Hematopoiesis Flashcards
RBCs
- Structure
- Function
Structure: Non-nucleated
Function: Carries Hb which carries O2 to tissues
WBCs
- Structure
- Function
Structure: Nucleated
Function: Fights infection and/or provide immunity
Platelets
- Structure
- Function
Structure: Fragment of cytoplasm from its precursor cell
Function: Forms platelet plug to stop bleeding (doesn’t matter how severe)
3 phases of fetal hematopoiesis
- Mesoblastic phase
- Hepatic phase
- Myeloid phase
Mesoblastic phase
- Anatomic site of active cell production
- Gestational period of active cell production
- Occurs in yolk sac
- Begins at day 19 to week 5
- Only RBCs forming (Gower Hb), no WBCs
Hepatic phase
- Anatomic site of active cell production
- Gestational period of active cell production
- Liver (major site), but also spleen, LN, and thymus
- Week 5 to month 5
Myeloid phase
- Anatomic site of active cell production
- Gestational period of active cell production
- BM
- month 5 to birth
Normal red and yellow marrow distribution
- Newborn
- BM is 100% cellular
- More RBCs (more Hb) circulating compared to WBCs
Normal red and yellow marrow distribution
- Child (~5-7 years old)
- Doesn’t need as many circulating cells but needs more bone development
- Marrow starts receding at distal portions of long bones and gets replaced by yellow marrow/fat
Normal red and yellow marrow distribution
- Adult (~18 years old)
- 7 active sites of hematopoiesis
- Cellularity = 100 – patient’s age
7 sites of hematopoietic tissue in the normal adult
- Skull
- Shoulder blades
- Sternum
- Ribs
- Vertebrae
- Pelvis (most common)
- Proximal portions of long bones
3 anatomic sites of extramedullary hematopoiesis in order of frequency of involvement
- Spleen (most common)
- Liver
- LN
* NEVER THE THYMUS!
Reactive form of extramedullary hematopoiesis
We know the reason
Non-reactive form of extramedullary hematopoiesis
We don’t know the cause
Location of hematopoietic marrow
B/w or outside of venous sinuses (sinusoids)
