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