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Phenotype of embryo
is established during week 7 when the indifferent embryo begins phenotypic sexual differentiation (which is determined by the SRY gene)
Three origins of the gonads
1. surface epithelium of the coelom (genital ridge)
2. underlying intermediate mesoderm (of the genital ridge)
3. primordial germ cells (which migrate into the gonad from the wall of the yolk sac)
Gonads by the 4th week
are a bilateral pair of genital ridges located between the mesonephros (which will form kidneys) and the dorsal mesentery
Gonads by the 6th week
primordial germs cells migrate from the yolk sac and embed themselves into the developing gonad
the lower portion of the paramesonephric duct that stays behind in the male
**MIS (from Sertoli cells) inhibits the growth of paramesonephric ducts
the upper portion of the paramesonephric duct that stays behind in the male; it's where the ducts made attachment to the bladder (urogenital sinus)
Efferent ductules are formed by the..
Middle portion of the mesonephric duct that attaches to the retes testis
The retes testis are formed by the..
medullary rays (that do not degenerate as the do in the female because of the presence of the Y chromosome, SRY, etc)
Sertoli cells are derived from..
the surface epithelial cells of the gonad
*they secrete MIS which inhibits the growth of paramesonephric ducts
Leydig cells are derived from...
the original mesenchyme of the gonad
*they secrete testosterone which
1. stimulates mesonephric ducts
2. is converted to DHT by 5-alpha-reductase which causes virlization
The seminal vesicles are derived from..
an outgrowth off of the mesonephric duct (the other outgrowth is the ureteric bud which joins the metanephric duct)
The scrotum is derived from..
the genital swellings of the external genitlia that grow up and out, swing towards each other and then come together
Urethral folds are derived from..
the cloacal folds. Deep inside these are the bulbs. The urethral folds grow together and the urethra is sitting captured in the middle.
There is no urethra passing through the penile urethra. The urethra stop at the membranous portion.
Epoophoron and Paraoophoron
remnants of the mesonephric duct system left behind. They are contained in the mesovarium.
The location of the ligament of ovary proper
between the ovary and uterus; remnant of the mesonephric duct (?)
The location of the round ligament
between the uterus and the labia; remnant of the mesonephric duct (?)
are derived from the surface epithelium of the primitive gonads and surround oogonia to form the ovary
The Fallopian tube is derived from...
the top end of the paramesonephric duct (which opens into the peritoneal cavity)
with the sperm and egg meet in the Fallopian tube, the fetus grows, gets stuck and bursts to cause hemorrhage; aka tubal pregnancy
when the sperm and egg meet in the abdomen; this is possible because when the ovary releases an egg, for a brief moment, the egg is present in the peritoneal cavity. If the sperm is not destroyed in the Fallopian tube, it can continue on to meet an egg in the peritoneal cavity.
The vagina is formed by which two embryological structures?
1. an outgrowth from the urogenital sinus, the sinovaginal bulb. This forms the lower 2/3 of the vagina.
2. the paramesonephric ducts which contain the fornices of the vagina and form the upper 1/3 of the vagina.
The labia minora are formed by the...
urethral folds as the increase in size; the inner portion of the urethral folds contain the bulbs
The crus are contained in the
inner portion of the genital tubercle (the case for both males and females)
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