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B-Haematology II > Haematopoiesis > Flashcards

Haematopoiesis Flashcards

1
Q

Haematopoiesis occurs earliest in the _________ ______, with erythrocyte and macrophage production.

A

Yolk sac

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2
Q

Where is primitive erythropoiesis accompanied by haemoglobin variants, such as Portland, Gower I, and Gower II?

A

Aorta-gonads-mesonephros

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3
Q

In the third month of gestation, the _______ produces erythroid cells and greater numbers of myeloid and lymphoid cells.

A

Liver

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4
Q

The spleen, _________, and lymph nodes are involved to a lesser degree.

A

Kidney

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5
Q

The bone marrow is the primary site of haematopoiesis by the __________ month of foetal life.

A

Sixth

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6
Q

Where is the bone marrow located?

A

Between the trabeculae of spongy bone

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7
Q

Describe the tissue of the bone marrow.

A

Cellular, highly-vascularised, loose connective tissue

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8
Q

The ____________ ___________ houses the formation and maturation of haematopoietic and stromal cells.

A

Haematopoietic compartment

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9
Q

List five features of the vascular compartment.

A

Nutrient artery

Periosteal arteries

Central longitudinal vein

Arterioles

Sinuses

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10
Q

Haematopoietic cells are arranged in _______ within the marrow cavity.

A

Niches

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11
Q

Erythroblasts compose 25-30% of the population, and are located near _________ ____________ in the bone marrow.

A

Venous sinuses

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12
Q

Define erythroblastic islands.

A

Composed of a single macrophage, surrounded by erythroblasts in different stages of maturation

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13
Q

List three functions of macrophages, in the context of haematopoiesis.

A

Cytoplasm stretches to contact nearby erythroblasts

Regulates erythropoietin by cytokine secretion

Phagocytose nuclei extruded from erythroblasts

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14
Q

_____________ are produced in nests, close to trabeculae and arterioles, but distant from sinuses.

A

Granulocytes

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15
Q

Where are megakaryocytes produced?

A

Near vascular sinuses

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16
Q

Lymphocytes are produced in lymphoid aggregates near ____________.

A

Arterioles

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17
Q

What is the haematopoietic microenvironment?

A

An appropriate milieu for the proliferation and maturation of haematopoietic precursor cells (HPCs)

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18
Q

What does the haematopoietic microenvironment consist of?

A

A complex network of stromal cells and extracellular matrix (ECM) components

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19
Q

Name two types of stromal cells.

A

Adipocytes

Osteoblasts

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20
Q

What is the function of the adipocytes?

A

Mechanically mediate the volume of BM in which haematopoiesis occurs, by secreting steroids and cytokines which reinforce osseous integrity and stimulate haematopoiesis

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21
Q

List six features of osteoblasts.

A

Produce cytokines that regulate stem cell activity

Provide 3-dimensional scaffold for haematopoietic cells

Express homing receptors (e.g., SDF-1, CXCR4, and others)

Produce soluble growth and differentiation factors

Produce integral membrane proteins that function as juxtacrine regulators (SCF, FL, etc..)

Produce ECM components (e.g., highly viscous proteoglycans)

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22
Q

Name four features, and their functions, of the extracellular matrix.

A

Cytokines and growth factors, to regulate haematopoietic cell differentiation and expansion

Collagen, to provide structural support
Glycosaminoglycans, which provide cell-to-cell interactions; localise growth factors

Cytoadhesion molecules, to allow adhesion of cells to extracellular matrix proteins

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22
Q

HPCs of different lineages and different stages can be found in distinct areas of the marrow called __________.

A

Niches

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23
Q

True or false: all precursor cells can interact with all areas of the extracellular matrix.

A

False

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24
Q

The structure of the BM allow for adhesive interactions between the stem cell, progenitor cell, and the ECM function to hold HPCs in microenvironment niches, and to allow for close proximity with _________.

A

Cytokines

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25
Q

List two other functions of niches.

A

Important molecular determinant for geographic location

Presence of membrane receptors for ECM proteins

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26
Q

Bone forms a _________compartment for the BM.

A

Rigid

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27
Q

Any change in volume of haematopoietic tissue must be compensated for by a change in space-occupying ______________.

A

Adipocytes

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28
Q

At greater than four years of age, adipocytes increase (in ___________ marrow).

A

Yellow

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29
Q

By ___ years of age, haematopoiesis is limited to marrow of skull, ribs, sternum, scapulae, clavicles, vertebrae, pelvis, upper half of sacrum, and proximal ends of long bones.

A

25

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30
Q

Red vs. yellow marrow is found in a ratio of _____.

A

1:1

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31
Q

Define ‘hyperplasia’.

A

An excessive proliferation of normal haematopoietic cells

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32
Q

List three features of hyperplasia.

A

Adipocytes may be replaced

Occurs in all conditions with impaired or increased haematopoiesis

Degree is related to severity and duration of the pathological state, as well as the root cause, such as anaemia or leukaemia

33
Q

When would hypoplasia occur?

A

When haematopoietic tissue becomes ineffective

34
Q

What cell type increases in amount in hypoplasia?

A

Adipocytes

35
Q

Why would hypoplasia occur?

A

Caused by genetics and environmental stressors, such as toxins

36
Q

Where does extramedullary haematopoiesis occur, and why?

A

Occurs in areas such as the liver and spleen, when hyperplasia of the marrow is unable to cater to haematopoietic needs

37
Q

Describe the egression of blood cells.

A

Blood cells migrate from the BM into the circulation by migrating between reticular cells, through endothelial cells, and via cell traffic across the sinuses. Reticular cells contract, creating a less continuous layer over the abluminal sinus walls, and thus producing compartments where mature cells congregate

38
Q

List three soluble factors required for cells to reach circulation.

