1-HEMATOPOIESIS Flashcards
1
Q
What are the four key functions of hematopoiesis?
A
Production, development, differentiation, and maturation of all blood cells.
2
Q
How does the efficiency of hematopoiesis compare to industrial manufacturing?
A
It surpasses high-scale manufacturers in production quotas, custom specifications, and quality of the final product.
3
Q
Why does blood remain fluid inside the body but coagulate outside?
A
Due to naturally circulating anticoagulants in vivo, whereas it coagulates within 5–10 minutes in vitro.
4
Q
What contributes to the red color of blood?
A
The presence of hemoglobin.
5
Q
What is the pH range of blood, and how does it maintain stability?
A
Blood has a pH of 7.4 (range: 7.35–7.45) and maintains stability through buffering mechanisms.
6
Q
How does the viscosity of blood compare to water?
A
Blood is 3.5–4.5 times thicker than water.
7
Q
How much of the total body weight does blood comprise?
A
7–8% of the total body weight, equivalent to 75–85 mL/kg body weight.
8
Q
What is the solid content in 100 mL of blood?
A
Approximately 20g of solid material.
9
Q
How does blood transport gases in the body?
A
It carries oxygen from the lungs to tissues and transports carbon dioxide from tissues to the lungs.
10
Q
How does blood distribute nutrients?
A
It supplies tissues with food materials and substances absorbed from the gastrointestinal tract.
11
Q
How does blood contribute to waste removal?
A
It carries metabolic waste products to excretory organs for elimination.
12
Q
What role does blood play in maintaining pH balance?
A
It selectively excretes solutes and acts as a buffer to preserve a near-neutral reaction in tissues.
13
Q
How does blood regulate body temperature?
A
It helps maintain a constant body temperature through heat distribution.
14
Q
What is the role of blood in hormone transport?
A
It transports hormones and endocrine secretions that regulate cellular functions.
15
Q
How does blood contribute to cellular excitability?
A
It maintains the degree of irritability in tissue cells.
16
Q
How does blood participate in immune defense?
A
It contains immune cells and molecules that protect the body against infections and foreign invaders.
17
Q
How does the bone marrow’s daily production capacity highlight the importance of hematopoiesis?
A
The bone marrow produces 3 billion red cells, 1.5 billion white cells, and 2.5 billion platelets per day per body weight, underscoring its critical function.
18
Q
What three mechanisms ensure a constant supply of blood cells from bone marrow?
A
Continuous release of mature cells into circulation. Mobilization of bone marrow to increase production when necessary. Compensation for reduced hematopoiesis by activating extramedullary sites (liver and spleen).
19
Q
What are the three main components of blood?
A
Liquid portion, solid portion, and gaseous portion.
20
Q
How does plasma differ from serum?
A
Plasma is the liquid portion of unclotted blood and contains fibrinogen, while serum is the liquid portion of clotted blood and lacks fibrinogen.
21
Q
What is the function of fibrinogen in plasma?
A
It is a clotting factor that is used to form fibrin threads during blood clotting.
22
Q
Why does serum have different biological properties than plasma?
A
Because serum contains growth factors and other proteins released from platelets during clot formation.
23
Q
What are the three major formed elements in blood?
A
Erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets).
24
Q
How does blood transport oxygen and carbon dioxide?
A
Oxygen is primarily bound to hemoglobin in erythrocytes, while carbon dioxide is transported as dissolved CO₂, bicarbonate (HCO₃⁻), or bound to hemoglobin.
25
How does the oxygen content in arterial blood compare to venous blood?
Arterial blood contains more oxygen, whereas venous blood has higher carbon dioxide content.
26
What are the key processes involved in hematopoiesis?
Cell renewal, proliferation, differentiation, and maturation.
27
What is the outcome of hematopoiesis?
Formation, development, and specialization of functional blood cells released from the bone marrow into circulation.
28
How does hematopoiesis differ between fetal development and adulthood?
In fetuses, hematopoiesis occurs in a sequential manner across different organs, while in adults, it is restricted primarily to the bone marrow.
29
What are the three major phases of prenatal hematopoiesis?
Mesoblastic Phase (Yolk sac & AGM region)
Hepatic Phase (Liver, spleen, thymus, lymph nodes)
Medullary Phase (Bone marrow)
30
Where does hematopoiesis take place during the mesoblastic phase?
