Introduction to Haematopoiesis Flashcards
Define ‘haematopoiesis’
Development of all cellular components of blood
List the sites of haematopoiesis in the foetus
- Aorta gonad mesonephros (AGM) - Yolk sac - Placenta - Liver - Spleen
List the sites of haematopoiesis in the adult
- Bone Marrow - Maturation in thymus, lymph nodes, and spleen
Define haematopoietic stem cells (HSCs)
precursor cells for all blood components.
Location of haematopoietic stem cells
Located in adult bone marrow
List two types of haematopoietic stem cells (HSCs)
Primitive and definitive
When do primitive HSCs develop?
Day 13-15 in human embryo
What do primitive HSCs develop into?
Primitive nucleated RBC with embryonic haemoglobin.
Primitive HSCs have a self-renewing capacity
False, they don’t.
When do definitive HSCs develop?
Develops in day 32-33 in humans.
Where do definitive HSCs occur?
Occurs in yolk sac, aorta gonad mesonephros (AGM), and placenta.
What do definitive HSCs develop into?
Myeloid and lymphoid progenitor cells.
Definitive HSCs have a self-renewing capacity.
True
What is the bone marrow niche?
Bone marrow niche (stem cell niche) is an anatomical site where: - Stem cells are maintained and reproduce - Stem cell differentiation is inhibited (i.e. stem cells keep multipotency) - Number of stem cells are limited.
Once stem cells leave stem cell niche (bone marrow niche), they have limited self-renewal capacity
True
In adults, bone marrow niche is located where?
Located at proximal ends of long bones.
Where are quiescent HSCs (G0) maintained?
They are maintained near arterioles.
Function of B-cells as a lymphoid progenitor?
Adaptive antibody production
List the T-cells of the lymphoid progenitors
- CD4+ Helper T cells
- CD8+ Killer T cells
- Suppressor T cells
- Memory T cells
Remember the lineages of the HSCs

Function of CD4+ Helper T cells
Release chemokines that act on other immune cells
Function of CD8+ Killer T cells
Kill microorganisms and tissue cells invaded by viruses
Function of Suppressor T cells
Suppress killer and helper T cells to prevent autoimmune damage
Function of Memory T cells
Activated by antigens to provide powerful response to duplicate antigen
List the myeloid progenitors
- Platelets
- Monocytes
- Basophils
- Neutrophil
- Eosinophil
- Erythryocytes
What are platelets?
Produced by megakaryocytes; promote clotting
Describe monocytes
These differentiate into dendritic cells and macrophages
Function of basophils
Fight parasitic infection
Function of neutrophils
50% for leukocytes in blood; pathogen fighting cells
Function of eosinophils
Fights bacteria, viral and parasitic infection; role in allergies
Describe erythryocytes (RBC)
Biconcave, anucleate cells that transport oxygen in blood
Describe erythroblast
Immature RBC with nucleus still
Describe reticulocyte
Round, immature RBC right after nucleus is ejected.