Cardiovascular system

• • There are 3 main types of blood vessels;

  1. Arteries
  2. Capillaries
  3. Veins
• Arteries

  • Arteries carry oxygenated blood away from the heart.
  • The largest artery is the aorta that leads directly from the left ventricle of the heart.
  • The aorta divides into smaller arteries supplying the all the organs of the body.
  • The smallest arteries are called arterioles.
• Blood vessel- arteries

  • Arteries have an outer layer of connective tissue that provides strength and support, they also have a thick layer of muscle and elastic tissue.
  • The muscle allows for constriction (narrowing) or dilation (widening) to regulate blood flow to different parts of the body.
  • The elastic tissue allows the artery to expand, helping to withstand pressure caused by the pumping of the heart.
• Blood vessels - capillaries

  • The arterioles lead to the capillaries.
  • These are the smallest blood vessels in the cardiovascular system and have a wall that is just a single cell thick. This allows for the diffusion of substances into the cells from the capillaries and out of the cells into the capillaries.
• Blood vessels- vein

  • The capillaries come together to form venules that merge to form larger veins.
  • The blood is deoxygenated and is at a much lower pressure in the veins because it has had to force its way through the narrow capillaries, so the lumen (the space in the middle) of a vein is much larger than that of an artery.
  • Veins also have thinner walls as they do not need to absorb the pressure of the pumping of the heart.
• heart

  • The heart is a pump. The blood enters via the atria and passes into the ventricles. The ventricles have thick muscular walls that contract to pump the blood to the lungs (right ventricle) or around the body (left ventricle)
  • To ensure the blood only flows in the right direction, the heart also contains valves that prevent back flow.
  • The left ventricle has a thicker, stronger muscle wall.This is because it has to pump blood around the whole body. The right ventricle has to pump blood a short distance to the lungs.
• Heart

  • The atria have relatively thin walls as they only need to pump blood into the ventricles below.
  • The bicuspid and tricuspid valves (also known as atrioventricular or AV valves) prevent blood flowing backwards from the ventricle into the atrium.
  • When the pressure is higher in the atrium than in the ventricle, the valves are pushed open. When the pressure is higher in the ventricle than in the atrium the valves are pushed closed.
  • The tendons prevent the valves from being pushed too far so they make a good seal.
• Heart 


  • The semi-lunar valves have a different structure, but they perform a similar function to the bicuspid and tricuspid valves.
  • Because the semi-lunar valves are located at the entrance to the pulmonary artery and the aorta they prevent back-flow from these blood vessels into the ventricles.
• Blood is made up of

  -Plasma

  -platelets

  -red blood cells

  -white blood cells
• Plasma 


  • is the straw coloured fluid that is left if you remove all of the cells. It contains proteins, known as plasma proteins, hormones and all the small molecules (carbon dioxide, glucose, amino acids) and ions transported in the blood.
• platelets

  • are small disc-shaped cell fragments without nuclei that are also called thrombocytes. They are present in large numbers in the blood and play an important role in blood clotting
• red blood cell ( erythrocytes) 


  are differentiated cells without a nucleus or the majority of their organelles. They are filled with haemoglobin, the protein that transports oxygen from the lungs to the tissues. They are bi-concave in shape to create a greater surface areas
• White blood cell ( leucocytes )


  • Are cells that are mostly involved in protection against infection, including the immune response.
• Blood groups

  • All body cells have antigens on their plasma membranes that allow the immune system to distinguish between self and non-self.
  • Two types of these antigens are found in the plasma membranes of erythrocytes and form the basis of the two most important types of blood group: ABO and Rhesus (Rh)
  • The ABO system is used to indicate the presence of one, both or neither of the A and B antigens on erythrocytes.

  .Group A blood only has the A antigen

  • Group B blood only has the B antigen

  . Group AB blood has both antigens

  . Group O blood has neither antigen.
• Blood group

  • This system is important when it comes to blood transfusions. You would normally be given blood of the same blood type as your own, otherwise your immune system would recognise it as foreign.
  • However a person with AB blood will have both antigens, so their immune system will not recognise A,B or O types of blood as foreign.
  • Similarly, because type O blood does not contain either antigen, it can be given to any recipients of ABO blood type.
  • Fortunately type O blood is the most common type inWestern Europe.
• Blood groups

  • The Rh system - is based around another set of antigens on erythrocytes. There are 49 defined Rh antigens, of which the RhD is by far the most common.
  • According to the NHS about 85% of the UK population have the RhD antigen and are described as Rh positive whilst about 15% lack the antigen and are described as Rh negative
• Blood groups

  • As group O and Rh are the most common, it is not surprising that O positive is the most common blood type. However O negative is probably the most useful, as these individuals do not carry ABO or Rh antigens, they are known as universal donors as their blood can be given to almost all recipients.
• Function of cardiovascular system

