Exam2Lec7Hematopoiesis&Bone Marrow&Thymus Flashcards
Which organs are primary lymphoid organs (2)? What cells do they produce?
- Thymus = T cells
- Bone marrow = B cells
Which organs and tissue are secondary lymphoid organs and tissues (4)?
- Diffuse lymphatic tissue (e.g. GALT)
- Lymphatic nodules and tonsiles
- Lymph nodes
- Spleen
Where are T cells found?
Thymus
Where are B cells found?
Bone marrow and gut associated lymphatic tissues (GALT) in humans
After birth, where does hemopoiesis occur?
occurs only in red bone marrow and lymphatic tissues
Explain the 3 phases/stages of fetal hemopoiesis
1st phase: Embryonic yolk sac = formation of blood islands (RBCs only)
2nd phase: red and some WBCs
3rd phase: Bone marrow = RBCs and WBCs, also spleen and lymphatic organs
What are the two types of bone marrow? Which one is active and inactive? What do they produce?
*Red marrow = active, produce blood cells
* Yellow marrow = inactive, produce fat cells
red marrow changes gradually to yellow (inactive)
What makes up active(red) normal bone marrow in adults (3)?
- stroma (reticular cells) = produce reticular fibers network
- blood-forming cords (dividing hemopoietic cords)
- endothelial-lined sinusoids with discontinuous base membrane
Newborns have which type of bone marrow?
red
Where are lymphocytes formed?
formed in red bone marrow and in the lymphatic tissues
In adults, erythrocytes, granulocytes, monocytes, and platelets are formed where?
red bone marrow
**Explain steps of bone marrow aspiration(3) **
- needle inserted into hip bone (preferred anatomical site)
- small amount of bone marrow obtained
- aspirate is spread on a glass slide
inject needle into bone marrow and smear on slide
Explain steps of bone marrow core biopsy (3)
- intact bone marrow is obtained by a small incision in the skin
- biopsy needle is inserted into bone using a corkscrew movement to obtain a solid piece of bone marrow
- biopsy is used to diagnose and stage different types of cancer or monitor the results of chemotherapy
take an actual piece of bone marrow and screen for cancer
Which cells are the last cell capable of mitosis for platelets (endomitosis)?
Megakaryoblasts = chromosome replication
Under hormone stimulation by ____ causes a megakaryoblast to become a megakaryocyte (platelet-producing cell).
thrombopoietin
Where do platelets originate in adults?
red bone marrow by fragmentation of the cytoplasm of mature megakaryocytes
a multipotential myeloid stem cell precursor->megakaryoblasts->megakarocyte by stimulation of thromboietin-> platelet
What is the precursor for the red cell and white cell lineage?
multipotential myeloid stem cell
before that is a pluripotential hematopoietic stem cell
Breifly explain cell movement to sinusoid capillary and platelet formation
slide 21
- Mature megakaryocye pushes against a sinusoial endothelial cells
- They get fusied into the membrane is this causes a temporary opening b/w endothelial cells and then closes after cell completes production of platelets
List stages of erythrocyte lineage (erythropoiesis) (6)
- Proerythroblast
- Basophilic erythroblast
- Polychromatophilic erythroBLAST (last mitosis)
- Orthochromatophilic erythroblasts aka normoblast
- Polychromatiphilic (polychromatic) erythroCYTE -Reticulocyte
- Erythrocyte (mature cell)
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All blasts are still mitotically active and can further differentiate
RBCs develop from the multipotential ______ stem cell in bone marrow under the influence of ____ and some cytokines.
- myeloid
- erythropoietin
helps with development
What are the major changes during the process of erythrocyte maturation (6)?
- Cell volume decreases
- Nucleoli diminish in size until they become invisible under LM
- Nuclear diameter decreases
- Chromatin becomes increasingly dense = thickened and reduced in size and finally extruded from the cell
- Cytoplasmic basophilia (ribosomes) decrease while acidophilia (hemoglobin) simultaneously increases
gradual reduction in cell diameter and incr nuclear condensation of chromatin
bigger cell=younger
becmes lighter and smaller as it matures
How many days does it take RBCs to develop?
7 days
How manys to RBCs circulate in the blood?
120 days
What occurs when a proerythroblast transitions to an erythrocyte (2)?
