anatomyphysiologyblog - PRINCIPLES OF TERATOLOGY AND CRITICAL STAGES OF DEVELOPMENT
This complaint defines a teratogen together with explains the principles governing the capacity of a teratogen to create teratogenic number amongst emphasis on the number of a teratogen on different developmental stages.
A teratogen is whatever agent/factor that tin create a congenital anomaly or enhance the incidence of an anomaly inwards the population. The teratogens convey potential to acquit on the normal evolution of human embryo next maternal exposure to them.
These agents are commonly environmental factors such every bit drugs, chemicals, radiation, maternal diseases together with viruses.The number varies from decease of embryo to whatever structural, functional, metabolic together with behavioral abnormalities. Developmental disorders introduce at nascency are termed either every bit birth defects, congenital anomalies or congenital malformation.
Teratology is the branch of scientific discipline that studies the cause, mechanisms, together with patterns of abnormal development. A key concept inwards teratology is that sure enough stages of embryonic evolution are to a greater extent than vulnerable to disruption than others.
Teratogenicity, the capacity of an agent to create nascency defects, is governed past times sure enough factors described every bit Principles of Teratology.
1. Developmental phase at the fourth dimension of exposure
2. Dose together with duration of exposure
3. Genotype of the embryo
4. Mechanisms of activity is specific together with may necessitate inhibition of specific biochemical or molecular process; prison theater cellular telephone death; decreased prison theater cellular telephone proliferation or other cellular phenomena.
5. Manifestation of abnormal evolution are death, malformation, increment retardation and functional disorders.
Stages of Developmental together with Effects of Teratogens
1) Pre-embryonic period
This is the kickoff 2 weeks afterward fertilization. During this period, the zygote divides; implantation occurs; amnion, chorionic sac together with yolk sac are formed together with the embryo becomes bilaminar.
Effect of teratogens:
Teratogens acting during this menstruum either kill the embryo (leading to spontaneous abortion which goes unnoticed every bit the adult woman may non realize that she is pregnant) or their disruptive effects are compensated for past times powerful regulatory properties of early on embryo (so unlikely to create congenital anomalies).
2) Embryonic menstruum or menstruum of embryogenesis or organogenesis
This is the menstruum from tertiary to 8th weeks of gestation, when organ systems are beingness established.
Effect of teratogens:
This is the most sensitive period for inducing major nascency defects.
3) Fetal period
This is the menstruum from ninth calendar week till birth. This menstruum is characterized past times rapid increment together with differentiation of the organ system.
Effect of teratogens:
Fetal harm is unlikely to create malformations but tin campaign death, increment retardation, disruptions or functional deficits.
Which phase of evolution is close vulnerable to teratogens?
The menstruum of embryogenesis is considered to locomote the close critical phase of evolution inwards price of teratogenic effect.
However, no phase of evolution is completely safe. Each part, tissue together with organ of an embryo has a critical menstruum for which its evolution may locomote disrupted. The type of congenital malformations produced depends on which parts, tissues, together with organs are close susceptible at the fourth dimension of exposure to teratogens.
REFERENCES:
Developing Human past times Moore together with Persaud
Langman's Medical Embryology past times T due west Sadler