Erythropoiesis, hematopoiesis, leukopoiesis, thrombopoiesis

Question 1

Where is bone marrow found in adults?

Answer 1

Bone marrow is found within the trabeculae or spongy bone of flat bones and ends of long bones
* Ex: pelvis, femur

Question 2

Three components of bone marrow

Answer 2

1. Hematopoietic tissue: gives rise to all blood cells
2. Sinusoids: connect arterial and venous circulation
3. Stroma: support and structure layer

Question 3

We lose about _ % of our bone marrow each decade that we age until age 70 when we reach an all time low of _

Answer 3

We lose about 10% of our bone marrow each decade that we age until age 70 when we reach an all time low of 70%

Question 4

What cells are found in the stroma of the bone marrow?

Answer 4

• Fibroblasts
• Macrophages
• Adipose cells
• Osteogenic cells
  Collagen and reticular fibers also provide a nice scaffording

Question 5

Answer 5

Question 6

Answer 6

Question 7

Which cell lineage makes up the largest percent in the bone marrow?

Answer 7

Neutrophils make up the largest percentage in the bone marrow
* Other granulocytes are present in much smaller numbers (eosinophils and basophils)

Question 8

The second largest cell lineage in the bone marrow is _

Answer 8

The second largest cell lineage in the bone marrow is erythroid series

Question 9

The typical myeloid: erythroid ratio is _

Answer 9

The typical myeloid: erythroid ratio is between 2:1- 4:1
* This represents neutrophils: red cells

Question 10

_ is the process of making red blood cells

Answer 10

Erythropoiesis is the process of making red blood cells

Question 11

Fetal erythropoiesis begins in the _ at approximately 3 weeks of gestation

Answer 11

Fetal erythropoiesis begins in the yolk sac at approximately 3 weeks of gestation
* Yolk sac –> liver –> spleen –> bone marrow

Question 12

What is the order of erythropoiesis sites

Answer 12

Young Liver Synthesizes Blood: Yolk sac, Liver, Spleen, Bone marrow

Question 13

Six stages/ cells of erythropoiesis

Answer 13

1. Proerythroblast: large, fine chromatin, basophilic cytoplasm, prominent nucleoli
2. Basophilic erythroblast: deep blue from free ribosomes
3. Polychromatophilic erythroblasts: hint of pink from hemoglobin production
4. Orthochromatophilic erythroblast: nucleus is dense, dark, small
5. Reticulocyte: light purple cytoplasm, nucleus extruded
6. Erythrocyte: all RNA leaves –> become pink and disk shaped

Question 14

Describe the changes that can be seen from proerythroblast –> erythrocyte

Answer 14

• Cell gets smaller in size
• Cytoplasm turns from deep blue –> red
• Nucleus shrinks and gets darker
• Chromatin becomes condensed

Question 15

How does oxygen demand stimulate erythropoiesis?

Answer 15

Low oxygen –> stimulates the kidneys via hypoxia-inducible factor –> kidney secretes erythropoietin (EPO) –> stimulates the bone marrow to make more erythrocytes

Question 16

The liver, like most other organs of the gut, originates from the _

Answer 16

The liver, like most other organs of the gut, originates from the endoderm

Question 17

The spleen is derived from the _

Answer 17

The spleen is derived from the mesoderm (from the dorsal mesogastrium)

Question 18

The skeletal bones arise from the _ while the bones of the head/face arise from the _

Answer 18

The skeletal bones arise from the mesoderm while the bones of the head/face arise from the neural crest

Question 19

Intramembranous ossification involves bone that is formed directly from _

Answer 19

Intramembranous ossification involves bone that is formed directly from mesenchymal tissue
* Mesenchymal cells –> osteoblasts –> osteoid –> hard bone
* This is the process used for flat bones like the skull

Question 20

Cell differentiation vs maturation:

Answer 20

Cell differentiation is the process by which cells decide which cell line to be; cell maturation is the movement through stages

Question 21

The three main hematopoietic cell lines are:

Answer 21

The three main hematopoietic cell lines are:
1. Red blood cells (erythrocytes)
2. White blood cells (leukocytes)
3. Platelets

Question 22

All hematopoietic cells come from the bone marrow where they start as uncommitted stem cells –> give rise to _ or _

Answer 22

All hematopoietic cells come from the bone marrow where they start as uncommitted stem cells –> give rise to lymphoid stem cell or myeloid stem cell

Question 23

All leukocytes (granulocytes and agranulocytes) have granules but only the granulocyte have specific granules; these cells are _ , _ and _

Answer 23

All leukocytes (granulocytes and agranulocytes) have granules but only the granulocyte have specific granules; these cells are neutrophils , eosinophils, and basophils
* The agranulocytes are the monocytes and lymphocytes

Question 24

Six stages of neutrophil maturation

Answer 24

1. Myeloblast: fine chromatin
2. Promyelocyte: very large, deep purple granules
3. Myelocyte: more condensed chromatin, specific granules which are pale pink
4. Metamyelocyte: more condensed chromatin, horseshoe nucleus
5. Band: nucleus thins and looks like U
6. Segmented neutrophil

Question 25

3 steps of monocyte maturation

Answer 25

1. **Monoblasts**: very large, indented nucleus, tiny granules 2. **Promonocyte**: "tissue-paper" nuclei 3. **Monocyte**: kidney bean nucleus, chromatin has raked pattern

Question 26

Answer 26

Question 27

Answer 27

Promonocyte

Question 28

Answer 28

Question 29

The lymphoid series (B cells, T cells, NK cells) have a simple maturation from _ to _

Answer 29

The lymphoid series (B cells, T cells, NK cells) have a simple maturation from **lymphoblasts** to **lymphocytes**

Question 30

Thrombopoiesis is the process of making _

Answer 30

Thrombopoiesis is the process of making **thrombocytes** (aka platelets)

Question 31

Platelets are really just fragments of cytoplasm derived from giant bone marrow cells called _

Answer 31

Platelets are really just fragments of cytoplasm derived from giant bone marrow cells called **megakaryocytes**

Question 32

Answer 32

Megakaryocyte

Question 33

What is unique about megakaryoctyes that makes them so large in size?

Answer 33

Megakaryocytes undergo **endomitosis** whereby they experience chromosomal replication that does not involve nuclear division * Small pockets of cytoplasm are formed in the cell and platelets are held until they are released into cytoplasm

Question 34

Megakaryocytes are derived from _ cells

Answer 34

Megakaryocytes are derived from **common myeloid progenitor cells**

Question 35

What are the stages of megakaryocyte progression?

Answer 35

Stem cell --> megakaryoblast --> promegakaryocyte --> megakaryocyte

Question 36

The major signaling molecule that stimulates growth and development of megakaryocytes is _

Answer 36

The major signaling molecule that stimulates growth and development of megakaryocytes is **thrombopoietin**

Question 37

Thrombopoietin is secreted constituitively by the _ and will increase when platelets decrease and will decrease when platelets increase such that the _ of platelets is constant

Answer 37

Thrombopoietin is secreted constituitively by the **liver** and will increase when platelets decrease and will decrease when platelets increase such that the **mass of platelets** is constant

Question 38

Megakaryocytes are found in the _

Answer 38

Megakaryocytes are found in the **sinusoids of the bone marrow**

Question 39

Megakaryocytes must be _ to produce platelets; once platelets are formed they either fracture or separate from the megakaryocyte

Answer 39

Megakaryocytes must be **hyperdiploid** to produce platelets; once platelets are formed they either fracture or separate from the megakaryocyte