Blood Development Flashcards
Hematopoiesis
Adults occurs in bone marrow
Fetus
- Hold sac
- Liver and spleen
- Bone marrow
Bone marrow structure
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
Red vs yellow bone marrow
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
Hematopoietic vs mesenchymal stem cells
H- precursors for RBC and wbc and lymphocytes
M- fetal precursors to cart, muscle, fat, OB, neurons
Sinusoids
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
Vascular niche vs endosteal niche
Bone marrow
Vas- blood vessels and supporting cells
Endo- storage of quiescent hemo stem cells, IL, osteoprogenitor cells
Bone marrow functions
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
Where does blood cell formation occur
Extravascularly
Between sinusoids
Hematopoietic stem cells
What do they diff into?
When are they committed?
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
Bone is made of what fibers
Reticular
Proerythroblast Basophilic Polychromatic —————————NO MITOSIS AFTER ortho—-> nucleus ejection Reticulocyte- aneuclate, makes hemoglobin Mature RBC What controls blood cell delivery to sinusoidal caps
Hematopoietic cytokines
Or releasing factors
Erythropoiesis steps
What happens to nucleus
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
Cells during erythroblastosis
Hemato stem cell Myeloid stem cell Proerythroblast Basophilic Polychromatic —————————NO MITOSIS AFTER ortho—-> nucleus ejection Reticulocyte- aneuclate, makes hemoglobin Mature RBC
What drives RBC development and where is it produced
Erythropoietin
Produced in kidney in response to low oxygen levels and anemia
What is the last step in formation of a mature RBC
Extrusion of nucleus
Key feature of erythroblastosis
Gets smaller and larger
Smaller: Basophilia (becomes less acidic) Nucleus Size Organelles
Larger:
Hemoglobin
O2 carrying capacity
Acidophilia (becomes more basic )
Granulopoiesis steps
Hemato stem cell Myeloid stem cell Myeloblast——————>no granules Promyelocyte—————> azure granules Myelocyte——————--> specific granules —————NO MITOSIS AFTER THIS Metamyelocyte Mature granulocyte (BEN)
Primary granules are ______ and ______ than specific granules
Primary are larger and more dense than specific
Monocyte development
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
GM CFUs are triggered by what and where does it come from
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
Leukocyte growth factors
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
Neutropenia
Insufficient neutrophils
Form of leukopenia
G-CSF is administered which enhances neutrophil differentiation
Myeloid leukemia
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
Megakaryocytes
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!
Thrombopoiesis
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
