Haemotology Flashcards

Question

Red blood cell function

Answer 1

RBCs dedicated to respiratory gas transport Specialized to transport oxygen and carbon dioxide Major factor contributing to blood viscosity Life span 120 days

Answer 2

As a RBC ages, its membrane grows increasingly fragile.

Answer 3

Without key organelles such as a nucleus or ribosomes, RBCs cannot repair themselves.

Answer 4

Structural characteristics biconcave discs anucleate No mitochondria or ribosomes essentially no organelles The benefit is that the cell has a greater ratio of surface area to volume, enabling O2 and CO2 to diffuse quickly to and from Hb.

Answer 5

ATP production anaerobic; do not consume O2 they transport

Answer 6

The plasma membrane of a mature RBC has glycoproteins and glycolipids that determine a person’s blood type. On its inner surface are two proteins called spectrin and actin that give the membrane resilience and durability. This allows the RBCs to stretch, bend and fold as they squeeze through small blood vessels, and to spring back to their original shape as they pass through larger vessels.

Answer 7

Filled with haemoglobin (Hb) for gas transport >97% haemoglobin (not counting water)

Answer 8

Haemoglobin binds reversibly with oxygen Specialized protein haemoglobin carries the O2 Globin is a large protein composed of 4 polypeptide chains (tetramer) Two alpha and two beta chains Each RBC contains 200 -300 million Hb molecules

Answer 9

Normal values Males: 130–180g/L Females: 120–160 g/L

Answer 10

Haem is bonded to each globin chain Gives blood red colour

Answer 11

Haem is made of an organic part a protoporphyrin ring made up of four pyrrole rings central iron ion in the ferrous state (Fe2+).

Answer 12

Each Hb molecule can transport four O2

Answer 13

Produces deoxyhaemoglobin or reduced hemoglobin (dark red)

Answer 14

When O2 binds to one subunit it induces a small change in the shape of Hb This makes the binding of the O2 next slightly easier

Answer 15

- Adult humans produce approximately 2.3 million red blood cells every second, or 138 million every minute - All cells of the blood originate from stem cells in the bone marrow - haematopoietic stem cells (HSCs)

Answer 16

The formation of red cells - erythropoiesis

Answer 17

myelopoiesis

Answer 18

Platelets - thrombopoiesis

Answer 19

Each day we make around 10^12 new RBCs

Answer 20

This process occurs in the bone marrow

Answer 21

Normoblasts is a large cell with dark blue cytoplasm - A central nucleus with nucleoli Playing a crucial role in the development of mature red blood cells in the bone marrow.

Answer 22

- Getting smaller - Increasing amount of haemoglobin - Losing RNA and protein synthesis apparatus

Answer 23

- Too few RBCs leads to tissue hypoxia - Too many RBCs increases blood viscosity Balance between RBC production and destruction depends on: - Hormonal controls - Adequate supplies of iron, amino acids, and B vitamins

Answer 24

- Rapid maturation of committed marrow cells - Increased circulating reticulocyte count in 1–2 days Testosterone enhances EPO production, resulting in higher RBC counts in males

Answer 25

Low O2 levels (hypoxia) in blood stimulate kidneys to produce erythropoietin

Answer 26

- Decreased RBC numbers due to haemorrhage or increased destruction - Insufficient haemoglobin per RBC (e.g., iron deficiency) - Reduced availability of O2 (e.g., high altitudes)

Answer 27

Erythropoiesis is the process by which red blood cells (erythrocytes) are produced in the bone marrow, starting from hematopoietic stem cells and culminating in mature, oxygen-carrying erythrocytes.

Answer 28

1) Low O2 levels in blood stimulate kidneys to produce erythropoietin. 2) Erythropoietin levels rise in blood. 3) Erythropoietin and necessary raw materials in blood promote erythropoiesis in red bone marrow. 4) New erythrocytes enter bloodstream; function about 120 days.

Answer 29

- Nutrients—amino acids, lipids, and carbohydrates - Iron - Available from diet 65% in Hb; rest in liver, spleen, and bone marrow - Free iron ions are toxic - Stored in cells as ferritin and haemosiderin - Transported in blood bound to protein transferrin - Vitamin B12 (cobalamin) and folic acid necessary for DNA synthesis for rapidly dividing cells (developing RBCs)

Answer 30

- Transferrin is the protein that transports iron around the body - The liver synthesizes transferrin and secretes it into the plasma.

