Week 1 - A - Intro to Haem - Constituents of Blood&Haematopoiesis - RBCs, WBCs, Platelets, Immunophenotyping&Marrow Examination Flashcards
Haematology is the study of blood, the blood-forming organs, and blood diseases What are the particular organs studied in haematology?
Study of bone marrow, liver, spleen and lymphatics
Blood is a specialized fluid (technically a tissue) composed of cells suspended in a liquid What is the fluid that blood is suspended in known as?
Blood is suspended in a fluid known as plasma
What are broadly, the three types of blood cells?
Red blood cells (erythrocytes) White blood cells (leukocytes) Platelets
Red blood cells are the most abundant cell type of the three What are main functions of blood?
They are important for: Fight infection Transport oxygen Prevent bleeding
The production of blood cells is termed haemopoiesis (or haematopoiesis) What is the type of cell that blood cells are derived from known as?
Blood is derived from a type of cell known as a Stem cell - these cells are pluripotent and capable of making all the different blood cells
What is the site of haematopoiesis during the developing embryo?
Yolk sac then liver then marrow From the 3rd to 7month of gestation - the production of blood also occurs in the spleen
Where does blood production take place from birth to maturity? State at which period of gestation the blood production is occurring at?
Blood production by the foetus starts at approximately 5 weeks gestation by the yolk sac This occurs from 5 weeks to 10 weeks The liver also starts producing blood from the 6th week Bone marrow becomes the main source of haemapoeisis at 16 weeks gestation The spleen contributes to haemopeosis from the 3rd to 7th month of gestation
During gestation - yolk sac then liver then bone marrow with spleen during this At birth, blood production is most in the bone marrow but also occurs in the liver and spleen when needed Where does blood production take place during adulthood?
From birth to maturity - blood production takes place in the bone marrow The number of active sites in the marrow decrease but the marrow still retains some sites to carry out haematopoesis From adulthood - only really the axial skeleton marrow involved - skull, sternum, ribs, pelvis & proximal ends of femur
Summarise the sites of haematopoesis from embryo to adulthood? (embryo, birth, birth to maturation, adulthood)
Embryo - yolk sac then liver then bone marrow Spleen from 3rd to 7th month gestation Birth - bone marrow is the main site of haematopoesis - liver and spleen when needed Birth to maturity - number of active sites decreases but bone still retains its ability for haematopoesis Adulthood - Bone marrow of skull, sternum, ribs, pevlis and proximal end of femur
In times of bone marrow stress, which organ may begin producing blood again? (due to its memory for when it produced blood in utero)
This would be the spleen
Haematopoietic stem cell generates a wide array of different cell types. Huge numbers are required to maintain the status quo Approximately: * 100 million red cells/minute * 60 million neutrophils/minute * 150 million platelets/minute What two things have to happen to the stem cell to make blood?
The stem cells need to undergo proliferation (increase in number) and differentiation (become specialised) (Development of the features of the specialised end cell population from stem cell )
What are the only two stem cells in the haematopoeitc tree? What two features msut stem cells have to be classified as stem cells?
This would be – * long term haematopoietic stem cells and * short term haematopoetic stem cells Stem cells must have the ability of: * Self-renewal: the ability to go through numerous cycles of cell division while maintaining the undifferentiated state. * Potency: the capacity to differentiate into specialised cell types.
What do short term haematopoeitc stem cells divide to form? (these are known as short term because they have a greater tendency to differentiate whereas the long term can remain quiescent for longer)
ST-HSC form mutlipotent progenitor cells - these have a great ability for potency but cannot self-renew and therefore do not classify as a stem cell
It is really the mature cells that come from the original LT-HSC, ST-HSC, MPP cells that are viewed on microscopy in the blood The early cells, such as the progenitor cells are not a distinct and the morphology is not as clear The MPP forms a common lympoid and common myeloid progenitor cell that produce different blood cells What cell do neutrophils stem from?
They come from myeloblasts - these come from the common common myeloid progenitor cells
What happens to the size of the cell as it differenitates from myeloblast to neutrophil? (this change in size is true for any cell coming from stem cells)
As the myeloblast continues to differentiate (to promyelocyte, then myleocyte and so on) it decreases in size until it form the neutrophil
The daughters of the precursor cells decrease in size as they divide – important to remember these cells are going through mitosis and therefore there is proliferation of cell – ie not 1 neutrophil forms from the myeloblast, instead many neutrophils will form from one myeloblast What are neutrophils also known as and why?
The neutrophils are also known as polymoprhs due to the multilobulated nucleus that is seen - usually has around 2-5 lobes in a neutrophil
What is the earliest stage in development of the erthrocyte? By earliest, this refers to when the differentiating cells can only become eryhtrocytes
The earliest stage would be when the erythrocyts is the dividing pronormoblast (proerythroblast)