Hematopoiesis

Question 1

What is characteristic of totipotent cells?

Answer 1

They give rise to all cells of an organism including embryonic and extra embryonic tissues (cells which support embryonic development). A zygote is totipotent.

Question 2

What is characteristic of pluripotent cells?

Answer 2

Pluripotent cells give rise to all cells of the embryo and subsequently adult tissues. (embryonic stem cells)

Question 3

What is characteristic of multipotent cells?

Answer 3

multipotent cells give rise to different cell types of a given lineage (adult stem cells)

Question 4

What are the two stem cell types?

Answer 4

1) embryonic stem cells 2) adult stem cells

Question 5

Where are embryonic stem cells derived from?

Answer 5

inner-cell mass of blastocyst

Question 6

Where are adult stem cells harvested from?

Answer 6

mature organs/tissues (bone marrow)

Question 7

What type of stem cells are embryonic stem cells?

Answer 7

pluripotent and differentiate to all cell lineages

Question 8

What type of stem cells are adult stem cells?

Answer 8

multipotent. (of note= “adult” does not mean that they simply come from the adult body, it means that they do not come from the inner cell mass of the blastocyst)

Question 9

What are the distinctions between embryonic and adult stem cells?

Answer 9

Embryonic -derived from inner-cell mass of blastocyst - pluripotent, differentiate to all cell lineages - technical and ethical limitations - may be induced from adult tissues Adult - harvested from mature organs/tissues (bone marrow) - multipotent - more restricted ability to produce different cell types and to self-renew

Question 10

Where is the site of hematopoiesis during 2-8 weeks of gestation?

Answer 10

islands of hematopoiesis found in the yolk sac wall. Gives rise to nucleated erythrocytes but no leukocytes.

Question 11

Where is the site of hematopoiesis during 2-28 weeks of gestation?

Answer 11

First occurs in the liver and then the spleen then ceases around birth.

Question 12

Where is the site of hematopoiesis during 6 months of gestation and beyond?

Answer 12

hematopoiesis occurs in red bone marrow

Question 13

What is the sequential order of sites at which hematopoiesis occurs during gestation?

Answer 13

blood islands of yolk sac –>liver—> spleen —> red bone marrow

Question 14

Where is the anatomical site of red bone marrow and thus hematopoiesis prior to puberty?

Answer 14

Prior to puberty red bone marrow is located in the skull, ribs, sternum, vertebrae, clavicles, pelvis, and long bones.

Question 15

Where is the anatomical site of red bone marrow and thus hematopoiesis after puberty?

Answer 15

After puberty red bone marrow is located in the skull, ribs, sternum, vertebrae, clavicles, and pelvis. Different from pre- pubescent red bone marrow is no longer found in long bones.

Question 16

In certain disease states, blood cell formation may occur elsewhere… Where is hematopoiesis located and what type of hematopoiesis is this called?

Answer 16

In certain disease states extra blood cell formation occurs in the liver and spleen and is called extra medullary hematopoiesis.

Question 17

As we age, what type is the large majority of our marrow and where is the remaining marrow located?

Answer 17

Most marrow is converted to yellow marrow and red marrow is usually restricted to the sternum and iliac crests.

Question 18

What does the stroma of bone marrow contain?

Answer 18

Stroma of bone marrow contains fibroblasts, reticular cells, adipose cells, and endothelial cells

Question 19

What is the function of the stroma of bone marrow?

Answer 19

the stroma synthesizes and secretes hematopoietic growth factors

Question 20

What doe the parenchyma of bone marrow contain?

Answer 20

the parenchyma consists of various lineages of hematopoietic cells in different stages of differentiation.

Question 21

What does the sinusoids of bone marrow contain?

Answer 21

The sinusoids have endothelial-lined spaces that connect arterial and venous vessels. This provides access for mature blood cells to move into the circulation.

Question 22

Identify this tissue.

Answer 22

Bone marrow.

The long canals are medullary venous sinuses lined with endothelial cells.

The box on the lower portion of pic is identifying mature blood cells entering the venous sinus.

Question 23

What are the hematopoietic cords of bone marrow?

Answer 23

Bands of parenchyma and stroma lying between the sinusoids.

Question 24

What is the distribution of hematopoietic cells?

Answer 24

60% granulocytopoiesis

30% erythrocytopoiesis

10% in thrombocytopoiesis, monocytopoiesis, and lymphocytopoiesis

Question 25

What is the equation for myeloid/erythroid ratio? and what is a normal ratio?

Answer 25

total volume of cells in granulocytopoiesis/ total volume of cells in erythrocytopoiesis

3: 1 normal
8: 1 chronic myelogenous leukemia
1: 5 polycythemia

Question 26

What are myeloid cells?

Answer 26

myeloid cells are precursor cells that include megakaryocytes, erythrocytes, mononuclear phagocytes (monocytes/macrophages) and all of the polymorphonuclear leukocytes (neutrophils, basophils, eosinophils). Myeloids help the body fight infection.

Question 27

What are erythroid cells?

Answer 27

Erythroid cells give rise to megakaryocytes and erythrocytes. It is derived from the common myeloid progenitor.