Hematopoiesis

granulopoiesis

production of granulocytes

erythropoiesis

production of erythrocytes

thrombopoiesis

production of platelets

fetal yolk sac

when does hematoipoiesis begin?

bone marrow

what is the primary site of hematopoisis after birth?

extramedullary hematopoiesis

hematopoiesis that occurs outside bone marrow

• Ej. SPLEEN

specific place of hematopoiesis in bone marrow

extravascular spaces between venous sinuses

red bone marrow

site of active hematopoiesis

main sites of active marrow

• flat bones, humerus, femur, vertebrae

bone marrow sampling

hematopoietic stem cells

•All hematopoietic cells originate from a common, pluripotent, self-renewing population of HSCs

•HSCs are the least mature cells in the marrow

•HSCs give rise to either lymphoid or myeloid common progenitor cells (first step of commitment)

increased peripheral demand

•Marrow preferentially releases the most mature cells first

•As mature cell stores are exhausted, progressively more immature forms may be released

senescence

• old cells

• generally removed from circulation by macrophages

• species dependent

• In disease, cells may instead be “used up” before their typical life expectancy

erythropoiesis

• stimulated by EPO

• •Early erythroid precursors are large and nucleated

  •During maturation, cells become smaller and the nucleus becomes more condensed

  •In mammals, the nucleus is extruded late in maturation, producing a reticulocyte

1. RUBRIBLAST

2. PRORUBRICYTE

3. RUBRICYTE

4. METARUBRICYTE

5. RETICULOCYTE

6. ERYTHROCYTE

Hemoglobin

•oxygen-carrying protein that gives mature RBCs the orange-red color on stained blood films

residual RNA

what is the blue-purple tint in a polychromatophil?

proliferation pool

1. rubriblast

2. prorubricyte

3. rubricyte

maturation and storage pool

1. metarubricyte

2. reticulocyte

3. eruthrocyte

erythroblastic islands

where does maturation of erythroid cells occur?

iron metabolism

•Iron is absorbed by enterocytes and stored in macrophages and hepatocytes (liver cells)

•Iron travels through the blood bound to the transport protein transferrin

•Most iron in adult animals is recycled from senescent RBCs by macrophages

iron restricted erythropoiesis

•Not enough iron for erythroid precursors to produce normal hemoglobin

•Can cause anemia (low RBCs in peripheral blood)

2 forms

iron deficiency

depleted iron stores

anemia of inflammation

iron sequestration due to inflammation

non mammalian erythropoiesis

•Mature RBCs retain nuclei

•Cytoplasm of immature cells is still polychromatophilic on routinely stained smears (like mammals)

granulopoiesis

neutrophils, eosinophils, and basophils

granulocyte CSF

what stimulates granulopoiesis?

segmented

most mature form of neutrophils

left shift

•increased numbers of less mature neutrophils in circulation

•Bone marrow response to increased peripheral demand (inflammation)

accelerated granulopoiesis

toxic change - indicated increased demand, morphologic changes

• basophilia, vacuolation, and dohle bodies

thrombopoiesis

• stimulated by thrombopoietin (liver)

paratrabecularly

early granulocytes are located