a diagram like this

Double Circulation • So we have two things going on in the heart, this is known as double circulation. • The blood is being pumped to the body to give it oxygen AND the blood is being pumped to the lungs to get more oxygen. • So we say that the heart is spilt into two sections, the left and the right.

So what is the structure of the heart?

The Heart • The heart is made of very special muscle, CARDIAC muscle. It must keep beating all the time for the rest of a persons life! If you tried to do the same action repeatedly (like the heart) your muscles would get tired and, after a while, they would stop working. • For example if you clench and unclench your hand continuously, it will get tired, and may even start to cramp.

4 Chambers • Each side has two chambers: 1. Atria at the top, 2. Ventricles are the bottom.

What are their functions? • Atria – Let blood pour into heart and down into ventricles. • Ventricles - Blood from ventricles pumped out of heat when muscle contracts.

How do we stop the blood from flowing backward? • Valves stop the flow of blood once it has entered the ventricles. • And also once the blood has been pumped out the valves stop it from coming back into the heart.

Why is the left side of the heart thicker? • Left ventricle muscle wall is thicker that the right ventricle as it has to pump blood all around the body, whilst the left only send it to the lungs.

The Circulatory System The circulatory system is made up of: • Blood • Arteries • Veins • Capillaries • The Heart

An organ system is a group of organs that work together to carry out a particular function in the body. The circulatory system is an organ system that consists of the heart, the blood vessels and the blood. Its function is to transport materials around the body. Below is an overview of the circulatory system.

Blood Vessels There are 3 types of blood vessel: 1. Arteries 2. Veins 3. Capillaries

Blood Vessels • Arteries carry blood Away from the heart • Veins carry blood towards the heart • Capillaries have thin walls to allow oxygen to pass into nearby cells and tissues

Describe what blood vessels are Artery (Arteries) • carry blood away from the heart • blood is under high pressure generated by the hear • thick outer walls and small lumen • thick layers of muscle and elastic fibres

Veins • carry blood back to the heart • blood is under low pressure • have thin walls and larger lumen • have thin layers of muscle and elastic fibres • have one-way valves

Capillary (Capillaries) • Tiny, thin-walled vessels • Carry blood close to all the body's cells in its tissues and organs. • Only one cell thick and has a very small lumen. • Where gas exchange takes place. Oxygen passes through the capillary wall and into the tissues, carbon dioxide passes from the tissues into the blood

Describe what blood vessels are Blood Vessels Summary Blood vessel Function Artery carry blood away from heart at high pressure Capillary allow exchange of materials between blood and tissues Vein return low pressure blood to heart Adaptations Thick, elastic, muscular walls to withstand pressure and to exert force (pulse) Thin permeable walls Large diameter to offer least flow resistance. Valves to prevent back flow.