Genital System I Flashcards
What germ layer to mammary glands originate from?
Ectoderm
What embryonic germ layers do vagina and vestibule originate from?
Ectoderm
What embryonic germ layers do penis and clitoris originate from?
Ectoderm
What embryonic germ layer do gonads originate from?
Mesoderm
What embryonic does the following originate from?
Uterus, cervix
Mesoderm
What embryonic does the following originate from?
Epididymis, ductus deferens
Mesoderm
What embryonic does the following originate from?
Accessory sex glands
Mesoderm
Where does the initial step in sex determination occur?
At fertilization
What 3 embryological events occur in development occur in the 1st trimester?
- Migration of primordial germ cells from yolk sac
- Sex cords develop in gonad, paramesonephric ducts develop
- Sex evident structures
What event begins in 1st semester and ends in 2nd trimester?
Development of male ducts and testes
OR
Development of female ducts and ovaries
What occurs in 2nd trimester?
Formation of broad ligament
Testicular descent in bull and ram
What embryological event occurs in development occurs in the 3rd trimester?
Testicular descent in boar and human as well as colt
Where do primordial germ cells originate from?
During formation of mesoderm and endoderm a population of epiblast cells are put aside for formation of the germ line
Where are these primordial germ cells displaced from and to where?
Displace from EMBRYONIC DISK to the DEFINITIVE YOLK SAC and part of the ALLANTOIS
What is primordial germ cell migration driven by?
Chemotaxis
What is terotomata?
Primordial germ cells that dont migrate properly, they can become tumours which have teeth, bone or any kind of development due to the stem cells function they have
What is the gonadal ridge also known as and why?
Bipotetential gonad because at this time of development it is capable of differentiating allong two different paths
- Ovary
- Testes
In relation to the kidneys, where does the gonadal ridge form?
Medial to the embryonic kidney
What occurs when primordial germ cells arrive in gonadal ridge?
They stimulate cells around them to proliferate causing ridge elongation
3 origins of gonadal ridge cells?
Local mesenchymal cells
Coelomic Epithelium
Cells from mesonephric tubules
What forms compact strands of tissue called primitive sex cords?
Cells from degenerating mesonephric tubules
What is WT-1 gene required for?
Required for formation of gonads
What is the function of Lim-1 gene?
Required for formation of gonads
What factor induces differentiation of Sertoli and Leydig cells?
Steroidogenesis Factor 1
What occurs beside the mesonephros is developing?
A new pair of ducts appear
Paramesonephric aka Mullerian ducts
What is known as sexually indifferent stage?
When mesonephros and paramesonephric ducts are developing along sid each other
What regulates sexual differentiation?
SRY
What does the Y chromosome contain that cause for a male to become?
A gen called Sex Determining Region on Y chromosome (SRY)
What form of sex differentiation is referred to as Genetic Sex Differentiation?
SRY
Events leading to development of male reproductive system
SRY Protein —> Testes Develop —> Sertoli cells secrete Anti-mullerian hormone (AMH) and Dihydrosterosterone (DHT) —–> AMH and testosterone degenerate paramesonephric duct.
Sertoli cells secrete Anti-mullerian hormone (AMH) and Dihydrosterosterone (DHT) —–> Desert Hedgehog (DHH) gene causes differentiation of fetal leydig cells –> DHT —> Development of penis, scrotum and accessory sex glands
Desert Hedgehog (DHH) gene causes differentiation of fetal leydig cells –> Testosterone –> Development of male duct system
Developmental Sequence of the testes
Undifferentiated sex cords allign with rete tubules. Mesonephric tubules penetrate into the primitive gonad but have not yet connected with rete tubules
Rete tubules and mesonephric tubules become interconnected
Sex cords become epithelial in nature
Paramesonephric duct begins to degenerate
What does the connection between rete tubules and mesonephric tubules provide?
Continuity between undifferentiated sex cords
What causes for the degeneration of paramesonephric duct?
Anti-Mullerian hormone (AMH)
What do primitive sex cords proliferate into?
Seminiferous cords that are solid tubules containing germ cells
What do mesenchymal cells between sex cords develop into?
Leydig cells
What is sertoli function with spermatocyte?
Form blood testes barrier by surrounding developing spermatocyte
Maintain elevated levels of testosterone around these cells which help them develop
What occurs at puberty in developmental sequence of the testes?
Seminiferous cords become seminiferous tubules (canalnicularize)
And there is continuity between rete testis and efferent ducts
What are responsible for carrying sperm through to the urethra
Efferent ducts
Epididymis
Ductus Deferens
What are 4 accessory sex glands?
Prostate
Bulbourethral glands
Seminal vesicles
Ampullae Ductus Deferentis
What accessory sex gland does a cat lack?
Seminal vesicles
What do seminal vesicles and ampullae ductus deferentis develop from?
Epithelial evaginations from mesonephric duct
What do the prostate and bulbourethral glands arise from?
Epithelial evagination from the urogenital sinus
What two layers of peritoneum cover the testis?
Visceral vaginal tunic
Parietal vaginal tunic
What are the 2 stages of testes descent?
Transabdominal phase
Inguinal-scrotal phase
Explain transabdominal phase
Retroperitoneal testes attached caudally to gubernaculum
Peritoneal cells form a junction with gubernaculum in the inguinal region
Gubernaculum grows toward scrotal region
Explain inguinal-scrotal phase
Once gubernaculum penetrate inguinal ring, rapid growth of the gubernaculum moves testes into inguinal canal - rapid growth dependent on testosterone
Gubernaculum shrinks once testes are in inguinal region
Shrinkage pulls testes deeper into scrotum
What covers the testis?
inner visceral vaginal tunic
what is the spermatic cord?
Ductus deferens
Nerves
Testicular artery and vein
Vaginal Fluids
What allows for testis to move around with in the scrotum?
The outer parietal vaginal tunic does not touch the visceral vaginal tunic and a vaginal cavity is created to allow for movement of testis within scrotum
What is failure of testes to descend known as?
Cryptorchidism
