Haematopoiesis

Question 1

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

Answer 1

Yolk sac

Question 2

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

Answer 2

Aorta-gonads-mesonephros

Question 3

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

Answer 3

Liver

Question 4

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

Answer 4

Kidney

Question 5

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

Answer 5

Sixth

Question 6

Where is the bone marrow located?

Answer 6

Between the trabeculae of spongy bone

Question 7

Describe the tissue of the bone marrow.

Answer 7

Cellular, highly-vascularised, loose connective tissue

Question 8

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

Answer 8

Haematopoietic compartment

Question 9

List five features of the vascular compartment.

Answer 9

Nutrient artery

Periosteal arteries

Central longitudinal vein

Arterioles

Sinuses

Question 10

Haematopoietic cells are arranged in _______ within the marrow cavity.

Answer 10

Niches

Question 11

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

Answer 11

Venous sinuses

Question 12

Define erythroblastic islands.

Answer 12

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

Question 13

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

Answer 13

Cytoplasm stretches to contact nearby erythroblasts

Regulates erythropoietin by cytokine secretion

Phagocytose nuclei extruded from erythroblasts

Question 14

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

Answer 14

Granulocytes

Question 15

Where are megakaryocytes produced?

Answer 15

Near vascular sinuses

Question 16

Lymphocytes are produced in lymphoid aggregates near ____________.

Answer 16

Arterioles

Question 17

What is the haematopoietic microenvironment?

Answer 17

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

Question 18

What does the haematopoietic microenvironment consist of?

Answer 18

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

Question 19

Name two types of stromal cells.

Answer 19

Adipocytes

Osteoblasts

Question 20

What is the function of the adipocytes?

Answer 20

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

Question 21

List six features of osteoblasts.

Answer 21

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)

Question 22

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

Answer 22

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

Question 22

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

Answer 22

Niches

Question 23

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

Answer 23

False

Question 24

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 _________.

Answer 24

Cytokines

Question 25

List two other functions of niches.

Answer 25

Important molecular determinant for geographic location Presence of membrane receptors for ECM proteins

Question 26

Bone forms a _________compartment for the BM.

Answer 26

Rigid

Question 27

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

Answer 27

Adipocytes

Question 28

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

Answer 28

Yellow

Question 29

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.

Answer 29

25

Question 30

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

Answer 30

1:1

Question 31

Define 'hyperplasia'.

Answer 31

An excessive proliferation of normal haematopoietic cells

Question 32

List three features of hyperplasia.

Answer 32

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

Question 33

When would hypoplasia occur?

Answer 33

When haematopoietic tissue becomes ineffective

Question 34

What cell type increases in amount in hypoplasia?

Answer 34

Adipocytes

Question 35

Why would hypoplasia occur?

Answer 35

Caused by genetics and environmental stressors, such as toxins

Question 36

Where does extramedullary haematopoiesis occur, and why?

Answer 36

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

Question 37

Describe the egression of blood cells.

Answer 37

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

Question 38

List three soluble factors required for cells to reach circulation.

Answer 38

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

Question 39

State three features of the thymus.

Answer 39

Lymphopoietic organ Located in the upper anterior mediastinum Bilobed

Question 40

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

Answer 40

Outer cortex

Question 41

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

Answer 41

Inner medulla

Question 42

What is the main function of the thymus?

Answer 42

To act as the site of maturation of T-cells

Question 43

True or false: the spleen is essential to life.

Answer 43

False

Question 44

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

Answer 44

Spleen

Question 45

Name the three zones of the spleen.

Answer 45

White pulp Red pulp Marginal zones

Question 46

List three features and functions of the white pulp.

Answer 46

Contains lymphocytes Located around a central artery Important in immune response

Question 47

Name two components of the red pulp.

Answer 47

Sinuses and cords

Question 48

List two features of the marginal zone.

Answer 48

Surrounds white pulp, and is reticular Contains specialised B-cells, macrophages, and blood vessels

Question 49

The __________ _______ branches into many vesicles in trabeculae.

Answer 49

Splenic artery

Question 50

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

Answer 50

True

Question 51

Describe the slow transit pathway of the spleen.

Answer 51

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

Question 52

What other pathway can the spleen operate under?

Answer 52

Rapid transit pathway

Question 53

Macrophages cull ___________ or damaged red cells.

Answer 53

Senescent

Question 54

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

Answer 54

Spherocytes

Question 55

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

Answer 55

Phagocytes

Question 56

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

Answer 56

Paediatric

Question 57

_______ ________ _________ act as reservoirs for platelets.

Answer 57

Red pulp cords

Question 58

Splenomegaly may result in ____________________.

Answer 58

Thrombocytopaenia

Question 59

List three findings of hypersplenism.

Answer 59

Enlarged spleen Exaggeration of normal functions, resulting in anaemia, leucopaenia, and thrombocytopaenia A hyperplastic BM may exist, corresponding to peripheral blood cytopaenia

Question 60

__________ hypersplenism has no identifiable cause.

Answer 60

Primary

Question 61

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

Answer 61

Secondary

Question 62

Briefly state four other causes of hypersplenism.

Answer 62

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

Question 63

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

Answer 63

Splenectomy

Question 64

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

Answer 64

Liver

Question 65

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

Answer 65

Kupffer

Question 66

What is functional splenectomy also known as?

Answer 66

Autosplenectomy

Question 67

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

Answer 67

Blockage of the blood vessels Infarcts of the surrounding tissue Tissue damage becomes progressive and leads to functional splenectomy (autosplenectomy)

Question 68

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

Answer 68

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

Question 69

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

Answer 69

Cortex

Question 70

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

Answer 70

Germinal centres

Question 71

In a lymph node, the _________ surrounds efferent lymphatics.

Answer 71

Medulla

Question 72

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

Answer 72

Plasma cells

Question 73

What is the major function of lymph nodes?

Answer 73

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

Question 74

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

Answer 74

Immunocompetent

Question 75

Stimulated B-cells move to _________ as plasma cells.

Answer 75

Medulla

Question 76

What is lymphadenopathy?

Answer 76

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

Question 77

State four causes of lymphadenopathy.

Answer 77

Inflammation of the lymph node Prolonged immune response to infectious agents Malignant transformation of lymphocytes or macrophages Metastatic tumours that originate in extranodal sites

Question 78

What does MALT stand for?

Answer 78

Mucosa-associated lymphoid tissue

Question 79

What is the MALT?

Answer 79

Collection of loosely-organised aggregates of lymphocytes

Question 80

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

Answer 80

True

Question 81

What is the main function of the MALT?

Answer 81

To trap antigens