Structure and Function of the Heart

• The Need To Circulate Blood

  • Blood

  • delivers raw materials from the external environment to cells

  • removes waste substances from cells and deliver them to the external environment

  • It must therefore be

  • replenished with materials that have been removed

  • cleaned of waste it has accumulated

  • To allow these two processes blood must be circulated.
• CVS

  • The cardiovascular system consists of the heart (muscular pump) and the blood vessels (system of tubes with carry blood to the rest of the body)

  • Heart is divided into 4 chambers: the left and right atrium and the left and right ventricle (N5 Recap).

  • The heart muscle pumps blood around the body to every organ and has a specific pattern in which it fills up and releases the blood.
• Thickness of ventricle walls

  • The ventricle walls on left and right side of the heart are of a different thickness

  • This is because the right ventricle only has to pump blood to the lungs.

  • However, the ventricle on the left has to pump blood all the way round your body.
• Valves

  • There are 4 valves in the heart. Two of these valves are placed between the atria and ventricles on both sides of the heart.

  • These are called the ATRIO-VENTRICULAR (AV)

  valves.

  • The valve on the left side of the heart is the BICUSPID valve and the right side is the TRICUSPID valve.

  • These allow the blood to pass from the atria to the ventricles but prevent it going in the other direction.
• Valves

  The other two valves are found at the base of the PULMONARY ARTERY and the AORTA.

  • These are called the SEMI-LUNAR (SL) valves.

  • These valves prevent the blood from going backwards back into the heart and keep the blood flowing in ONE DIRECTION.
• Blood flow through the Heart

  • The right atrium receives deoxygenated blood from all parts of the body through the VENA CAVA (Vein) (1).

  • This deoxygenated blood passes into the right ventricle through the Atrioventricular (AV valve).

  • The blood then leaves the heart through the PULMONARY ARTERY (5) and branches of to go to each lung.
• Blood flow through the heart (cont'd)

  • After the blood is oxygenated in the lungs the blood is then passed back to the heart through the PULMONARY VEIN into the left atrium.

  • From there the blood enters the left ventricle through the Atrioventricular (AV valve).

  • The blood is then pumped out of the heart through the AORTA (Artery) to the rest of the body.
• Cardiac Function

  • With each contraction of the heart the right ventricle pumps the same volume of blood through the pulmonary artery (to the lungs) as the left ventricle pumps through the aorta (to the rest of the body).

  • HEART RATE (pulse) = the number of heartbeats that occurs per minute.

  • STROKE VOLUME = the volume of blood expelled from each ventricle on contraction.

  • CARDIAC OUTPUT = the volume of blood pumped out of each ventricle per minute.
• Cardiac Output

  CARDIAC OUTPUT = the volume of blood pumped out of each ventricle per

  minute.

  Calculation:

  Cardiac output (CO) = heart rate (HR) X stroke volume (SV)

  Heart rate = 60 beats/min

  Stroke volume = 80 ml

  Cardiac output = 60 x 80 = 4800 ml/min