The heart is a powerful muscle that pumps blood through the body using double circulation. The right side of the heart pumps deoxygenated blood to the lungs, while the left side pumps oxygenated blood from the lungs to the head and body. Blood flows into the four chambers - the atria on top and ventricles below - with valves ensuring it only flows in one direction to prevent backflow. The pulse indicates the heart rhythm and rate as it can be felt where arteries cross bone.

1. The Heart Muscle tissue as a pump

2. Learning objectives To understand what is meant by double circulation To understand why one side of the heart has thicker muscle than the other To be able to name the main structures of the heart To appreciate what the pulse tells us

3. The beating heart The heart is a powerful muscle which provides the pressure to force blood through the arteries to the body’s cells by making powerful contractions. The right hand side pumps deoxygenated blood to the lungs the left pumps oxygenated blood to head and body. Blood always enters at the top. The incoming blood enters chambers known as atria (s. atrium) The blood passes next into the two lower chambers ventricles (these are surrounded by thicker muscle) which contract to force blood out into the arteries.

4. Structures of the heart… The four chambers of the heart are divided by the septum There is no way through in the adult heart At ria are at the top Ventric l es are be l ow Blood flow is from top to bottom then back out of the top

5. Valves of the heart As you can see from this animated diagram the valves only open in the direction of true flow. Backwards flow by pressure surges closes the valves tightly – so blood cannot flow the wrong way (backflow)

6. The pulse A pulse can be found wherever an artery crosses a bony structure. The pulse is a good indicator of heart rhythm and beats per minute

7. Exam Questions Explain what the pulse can tell us 1 mark Which side of the heart carries deoxgenated blood to the lungs? 1 marks What are the heart valves for? 1 mark Why is the left hand side of the heart thicker with muscle than the right?