Lecture 2

Question 1

Hematopoiesis

Answer 1

process through which formed elements of the blood are produced

Question 2

Vital role in these are:
Erythrocytes
Leukocytes
Platelets

Answer 2

erythrocytes: gas exchange
leukocytes: immunity
platelets: clotting disorders

Question 3

Explain the formation of erythrocytes and leukocytes in several organs before their differentiation in the bone marrow

Answer 3

1. yolk sac phase: hematopoiesis begins in the 3rd week of gestation formation of “blood islands”
2. hepatic phase: major blood forming organ in second trimester; (and the spleen)
3. bone marrow phase: begins during second trimester as well (also involves other lymphatic tissue)

Question 4

Hematopoietic stem cells can differentiate into….

Answer 4

skeletal muscle
cardiac muscle
neurons, glia
liver cells

Question 5

Bone marrow stromal cells can differentiate into…

Answer 5

skeletal muscle

cardiac muscle

Question 6

Neural stem cells can differentiate into….

Answer 6

skeletal muscle

blood cells

Question 7

Def. Totipotent

Answer 7

all embryonic tissue

i.e- morula

Question 8

Def. Pluripotent

Answer 8

all adult tissue cells

i.e- inner cell mass

Question 9

Def. Multipotent

Answer 9

small # of cells

Question 10

Def. Unipotent

Answer 10

only 1 cell type

Question 11

• Def. Hematopoietic Stem Cells

- Where are they found?

Answer 11

in bone marrow, give rise to multiple colonies of progenitor stem cells

Cavity of long and axial bones (epiphyseal plate- spongy or cancellous bone). They are surrounded by stroma (mesenchymal origin) and give rise to:

• fibroblasts
• adipocytes
• endothelial cells
• osteoblasts *closely associated with stem cells as they regulate number and fate of HSCs in that specific niche and they are necessary to produce cytokines

Question 12

Def. Progenitor Stem Cells

Answer 12

(CMP) common myeloid progenitor
-G E M M- granulocytes, erythrocytes, monocytes, megakaryocytes

(CLP) common lymphoid progenitor
-T- cells, B- cells, NK cells

Question 13

Stem cell vs. Progenitor Cell

Answer 13

Stem cell yields a copy of itself and a specialized cell

Progenitor cells yield two specialized cells

Question 14

stem cell niche

Answer 14

spatial structure (microenvironment) in which HSCs are housed an maintained by allowing self-renewal in the absence of differentiation

1. storage
2. self-renewal
3. no differentiation

Question 15

vascular niche

Answer 15

inactive HSCs migrate to the center of bone into this area to establish hematopoiesis

• endothelial cells, fibroblasts and adipocytes are all found here
• supports and promotes differentiation and progenitors into formed elements of blood
• *stromal cells secrete growth factors (glycoproteins) here

Question 16

What are the growth factors secreted by stromal cells in the vascular niche? (progenitor cells have surface receptors)

Answer 16

1. EPO: (kindeys) increase erythrocyte precursors
2. TPO: (liver) stimulates thrombocyte formation
3. Cytokines: (bone marrow) stimulate proliferation in other marrow cells.
   - Colony-stimulating factor (CSF) and Interleukin stimulate leukocyte production

Question 17

Explain the structure of bone marrow

Answer 17

• Loose cells of reticular fibers
• sinusoidal capillaries in bone marrow to allow spaces between endothelial cells
• veins
• arteries
• islands of cells

Question 18

red marrow vs yellow marrow

Answer 18

red: active hematopoiesis
yellow: inactive hematopoiesis; fat, capillaries, reticular cells

Question 19

Erythropoiesis.
Where does it take place?
Main stimulus?
Precursor?

Answer 19

• adult red bone marrow of certain bones
• Hypoxia
• Proerythroblast

Question 20

End Stage Kidney Disease.

Answer 20

decrease EPO
decrease RBCs
reduced Oxygen

Question 21

Explain cycle of erythropoiesis stimulation.

Answer 21

1. Hypoxia due to a decrease in RBC count
2. decrease in O2 in the blood and increased demand of oxygen in the tissues
3. kidneys release EPO
4. EPO stimulates red bone marrow
5. increase in RBC count
6. increase in the ability of RBC to carry blood

Question 22

Granulocytopoiesis
Controlled by?
Common precursor?

Answer 22

takes 11 days
Neutrophils
Eosinophils
Basophils

• controlled by cytokines
• precursor: myeloblast

*myelocyte: condensed, round nucleus; specific granules; in this phase depending what they contain determines what they become

Question 23

Thrombopoiesis

Controlled by?

Answer 23

formation of thrombocytes (platelets)
-controlled by thrombopoietin in the liver

• megakaryoblast: 25-40 um (32 nuclear)
• megakaroycyte: 40-100 um (large, multi-lobed nuc)

Question 24

Lymphopoiesis

Answer 24

lymphoblasts: large, undifferentiated cells
pro lymphocytes: medium sized cells, condensing chromatin, no cell surface antigens

• some migrate from bone marrow to thymus to differentiate and divide into T-cells
• others remain in bone marrow to differentiate to B-cells, migrate to lymph nodes

Question 25

Mast cells

Answer 25

made in the bone marrow but migrate to the CT to differentiate

Question 26

When are bone marrow studies done?

Answer 26

• prolonged fever
• anemia
• bleeding disorders

*sample taken from iliac crest

Question 27

Leukemia

Answer 27

no WBCs being made in the bone marrow

Question 28

Aplastic anemia

Answer 28

no RBC being made in the bone marrow