Blood Development

Question 1

Hematopoiesis

Answer 1

Adults occurs in bone marrow

Fetus

1. Hold sac
2. Liver and spleen
3. Bone marrow

Question 2

Bone marrow structure

Answer 2

Framework of reticular CT
Islands of developing and mature blood cells
Megakaryocytes that turn into platelets 
Fat
Sinusoid made of discont capillary
Macrophages that kill dead RBC

Question 3

Red vs yellow bone marrow

Answer 3

Red= hematogenous
Infants have all red bone marrow
Adults have it in pelvis, spinal cord, ribs

Full of blood, no fat

Yellow= increased fat content hence yellow color
Adults have red and yellow bone marrow, mostly yellow

Question 4

Hematopoietic vs mesenchymal stem cells

Answer 4

H- precursors for RBC and wbc and lymphocytes

M- fetal precursors to cart, muscle, fat, OB, neurons

Question 5

Sinusoids

Answer 5

Discont caps in bone marrow

Important bc bone marrow is making important cells to transport!
Needs easy barrier to get through

Have a lumen with sim squamous ET
Basal lamina separates sset from stromal cells

Question 6

Vascular niche vs endosteal niche

Bone marrow

Answer 6

Vas- blood vessels and supporting cells

Endo- storage of quiescent hemo stem cells, IL, osteoprogenitor cells

Question 7

Bone marrow functions

Answer 7

Makes, stores, and destroys blood cells
Stores iron from hemoglobin

Produces:
3 bil RBC per day
1 bil WBC per day
2 bil platelets per day

Question 8

Where does blood cell formation occur

Answer 8

Extravascularly

Between sinusoids

Question 9

Hematopoietic stem cells
What do they diff into?
When are they committed?

Answer 9

Self renewing
Multipotent

Diff into more multipotent cells:
Myeloid stem cell= turns into any leukocyte, RBC or platelet

Lymphoid stem cell= turns into lymphocyte or nk cell (comes from T cell precursor)

Once these diff—-> they become COMMITTED

Question 10

Bone is made of what fibers

Answer 10

Reticular

Question 11

Proerythroblast
Basophilic
Polychromatic
—————————NO MITOSIS AFTER
ortho—-> nucleus ejection
Reticulocyte- aneuclate, makes hemoglobin
Mature RBC 
What controls blood cell delivery to sinusoidal caps

Answer 11

Hematopoietic cytokines

Or releasing factors

Question 12

Erythropoiesis steps

What happens to nucleus

Answer 12

HSC —-> committed cell ——> phase 1 —-> 2 ——> 3
Becomes SMALLER in size

Phase one:
Ribosomal synthesis

Phase two:
Hemoglobin accumulation

Phase three:
Ejection of nucleus and becomes sack of hemoglobin

Ejected nucleus is eaten my macrophages

Question 13

Cells during erythroblastosis

Answer 13

Hemato stem cell
Myeloid stem cell
Proerythroblast
Basophilic
Polychromatic
—————————NO MITOSIS AFTER
ortho—-> nucleus ejection
Reticulocyte- aneuclate, makes hemoglobin
Mature RBC

Question 14

What drives RBC development and where is it produced

Answer 14

Erythropoietin

Produced in kidney in response to low oxygen levels and anemia

Question 15

What is the last step in formation of a mature RBC

Answer 15

Extrusion of nucleus

Question 16

Key feature of erythroblastosis

Gets smaller and larger

Answer 16

Smaller:
Basophilia (becomes less acidic)
Nucleus
Size
Organelles

Larger:
Hemoglobin
O2 carrying capacity
Acidophilia (becomes more basic )

Question 17

Granulopoiesis steps

Answer 17

Hemato stem cell
Myeloid stem cell
Myeloblast——————>no granules
Promyelocyte—————> azure granules
Myelocyte——————--> specific granules
—————NO MITOSIS AFTER THIS
Metamyelocyte
Mature granulocyte (BEN)

Question 18

Primary granules are ______ and ______ than specific granules

Answer 18

Primary are larger and more dense than specific

Question 19

Monocyte development

Answer 19

Hemato stem cell
Myeloid stem cell
Monoblast 
GM CFU
Promonocyte—- primary granules
————————-NO MORE MITOSIS
Monocyte: immature macrophage
Becomes a type of macrophage in specific tissue

Question 20

GM CFUs are triggered by what and where does it come from

Answer 20

Granulocyte/monocyte forming units

Triggered by growth factor M-CSF (macrophage colony stimulating factor) to differentiate into a monocytes/osteoclasts

Released by stromal cells or osteoblasts

Question 21

Leukocyte growth factors

Answer 21

M-CSF: stims cells to turn into monocytes

G-CSF: stims cells to become neutrophils

IL5: myeloid to eosinophil

GM-CSF: myeloid to basophil

C-KIT receptor: binds to SCF which makes hemato stem cells responsive to cytokines to trigger differentiation

Question 22

Neutropenia

Answer 22

Insufficient neutrophils
Form of leukopenia

G-CSF is administered which enhances neutrophil differentiation

Question 23

Myeloid leukemia

Answer 23

Form of leukocytosis

Excess myeloid stem cells that can cause cancer

C-kit inhibitors are administered to lower HSC diff into myeloid cells, thus lowering the number of cells causing the cancer

Question 24

Megakaryocytes

Answer 24

megakaryocytes —> giant cells in bone marrow

Made form megakaryoblast in response to thrombopoietin made in liver
Has a huge nucleus w many lobes due to serial mitotic division (lots of mitosis w no cell division)
Often mistaken for osteoclasts!

Question 25

Thrombopoiesis

Answer 25

Platelet formation From megakaryocyte

Serial mitotic divisions w no cell division
Cytoplasm matures w increased granules and tubules called the “demarcation membrane system” ie invagination of membrane
Sheds protoplatelets of cytoplasm into sinusoid caps of bone marrow by extending a toe between endothelial cells
Nucleus is eaten by macrophages