Function and structure of blood cells
Hello, in this third class of the Hematology course provided by the Universidad of Guanajuato, we are going to study the blood cells formation in the bone marrow, a process known as hematopoiesis.
This class starts with some basic concepts about stem cells because the hematopoietic cells have these developmental stages. The hematopoiesis process is reviewed from the embryonic phase with all the organs involved. Briefly, the extramedullary hematopoiesis process is revised as well. It is important to check the obtention of a bone marrow aspirate and a bone marrow biopsy in order to study the hematopoiesis process.
In the adults, every cell lineage is revised, from its precursor to its mature form, as well as some cytokines involved in the maturation process.
Hope this class helps you understand this complex process because it will be reviewed again in next classes when some pathologies are discussed.
Let’s get started.
The cells that give rise to blood cells are divided into several compartments:
Hematopoietic stem cells (HSCs). Also called stem cells, which are capable of self-renewal and are multipotent (can differentiate into any blood lineage). Their surface markers are CD34, CD133, CD90 and they lack lineage-specific markers.
Hematopoietic progenitor cells (HPC). They cannot self-renew but retain the ability to proliferate. They can differentiate into several lineages (multipotent), into two lineages (bipotent) or into a single lineage. They retain the CD 34 marker, but already acquire markers specific to the lineage to which they will give rise. Both HSCs and HPCs have a morphology like lymphocytes and cannot be distinguished in the bone marrow smear.
Precursor cells. Precursor cells are those that upon maturing give rise to the cells that circulate in the blood, form more than 90% of the cells in the bone marrow and are recognizable by their morphology.
Physiological mechanism responsible for the continuous formation of the different types of blood forming elements, keeping them within the limits of normality in the peripheral blood.
Takes place in organs external to the bone marrow.
Fetal development, normal active immune responses to pathogens and pathological circumstances.
Spleen and liver: main function: production of antigen-presenting cells and phagocytes
Myelofibrosis (stem cells replaced by collagen fibers of connective tissue).
A classic example of EMH is increased ectopic erythropoiesis in the liver or spleen under conditions of hypoxia due to increased erythropoietin production.
Bone marrow observation
In order to observe these processes, a bone marrow sample must be obtained:
You can watch the following the videos:
Animation and promoting the use of some brand of special equipment: https://ugtomx-my.sharepoint.com/:v:/g/personal/c_albabetancourt_ugto_mx/EQZheH1YVjBKt6YQzXCrAdQBWyOoEMWfp7P9DXfWEg4teA?e=xm87KX
Bone marrow aspiration and biopsy from the iliac crest: https://ugtomx-my.sharepoint.com/:v:/g/personal/c_albabetancourt_ugto_mx/EZNBzWLCDItOvtmqR2EMbacB6uPHxZ-iDecSO-NMp2jBNg?e=tmUNAN
Hematopoietic cells are conformed In bone marrow specialized environments.
- Neutrophil: Myeloperoxidase.
- Eosinophil: Myeloperoxidase, eosinophil cationic protein.
- Basophil: Heparin, histamine.
- Extramedullary hematopoiesis is normal in the embryonic developmental stage.
- The bone marrow is the final site for hematopoiesis.
- Erythropoietin is exclusive for erythrocytes maturation.
- Thrombopoietin is exclusive for platelets maturation.