Hematopoiesis

Question 1

1st Trimester

Answer 1

• Primordial erythroblasts in yolk sac

Question 2

2nd Trimester

Answer 2

• Hepato-Spleno-Thymic Phase
• Produce precursor granulocytes and megakaryocytes, and also definitive erythroblasts
• Liver and Spleen

Question 3

3rd Trimester

Answer 3

• Medullo-Lymphatic Phase

- bone marrow and lymph nodes produce all cell types

Question 4

2 Pathways for Hematopoiesis

Answer 4

1) Myeloid

2) Lymphoid

Question 5

Myeloid Stem Cells

Answer 5

• multipotential lineages, capable of self renewal
• erythrocytes
• megakaryocytes
• granulocytes
• Monocytes

Question 6

Lymphoid Stem Cells

Answer 6

• multipotential lineages, capable of self renewal

- Lymphocytes (T&B)

Question 7

General Trends During Myeloid Hematopoiesis

Answer 7

• Reduction of potentiality- As cells progressively differentiate, they can not go back the opposite way of the pathway
• increase in mitotic activity
• Leukemias/ Lymphomas- intermediate froms are not progresing to the final form of blood, functional deficit of final product

Question 8

Red Marrow

Answer 8

• Hematogenous (young)

- hematopoeitic tissue is very active

Question 9

Yellow Marrow

Answer 9

• Older

- replacement with adipose cells (fat cells)

Question 10

Vasculature of Bone Marrow

Answer 10

• Occurs after birth
• Blood vessels msut penetrate into bone marrow
• Brings in oxygen and nutrients and also a pathway for mature cells

Question 11

Stromal Cells

Answer 11

• Support cell

- Provides environment that induces hematopoiesis

Question 12

Erthropoietin

Answer 12

• Secreted into the blood by the kidney when oxygen levels are low
• stimulates the proliferation and differentiation of erythroid progenitors into reticulocytes
• Reticulocytes differentiate into erythrocytes
• Increases oxygen to tissues

Question 13

Erythropoiesis

Answer 13

• Proerythroblast differentiates into Basophilic Erythroblast
• Then that differentiates inot polychromatophilic erythroblasts (two colors) where the nucleus is starting to condense
• further condensation until dark nucleus with little cytoplasm- Normoblast
• Gets rid of nucleus to become polychromatophilic erythrocyte (reticulocyte)
• Then it becomes a mature red blood cell

Question 14

Hemoglobin and RNA during Erythropoiesis

Answer 14

• As erythropoiesis progresses, Hemoglobin increases while RNA content and mitochondria decrease

Question 15

Reticulocytes

Answer 15

• No nucleus but have some RNA left

- Normally, about 1% of the RBC’s in blood are reticulocytes

Question 16

Granulopoiesis (Neutrophil)

Answer 16

• promyelocyte- has non specific granules
• Differentiates into Myelocyte, which has specific granules
• Specifically Neutrophillic myelocyte
• Differentiates into Metamyelocyte, where lobulation begins, looks like a kidney bean
• Differentiates into band cell- looks like a horseshoe
• Then differentiates into neutrophil

Question 17

Excess Band Neutrophil Accumulation

Answer 17

• indicates bacterial infection

Question 18

Lymphoma

Answer 18

• neoplasm of lymphoid system
• Hodgkin’s disease, characterized by the presence of giant Reed-Sternberg (RS) cells- 5 subtypes
• Non Hodgkin’s Lymphomas- 12 B cell types, 12 T cell types

Question 19

Leukemias

Answer 19

• neoplasm of leukocytes and precursors
• acute- immature cells- progresses rapidly
• chronic- more mature cells- less aggressive

Question 20

Myelogenous Leukemia

Answer 20

• Myeloid Lineage
• primarily involves bone marrow
• classified based on type of precursor cell (erythrocytic, granulocytic, monocytic)
• acute and chronic
• tumor cells replace normal hematopoietic tissue