Composition and general functions of blood Flashcards
Transport function of blood
Delivering oxygen, water and nutrients around the body and removing carbon dioxide and waste products. Moving ions around (calcium, sodium), controlling pH, delivering heat to the surface, transporting hormones to organs when required, delivering immune cells and coagulation factors
Immune function of blood
Fights infection and produces immune response
White blood cells are important as they allow us to fight pathogens, viruses, allergens etc.
Immunoglobulins which are proteins that have an immunological effect
Coagulation function of blood
Stops bleeding using platelets (bits of blood cells that form a plug) and coagulation factors in plasma (proteins which create a clot so we stop bleeding)
Plasma in blood
Most of plasma is water, makes up around 46-63% of blood (depending on mass, height etc.)
Maintains osmotic pressure (albumins), immune response (globulins), coagulation factor (fibrinogen), lots of functions (enzymes and hormones), maintains pH and ion balance (electrolytes), can hold a lot of heat due to being 92% water
Formed elements in blood
Formed elements make up the other 37-54% of blood
Platelets: <0.1% cell fragments that participate in clotting to stop bleeding
White blood cells: <0.1% immune response and defence mechanisms, seek and destroy invading pathogens
Red Blood cells: 99.9% most common cell in blood, highly specialised to transport oxygen
What is haematopoiesis?
Haematopoiesis is the formation of blood cells. Initiated in red bone marrow, which contains blood stem cells (pluripotent) which are the progenitors for all blood cells
Functions and characteristics of RBC’s -> oxygen transport
Biconcave disc shape: large surface area:volume ratio allowing for efficient diffusion of gases, flexibility for movement through narrow capillaries
Contain large amounts of haemoglobin, uses iron as part of haem structures to bind oxygen (4 units, each can bind 4 oxygen units)
What is Haematocrit/PCV?
Fraction of blood occupied by the red cells is called the haematocit or packed cell volume (PCV) - how much RBC is in someone’s blood
Centrifuged blood separates into its main components (plasma, platelets and WBC, RBC)
Typically red cells make up about 50% of blood volume, rest is plasma/white cells
What is anaemia?
Haemoglobin concentration determines how much oxygen can be carried in the blood, if you have low haemoglobin levels anaemia occurs, blood carries less oxygen, reduces amount delivered to tissues, reduces exercise ability
What is erythropoiesis?
All blood cells derived from a common stem cell. RBC production stimulated by erythropoietin (EPO). Require iron to make haemoglobin. Process augmented by testosterone
What happens when there are low levels of oxygen in the blood?
If low levels of oxygen in blood kidneys sense that levels are depressed and release EPO. EPO circulates to bone marrow, stimulates the production of more RBC’s hence blood can carry more oxygen
