Lecture 50 Flashcards
What are the components of the reproductive tract development?
The components of the reproductive tract development are the gonad development (site of gamete production), oocytes and sperm develop from sperm cells, development of the male and female ducts and structures to deliver sperm to the oocyte.
What do the main parts of the reproductive systems form from? What causes differentiation?
The reproductive systems form from the intermediate mesoderm and germ cells migrate from the yolk sac. The germ cells are first seen in the wall of the yolk sac at week 3 and by week 6 they migrate via movement along the gut tube, leaving where the gonads are forming. The gonad is indifferent until about day 40, at which point they will become testes if the SRY (sex determining region of Y chromosome) gene is present and if not it will become an ovary.
How does reproductive development of the ducts occur?
The ducts are developed early, before sexual differentiation, forming two tubes from the mesoderm. The indifferent system involves mesonephric (wolffian, more medial) duct and the para-mesonephric (mullerian, more lateral) duct, these are both found in the mesonephron. For the male the wolffian duct is kept as the epididymis, ductus deferens and seminal vesicles and the mullerian is lost, for the female the mullerian duct is kept as the uterine tubes (oviduct), the uterus and upper vagina and the wolffian duct is lost. If there is no SRY gene no androgens will be produced by the gonad and the wolffian duct will disappear, the lower parts of the 2 mullerian ducts will fuse. If the SRY is there testosterone is produced and the wolffian duct will persist, the mullerian duct is degenerated via mullerian inhibiting substance produced in the male, the tube gets pulled down with the testes as it descends from the abdominal cavity via the inguinal canal (normally in scrotum by 33 weeks).
What is the path for production of the external reproductive organs?
The indifferent external genitalia of the embryo is the genital swelling (outer layer), then genital folding (inner layer) and then at the top the genital tubicle. In females the genital swelling forms the labia, the genital folds form the urethra and vagina. At the top the genital tubicle becomes the clitoris. If androgen (male) is present the genital swellings will grow out and form the scrotum, the genital swelling will form the spongy/penile urethra and the genital tubicle will lengthen out and form the glans of the penis. By 12 weeks the urogenital fold is the labia minora or spongy urethra, the genital swelling will be the labia majora or scrotum.
Where can problems with the external genitalia arise?
Abnormalities of external genitalia can arise if: the female fetus is exposed to androgen or the male fetus can not respond to androgens (androgen receptor mutation), XY females (lack of functional SRY gene)
