, Foster D. Lasley2, Indra J. Das2, Marc S. Mendonca2 and Joseph R. Dynlacht2
(1)
Department of Radiation Oncology, CHRISTUS St. Patrick Regional Cancer Center, Lake Charles, LA, USA
(2)
Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, IN, USA
Stages of in Utero Development
Preimplantation (conceptus): Limited number of cells, no differentiation.
Days 0–5 in mice, Weeks 0–2 (Days 0–9) in humans.
Organogenesis (embryo): Cells begin to differentiate into organs and tissues.
Days 5–13 in mice, Weeks 2–6 (Days 10–42) in humans.
Fetal Growth (fetus): Structures are formed, and only need to grow and mature.
Days 13–20 in mice, Weeks 6–40 in humans (Fig. 32.1).
Fig. 32.1
Relative risk of various effects of ionizing radiation administered during specific phases of intrauterine development.
Of Mice and Men
The mouse is the most common experimental animal for gestational defects.
In mice, the conceptus, embryo, and fetal stages are roughly equal in length, with full-term gestational period of 20 days.
In man, the fetal stage is overwhelmingly longer, comprising the majority of the 9 months.
Mice appear to be more susceptible to organ malformations while humans appear to be more susceptible to growth retardation and mental retardation.
Preimplantation Damage: All or Nothing
The pre-implantation conceptus has the highest radiosensitivity, 0.05–0.15 GyRelated posts:
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