4.5 - Blood, Haematopoiesis, & Haemostasis

Question 1

What is blood?

Answer 1

The circulating component of extracellular fluid responsible for carrying substances around the body

Question 2

List the 4 components of blood:

Answer 2

1. Plasma
2. Red Blood Cells (RBCs)
3. White Blood Cells
4. Platelets

Question 3

What is plasma?

Answer 3

The fluid aspect of blood

Question 4

What does “erythro” mean literally?

Answer 4

Red

Question 5

List the characteristics of RBCs

Answer 5

• also known as erythrocytes
• shape: bi-concave
• contain haemoglobin protein
• major function: gas transport (O2 and CO2)

Question 6

TRUE OR FALSE:

Rectify statement if false

White blood cells are the most abundant cells in blood

Answer 6

FALSE:

RBCs are the most abundant cells in blood

Question 7

TRUE OR FALSE:

Rectify statement if false

In humans (mammals), RBCs lack a nucleus only.

Answer 7

FALSE:

lack BOTH nucleus and mitochondria

Question 8

White blood cells (leukocytes) function in immune responses. List the different types:

Answer 8

• Lymphocytes
• Monocytes (mature macrophage)
• Granulocytes: Neutrophils, eosinophils, basophils (mast cells)

Question 9

What are the professional phagocytes in the body? What do they do?

Answer 9

• macrophage and neutrophils

- they engulf and destroy foreign entity in tissues

Question 10

Why is the synthesis of haemoglobin crucial?

Answer 10

• for RBCs to transport O2

Question 11

What is haemoglobin? List some characteristics:

Answer 11

• 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

Question 12

Define platelets and their functions:

Answer 12

• also known as thrombocytes
• involved in blood clotting
• derived from megakaryocytes: pinch off and have no nucleus

Question 13

Low dietary iron can result in ____

Answer 13

anemia

Question 14

Explain the haemoglobin/oxygen saturation

Answer 14

• 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

Question 15

What are factors affecting haemoglobin-O2 binding? What type of modification is that?

Answer 15

• allosteric modification
• temperature and pH
• increases in temperature decreases haemoglobin-oxygen affinity
• increases in blood CO2 and H+ decreases haemoglobin-oxygen affinity

Question 16

What is the Bohr effect?

Answer 16

• shift in haemoglobin saturation due to pH

Question 17

How does O2 unloading happen at the tissues?

Answer 17

• 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

Question 18

What do “haima” and “poeisis” mean?

Answer 18

haima = blood

poeisis = formation

Question 19

Where are blood cells produced?

Answer 19

RED Bone marrow

Question 20

What is the precursor from which all blood cells arise?

Answer 20

pluripotent haematopoietic stem cell

Question 21

What are uncommitted stem cells?

Answer 21

lymphocyte stem cells

Question 22

Progenitor stem cells are committed to one or two cell types; list them.

Answer 22

• eosinophil
• mast cell
• basophil
• neutrophil
• dendritic cell
• monocyte (macrophage)
• megakaryocytes ( platelets)
• Reticulocyte (Erythrocyte)

Question 23

What are cytokines?

Answer 23

• 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

Question 24

What is leukopoeisis and what regulates it?

Answer 24

• formation of white blood cells

- regulated by colony stimulating factors (CSFs)

Question 25

Where do CSFs come from and what do they do?

Answer 25

- released by endothelial cells, marrow fibroblasts, and white blood cells - induce cell division and cell maturation in stem cells

Question 26

Cytokines released by leukocytes regulate further leukocyte production. What would happen if you had an active bacterial infection?

Answer 26

- goal is to fight infection: immune system | - cytokines will push for production of macrophage and neutrophils (professional phagocytes of the body)

Question 27

What is thrombopoeisis?

Answer 27

Formation of thrombocytes (platelets)

Question 28

What are the parent cells of thrombocytes?

Answer 28

Megakaryocytes

Question 29

Growth and maturation of thrombocytes is regulated by ____

Answer 29

cytokine thrombopoeitin (TPO)

Question 30

Where does the megakaryocte reside?

Answer 30

- 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

Question 31

Are platelets always present in the blood? Explain

Answer 31

Yes, but not activated until there is damage to the walls of the circulatory system

Question 32

What is erythropoeisis? What regulates it?

Answer 32

- formation of red blood cells | - cytokine erythropoeitin (EPO)

Question 33

What is erythropoeitin? Where is it made? What is EPO used for?

Answer 33

- cytokine that regulates erythropoeisis - glycoprotein made primarily in kidneys - genetically engineered to stimulate RBC production in patients

Question 34

What is haemostasis?

Answer 34

haeme = blood, stasis = stoppage - prevents blood from being loss from damaged vessels - must be fixed under pressure

Question 35

What are the steps of haemostasis?

Answer 35

1. 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 2. 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 3. 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

Question 36

explain healing

Answer 36

- 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