4.5 - Blood, Haematopoiesis, & Haemostasis Flashcards
What is blood?
The circulating component of extracellular fluid responsible for carrying substances around the body
List the 4 components of blood:
- Plasma
- Red Blood Cells (RBCs)
- White Blood Cells
- Platelets
What is plasma?
The fluid aspect of blood
What does “erythro” mean literally?
Red
List the characteristics of RBCs
- also known as erythrocytes
- shape: bi-concave
- contain haemoglobin protein
- major function: gas transport (O2 and CO2)
TRUE OR FALSE:
Rectify statement if false
White blood cells are the most abundant cells in blood
FALSE:
RBCs are the most abundant cells in blood
TRUE OR FALSE:
Rectify statement if false
In humans (mammals), RBCs lack a nucleus only.
FALSE:
lack BOTH nucleus and mitochondria
White blood cells (leukocytes) function in immune responses. List the different types:
- Lymphocytes
- Monocytes (mature macrophage)
- Granulocytes: Neutrophils, eosinophils, basophils (mast cells)
What are the professional phagocytes in the body? What do they do?
- macrophage and neutrophils
- they engulf and destroy foreign entity in tissues
Why is the synthesis of haemoglobin crucial?
- for RBCs to transport O2
What is haemoglobin? List some characteristics:
- large complex molecule made up of 4 protein chains (globins), 2 Alphas and 2 Betas
- each globin subunit is wrapped around an iron containing haeme group
- haeme group C-H-N porphyrin ring contains an Fe in the center
Define platelets and their functions:
- also known as thrombocytes
- involved in blood clotting
- derived from megakaryocytes: pinch off and have no nucleus
Low dietary iron can result in ____
anemia
Explain the haemoglobin/oxygen saturation
- curve is s-shaped with a steep portion followed by plateau
- O2 highest partial pressure @ alveoli where RBCs are packed
- RBCs travel to arteries and reach capillaries where they give off the O2 and partial pressure decreases
What are factors affecting haemoglobin-O2 binding? What type of modification is that?
- allosteric modification
- temperature and pH
- increases in temperature decreases haemoglobin-oxygen affinity
- increases in blood CO2 and H+ decreases haemoglobin-oxygen affinity
What is the Bohr effect?
- shift in haemoglobin saturation due to pH
How does O2 unloading happen at the tissues?
- the more active the tissue, the greater the increase in temperature, PCO2, and H+
- relative to the lungs, these factors are elevated in tissues
- leads to more O2 released
What do “haima” and “poeisis” mean?
haima = blood
poeisis = formation
Where are blood cells produced?
RED Bone marrow
What is the precursor from which all blood cells arise?
pluripotent haematopoietic stem cell
What are uncommitted stem cells?
lymphocyte stem cells
Progenitor stem cells are committed to one or two cell types; list them.
- eosinophil
- mast cell
- basophil
- neutrophil
- dendritic cell
- monocyte (macrophage)
- megakaryocytes ( platelets)
- Reticulocyte (Erythrocyte)
What are cytokines?
- small peptides/proteins secreted by one cell to send signals to another
- cytokines guide the paths taken by committed progenitor cells
- e.g. growth factor, modifying factor
What is leukopoeisis and what regulates it?
- formation of white blood cells
- regulated by colony stimulating factors (CSFs)
Where do CSFs come from and what do they do?
- released by endothelial cells, marrow fibroblasts, and white blood cells
- induce cell division and cell maturation in stem cells
Cytokines released by leukocytes regulate further leukocyte production. What would happen if you had an active bacterial infection?
- goal is to fight infection: immune system
- cytokines will push for production of macrophage and neutrophils (professional phagocytes of the body)
What is thrombopoeisis?
Formation of thrombocytes (platelets)
What are the parent cells of thrombocytes?
Megakaryocytes
Growth and maturation of thrombocytes is regulated by ____
cytokine thrombopoeitin (TPO)
Where does the megakaryocte reside?
- in the bone marrow
- extends its outer edges through the endothelium (cells lining the blood vessels) into the blood stream
- ends fragment into disk-like platelets, no nucleus, have mitochondria, smooth ER, granules filled with clotting proteins and cytokines
Are platelets always present in the blood? Explain
Yes, but not activated until there is damage to the walls of the circulatory system
What is erythropoeisis? What regulates it?
- formation of red blood cells
- cytokine erythropoeitin (EPO)
What is erythropoeitin? Where is it made? What is EPO used for?
- cytokine that regulates erythropoeisis
- glycoprotein made primarily in kidneys
- genetically engineered to stimulate RBC production in patients
What is haemostasis?
haeme = blood, stasis = stoppage
- prevents blood from being loss from damaged vessels
- must be fixed under pressure
What are the steps of haemostasis?
- Vascular spasm:
- similar to putting pressure on a bleeding wound
- damaged endothelium of blood vessel releases vasoconstrictive paracrines
- leads to decreased blood flow due to increasing resistance
- promotes formation of platelet plug - Platelet plug temporarily block break:
- collagen is normally in the sub endothelial layer
- platelets stick together and become activated
- releases cytokines, which activates more platelets
- activated platelets stick together (aggregation) to form loose platelet plug
- slows down blood flow in the vessel and provides a framework for clotting - Blood clot to seal the break: result of coagulation cascade
- inactive plasma proteins are activated by exposure to either factor XII to collagen (intrinsic pathway) or exposure to tissue factor III ( extrinsic pathway) released from damaged cells
- both pathways merge into the common pathway and lead to activation of thrombin, which cleaves fibrinogen into fibrin
- thrombin activates factor XIII which cross-links fibrin into long fibres that intertwine to form a fibrin network
- intertwined fibres reinforce the platelet plug making it a clot
- excessive clotting produces a thrombus: clot to block blood vessels
explain healing
- during clot formation, plasminogen is converted into plasmin by thrombin or tissue plasminogen activator (tPA)
- plasmin enzyme dissolves the clot -> fibrinolysis
- as repair progresses, the clot slowly shrinks
