Topic 48 Subject, tasks and methods of general embryology.
Introduces embryology as a branch of biology and separates general embryology, which covers the first eight weeks, from special embryology and teratology. Sets out the prenatal periods, the trimester division used clinically, and the main phases from gametogenesis through gastrulation to organogenesis. Ends with the origin of primordial germ cells, the formation of genital ridges and the start of gametogenesis.
Topic 48 of 59 in the MU Pleven syllabus for Cytology (Medicine, Year 1). The free AceMed note covers it in 7 sections, about 513 words (4 min of reading), with 16 flashcards.
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Topic 48 Subject, tasks and methods of general embryology.
Embryology
Periods of human development
Phases of human embryology
Sex cells (gametes)
Genital ridges
Gametogenesis
Embryology
Embryology (from Greek, embryon, "the unborn, embryo"; and ‑logia) is the branch of biology that studies the development of gametes (sex cells), fertilization, and development of embryos and fetuses.
General embryology (embryogenesis) – the process of progressing from a single cell through the period of establishing organ primordia (the first 8 weeks of human development).
Special embryology – differentiation and development of organs and organ systems while the fetus grows and gains weight.
Teratology – the study of the embryological origins and causes for birth defects.
Periods of human development
I. Prenatal period
1. Period of the preimplantation embryo (egg or ovum) – from fertilization to the end of the first week (beginning of implantation).
2. Period of postimplantation embryo – begins at the end of the first week of gestation, after implantation is initiated till the end of the eighth week of gestation.
3. Period of fetus – from the beginning of the third month to birth.
II. Postnatal period
From a medical or prospective parent’s viewpoint, human prenatal development is subdivided into three main intervals called the first, second and third trimesters: three – month periods (zero to three months, three to six months, and six to nine months) starting with the date of the onset of the last menstrual period (a memorable landmark) and ending at birth.
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