The septum between the right and left sides of the heart isn't complete, blood can flow from one
side to the other. This means that the blood going around the body will carry less oxygen, leading to
tiredness + shortness of breath. Closed by surgery. Unborn babies get the oxygen they need from
their mother + don't need working lungs. They don't need a double circulatory system, their heart
has a hole between the right + left side. This closes soon after birth so that the double circulatory
system can be established. When it fails to close, the baby has a ‘hole in the heart’.
Heart valves
The valves in the heart stop the blood flowing backwards. If the valves are damaged or weak, they
cannot stop this backflow so well. The blood circulation is reduced, again leading to tiredness and
shortness of breath. The faulty valves can be replaced by artificial valves.
Blocked coronary arteries
Fatty deposits build up in the walls of the coronary arteries, particularly smokers or diets high in
saturated fats. These block the arteries, reducing flow of blood to the heart muscles. It can lead to a
heart attack. By-pass surgery involves transplanting a vein from the leg to provide a route past the
blockage.
Different types of Surgery
A heart transplant is a major operation and there is a shortage of suitable donors. The patient has to
take drugs to suppress their immune system for the rest of their life - otherwise the new heart will be
rejected by the body. Less difficult operations involve fitting a pacemaker or an artificial valve, and
the body is unlikely to reject them. They may need to be replaced.
Blood clotting
Controlling clotting
Sometimes clotting can happen abnormally inside the blood vessels, leading to
heart attacks or strokes. The ability of the blood to clot can be reduced using
anti-coagulant drugs such as: warfarin heparin aspirin
It is important that blood is able to clot, otherwise a cut or similar injury could lead
to dangerous blood loss. Blood contains tiny structures called platelets, and a
protein called fibrin. When a blood vessel is damaged, a series of chemical
reactions happen. Fibrin fibres form a mesh at the site of the wound and the
platelets get stuck in this, forming a scab.
Haemophillia
Haemophilia is an inherited disorder in which the blood does not clot easily. Its
ability to clot is severely reduced because an essential clotting factor - a chemical
within the blood - is partly or completely missing. This means that people bleed for
longer than normal. People with haemophilia are treated with injections of the
missing clotting factor, although there is no permanent way of increasing its level.
Blood tranfusions
Blood groups
A B AB O
These are further subdivided into Rhesus positive and Rhesus negative (Rh+ and Rh–).
A blood transfusion may be needed in a medical emergency or during an operation. The blood
used in the transfusion comes from stored donor blood. When a donor gives blood their blood group
is determined and blood is collected from a vein. It is mixed with an anti-coagulant to stop it
clotting, and stored in a fridge. When a patient requires a transfusion, their blood group is checked
and matched with donor blood. The donor blood is warmed and put into the patient through a
vein.
Agglutination
Antigens
Red blood cells carry antigens. These are substances that cause an
immune response by the body and the production of antibodies.
Antigen A and antigen B are two major blood group antigens
Agglutinins
Agglutinins are substances that can react with a particular antigen
and cause agglutination or 'blood clumping'. Blood plasma may
contain antibodies that can act as agglutinins with red blood cells.
The table summarises which antibodies are present.
Blood groups and transfusions
A blood transfusion will fail if the recipient has antibodies that will
agglutinate the red blood cells in the donated blood.
someone with blood group O can donate to anyone, because their
red blood cells do not carry A or B antigens - they are 'universal
donors'
group AB patients can receive any type of blood, because they do
not have anti-A or anti-B antibodies - they are 'universal recipients'
It is important to match the
blood group of the donated
blood to the patient for a blood
transfusion to be successful.
Unsuccessful blood transfusions
can lead to agglutination.