In the fetal yolk sac (mesodermal extraembryonic layer).
31
What type of blood cells are produced during the mesoblastic phase?
Primitive erythroblasts.
32
What are the types of embryonic hemoglobins (Hgb) produced in the mesoblastic phase?
Hgb Gower I
Hgb Gower II
Hgb Portland
33
What are the globin chain compositions of embryonic hemoglobins?
Hgb Gower I & II: Two alpha chains combined with either epsilon or zeta chains.
Hgb Portland: Also contains embryonic globin chains.
34
Do embryonic hemoglobins participate in oxygen delivery or persist into adult life?
No, they do not survive into adult life or participate in oxygen delivery.
35
Which organ becomes the chief site of hematopoiesis during the hepatic phase?
The liver (by the 3rd month of fetal life).
36
What types of cells appear during the hepatic phase?
White blood cells and megakaryocytes.
37
What is the major hemoglobin produced during the hepatic phase?
Fetal hemoglobin (Hgb F), composed of alpha and gamma chains.
38
Which organs are active in hematopoiesis during the hepatic phase?
Liver – Primary site of erythropoiesis.
Spleen, thymus, and lymph nodes – Become hematopoietically active, producing red cells and lymphocytes.
39
What is the first fully developed organ in the fetus, and what is its function?
The thymus, which becomes the major site of T cell production.
40
Which organ is the primary site of B cell production during fetal life?
The kidney.
41
What are the hematopoietic functions of the spleen during fetal development?
Erythropoiesis – Active until the end of gestation.
Myelopoiesis – Minimal activity by the 5th month.
Lymphopoiesis – Continues throughout life.
42
When does the bone marrow take over as the primary site of hematopoiesis?
From the 7th month of fetal life and continuing into adulthood.
43
Which bone marrow type serves as the chief site of blood cell production?
Red bone marrow.
44
When does hemoglobin A (Hgb A) production begin?
Around the 5th month of fetal life.
45
What is the composition of hemoglobin A (Hgb A)?
Alpha₂ Beta₂.
46
What measurable factors can be detected during the medullary phase?
Erythropoietin (EPO)
Granulocyte Colony-Stimulating Factor (G-CSF)
Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF)
Hemoglobin F (Hgb F)
Hemoglobin A2 (Hgb A2)
47
Where does erythropoiesis, myelopoiesis, and thrombopoiesis take place in adults?
In the bone marrow.
48
What are the two types of bone marrow, and what are their functions?
Red marrow – Hematopoietically active, responsible for blood cell development (~50% of marrow cavity space).
Yellow marrow – Composed primarily of adipocytes and serves as energy storage.
49
How does bone marrow composition change with age?
By 4–7 years, adipose tissue starts occupying spaces in long bones.
By 18 years, active hematopoiesis remains only in the pelvis, vertebrae, ribs, scapulae, sternum, skull, and proximal extremities of long bones.
50
What is retrogression in bone marrow?
The process of replacing active red marrow with adipose tissue (yellow marrow), which can revert back to red marrow when needed.
51
What is the characteristic of bone marrow in terms of cell development?
It contains developing precursor cells at all maturation stages, with only mature cells normally released into circulation.
52
What is the first recognizable precursor in each cell line?
A blast cell.
53
What imaging technique is used to study blood cell production in the bone marrow?
Radioactive imaging, using iron isotopes that mimic ingested iron bound to transferrin.
54
What is extramedullary hematopoiesis?
Blood cell production occurring outside the bone marrow, primarily in the liver and spleen.
55
Why do the liver and spleen retain their hematopoietic capability?
Because they played major roles in early fetal hematopoiesis.
56
What happens when extramedullary hematopoiesis develops?
The liver and spleen enlarge, leading to hepatosplenomegaly.
57
What is a physical indicator of hepatosplenomegaly?
A puffy and protrusive left upper abdominal area.
58
Why is hepatosplenomegaly clinically significant?
It always indicates compromised hematological health.
59
What is the fundamental concept of the Stem Cell Theory?
All blood cells are derived from a pool of self-renewing stem cells.
60
What are the two types of hematopoietic stem cells (HSCs)?
Pluripotent HSCs – Can produce blood cells of all lineages and are capable of self-renewal.
Multipotent HSCs – Can produce cells of multiple lineages but have limited self-renewal.
61
What is a committed stem cell?
