Carbon dioxide and lactic acid from cellular respiration act as vasodilators
E.g. when exercising muscle cells continually require energy so they produce extra CO2 and lactic acid
Oxy blood -
Refers to blood that has been exposed to oxygen in lungs
Also called arterial blood
Oxygen concentration is high
Carbon dioxide concentration is low
Bright red
Deoxy blood -
Refers to blood that has a low oxygen saturation relative to the blood leaving the lungs
Venous blood
Concentration is low
Concentration Is high
Dirty dark red
Oxyhaemoglobin = Haemoglobin + Oxygen (HbO2)
This is how oxygen gets the bright red colour
The more oxygen the brighter colour
Oxygen transport
Haemoglobin binds to oxygen as red blood cells travel through the lungs
Red blood cells transport circulating oxygen to organs where they need them
When red blood cells reach their target haemoglobin releases oxygen
Oxygen transport:
Oxygen is not very soluble in water and therefore only 3% is carried in solution in the blood plasma
The other 97% is carried in combination with haemoglobin molecules which are found only in red blood cells
Haemoglobin is able to combine with oxygen to form a compound called oxyhaemoglobin
The presence of haemoglobin increases oxygen carrying capacity by 60-70x
Carbon dioxide transport:
7-8% in plasma
22% combines with globin to form a compound called carbaminohaemoglobin
70% is carried into the plasma as bicarbonate ions (CO2 reacts with water in plasma to form carbonic acid, carbonic acid then forms H+ and bicarbonate ions
Carbon dioxide transport -
CO2 from cells into plasma and air in alveoli
Carbaminohaemoglobin breakdown - diffuse into air in alveoli
H+ and bicarbonate ions recombine into carbonic acid
Blood Clotting:
Damage to blood vessels
Steps to minimise blood loss from broken vessel and prevent entry of infecting micro-organisms
Vasoconstriction
The muscles in the walls of the small arteries which have been damaged constrict to reduce blood flow and therefore reduce blood loss
Vaso = vessel
Constriction = contract
2. Platelet plug
Damage to the vessel creates a rough surface on a normally smooth surface
Platelets stick to rough surface
Sticking platelets attract others
Plug gets built up at site of injury
Plug helps reduce blood loss
Platelets release substances that act as vasoconstrictors
These enhance and prolong constriction of the damaged vessel
For small tears in capillaries - plug and constriction of blood vessels is sufficient to stop any bleeding
3. Coagulation
Formation of a blood clot
Large number of clotting factors in plasma form clot
Complex series of reactions result in formation of fibrin threads
Fibrin threads form a mesh that traps blood cells, platelets and plasma
This mesh with the trapped material is known as a clot
Threads stick to damaged walls of vessel, holding the clot in place
Clot retraction
After formation of a clot
Slow process
Threads contract becoming denser and stronger, pulling edges of damaged threads together
Serum - a fluid is then squeezed out
Clot dries forming scab over wound preventing entry of microorganisms
Antigen: surface of RBCs coated with sugar and protein molecules that can stimulate the immune system
Antibody: protein produced by the immune system
Antigen and antibody combine to form a complex and cause a reaction
2 antigens – antigen A & antigen B
People may either have antigen A, B, both, or neither on the surface of their RBCs
Antibody that reacts against antigen A is called anti-A
Persons immune system recognises own antigens and will not produce antibodies for them
Will produce antibodies for antigens that are non-self
Rh antigens on surface of RBCs
Rh antigens are proteins
Person with Rh antigens are Rh positive
Person without Rh antigens are Rh negative
Person without Rh antigens is able to produce an anti-Rh antibody that reacts against those antigens
Rh positive individuals cannot produce an anti-Rh antibody
Transfusions:
Transfer blood or one of the components of blood from one person to another
Need to match blood group of donor to recipient
Mixing of blood types that are not compatible can cause RBCs to clump or agglutinate
If recipient blood contains or is able to make antibodies against the antigens on the donors RBCs, the foreign cells will clump together and disintegrate
ABO and Rh matched
Autologous transfusion:
Patients own blood used, blood collected form patient prior to operation that may require a transfusion
e.g. for elective surgery
In cases of severe blood loss:
Whole blood - has a chemical added to prevent clotting, transfused mainly in severe cases of blood loss
Red cell concentrates - the most widely used component, made by centrifuging whole blood to separate cells from plasma
Platelet concentrates - gives to patients with abnormal platelets or a reduced number of platelets
Plasma - the liquid part of the blood, may be given to patients needing extra clotting factors or to patients with severe liver disease
Immunoglobulins - a group of proteins that act as antibodies, extracted from plasma of suitable donors
Cryoprecipitate - obtained by freezing the plasma and thawing it slowly, when thawed it contains many of the substances needed for blood clotting remains solid
Agglutination: The mixing of blood types that are incompatible which causes the erythrocytes to clump together