Reproductive system 2: Genital ducts and external genitalia Flashcards
From which germ layer are the reproductive and urinary systems derived?
Intermediate mesoderm.
What is the urogenital ridge?
Formed by the intermediate mesoderm. Protrudes from the posterior abdominal wall and covered by epithelium.
In the male, what eventually forms the genital tract?
Mesonephric duct. Paramesonephric duct degenerates.
In the female, what eventually forms the genital tract?
Paramesonephric duct. Mesonephric duct degenerates.
Which gene drives the development of the male genital ducts?
SRY gene.
How does SRY drive development of the male genital duct?
Encodes testis determining factor - causes differention of epitelial cells into Sertoli cells. Sertoli cells secrete anti-Mullerian hormone (AMH). AMH causes degeneration of paramesonephric ducts.
What is the function of Sertoli cells in male genital tract development?
Cause differentiation of mesoderm of the gonad into Leydig cells. These produce testosterone - promotes survival and further development of mesonephric ducts.
What is the name of the structures that connect the mesonephric duct to the rete testis? What do they develop into?
Epigenital tubules - efferent ductules.
Which structures are ultimately derived from the mesonephric duct?
Seminal vesicle (out-pouching), vas deferens, efferent ductules, epididymis.
Which structures are remnants of the paramesonephric ducts?
Utriculus prostaticus and appendix testis.
What is the signal for the development of the female reproductive tract?
The absence of the SRY gene.
Why does the female reproductive tract develop in the absence of the SRY gene?
No anti-Mullerian hormone - paramesonephric ducts remain. No testosterone - mesonephric ducts degenerate.
Describe the derivatives of the paramesonephric ducts.
Cranial and horizontal - uterine tubes. Caudal - uterus.
Why are the uterine tubes not attatched to the ovaries?
The paramesonephric duct is not attached to the gonad.
Describe the development of the vagina.
Urogenital sinus develops sinovaginal bulbs that fuse with caudal tips of paramesonephric ducts to form vagina.
Describe possible remnants of the mesonephric ducts.
Epoophoron, Paroophoron and Gartner’s cyst.
What might be the consequences of a failure of paramesonephric ducts to fuse?
Double uterus and double vagina or just double uterus.
What might be the consequences of failure of the uterine septum to degenerate?
Bicornate uterus (two-horned), septated uterus, cervical atresia
What might be the consequence of failure of one paramesonephric duct to elongate?
Unicornate uterus.
What is the cause and the symptoms of anti-Mullerian hormone syndrome?
Mutation in the AMH gene resulting in no AMH production so paramesonephric ducts persist. Both mesonephric and paramesonephric derivatives develop. Normal male external genitalia but may have cryptorchidism
From which structure will either the penis or clitoris develop?
The genital tubercule.
From which structure are the external genitalia derived?
The cloacal folds.
At how many weeks can penile development be seen?
10 weeks
How does the penile urethra develop?
Urethral folds pulled forwards and form lateral walls of urethal groove. Urethral groove is lined by epithelium and forms urethral plate. At the end of third month urethral folds close over urethral plate to form penile urethra.
What is hypospadias?
Incomplete fusion of urethral folds - urethra opens on ventral surface of penis. 3-5/1000 births. Difficulty urinating. Can be repaired surgically using the foreskin.
What is epispadias?
Usually arises as a result of the urethra opening on the dorsal surface of the penis. Often associated with exstropy of the bladder. 1/30,000 births. Results from improper location of the genital sinus - urethral groove located on dorsal surface.
What is development of the female external genitalia dependent on? How does it happen.
Oestrogen. Genital tubercule elongate. Urethtral folds DO NOT elongate form labia minora. Genital swellings form labia majora. Urogenital groove remains open.