A

Granulocyte-colony stimulating factor (G-CSF)

Granulocyte-monocyte-colony stimulating factor (GM-CSF)

Chemokines

39
Q

State three features of the thymus.

A

Lymphopoietic organ

Located in the upper anterior mediastinum

Bilobed

40
Q

The _________ ________ of the thymus is densely packed with thymocytes, cortical epithelial cells, and some macrophages.

A

Outer cortex

41
Q

The __________ __________ of the thymus contains mature thymocytes, epithelial cells, dendritic cells, and macrophages.

A

Inner medulla

42
Q

What is the main function of the thymus?

A

To act as the site of maturation of T-cells

43
Q

True or false: the spleen is essential to life.

A

False

44
Q

The __________ contains the largest collection of lymphocytes and mononuclear phagocytes in the body.

A

Spleen

45
Q

Name the three zones of the spleen.

A

White pulp

Red pulp

Marginal zones

46
Q

List three features and functions of the white pulp.

A

Contains lymphocytes

Located around a central artery

Important in immune response

47
Q

Name two components of the red pulp.

A

Sinuses and cords

48
Q

List two features of the marginal zone.

A

Surrounds white pulp, and is reticular

Contains specialised B-cells, macrophages, and blood vessels

49
Q

The __________ _______ branches into many vesicles in trabeculae.

A

Splenic artery

50
Q

True or false: the spleen’s blood supply may terminate in any of the three main zones.

A

True

51
Q

Describe the slow transit pathway of the spleen.

A

Plasma moves into the sinuses via macrophage-lined cords, involves elevated haematocrit

52
Q

What other pathway can the spleen operate under?

A

Rapid transit pathway

53
Q

Macrophages cull ___________ or damaged red cells.

A

Senescent

54
Q

The spleen pits particles, such as antibody, from erythrocytes, without destroying the cells, resulting in _______________.

A

Spherocytes

55
Q

For immune defence, the white pulp and marginal zones are rich in lymphocytes and ______________.

A

Phagocytes

56
Q

What population is the spleen’s immune function especially important for?

A

Paediatric

57
Q

_______ ________ _________ act as reservoirs for platelets.

A

Red pulp cords

58
Q

Splenomegaly may result in ____________________.

A

Thrombocytopaenia

59
Q

List three findings of hypersplenism.

A

Enlarged spleen

Exaggeration of normal functions, resulting in anaemia, leucopaenia, and thrombocytopaenia

A hyperplastic BM may exist, corresponding to peripheral blood cytopaenia

60
Q

__________ hypersplenism has no identifiable cause.

A

Primary

61
Q

_____________ hypersplenism occurs in conditions such as hereditary spherocytosis, liver disease, myelofibrosis, immune thrombocytopaenia, etc..

A

Secondary

62
Q

Briefly state four other causes of hypersplenism.

A

Infiltration of the spleen with additional cells or metabolic by-products

Gaucher’s disease, where macrophages accumulate large quantities of undigestible material

Neoplasms in which malignant cells occupy much of the splenic volume

Congestive splenomegaly can occur following liver cirrhosis with portal hypertension, after congestive heart failure, and when blood that does not flow easily through the liver is rerouted through the spleen

63
Q

_______________ appears to be most beneficial in patients with hereditary or acquired conditions.

A

Splenectomy

64
Q

What organ assumes culling functions, in the absence of the spleen?

A

Liver

65
Q

__________ cells of the liver can perform functions similar to phagocytes lining splenic cords, but are not as effective as the spleen.

A

Kupffer

66
Q

What is functional splenectomy also known as?

A

Autosplenectomy

67
Q

List three events to which enhanced sickling of RBCs, due to acidic, hypoxic, and hypoglycaemic environment of the spleen, leads.

A

Blockage of the blood vessels

Infarcts of the surrounding tissue

Tissue damage becomes progressive and leads to functional splenectomy (autosplenectomy)

68
Q

State five features of lymph nodes, vessels, and fluids.

A

Lymph nodes and lymphatic vessels drain into left and right lymphatic ducts

Lymph empties into blood

Vessels originate in connective tissue

Lymph is formed from blood fluid that escapes into tissue

Nodes are bean-shaped

69
Q

The _________ of a lymph nodes contains B-cell follicles, surrounded by T-lymphocytes and macrophages.

A

Cortex

70
Q

Follicles of lymph nodes contain areas of B-cells called _____________ _____________.

A

Germinal centres

71
Q

In a lymph node, the _________ surrounds efferent lymphatics.

A

Medulla

72
Q

Lymph nodes contain cords of __________ ________, that lie between sinusoids.

A

Plasma cells

73
Q

What is the major function of lymph nodes?

A

To act as filters, removing foreign particles from lymph by phagocytic cells

74
Q

Antigens in lymph come into contact with, and stimulate, ________________ lymphocytes to proliferate and differentiate into effector cells.

A

Immunocompetent

75
Q

Stimulated B-cells move to _________ as plasma cells.

A

Medulla

76
Q

What is lymphadenopathy?

A

The enlargement of the lymph nodes by expansion of the tissue within the node

77
Q

State four causes of lymphadenopathy.

A

Inflammation of the lymph node

Prolonged immune response to infectious agents

Malignant transformation of lymphocytes or macrophages

Metastatic tumours that originate in extranodal sites

78
Q

What does MALT stand for?

A

Mucosa-associated lymphoid tissue

79
Q

What is the MALT?

A

Collection of loosely-organised aggregates of lymphocytes

80
Q

True or false: the MALT is not as well demarcated as lymph node tissue.

A

True

81
Q

What is the main function of the MALT?

A

To trap antigens

B-Haematology II (2 decks)

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