hemopoiesis Flashcards
hematopiesis is the development of what?
what does this process invovle?
what are the moecular signals invovled in hematopoiesis?
Hematopoiesis is the development of different blood cells from precursor cells.
It is a process that involves cell-cell signaling, cell division and cell differentiation.
Some of the molecular signals involved include the interleukins (IL), Granulocyte signaling factor, macrophage inhibitory protein and erythropoietin
hemopoiesis or blood cell formation begins when ?
what are the different phases that are in hemopoiesis?
what does the first stage involve?
what then does the next 2 stages do?
the last phase involves what?
Prenatally, hemopoiesis or blood cell formation begins two weeks after conception, and is subdivided into several phases- mesoblastic, hepatic, splenic, and myeloid.
The first stage involves mesenchymal cells aggregating into blood islands.
The next two stages involve further blood cell formation in the liver and spleen.
The last phase- the myeloid phase involves the formation of blood cells in the bone marrow- a process which continues post-natally for the rest of life. Blood cells are short lived, and thus new blood cells are continually being formed
where does postnatal hemopoiesis occur exclusively?
what is the bone marrow like?
what is found surrounding the sinues?what are these cords part of?
what is another major type of cell found in the bone marrow?
what will bone marrow contain when hemopoiesis is not active?
Postnatal hemopoiesis occurs exclusively in the bone marrow.
The bone marrow is a gelatinous cavity with vasculature that includes arteries, veins and capillaries called sinuses.
Surrounding the sinuses, cords of cells are found. These cords of cells are in the hemopoietic lineage. Another major cell type found in the bone marrow is adipose tissue.
In fact, bone marrow that is not active in hemopoiesis will contain an abundance of adipose cells, and thus be called yellow marrow
what is hemopoiesis based on?
what does this stem cell do?
how is PHSC identified?what can PHSC differentiate into?
what does CFU-GEMM give rise to?
Hemopoiesis is based on the theory that all types of blood cells derive from a common precursor cell- called the pluripotential hemopoietic stem cell (PHSC).
This stem cell divides and gives rise to more stem cells as well as to more differentiated and restricted stem cells in the hemopoietic lineage.
The PHSC is identified by expression of the marker CD34 on its surface.
The PHSC can differentiate into two more restricted stem cells called colony forming units.
The two stem cells are thus CFU-GEMM (also called CFU-S or colony forming unit spleen).
CFU-GEMM will give rise to granulocytes, erythrocytes, monocytes and megakaryocytes, and CFU-Ly (will give rise to lymphocytes).
in erythrocytes what does CFU-GEMM give rise to?
What is the differentiation between CFU-GEMM into BFU-E regulated by?
what does CFU-E get stimulated by?and once stimulated what does it differentiate into?
what do proerythroblasts differentiate into?
what happens to the nucleus in orthrochromatophillic erythroblast?
Do orthrochromatophillic erythroblast have the ability to divide? Y/N
what can orthrochromatophillic erythroblast differentiate into?
what are reticulocytes called when they accumulate enough hemoglobin?
what happens after 120 days to RBC?
We will focus first on the formation of erythrocytes. In the formation of erythrocytes, CFU-GEMM gives rise to BFU-E (burst forming unit –erythrocyte) and CFU-E (colony forming unit-erythrocytes).
Differentiation of CFU-GEMM into BFU-E is regulated by the cytokines IL-3, IL-9, steel factor and granulocyte-monocyte stimulating factor (GMSF) as well as erythropoietin.
CFU-E, stimulated by erythropoietin, will differentiate into a proerythroblast, the first morphologically distinguishable erythrocyte precursor. Proerythroblasts differentiate into basophilic, polychromatophilic and orthochromatophilic erythroblasts.
The nucleus becomes noticeably smaller and eccentrically located in the orthrochromatophilic erythroblast.
Also, orthochromatophilic erythroblasts cannot divide. Orthochromatophilic erythroblasts will differentiate into reticulocytes, which lack a nucleus.
When reticulocytes accumulate enough hemoglobin they are called erythrocytes and released into circulation.
After 120 days or so, red blood cells will display specific antigens on their surface that will signal for them to be sent to and destroyed in the spleen.
what is ganulocytopoiesis? what are each of these cells derived from?
what does CFU-GEMM give rise to in each type of cell?
what do each of these stem cells differentiate into?
What can occur only at the myelocyte stage?
what dpes CFU-GM differentiate into?
Granulocytopoiesis involves the differentiation of each of the granulocytes(basophils, eosinophils, neutrophil).
Each of these three cells derives from its own unipotential (or bipotential) stem cells, which is a descendent of the pluripotential stem cell CFU-GEMM.
The three lineages follow a similar pattern, and thus are usually considered together.
CFU-GEMM will give rise to CFU-Eo (of the eosinophil lineage), CFU-Ba (of the basophil lineage) and CFU-GM (of both the neutrophil and monocyte lineages).
Each of these stem cells differentiates into the myeloblasts of its lineage, which divide and give rise to promyelocytes, and then to myelocytes.
Only at the myelocyte stage can specific granules be resolved, and the three granulocytes differentiated from one another histologically.
(Note that CFU-GM differentiates into CFU-G (which will give rise to myeloblasts of the neutrophil lineage), and to CFU-M (of the monocyte lineage).
where are monocytes derived from?
what are CFU-M called and what do they give rise to?
what do monocytes then differentiate into?
Monocytes derive from CFU-M (which derived from CFU-GM- the bipotential stem cell that gives rise to both the monocyte and neutrophil lineage). CFU-M are called monoblasts, and they give rise to promonocytes which will differentiate into monocytes.
Monocytes then differentiate into macrophages when they enter the connective tissue.
what does CFU-GEMM also give rise to?
what does CFU-Meg differentiate into? and through what process?
what are Megakaryoblasts like?what will they differentiate into?
what will Megakaryocytes do when they extend cytoplasmic processes into sinusoids of the bone marrow?
What happens when the cytoplasmic processes fragment along the demarcation channels?
What will occur with the proplatelets?
CFU-GEMM also gives rise to CFU-Meg the unipotential stem cell of the megakaryocyte lineage. CFU-Meg will differentiate into megakaryoblasts by a process called endomitosis (in which the cell replicates its genetic material and cytoplasm, but does not divide, and the nucleus does not divide as well). Megakaryoblasts are huge cells with a polyploid nucleus. Megakaryoblasts will differentiate into megakaryocytes, large cells with a single multi-lobulated nucleus. Megakaryocytes will extend cytoplasmic processes into sinusoids of the bone marrow and form plasma membrane invaginations called demarcation channels between these processes. The ctyoplasmic processes will fragment along the demarcation channels, releasing clusters of proplatelets into the blood stream. The proplatelets will quickly fragment into platelets in the blood stream
what is lymphopoiesis invoved in?
what will happen with CFU-LyB and CFU-LyT?
What happens once B and T lymphocytes are immunocompetent?
Lymphopoiesis involves the differentiation of CFU-Ly into two unipotential progenitor cells- CFU-LyB and CFU-LyT, both of which then go on to become immunocompetent. CFU-LyB will stay in the bone marrow to become immunocompetent B lymphocytes, while CFU-LyT will migrate to the thymus to become completely immunocompetent T lymphocytes. Once B- and T-lymphocytes are immunocompetent, they will migrate to lymphoid organs such as the spleen and thymus to form clones.
