Blood Flashcards
What is blood?
A specialised fluid (Tissue) composed of a variety of cellular components suspended in a liquid known as plasma
How are blood components separated?
Centrifugation
What are the 3 layers of centrifuged blood?
Plasma - Top
Buffy coat
Erythrocyte layer - Bottom
What is contained in the buffy coat layer of centrifuged blood?
Platelets and leukocytes
What is the haematocrit?
The percentage of blood that is formed of erythrocytes
What is the average male haematocrit?
42
What is the average female haematocrit?
38
What is the lifespan of a red blood cell?
120 days
What is the lifespan of a neutrophil?
7-8 hours
What is the lifespan of a platelet?
7-10 days
What is haemopoiesis?
The formation of blood cells
What is the process of forming erythrocytes called?
Erythropoiesis
What is the process of forming platelets called?
Thrombopoiesis
What is the process of forming granulocytes called?
Myelopoiesis or granulopoiesis
What is the process of forming lymphocytes called?
Lymphopoiesis
What are blasts?
Nucleated blood cell precursor cells
What are megakaryocytes?
Multi-nucleated platelet precursor cells
What are reticulocytes?
Immediate red cell precursor cells
What are myelocytes?
Nucleated precursor cells between neutrophils and myeloblasts
What are some definitions of “myeloid”?
Bone marrow
Non-lymphoid lineage
Granulocytes and precursor pathways
What is meant by red marrow?
Haemopoietically active bone marrow
What is meant by yellow marrow?
Fatty, inactive bone marrow
How is yellow marrow effected by age?
Percentage of yellow marrow increases with age
What is the myeloid:erythroid ratio?
Relationship of neutrophils and precurosrs to proportion of nucleated red cell precursors (Range from 1.5:1 - 3.3:1) - This can change such as in reversal in haemolysis as a compensatory response
What is the first cell in the haemopoietic lineage?
Long term haematopoietic stem cells
What are the 2 main progenitor cells in haematopoiesis?
Myeloid progenitor cells
Lymphoid progenitor cells
What are the 3 cells arising from myeloid progenitor cells?
Megakaryocyte erythroid progenitors
Granulocyte-Monocyte progenitors
Pro-dendritic cells
What 2 cells are formed from megakaryocyte progenitors?
Megakaryocytes
Erythrocytes
What 2 cell types are formed from granulocyte-monocyte progenitors?
Granulocytes
Macrophages
What precursor cells are formed from the common leukocyte progenitor cells?
- Pro-dendritic cells
- Pro-T cells
- Pro-NK cells
- Pro-B cells
What are the 7 stages of erythropoiesis?
- MEP
- Pronormoblast
- Early normoblast (Basophilic)
- Intermediate normoblast (Polychromatophilic)
- Late normoblast (Orthochromatic)
- Reticulocyte (Anucleated)
- Erythrocyte
What are the 5 main stages of neutrophil production?
- Promyelocyte
- Myelocyte
- Metamyelocyte
- Band cell
- Neutrophil
Describe the process of thrombopoiesis?
When a megakaryocyte divides, the cytoplasm does not, so there are multiple nuclei in a single, very large cytoplasm, the edge of which buds off to form platelets that are released into the bloodstream
How do mature cells leave the bone marrow?
- Formed blood cells can pass through fenestrations in endothelial cells to enter the circulation
- Release of red cells is associated with sinusoidal dilatation and increased blood flow
- Neutrophils acyively migrate towards the sinusoid
- Megakaryocytes extend long branching processes called proplatelets into the sinusoidal blood vessels
What are the main developmental events in haemopoiesis?
- Self-renewal - Form 1 new copy of itself
- Proliferation - Increase in numbers
- Differentiation - Commit to a lineage
- Maturation - Acquire functional properties
- Apoptosis - Cell death
Where do haematopoietic stem cells originate embryologically?
Mesoderm
During what week of development are circulating progenitor cells detectable?
Week 5
What is the first site of erythroid activity in development?
Yolk sac
In what week of development does erythroid activity in the yolk sac end?
Week 10
During what week of development does the liver become haematopoietically active?
Week 6
During what week of development does bone marrow become haematopoietically active?
Week 16
Where does haematopoeis occur in adults?
Axial skeleton, pelvis and proximal long bones
What parts of the body are haematopoietically active at birth?
All bones
What are some factors that regulate haematopoiesis?
Intrinsic cell properties (E.g. stem cells vs mature)
Signals from immediate surroundings
Specific anatomical area
Erythroid island ‘nurse’ macrophages