Haematopoiesis Flashcards
Definition of haematopoiesis
Process by which blood cells are generated from precursor cells
Definition of totipotent
Stem cells that can divide to produce all differentiated cells in an organism (zygote)
Definition of pluripotent
Stem cells that can divide into endoderm, mesoderm or ectoderm
All blood cells arise from a common pluripotent stem cell
Definition of multipotent
Stem cell that has the ability to divide into a restricted no of cell types
Definition of unipotent/progenitor
Restricted to a single lineage
Multiplication regulated by a lineage specific growth factors
No self renewal
Definition of haematopoietic stem cells
Give rise to all circulating blood cells
Definition of platelet demarcation channels
Platelets are held here within cytoplasm and are released when ER vesicles fuse with the cell membrane
What is the composition of blood
Plasma (50-60% of BV)
-Contains soluble proteins, mediators
Packed cells
- Haematocrit (RBCs, 40-45% of BV)
- WBC, platelets
Location Size Volume What % of blood is made up of RBCs Lifespan Organelles found here
Blood vessels 7um 4.8-5.5x10 12/L 45% v/v 120 days Lack organelles, have glycolysis enzymes
What is the difference between a normoblast and reticulocyte
Normoblast (8-10um)
- found in BM
- has mitochondria, ribosomes, nucleus (lost as it enters blood)
Reticulocyte
- 1-2 days needed to lose RNA, organelles
- 1% of blood
Location Size Volume Lifespan Shape How are platelets produced
Blood 2-4um 150-400x10 9/L 8-12 days Unclear discoid Produced in BM form megakaryocytic fragments via thrombopoietin
Location
Size
Nucleus shape
How do megakaryocytes release platelets
BM
50-70um
Polyploidy large irregular nucleus
Platelets held in platelet demarcation channels, released from vesicles
Location
Volume
What % of BV do WBCs make up
Blood and tissues
4-11 x 10 9/L
<1% v/v
What % of BV do neutrophils make up
Lifespan
Nucleus shape
Granule contents and their function
60% of WBC
6.7hr half life
Polymorphonuclear, move via chemokine gradients
Granules used in phagocytosis
- acid hydrolase
- neutral protease
- microbicides
Location What % of BV do eosinophils make up Lifespan Nucleus shape Granule contents and their function
GI
1% of WBC
A few days
Bilobed nucleus
Basic proteins
Cationic proteins
Neurotoxins
Peroxidases
Location
Nucleus shape of monocytes
Size
Blood
Kidney mononucleus
20um
B cell shape and nucleus structure
Size
Condensed nucleus with surface AB
6-9um
Plasma cell function
Size
Release AB
9-15um
NK cell function
Size
Kill tumor/viral infected cells
9-15um
T cell types and function
Size
Helper, cytotoxic
6-9um
Describe the
- site prenatally and postnatally
- start of haematopoesis prenatally
- steps involved
Prenatal from month 7 onward => BM
Postnatal in larger bones
Lymphocyte prod continues in lymph nodes in life
2-2.5 weeks in utero
Blood islands surrounded by endothelium, surrounded by mesenchyme
Myeloid/lymphoid stem cell
Progenitor
Precursor
Differentiated functional cell in the blood
Describe the macrostructure of the BM
Periosteal, endosteal capillaries supply bone and anastomose
BM made up of medullary vascular sinus in medullary cavity
Haematopoiesis occurs in the medullary cavity outside the sinus, supported by adventitial reticular cells structurally
Describe the steps in RBC development
- stem cell division
- RBC protein synth
- enucleation
- maturation
Stem cell division
-mitotic division => gets smaller, nucleus condenses
RBC protein synth
- Fe receptor => moves Fe into cell and mitochondria
- Fe+ protoporphyrin =haem
- combines with a, b globing chain => haemoglobin
Enucleation
- gather around nurse macrophages
- normoblasts enucleated => reticulocyte
Maturation
- reticulocutes travel to spleen
- loses organelles
Describe how neutrophils move
Have a pseudopod that retracts
Uropod provides traction
Move down chemokine/chemical gradient
