![]() ![]() Induction is a key mechanism of cell fate specification (the process in which the cell is designated to follow a developmental path unless extrinsic cues direct an alternative fate) during embryonic development. Gastrulation Prospective mesoderm involutes first followed by prospective endoderm The animal cap ectoderm eventually covers the whole embryo by spreading (epiboly) of animal pole ectoderm cells Gastrulation -> Neurulation Mesoderm induces overlying ectoderm to become neural tissue. The dorsal lip of the blastopore is essential for normal embryonic development. The region immediately above the blastopore forms the dorsal lip of the blastopore. The cell shape change drives the bottle cells into the interior of the blastula by invagination (the action or process of being turned inside out or folded back on itself to form a cavity) resulting in the formation of the blastopore. The cells become elongated to form bottle cells. Examples of teratogens: Drugs - thalidomide, anti-epileptic drugs, antibiotics Methotrexate - antimetabolite that treats cancer by slowing the growth of cancer cells Maternal infections - zika virus, chickenpox, Group B strep (GBS), toxoplasmosis Alcohol Gastrulation in Xenopus laevis blastula Gastrulation begins when a few epithelial cells in the vegetal pole (the point on the surface of an egg that is diametrically opposite the animal pole and usually marks the centre of the protoplasm containing more yolk) region undergo a morphological change. Teratogens disrupt complex normal cellular and molecular developmental programs. The risk is highest during embryonic development as this is when the organs are developing. It is the leading cause of infant mortality and occurs in approximately 2-3% of live-born infants. ![]() ![]() Birth Defects - Teratology Teratology - the study of the causes of congenital defects and developmental abnormalities due to teratogens. Embryonic Development Key Stages of Vertebrate Development Key stages of vertebrate development include: Fertilisation Cleavage Gastrulation Neurulation (transformation of the neural plate into a neural tube) Organogenesis Human Embryonic Development During embryogenesis, the growth of the blastocyst into an embryo is driving by precisely orchestrated complex cellular and molecular mechanisms that operate during: Gastrulation Neurulation Neural crest cell formation Organogenesis Deviation from these mechanisms will result in birth defects and congenital disorders. ![]()
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