YOUR Cardio Vascular System and Energy + FREE PRINTABLE


Main Function of The Cardio Vascular System in Supplying Energy to The Cells

  • To transport the simple materials (broken down food) that transfers from the digestive system into the adjacent capillaries to the liver and body cells via the blood stream driven by the pumping action of the heart.


The Cardiovascular System – An Over View

  • The heart is a muscle that acts like a pump.
  • The heart forces the blood around the body through a system of blood vessels.
  • These blood vessels are arteries, veins and capillaries.
  • Blood carries dissolved oxygen to the body cells.
  • At the same time blood removes the waste products of cellular respiration (water and carbon dioxide)
  • The blood also distributes heat, hormones, nutrients, salts, enzymes and urea around the body.



The Structure of The Heart

  • The adult heart is the size of a fist.
  • The heart is in the thoracic cavity between the 2 lungs and is protected by the rib cage.
  • The heart is surrounded by a tough membrane called the pericardium which contains a thin layer of fluid that prevents friction.
  • The heart is a double pump.
  • The heart has four chambers – two atria and two ventricles.
  • The walls of these chambers are mainly made of specialised heart muscle called myocardium.
  • During each heartbeat both of the atria squeeze (contract), first to pump blood into the ventricles.
  • Then both ventricles contract to pump blood out of the heart into the arteries.
  • There are one-way valves between the atria and ventricles and between the ventricles and the large arteries coming from the heart.
  • The valves make sure that when the atria or ventricles contract, the blood flows in the correct direction.
  • The right side of the heart pumps deoxygenated blood from the veins into the lungs.
  • The left side of the heart pumps oxygenated blood from the lungs to the body.
  • The 2 sides are completely separated by the septum.
  • The blood passes twice through the heart in any one cycle – double circulation.
  • Veins enter the atria, Arteries leave the ventricles.
  • The circulation to and from the lungs is known as pulmonary circulation.
  • Arteries are blood vessels that leave the heart, veins are blood vessels that enter the heart.
  • There are 2 pulmonary arteries that supply blood to each lung.
  • There are 4 pulmonary veins that bring the oxygenated blood back into the hearts left atrium.
  • The main artery that leaves from the heart to the body is the aorta.
  • The main vein that enters the heart from the body is the vena cava. The vena cava has two branches. The superior vena cava supplies blood from the head and neck. The inferior vena cava supplies blood from the rest of the body.
  • It is important that blood only flows in one direction. Therefore, there are sets of values between the atria and the ventricle. Tricuspid – Right hand side. Bicuspid -Left hand side. Before the muscle in the ventricle fully contracts papillary muscles contract pulling on these thin flaps of skin (cusps vales) using tendinous cords ( like ropes) to hold them in place and stop the back flow of blood.
  • The pulmonary artery (to the lungs) and the aorta (to the body) also have vales. These are called semi-lunar valves because of their half-moon like shape. These stop the blood flowing backwards into the ventricle. They are sometimes called the pulmonary and aortic valves.
  • Murmurs are the result of disturbed blood flow. Some are related to disease. Murmurs are the sound of blood swishing around.
  • The walls of the heart and made of cardiac muscles.
    • The atria walls are much thinner as they rely on gravity to draw blood in and release it into the ventricle.
    • The right-hand ventricle wall is thick as it must pump the blood up to the lungs.
    • The left hand ventricle wall is the thickest as it must pump blood a further distance to the whole body.



The Cardiac Cycle

  • The cardiac cycle is a series of events that take place in the heart during 1 heartbeat.
  • The cardiac cycle is about 0.8 seconds at an average person’s normal resting beats per minute heart rate. This speed up to about 0.5 seconds when you are doing exercise and have more beats per minute to supply blood to your bodies muscles more rapidly.
  • The correct terms for cardiac muscle relaxing is diastole and the tensing is called systole.
  • The heart is never empty of blood.



  1. Both atria contract forcing blood into ventricles due to pressure.
  2. Ventricles bursting with blood and increased pressure – causing atrio-ventricular valves shut. (first heart sound)
  3. Muscle in the ventricular walls begin to contract. Pressure on blood inside the ventricles rises. These forces open the semi lunar valves in the aorta and pulmonary artery open.
  4. The ventricular contraction causes the blood to be forced into the aorta and pulmonary artery. The elastic walls in these arteries begin to stretch.
  5. The ventricular muscles start to relax. The blood falls backwards catching the semilunar valves and making them close. (the second heart sound)
  6. Because the ventricular walls have relaxed the atrio-ventricular valves have pushed open by the blood that has been filling the aorta. And blood rushes in. – THE NEXT CYCLE BEGINS.






Heart Rate and Stroke Volume

Cardiac Output – The amount of blood expelled from heart in 1 minute.

