MEDRADSC 2X03 Lecture Notes - Lecture 8: Radioresistance, Stem Cell, Haematopoiesis
24 Jun 2016
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Unit 4. 2 organ system responses to radiation. Stem cell tissues located primarily in red bone marrow of flat bones, spine and proximal femur, humers (in adult) Very small number of stem cells in circulating blood. Liver and spleen are normally dormant for hematopoiesis but can be stimulated to produce. Form immature cells: erythroblasts rbc"s, myeloblasts immature bone marrow cells, megakaryoblasts large bone marrow cells, monoblasts give rise to monocytes large leukocyte, lymphoblasts wbs"s. These multiply and differentiate into mature cells. Located in tonsils, lymph nodes, spleen, thymus: produces lymphocytes. Tissues are very radiosensitive, largely due to apoptosis: depleted of cells by small doses. Very little repair, very radiosensitive! (d0 < 1gy) Slight depletion, regeneration in a few weeks. Numbers of cells in blood reflect damage to marrow and lymphoid tissues. Depends on: sensitivity of the different precursor cells, lifespan of each type in blood. Damage to stem cells is reflected only when mature cells die and must be replaced.
