Week 10 Flashcards
(47 cards)
What are the two main components of blood and their proportions?
Blood is composed of Plasma (~55%) and Formed Elements (~45%), which include red blood cells, white blood cells, and platelets.
What are the structure and main functions of red blood cells (erythrocytes)?
- Structure: Biconcave, flexible, anucleate, 33% hemoglobin.
- Function: Transport oxygen and carbon dioxide via hemoglobin.
What is the life cycle of a red blood cell?
Produced in bone marrow → lives ~120 days → removed by spleen and liver when old or damaged.
What are the two types of white blood cells and examples of each?
Granulocytes: Neutrophils, Eosinophils, Basophils.
Agranulocytes: Lymphocytes, Monocytes.
What are the functions of the five types of white blood cells?
- Neutrophils: Phagocytose bacteria.
- Eosinophils: Attack parasites, allergic response.
- Basophils: Release histamine/heparin, allergy/inflammation.
- Lymphocytes: Immune memory, viral defense.
- Monocytes: Become macrophages, phagocytosis.
What are the structure and roles of platelets (thrombocytes)?
- Structure: Cell fragments from megakaryocytes, no nucleus.
- Functions: Clotting, vessel repair, immune response, release of clotting factors and growth factors.
What is plasma made of and what are its functions?
- Composition: ~92% water, proteins (albumin, globulins, fibrinogen), nutrients, gases, electrolytes, wastes.
- Functions: Transport, osmotic balance, immune defense, clotting.
What are haematocrit and haemoglobin, and how are they measured or characterized?
- Haematocrit: % of blood made up of RBCs (≈42% in females, 47% in males).
- Haemoglobin: Oxygen-carrying protein in RBCs with 4 O₂ binding sites and iron that gives blood its red color.
Why is it important to keep red blood cell (RBC) numbers within a homeostatic range?
- Too few RBCs: Reduced oxygen-carrying capacity → risk of hypoxia.
- Too many RBCs: Increased blood viscosity, resistance, and risk of clotting.
What hormone regulates red blood cell production and how?
- Erythropoietin (EPO), produced mainly by the kidneys, stimulates erythropoiesis.
-Circulates at low levels to maintain RBCs at a basal rate; increases in response to low oxygen levels.
How does the body maintain a constant RBC count?
Through a negative feedback loop balancing RBC production (stimulated by EPO) and destruction, ensuring stable oxygen delivery.
What is haemostasis and why is it essential?
Haemostasis is the process that stops bleeding when a blood vessel is injured. It prevents blood loss even from small cuts by initiating rapid defensive reactions like clot formation.
What prevents platelet activation in healthy blood vessels?
The endothelium of intact vessels secretes Nitric Oxide (NO) and Prostacyclin (PGI₂), which inhibit platelet adhesion and activation, keeping the vessel surface smooth.
What is the first step in haemostasis and its function?
Step 1: Vascular spasm – Injured vessels contract (vasoconstriction) to reduce blood flow and limit blood loss. Triggered by injury, pain, and inflammation.
What happens during platelet plug formation (Step 2 of haemostasis)?
Platelets aggregate, swell, become sticky, and release ADP, thromboxane A₂, and serotonin to recruit more platelets and form a temporary plug at the injury site.
How does coagulation (Step 3) stabilize the platelet plug?
Fibrinogen is converted to fibrin, forming a solid mesh that reinforces the plug and traps red blood cells, creating a stable clot to seal the vessel.
What is coagulation and what does it involve?
Coagulation is the process of blood clot formation. It involves:
- Activation, adhesion, and aggregation of platelets
- Deposition and maturation of fibrin to form a stable clot
What is the coagulation cascade?
The coagulation cascade is a series of enzyme-driven reactions involving clotting factors that activate each other.
Initiated by intrinsic or extrinsic pathways
Both pathways converge at Factor X, leading to the formation of fibrin, which forms a mesh that traps blood cells to stabilize the clot
What are natural anticoagulants that regulate coagulation?
Protein C: Degrades Factors Va and VIIIa
Antithrombin: Inhibits thrombin, Factors IXa, Xa, XIa, XIIa
Plasmin: Breaks down fibrin
Prostacyclin: Inhibits platelet activation
What are coagulation disorders and their effects?
Coagulation disorders are imbalances in clotting ability.
- Haemorrhage: Too little clotting → excessive bleeding
- Thrombosis: Too much clotting → blood flow obstruction
What are two serious conditions caused by excessive clotting?
Deep Vein Thrombosis (DVT): Clot in a deep leg vein
Pulmonary Embolism: Clot travels to the lungs, potentially life-threatening
What is the purpose of clot retraction and how does it help wound healing?
Clot retraction stabilizes the clot and helps close the wound by using actin and myosin to contract fibrin strands, squeezing out serum and drawing wound edges together. PDGF stimulates tissue regrowth.
What is fibrinolysis and why is it important?
Fibrinolysis is the process of breaking down clots after healing. It prevents vessel blockage by removing unneeded clots, which form naturally and continuously throughout the body.
What enzyme is responsible for breaking down fibrin and how is it activated?
Plasmin digests fibrin. It is formed from plasminogen, which is activated by tissue plasminogen activator (tPA), thrombin, and Factor XII after a clot forms.
