4. Hematopoiesis Flashcards by Trisha Anne

Other term for hematopoiesis

Hemopoiesis

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The process of blood cell formation

Hematopoiesis

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Classical marker of HSC

CD34

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Hematopoiesis is considered to start around the ______ of embryonic development after fertilization

19th day

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2 Theories on the origin of hematopoietic progenitor cells

polyphyletic theory
monophyletic theory

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This theory suggests that each of the blood cell lineages is derived from its own unique stem cell

Polyphyletic theory

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This theory is the most widely accepted theory among experimental hematologists

Monophyletic theory

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Monophyletic theory suggests that all blood cells are derived from a single progenitor stem cell called a

pluripotent stem cell

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Three phases of hematopoiesis

Mesoblastic/Megaloblastic
Hepatic
Medullary/Intramedullary/Myeloid

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Chief site of hematopoiesis in the mesoblastic phase

yolk sac

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chief site of hematopoiesis in the hepatic phase

fetal liver

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chief site of hematopoiesis during the medullary phase

bone marrow

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During the hepatic phase, hematopoiesis can also occur on these sites (3)

spleen
thymus
lymph nodes

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The first blood cells in mesoblastic phase are called

primitive erythroblasts

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Primitive erythroblasts are formed during the

first 2-8 weeks of life

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Primitive erythroblasts are important in the early embryogenesis to produce (3 types of Hgb) that are necessary to supply oxygen to embryonic tissues

Gower-1
Gower-2
Portland

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How is yolk sac hematopoiesis different from the hematopoiesis that occurs during the subsequent fetal and adult stages?

Yolk sac hematopoiesis occurs intravascularly

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The predominant Hgb during the hepatic phase

Hb F (Fetal Hemoglobin)

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The first fully developed organ in the fetus

Thymus

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Thymus is the major site for

T cell production

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These 2 organs produce B cells during fetal phase

Kidneys
Spleen

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Hematopoiesis starts in the bone marrow cavity ______ of fetal development

before the 5th month

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The bone marrow becomes the chief site of hematopoiesis by the

end of 24 weeks’ gestation

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Hematopoietic tissues of adults are located not only in the bone marrow, but also in the

lymph nodes
spleen
liver
thymus

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The bone marrow contains developing (4) cells

erythroid myeloid lymphoid megakaryocytic

The bone marrow is considered to be a primary lymphoid organ with functions equivalent to that of

Bursa of fabricus (birds)

The bone marrow is capable of generating around _____ per kg of body weight daily

2.5 billion rbcs 1 billion granulocytes 2.5 billion platelets

The process of replacing red marrow by yellow marrow during development

Retrogression

Between ages ______, adipocytes become more abundant and start to occupy the spaces in the long bones previously dominated by active marrow

5 and 7 years old

Retrogression ultimately results in the restriction of the red marrow (adult) to the (4)

ribs sternum, skull, shoulder blades vertebrae pelvis and proximal ends of long bones

T/F Yellow marrow is incapable of reverting back to active marrow in cases of increased demand in the bone marrow.

False

Hematopoietically active marrow

red marrow

The yellow marrow is hematopoietically inactive and is primarily composed of

adipocytes

primary lymphoid organs

bone marrow thymus

secondary/peripheral (major) lymphoid organs

spleen lymph nodes

Thymus develops during fetal development and continues until puberty. It then undergoes

atrophy with aging

Lymphoid cells fated to become B cells undergo their early stages of differentiation within the

bone marrow

2 major functions of the secondary/peripheral lymphoid organs

trapping and concentrating foreign substances main sites of antibody production and induction of Ag-specific T lymphocytes

The largest of the secondary lymphoid organs

Spleen

Lymph nodes are small ovoid, bean-shaped structures measuring

<1 cm in diameter

Spleen is a major organ in the body in which ______ are synthesized and from which they are released into the circulation.

antibodies

Effect of splenectomy to children

increased incidence of bacterial sepsis

causative agents of bacterial sepsis in children who had splenectomy

streptococcus pneumoniae Neisseria meningitidis haemophilus influenzae

Effect of splenectomy in adults

> less adverse effects > increase in blood-borne bacterial infections/ bacteremia

Removal of spleen

Splenectomy

Refers to the increased hemolytic activity of the spleen caused by splenomegaly

hypersplenism

Any disorder characterized by a localized/generalized enlargement of lymph nodes/vessels

lymphadenopathy

Solid tumor neoplasm of lymphoid tissue

lymphoma

Minor secondary lymphoid organs (4)

tonsils appendix peyer's patches MALT

This organ detects and responds to antigens in the respiratory and alimentary secretions

tonsil

These are clusters of lymphocytes distributed in the lining of the small intestine

peyer's patches

peyer's patches detect substances that diffuse across the

intestinal epithelium

MALT stands for

mucosa-associated lymphoid tissue

This is a general term for the unencapsulated lymphoid tissues present in regions underlying the mucosal areas

mucosa-associated lymphoid tissue

Bone marrow collection sites (5)

Posterior superior iliac crest Anterior superior iliac crest Sternum Anterior medial surface of the tibia Spinous process of the vertebrae, ribs, and other red marrow containing tissues

preferred collection site for bone marrow aspiration in adults

posterior superior iliac crest anterior superior iliac crest

preferred collection site for bone marrow aspiration in children <2 years old

anterior medial surface of the tibia

This organ can maintain hematopoietic stem cells and progenitor cells to generate various blood cells as a response to infectious agents or pathologic myelofibrosis of the bone marrow.

Liver

the largest cell in a normal marrow

megakaryocyte (30-50 um)

normal marrow cells

developing HSCs macrophages mast cells osteoblasts osteoclasts

macrophage size

40-50 um in diameter

Macrophages are + for this cytochemical stain

nonspecific (alpha napththyl acetate or alpha naphthyl butyrate) esterase

diameter of mast cells

12-25 um

mast cells are + for this cytochemical stain

chloroacetate esterase

these cells synthesize new bone matrix

osteoblasts

osteoblasts appearance

waterbug/comet

These are large, multinucleated cells with >100 um diameter

osteoclasts

M:E ration in leukemia

10:1

normal M:E ratio

2:1 to 4:1

In marrow differential, it is recommended to count

at least 500 preferably 1000 cells (500 cells on each of 2 slides)

myeloid cells will become

wbcs

erythroid cells will become

rbcs

bone marrow aspirate vs bone marrow biopsy

BMA disturbs bone marrow architecture; BMB does not

Bone marrow aspirate is used for

analysis of individual cell morphology

Bone marrow aspirate smears should be retained for

10 years

Advantage of bone marrow biopsy

gives a better picture of the real structure of the bone marrow

blood cell production outside of the bone marrow

extramedullary hematopoiesis

The spleen normally produces

lymphoid cells

Extramedullary hematopoiesis mainly occurs in the

liver spleen

extramedullary hematopoiesis is often accompanied with

splenomegaly hepatomegaly