A stem cell with receptors for specific growth factors, leading to differentiation into a single cell lineage (e.g., erythroid CFU, granulocyte-macrophage CFU).
62
What is the function of hemocytoblasts?
They are hematopoietic stem cells that give rise to all formed elements under the influence of hormones and growth factors.
63
What is erythropoietin (EPO), and what is its role?
A cytokine and hormone produced by the kidneys.
Stimulates erythroid progenitor cells to regulate RBC production.
64
What is thrombopoietin (TPO), and what is its function?
A cytokine that stimulates megakaryocyte CFU cells.
Increases platelet production.
65
What is granulocyte colony-stimulating factor (G-CSF), and what does it stimulate?
A cytokine that stimulates granulocyte-macrophage CFU cells.
Increases neutrophil production.
66
What is granulocyte-macrophage colony-stimulating factor (GM-CSF)?
A cytokine that increases macrophage production by stimulating granulocyte-macrophage CFU cells.
67
What is the role of interleukins in hematopoiesis?
They stimulate B-cell and T-cell formation, often working alongside G-CSF and GM-CSF.
68
What is the marker for hematopoietic stem cells?
CD34.
69
What is the CFU specific for megakaryocytes?
CFU-meg.
70
What growth factor is necessary for megakaryocyte development?
Thrombopoietin (TPO).
71
What growth factor is required for red blood cell formation?
Erythropoietin (EPO).
72
Can hematopoietic stem cells mature without growth factors?
No, missing any growth factor prevents the formation of that cell lineage.
73
What is the earliest growth factor required for hematopoietic stem cell development?
Kit Ligand.
74
What is Megakaryopoiesis?
Maturation of megakaryocytes
75
What is Thrombopoiesis?
Genesis of platelets
76
What is the stem cell for platelets?
Hemocytoblast
77
What hormone is responsible for committing the megakaryoblast to differentiate into mature stages?
Thrombopoietin
78
What is the earliest recognizable stage of megakaryocyte maturation?
Megakaryoblast (MK1)
79
What are key characteristics of a megakaryoblast?
Large, irregularly shaped cell; single or multiple round/oval nuclei; blue, non-granular cytoplasm; nucleoli present; centrally located nucleus with fine chromatin strands; high nuclear-to-cytoplasmic ratio; basophilic cytoplasm
80
What is the defining feature of a promegakaryocyte?
Presence of bluish granules in the cytoplasm adjacent to the nucleus
81
How does a promegakaryocyte differ from a megakaryoblast?
It has granules (dense, alpha, lysosomal) dispersed in the cytoplasm
82
What changes occur in the nucleus at this stage?
The nucleus has divided one or more times (2N), and the cell has increased in size
83
What are the key characteristics of a megakaryocyte without platelets?
Abundant light blue to pink cytoplasm; numerous purple-red or pink granules; nucleus with 8, 16, or 32 overlapping lobes (sometimes up to 64 lobes); develops copious cytoplasm, which differentiates into platelets; matures in the bone marrow in approximately 5 days
84
What significant membrane system forms in this stage?
Demarcating Membrane System (DMS)
85
What is the function of the Demarcating Membrane System (DMS)?
It serves as the future membrane system of the platelet
86
What process allows megakaryocytes to become polyploid without cell division?
Endomitosis
87
What happens during endomitosis?
The nucleus duplicates without cell division, resulting in a polyploid cell
88
What is the key difference between a megakaryocyte without platelets (MK3) and a megakaryocyte with shedding platelets (MK4)?
In MK4, the Demarcating Membrane System (DMS) has fully matured, and platelets are streaming from the margins.
89
What is the lifespan of the cytoplasmic fragments of a megakaryocyte?
9-12 days
90
What process allows MK4 to increase nuclear content without cell division?
Endomitosis
91
What is the final stage of cell line maturation in megakaryopoiesis?
Megakaryocyte with shedding platelets (MK4)
92
Where do megakaryocytes release platelets?
Near the bone marrow sinusoids, where fragmented cytoplasm is released as platelets.
93
What process do metamegakaryocytes undergo instead of complete cell division?
Endomitosis
94
What is the primary function of metamegakaryocytes?
To release platelets
95
Where do platelets originate from in the metamegakaryocyte?
Demarcating Membrane System (DMS)
96
Where do platelets originate?
Bone marrow
97
What are platelets?
