The Heart

Muscle tissue as a pump

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

The beating heartThe 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.

Structures of the heart…

The four chambers of the heart are divided by the septumThere is no way through in the adult heartAtria are at the topVentricles are belowBlood flow is from top to bottom then back out of the top

Valves of the heartAs 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)

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

Exam Questions Explain what the pulse can tell us 1 mark Which side of the heart carries deoxgenated blood to the lungs?

1 marksWhat are the heart valves for? 1 markWhy is the left hand side of the heart thicker with muscle than the right?