- increase in cytoplasmic hemoglobin concentration
- decrease in nuclear volume and an increase in chromatin condensation followed by extrusion of a pyknotic nucleus
Explain the process of a reticulocyte becoming a mature erythrocyte
- Nuclues is extruded to become a an immature erythocyte (reticulocyte)
- Reticulocyte will leave the bone marrow, pass to bloodstream, lose its mitochondria and ribosomes within 1-2 days = becomes a mature erythrocyte
macrophages will then phagocytize discarded nucleu
1-2% of total RBC count in peripheral blood, but may be elevated in blood to compensate for blood loss
Reticulocyte
What are the possible pathological causes involving RBCs?
- anemia
- thalassemia
- miliary tuberculosis
- cancers involving bone marrow (myelomas, leukemias, lymphomas) and chronic hypoxemia
What are the 6 stages of leukopoiesis?
- Myeoblast
- Promyelocyte = largest cell, primary azurophilic granules only produced in this stage
- Myelocyte = primary (azurophilic) granules + secondary (specific) granules produced (1st time secondary granules are produced)
- Metamylocyte (only in neutrophils and eosinophils) = nucleus is kidney shaped
- Band cell = only in neutrophils
- Neutrophilic granulocyte = 1st sign of the development of neutrophil, eosinophil, basophil
myelo-oval
meta-indented
mature-segemented
Where are monocytes produced?
in bone marrow from a biopotential stem cell
monocyted and neutrophils are formed from the same stem cell
Do monocytes have specific cytoplasmic granules?
NO, only azurophillic granules with lysosomal enzymes
Monocytes travel to tissues where they become…?
macrophages
Cell stages for monocyte formation
ly
myeloid stem cell->myeloblast-> promonocyte (monoblast)->monocyte
Leukopoesis-Lymphocyte
Lymphocyte
produced where?
contains what type of granules?
what can it do?
produces in bone marrow (primary lymphoid organ)
Contain only primary azuro granules
only cells to be able to recirculate blood
3 characteristics of lymphocytes
- thin (basophilic) cytoplasm
- large nucleus (takes up entire cell)
- T-cells (thymus), b cells (bone marrow)-immune fxn
What is aplastic anemia also called?
hypocellular bone marrow
What is aplastic anemia marked with pancytopenia?
reduction in the # of erythrocytes, all WBCs, and platelets in blood circulation
What causes aplastic anemia (aka hypocellular bone marrow)?
- Many cases are idopathic = unknown
- Some can follow toxic exposure to chemotherapy drugs or to chemicals such as benzene, radiation, and infection with viral hepatitis
How is aplastic anemia (aka hypocellular bone marrow) treated?
- bone marrow transplantation
- anti-lymphocyte globulin (in idopathic cases)
What is the function of the thymus?
- primary lymphatic organ
- educates thymocytes (before becoming T-cells)
What makes up the structure of the thymus?
- capsule: poorly developed
- **epithelioreticular cells (aka nurse cells) = responsible for development and maturation of T-cells **
- few fibers
- No lymphatic nodules = no interaction with B cells
lymphatic nodules are where T and B cells interacts, so w/o it, T cells are able to develop w/o B cells coming in the way
What is the function of Hassall’s corpuscle (thymic corpuscle)?
produce interleukins that function in differentiation and education of T cells
site of final stage of T-cell education
hassal corpuscle=medullary epithoreticular cells=located in medulla
Lymphatic vessels of the thymus are?
efferent
What is the purpose of the blood thymus barrier?
To keep B cells from penetrating and interacting with T cells
microcirculation: postcapillary venules and thymus blood barrier to protect T cells
How do mature T cells (CD8+ and CD4+) leave the cortex?
through postcapillary venules in medulla and enter the blood circulation
early stage T cells in the cortex migrate to medulla for education. Mature T-cells (in medulla) leave the thymus via post capillary venules-> Tcells enter blood circulation
What is DiGeorge Syndrome?
an inherited immunodeficiency disease
What causes DiGeorge Syndrome?
- the cortical epithelial (epithelioreticular) cells did not develop = thymus is underdeveloped = no T cell education b/c lack of epithelioreticular cells
What is the result of DiGeorge Syndrome?
- lack of cell-mediated immunity (low T cell count)
- loss of parathyroid gland and cardiac abnormalities