Small fragments of megakaryocytes
98
What regulates platelet formation?
Thrombopoietin
99
What are the key structural characteristics of platelets?
1-4 µm in diameter; Disc-shaped in circulation; Irregularly shaped when activated; Non-nucleated; Dense blue to purple with fine red-purple granules
100
What substances are found in platelet granules?
Serotonin, Ca²⁺, enzymes, ADP, and platelet-derived growth factor (PDGF)
101
What is the lifespan of platelets?
9-12 days (or 4-9 days in circulation)
102
Why is platelet lifespan sometimes considered 9-12 days instead of 4-9 days?
Proplatelets from the bone marrow are counted, extending the lifespan estimate.
103
What is the normal range (N.V.) of platelets in the blood?
150,000 – 400,000 cells/cu.mm (150 – 400 × 10⁹/L)
104
How many platelets are produced daily to maintain hemostatic balance?
15,000 – 45,000 platelets
105
How does the size of cells change in megakaryopoiesis compared to erythropoiesis and leukopoiesis?
Megakaryocytes get larger as they mature, whereas RBCs and WBCs get smaller.
106
What is released into circulation in megakaryopoiesis?
Not the entire metamegakaryocyte, but its fragmented cytoplasm (platelets).
107
What are proplatelets, and where do they mature?
They are premature platelet fragments that mature in circulation.
108
From which precursor cell do megakaryocytes differentiate?
Myeloid stem cell
109
What is the function of megakaryocytes?
Production of platelets
110
What is another name for the basophilic stage?
Megakaryoblast
111
What are the key characteristics of megakaryocytes in the basophilic stage?
Small size; Diploid nucleus (2N); Abundant basophilic cytoplasm (bluish staining)
112
How does the nucleus change in the granular stage?
Becomes more polyploid (more than 2 complete sets of chromosomes)
113
How does the cytoplasm change in the granular stage?
Becomes more eosinophilic and granular
114
What is another name for the mature stage?
Metamegakaryocyte
115
What are the key characteristics of megakaryocytes in the mature stage?
Very large size; 16-32 nuclei; Abundant granular cytoplasm; Undergoes shedding to form platelets
116
What is endomitosis?
A process where megakaryocytes undergo nuclear replication without completing cell division (telophase is missing).
117
What is the result of endomitosis in megakaryocytes?
A cell with a multilobed nucleus
118
What is the ploidy of each lobe in a megakaryocyte?
Diploid (2N), containing a full set of 23 chromosome pairs
119
What determines the size of the megakaryocyte’s cytoplasm?
The degree of ploidy (higher ploidy = larger cytoplasm volume).
120
What is the maximum ploidy level megakaryocytes can achieve?
32N (16 lobes)
121
How many platelets does an average megakaryocyte (8N or 16N) produce?
2,000 – 4,000 platelets
122
What is hematopoiesis?
The continuous, regulated process of blood cell production, including renewal, proliferation, differentiation, and maturation.
123
What are the three stages of prenatal hematopoiesis?
Mesoblastic Period – Yolk sac; Hepatic Period – Liver; Medullary/Myeloid Period – Red bone marrow
124
What does the Stem Cell Theory of Hematopoiesis state?
All blood cells derive from a pool of self-renewing stem cells.
125
Megakaryoblast (MK1) – Earliest stage, dependent on thrombopoietin
126
Promegakaryocyte (MK2)
127
Megakaryocyte without platelets (MK3) – Formation of Demarcating Membrane System (DMS)
128
Megakaryocyte with shedding platelets (MK4)
129
Megakaryocyte producing platelets (Metamegakaryocyte)
130
Basophilic stage
131
Granular stage
132
Mature stage
133
Platelets/Thrombocytes
134
Which cytokine stimulates T cells, B cells, and NK cells?
IL-2
135
Which cytokine is a multilineage stimulating factor?
IL-3
136
Which cytokine affects B cells, T cells, and mast cells?
IL-4
137
Which cytokine stimulates stem cells and B cells?
IL-6
138
Which cytokine stimulates pre-B cells, T cells, and early granulocytes?
IL-7
139
Which cytokine stimulates megakaryocytes?
IL-11
140
Which cytokine stimulates granulocytes, macrophages, fibroblasts, and endothelial cells?
GM-CSF
141
Which cytokine stimulates red cell progenitor cells?
Erythropoietin (EPO)
