Development Of Repro Tract Flashcards
What is a germ cell?
Any biological cell that gives rise to gametes
What is a karryotype?
Number and characteristics of a complete set of chromosomes within an individual
Name the male internal genitalia
Testis Duct system - epididymis, vas deferens, urethra Seminal vesicles Prostate Bulbs-urethral glands
Name the female internal genitalia
Ovaries
Duct system - Fallopian tube, uterus, cervix, vagina
Name the male external genitalia
Penis
Scrotum
Name the female external genitalia
Vagina
Vestibule
Labia majora and minora
Clitoris
What are the male secondary sexual characteristics?
Larger body size Body composition and fat composition Hair and skin Facial hair Male pattern baldness Central nervous system effects Smell
What are the female secondary sexual characteristics?
Smaller body size Subcutaneous fat deposition Hair and skin Breasts Central nervous system effects
What is the gonad derived from and what else derived from here?
Intermediate mesoderm
Kidney
What are the gonads known as at the very early stage?
Sex chords
When do the sex cords acquire male/female characteristics?
Week 7
Where do primordial germ cells arise from and where do they go?
Arise in the yolk sac
Migrate along the dorsal mesentery of the hindgut to the primitive gonads
What is the gene that the Y chromosome carries and what does it drive development of?
SRY
Testis, duct system and external genitalia of the male
What does the absence of the SRY a gene lead to?
Development of the female gonad (ovary), external genitalia and duct system
What does the SRY gene code for?
Testis-determining factor
How do the testis develop?
SRY gene codes for testis-determining factor
Primitive sex cords proliferate deep into the medulla to form the medullary cords
Towards the hilum of the gland, the cord breaks up into a network that later give rise to rete testis
What separates the testis cords from the surface epithelium?
Dense layer of fibrous connective tissue - tunica albuginea
What do the testis cords/medullary cords become composed of?
Primitive germ cells and Sertoli cells
What lies between the medullary cords?
Leydig cells which start to produce testosterone at week 8
What happens at puberty to the testis cords?
Until puberty they are solid
Acquire a lumen forming seminiferous tubules
Join the rete testis which join the ductili efferentes which are remaining parts of the mesonephric system
They link the rete testis and mesonephric duct which becomes the vas deferens
What happens without the presence of the SRY gene?
Medullary cords in the gonad regress
Production of cortical cords
They split into isolated cell clusters which continue to proliferate
They surround each oogonium with a layer of epithelial cells - follicular cells
What are the two sets of genital ducts which initially develop in both sexes?
Mesonephric (Wolffian) ducts
Paramesonephric (Müllerian) ducts
Where do the genital ducts end?
At the cloaca
Difference between mesonephric ducts and mesonephric tubules?
Tubules form a renal function
Ducts and tubules make up the embryonic kidney
Where do the paramesonephric ducts arise from?
As an invagination of the epithelium of the urogenital ridge
Where do the paramesonephric ducts run from and to?
Caudally they contact the cloaca
Cranially they open into the abdominal cavity
What happens in the midline with the paramesonephric ducts?
They come into close contact
Initially separated by a septum
Fuse to form the uterine canal
What does the caudal tip of the combined paramesonephric ducts do?
Projects into posterior wall of the urogenital sinus where it causes a small swelling - the paramesonephric/Müllerian tubercle
What is on either side of the Müllerian tubercle?
Mesonephric ducts open on either side into the urogenital sinus of the tubercle
In the XY embryo, how are the different ducts supported/not supported?
Androgen secretion supports mesonephric/Wolffian ducts from Leydig cells
Sertoli cells secrete Müllerian inhibiting substance so paramesonephric duct degenerates
In the XX embryo, how are the different ducts supported?
No androgen/testosterone so mesonephric/Wolffian duct degenerates
No testis-derived Müllerian inhibiting hormone so the Müllerian ducts stay
At the basic stage, what is there in regards to external genitalia?
Genital tubercle
Genital folds
Genital swellings
What happens in males to produce the external genitalia?
Genital tubercle elongates and genital folds fuse to form the spongy urethra
Happens under the influence of testis-driven androgen hormones -dihydrotestosterone
What happens in the females to produce external genitalia?
No fusion occurs so urethra opens into the vestibule
In which region do the testes arise?
Lumbar region, tethered to labioscrotal folds (future scrotum) by the gubernaculum
How does the processus vaginalis develop?
A musculo-fascial layer with the peritoneal membrane evaginates into the scrotum as it develops
This forms the processus vaginalis
How do the testes descend?
Migrate over the pubic bone behind the processus vaginalis
Above the testes, the fascia and peritoneum become closely apposed
Fascial layers are obliterated by the stem of the processus vaginalis, testicular vessels and nerves from the spermatic cord
What is the remnant of the gubernaculum?
The scrotal ligament
Where do the ovaries begin?
Posterior abdominal wall, attached to the labioscrotal folds by the gubernaculum
What does the gubernaculum become in females?
Ovarian ligament which connects the ovaries to the uterus
Round ligament of the uterus which attaches the uterus to the labia
What do the wolffian ducts develop into?
Epididymis
Vas deferens
Seminal vesicles
What do the Müllerian ducts develop into?
Uterine tubes
Uterus
Cervix
Upper vagina
