4.3 - Blood and Circulation Flashcards
What are the parts that the blood is composed of?
- Plasma
- Erythrocytes (RBC)
- Leucocytes (WBC)
Explain the structure and role of plasma
STRUCTURE:
- mainly consists of water (90%)
- 10% consists of dissolved substances like proteins, electrolytes and other nutrients
FUNCTION:
- transports digested food products, nutrients, hormones and excretory products like CO2
- transfers heat around the body
RBCs structure and function
STRUCTURE:
- have a biconcave disk shape which helps to increase their surface area for oxygen exchange, this shape allows them to quickly take up and release oxygen when needed
- has no nucleus meaning they have more space to pack in as much haemoglobin as possible so they can carry as much oxygen as possible
FUNCTION:
- act as carriers of oxygen, transporting oxygen around the body
- they contain a pigment called ‘haemoglobin’ which binds to oxygen forming ‘oxyhemoglobin’ and remains in this form until it reaches the respiring tissues
What are the two types of WBCs?
- Granulocytes - they have granules in the cytoplasm that take up the stain, have lobed nuclei
- Agranulocytes - they do not have granules that take up the stain in their cytoplasm, have unlobed nuclei
Give examples of granulocytes
- Neutrophils
part of the non-specific immune system, they engulf and digest pathogens by phagocytosis and are multi-lobed - Eosinophils
part of the non-specific immune system, important for the response to parasites, allergic reactions, inflammation, immunity - Basophils
part of the non-specific immune system, have two-lobed nuclei, they produce histamines involved in inflammation and allergic reaction
Give examples of agranulocytes
- Monocytes
part of the specific immune system, they can move out the blood into tissues to form macrophages which also play a part in the specific immune system by engulfing pathogens by phagocytosis - Lymphocytes
very important in the specific immune system and are quite small with very large nuclei
What a platelets?
- are tiny fragments of large cells (megakaryocytes)
- found in bone marrow
- are involved in blood clotting
What does blood clotting do?
Prevents excess blood loss
Prevents pathogens from entering via the cut/ wound
What are the two key chemicals involved in blood clotting?
1) Serotonin: smooth muscle of the blood vessels contract, which narrows the blood vessel which cuts off the blood flow to that area
2) Thromboplastin: enzyme causing the cascading effects that lead to formation of a clot.
Explain the blood clotting process
Platelets (thrombocytes) —releases—> enzyme thromboplastin, which only gets released when wound occurs ——> this enzyme converts prothrombin (soluble protein + inactive enzyme) —– (main factor: thromboplastin/side factors: vitamin K, calcium ions and factor 8 required)—-> into thrombin (enzyme) —-> thrombin converts fibrinogen (soluble blood protein) into fibrins (insoluble fibres) —–> these fibrins and trapped cells form the blood clot
Explain the roles of each events leading to blood clots
Injury: exposes collagen fibres to blood and platelets stick onto these collagen fibres
Release of chemicals from platelets: makes the surrounding platelets sticky
Clumping of platelets at the wound site: forms an emergency protection against blood loss and invasion of pathogens, this clump is called ‘platelet plug’
Formation of fibrin clot: reinforces the seal and traps blood cells
What is the role of clotting factors in the formation of the clot?
It catalyses the conversion of prothrombin to thrombin.
Why are these clotting factors not normally present in the plasma?
Because they only happen in the tissue cells of the one being damaged otherwise they will not be produced
Why does internal bleeding from tears or puncturing of blood vessels occur?
Happens due to high blood pressure.
