Embryology

The internal and external genitalia of both sexes are genetically ‘programmed’ to differentiate passively down a ‘default’  female pathway unless actively switched down a male pathway by the genetic information carried by the testis-determining gene (SRY).  Until the sixth week […]

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The lower urinary tract originates from the cloaca, the section of primitive hindgut into which the mesonephric ducts and embryonic ureters drain. Between the fourth and sixth weeks of gestation, the cloaca is subdivided by the descent of the urorectal […]

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In the cervical portions of the paired blocks of intermediate mesoderm the primitive precursor of the kidney,  the pronephros,  first appears in the fourth week of gestation.  This structure rapidly regresses in the human embryo.  The midzone mesonephros, however, continues […]

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Human gestation spans a period of 38 weeks, from fertilisation to birth. Conventionally, pregnancy is divided into three trimesters,  each of 3 months’ duration.  The formation of organs and systems (embryogenesis)  takes place principally between the third and 10th weeks […]

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