Hematopoesis Flashcards
Where is myeloid tissue found?
Medullar cavity of bone
Where is lymphoid tissue found?
thymus, LN, spleen, non-encapsulated lymph nodules
Where is hematopoietic tissue derived from?
Mesoderm
- except the thymus which is endoderm
What is the prenatal progression of dev of the hematopoiesis?
yolk sac liver spleen lymph nodes bone marrow thymus
What cell types does the yolk sac form?
Endothelial cells - primitive vessels
- undiff pluripotential stem cells
What makes up the undiff pluripotential stem cells?
Hematopoietic sc (HSC)
Colony forming units (CFU’s)
-HSC seed liver spleen LN and BM
- originate from mesoderm
When does BM take over hematopoiesis from liver?
Middle of fetal life
- 5th fetal month
- clavicle is first bone
What dominates during liver hematopoiesis?
erythropoiesis
- RBC’s nucleated at weeks 7 and un at weeks 11
When does hematopoiesis begin in the spleen?
3rd fetal month
- erthropoiesis and granulopoiesis reach peach at 3-5 months and last till 7-8
- lymphopoiesis continues through life
What is the function of the thymus?
Lymphopoiesis only
- 5th fetal month
- t-cell fromation
- only 2-4% succeed others go to apoptosis and get phagoctyosed by macs of thrymus
What is extramedullar myelopoiesis?
development of the the myeloid tissue outside of the BM
- pathological condition
What is yellow marrow?
occupies diaphysis of long bones
- fat and blood vessels
- increases with age
- thus most BM in adults is yellow
What is red marrow?
Site of hematopoiesis
- decreases with age
- long/short bones, iliac crest, vertebral bodies, ribs and skull diploe
What are the components of myeloid tissue in BM?
Stroma
Sinusoids
Dev blood cells
What cells are considered stroma?
- Fibroblasts
- macs
- adipocytes
- osteogenic cells (clasts and blasts)
- endothelial cells
What fibers are considered stroma?
collagenous
reticular
What are the purpose of sinusoids?
connect arterial and venous side of circulation via capillaries in bone.
- permit red and white cells to enter circulation
What 2 ways can RBC’s and WBC’s enter our circulation?
Intercellular gaps
Endothelial cell pores
What are poietins? and a common one?
Usually glycoproteins that act as diff and growth regulation factors
- erythropoietin
Where is erythropoietin found and what is its function?
Kidney and other sites
- increased # of hemoglobin- forming cells by stimulation stem cells (CFU-E)
- CFU-E is the hematopoietic colony forming unit
- induced by hypoxia
What is the cytoplasm dev of RBC’s?
Basophilic then eosinophilic
- volume decreases
What is the nucleus dev of RBC’s?
large to small to gone
- light/euchromatic to dark/heterochromatic
- fine to clumped chromatin pattern
What are some fun facts about erythropoiesis?
- 5 mil released/sec- matched by destruction in BM and Spleen
- 20-30% of BM cell involved in RBC’s production
- 1 week to mature
What is the progression of cytoplasm in ganulopoiesis?
basophilc to lack of it
- increase # of specific granules
- Decrease # in azurophilic granules
