Development of the Reproductive System Part 1 Flashcards
What protein causes a differentiation into male genitalia?
SRY protein
Under it’s influence, male development occurs, in it’s absence, female development occurs.
What is the sex-determining gene?
And where is it found?
SRY gene (sex-determining region on Y) On the short arm of the Y chromosome.
When do the gonads acquire male or female morphological characteristics?
The seventh week of development.
How do gonads initially appear?
As a pair of longitudinal ridges
The genital or gonadal ridges
When do germ cells appear in the genital ridges?
The sixth week of development.
Where do primordial germ cells originate?
The epiblast.
Describe the path of the primordial germ cells, from their origin to the genital ridges.
They start in the epiblast
They migrate through the primitive streak
By the third week, they reside among endoderm cells in the wall of the yolk sac close to the allantois.
During the fourth week they, they migrate by ameboid movement along the dorsal mesentery of the hindgut.
They arrive at the primitive gonads at the beginning of the fifth week
And they invade the genital ridges in the sixth week.
Shortly before and during arrival of primitive germ cells, the epithelium of the genital ridge proliferates, and epithelial cells penetrate the underlying mesenchyme. What does this form?
And can you differentiate between male and female? And why?
The primitive sex cords
These are irregularly shaped cords that are connected to the surface epithelium.
This is the same in both males and females, and so you cannot differentiate.
What does the SRY gene influence the primitive sex cords to do?
They continue to proliferate and penetrate deep into the medulla to form the testis or medullary cords.
After the primitive sex cords have begun to proliferate, towards the hilum, what happens?
The cords break up into a network of small cell strands that later give rise to tubules of the rete testis.
As the primitive sex cords proliferate, what develops to separate the testis cords from the surface epithelium?
The tunica albuginea.
It is a dense layer of fibrous connective tissue.
Describe the testis cords in the fourth month
They become horseshoe-shaped
Their extremities are continuous with those of the rete testis
The testis cords are now composed of primitive germ cells and sustentacular cells of Seretoli derived from the surface epithelium of the gland.
What lies between the testis cords?
Interstitial cells of Leydig.
Tell me about interstitial cell of Leydig.
Derived from the original mesenchyme of the gonadal ridge.
They begin development shortly after differentiation of the testis cords
By the eight week of gestation, they begin production of testosterone, enabling the testis to influence sexual differentiation of the genital ducts and external genitalia.
When do the testis cords acquire a lumen?
Puberty, thus forming the seminiferous tubules.