Stroke Volume – The volume of blood forced out the heart in one heart beat

Heart rate – Number of beats counted in 1 minute


Cardiac Output = Stroke Volume x Heart Rate



Control of The Cardiac Cycle

The heart is controlled by the automic nervous system and it’s two branches – symphetic and parasymphatic nervous system.

Symphatic – Speeds up heart rate due to work, stress and fear. (largely affected by the hormone adrenaline produced in fight or flight response)

Parasymphatic – Calms heart rate and output down after a period of stress and also during periods of peace and contentment.




Blood Pressure

  • Blood pressure is the force that blood exerts on the walls of the blood vessels.
  • It is measured using a sphygmomanometer.
  • Systolic blood pressure is the pressure when ventricles are contracting.
  • Diastolic blood pressure is the pressure when the ventricles are relaxed and filling
  • Blood pressure is usually written as = systolic/diastolic.
  • A healthy adults blood pressure is 120/80
  • Blood pressure is highest in the blood vessels near the heart – medium sizer arteries and arterioles put up resistance slowing the blood pressure.




Blood Vessels

Arteries and arterioles

  • Arteries leave the heart and supply smaller vessels (arterioles) which go on to supply the smallest blood vessel – capillaries.
  • Arteries usually carry oxygenated blood, the exception being the pulmonary and umbilical arteries (baby).
  • Arterioles provide a network of blood vessels that supply the capillaries.
  • In doing this, the blood incurs resistance and the blood pressure drops.
  • Arteries and arterioles are lined by endothelium (simple squamous epithelial tissue) and has a thick muscular coat.
  • The lumen (central hole) is round.



  • They are supplied with blood by the arterioles.
  • Their walls are a single cell thick.
  • Body cells are never far from capillaries.
  • Body cells rely on capillaries for oxygen and nutrients.
  • Tissue fluid is draw out of the arterial ends of the capillaries. (containing oxygen and nutrients)
  • Tissue fluid re-enters the venous ends of the cappilaries and takes the waste products of metabolic activities in the body cells back. E.g. water and CO2



Venules and Veins

  • Venules are small veins supplied by capillaries and are feed into veins.
  • Limb veins contain valves to assist blood flow back to the heart because the blood pressure has dropped so much.
  • Veins have a much thinner muscular coat than arteries (less pressure to withstand)
  • Veins have more fibrous tissue that arteries and oval lumen.
  • Blood pressure is low in veins and venules.
  • Generally veins carry de-oxygenated blood with the exception of the pulmonary (lung) and umbilical (baby) arteries.




Pulmonary and Systemic Circulations

Pulmonary Circulation

  • Consists of pulmonary arteries that supply blood to the lungs with de oxygenated blood from the left ventricle of the heart. And the pulmonary veins that bring oxygenated blood from the lungs into the left atrium of the heart.

Systemic Circulation

  • All blood vessels not involved in pulmonary circulation.
  • Each organ has a Venus and arterial supply that brings blood in and drains it away again.



Structure and Function of Blood





Functions of Blood

  • supplying oxygen andnutrients to tissues
  • Removing waste from tissues
  • Transportinghormones and other signals throughout the body
  • Regulating body pH and core body temperature.
  • Part of the immune response



  • Blood is composed of plasma, red blood cells, white blood cells, and platelets. – It is the red blood cells that transport oxygen and carbon dioxide
  • It is a type of connective tissue
  • Red blood cells are within the plasma. Plasma is mainly water in which things dissolve






Plasma is mainly water in which substances such as nutrients, enzymes, hormones, glucose, amino acids and gasses are transported.



Red blood cells (Erythrocytes) are very small cells with elastic membranes to fit through capillaries. They have no nucleus to make more room / space. They have a bi-concave shape to increase surface area for greater exposure to oxygen. They are packed full of haemoglobin. This is a protein that carries oxygen. When it is saturated it forms oxyhaemoglobin (bright red) when it is low in oxygen it is haemoglobin (dark red).



Platelets are broken bone marrow (megakaryocytes) cells. They coagulate by clumping together and clotting blood vessels temporarily at the injury site- avoiding blood loss. It is part of the immune response. These are also biconcave shaped with no nucleus. However, they are about 20% of the size of a red blood cell – they are broken cells not whole ones.



Granulocytes (Also known as polymorphs, neutrophils and phagocytes) contain granules in their cytoplasm and a lobed nucleus. They change their shape to engulf foreign materials and bacteria – phagocytosis.

Lymphocytes are smaller cells with round nuclei and clear cytoplasm. The assist the production of antibodies. Antigens are shapes found on the surface of disease-causing microbes. The body uses these marker shapes and produces antibodies to neutralise antigens and stop microbes multiplying. They can then be phagocytosed by the granulocytes.

Monocytes are larger white blood cells than lymphocytes. They have a large round nuclei and clear cytoplasm. They like granulocytes can perform phagocytosis.





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