  • The cardiovascular system circulates blood around then body transporting;
  • Nutrients (glucose, amino acids, lipids, vitamins etc) required for cell growth and repair.
  • Oxygen, required for cellular respiration
  • Carbon dioxide, transported to the lungs to be eliminated from the body.
  • Hormones, transported to target cells
  • Blood cells;
  • Erythrocytes for transport of oxygen
  • Leucocytes as part of the immune system
• Circulatory system

  • The circulatory system is known as a double circulatory system. This is because the blood passes through the heart twice for every circuit around the whole body.
  • The first loop is from the heart to the lungs, then back to the heart.
  • The second loop is from the heart, through all the other organs and back to the heart.
• Cardiac cycle

  • The heart pumps blood through a series of muscle contractions and relaxations called the cardiac cycle.
  • Below is the path taken by the blood through the heart
  • Blood enters the right atrium from the vena cava
  • It the flows via the tricuspid valve into the right ventricle
  • From the right ventricle it is pumped into the pulmonary artery to the lungsReturning from the lungs via the pulmonary veins, the blood enters the left atrium
  • It then flows into the left ventricle
  • From the left ventricle, blood pumped into the aorta and around the body.
• The regulation of the heart rate

  • The heart contains a specialised type of muscle known as cardiac muscle.
  • Contraction of the heart muscle is initiated by a small patch of specialised cardiac muscle on the wall of the right atrium known as the sinoatrial node or SAN
  • The SAN generates electrical signals that spread out over the surface of the right and left atria, leading to contraction (atrial systole)

  • This ele othe ventricle able to i a layeror colagen

  that stops it.
• The regulation If the heart rate

  • However, these electrical signals do reach another patch of specialised cardiac muscle known as the atrioventricular node (AVN)
  • After a brief pause the AVN generates more electrical signals that pass along another type of specialised muscle cells that act like nerve fibres. These are called the bundle of His.
  • The electrical activity generated passes down the muscle separating the two ventricles and then passes up the walls of the two ventricles. As it does, it initiates contraction of the ventricles.
• There are two important consequences of this complex arrangement:

  1. The pause caused by the AVN means that the atria can complete their emptying into the ventricles before the ventricles start to contract.
  2. Contraction of the ventricles from the base of the heart upwards, towards the pulmonary artery and aorta, means that the ventricles are not trying to pump blood against a blind end.
• • This is under nervous control, coordinated by the cardioregulatory centre in the medulla.
  • Two types of receptors, chemoreceptors and pressure receptors detect changes in the acidity of the blood and the blood pressure.
  • These are located in the aorta and in the carotid arteries that pass through the neck to the brain.
  • The cardioregulatory centre responds to inputs from these receptors and sends nerve impulses to the SAN that either speed up or slow down the heart rate.
• Use of electrocardiography to monitor heart activity

  • The electrical activity of heart muscle that causes a heartbeat can be detected using electrocardiography.
  • Electrodes are placed on the skin to detect electrical signals and produce an electrocardiogram. (ECG)
  • The picture shows an ECG of a healthy heart.
• ECG


  • The diagram shows several distinctive waves caused by the heart activity;& The P wave is caused by depolarisation of the atria initiated by the electrical signals generated by theSAN (atrial systole)
  • The QRS complex is caused by depolarisation of the ventricles initiated by the electrical signals generated by the AVN and transmitted along the bundle of His (ventricular systole)& The T wave is caused by repolarisation of the ventricles (diastole)
• Atrial fibrillation AF


  • Is a faster and more irregular heartbeat caused by disorganised electrical signals in the atria. It Is the most common serious abnormal heart rhythm that affects more than 33 million people worldwide.
• Ventricular fibrillation VF


  This is caused by disorganised electrical signals in the ventricles causing them to twitch randomly rather than contracting in an organised way. If it is not treated it can rapidly lead to a cardiac arrest and death.
• • Tachycardia, where the heart beats too rapidly - a resting heart rate greater than 100 beats per minute (bpm). The peaks on the ECG are too close together
  • Bradycardia, where the heart beats too slowly - a resting heart rate less than 60bpm. The peaks are too far apart . .Ectopic heartbeat, where the heart beats too early, followed by a pause. This is quite common and usually does not require any treatment.
•   label

  A) lungs

  B) pulmonary artery

  C) pulmonary vein

  D) vena cava

  E) left atrium

  F) right atrium

  G) right ventricle

  H) left ventricle

  I) aorta

  J) valve

  K) hepatic artery

  L) hepatic vein

  M) renal vein

  N) renal artery

  
• label

  A) sinoatrial node

  B) layer of insulating tissue

  C) atrioventricular node

  D) bundle of his

  
• what is this

  A) normal sinus rhythm

  
• what is this

  A) atrial fibrillation (AF)

  
• what is this

  A) ventricular fibrillation (VF)