Answer 31

Life span: 100–120 days Recycled in the spleen

Answer 32

Three main causes: - Blood loss - Low RBC production - High RBC destruction Accompanied by fatigue, pallor, shortness of breath, and chills

Answer 33

Haemorrhagic anaemia resulting from excessive blood loss - Acute - Blood loss rapid (e.g., stab wound) Treated by blood replacement - Chronic Slight but persistent blood loss (e.g. haemorrhoids, bleeding ulcer) Primary problem treated

Answer 34

- Treated with iron supplements - Most common cause of anaemia - Prevalence of 2–5% among adult men and post-menopausal women in the developed world - Caused by haemorrhagic anaemia, low iron intake, or impaired absorption - RBCs are small (microcytic) and pale (hypochromic)

Answer 35

The mechanism for dealing with bleeding and clotting is called haemostasis Haemostasis comes from the Greek - heme meaning blood and stasis to halt

Answer 36

Maintain the fluidity of circulating blood Limit and arrest bleeding following injury by formation of a blood clot whilst at the same time maintaining blood flow through the damaged vessel Removal of a blood clot upon completion of wound healing

Answer 37

compartments: The blood vessels The platelets The coagulation factors (soluble plasma proteins) -Must be tightly controlled Do not want uncontrolled bleeding or inappropriate clotting

Answer 38

- Anuclear (no nucleus) - 1-3μm in diameter - Normal = 150 – 400 x 109/L - Higher than normal thrombocytosis - Lower than normal thrombocytopenia - Each day, 100 billion platelets must be produced from megakaryocytes (MKs) to maintain the normal platelet count - Platelet circulate for 7-10 days

Answer 39

Their primary physiological role is in blood clotting Detect damaged vessel endothelium Accumulate at the site of the vessel injury initiate blood clotting to block the circulatory leak

Answer 40

They are involved in ALL stages of haemostasis Primary haemostatic plug (platelet to platelet interactions) Secondary haemostatic plug (platelet – coagulation protein interactions) Involved in tissue injury, inflammation and wound healing by attracting and binding leukocytes

Answer 41

Largest (50-100µm) and rarest cells in BM Polyploidal (More than one nucleus) Unique to mammals Can produce ~3000 platelets (compared to 2 daughter cells in other lineages) Platelet formation is far more complicated than the production of white cells

Answer 42

Phase I Megakaryocyte maturation - Endomitosis (DNA replication without cell division) - Cytoplasm enlargement (cytoskeletal proteins and platelet granules)

Answer 43

Platelet generation - Mature megakaryocytes extend long branching processes (proplatelets) - Organelles and granules are transported to proplatelets Driven by the cytoskeleton Stimulated by thrombopoietin (TPO

Answer 44

Protection by endothelium is lost Balance is tipped in favour of thrombosis Platelets stick to collagen and von Willebrand Factor (VWF) at site of blood vessel damage Platelets become activated, change shape, release granules and aggregate

Answer 45

- Fast series of reactions for stoppage of bleeding - Requires clotting factors, and substances released by platelets and injured tissues

Answer 46

Three steps: 1) Constriction of blood vessels (vasoconstriction) 2) Platelet plug formation 3) Coagulation (blood clotting)

Answer 47

- Direct injury to vascular smooth muscle - Chemicals released by endothelial cells and platelets - Pain reflexes

Answer 48

- Platelet plug is not stable needs to be reinforced - Platelet plug reinforced with fibrin threads - Happens through a series of reactions using clotting factors (procoagulants proteins)

Answer 49

Platelet plugs, the initial response to blood vessel damage, are temporary and need replacement with a stronger, more permanent clot (fibrin clot) to effectively stop bleeding and allow for tissue repair.

Answer 50

Coagulation is a step wise series of reactions that lead to the conversion of fibrinogen to fibrin

Answer 51

The conversion of fibrinogen to fibrin is crucial for blood clot formation, a process essential for hemostasis (stopping bleeding) and wound healing, as fibrin forms a stable meshwork that traps blood cells and platelets, preventing excessive blood loss

Answer 52

Fibrinolysis breakdown of clots - Removes clots after healing - Begins within two days; continues for several

Answer 53

Two mechanisms limit clot size: - Swift removal and dilution of clotting factors - Inhibition of activated clotting factors

Answer 54

1) Thromboembolic disorders: undesirable clot formation 2) Bleeding disorders: abnormalities that prevent normal clot formation

Answer 55

- Thrombus: clot that develops and persists in unbroken blood vessel - Embolus: thrombus freely floating in bloodstream - Embolism: embolus obstructing a vessel - Risk factors – atherosclerosis, inflammation, slowly flowing blood or blood stasis from immobility

Answer 56

- Aspirin - Cyclooxygenase inhibitor, that blocks thromboxane A2 synthesis and inhibits platelet aggregation - Heparin - Anticoagulant used clinically for pre- and postoperative cardiac care - Warfarin - Used for those prone to atrial fibrillation, interferes with action of vitamin K - Apixaban, Rivaroxaban - Factor X Inhibitors (DOACs (direct oral anticoagulants)/NOACs (novel oral anticoagulants)

Answer 57

- Thrombocytopenia - deficient number of circulating platelets - Haemophilia includes several similar hereditary bleeding disorders - Von Willebrand’s Disease most common inherited bleeding disorder.