Reproductive system 1: Gonads Flashcards
How is biological sex determined?
The SRY gene (of the Y chromosome) initiates production of testis-determining factor. No Y chromosome = no TDF = female development.
From what germ layer is the reproductive system derived?
The intermediated mesoderm. Also gives rise to urinary system.
From where does the urogenital ridge develop?
Protrudes from the posterior abdominal wall. Covered by layer of epithelium.
How are the primitive sex cords formed?
Epithelium proliferates and penetrates the underlying mesoderm. Week 5-6.
Which event, occuring in week six, is essential for development of the gonads?
Migration of primordial germ cells to the genital ridges.
What are the two distinct developmental regions of the ‘indifferent gonad’?
Inner medulla and outer cortex.
From where do the primitive sex cords detach to form the medullary cords?
The cortex of the indifferent gonad.
What determines what happens to the medullary and cortical regions of the indifferent gonad?
Testis-determining factor
What SRY-influenced developmental events occur in the male to allow development of the testis?
Medullary cords develop and thick tunica albuginea.
What SRY-influenced developmental events occur in the female to allow development of the ovary?
Medullary cords degenerate. Cortical cords develop. No tunica albuginea.
What structures develop at the hilum of the medullary cords?
Rete testis.
What happens to the cortical cords during ovarian development?
Split and surround oocytes.
During which week do the gonads become distinguishable?
Week 7
Describe the descent of the testes.
Extraabdominal gubernaculum shortens, pulling testes towards anterior abdominal wall. Arrive at internal inguinal ring and remain their from 3rd to 7th month. Gubernaculum shortens again at 7 months and pulls testes through the inguinal canal.
When do the testes reach the scrotum?
9th month.
What is the processus vaginalis and what does it become?
Forms the inguinal canal. Becomes the tunica vaginalis.
Where is the deep inguinal ring located?
Tranversalis fascia (a defect).
Where is the superficial ring located?
A hole pierced through external oblique.
What is the aetiology of testicular hydrocele?
Patent processus vaginalis (can also cause indirect inguinal hernias).
What is cryptorchidism?
Failure of both or single testes to descend. Present in 1-4% but usually self-corrects by 3 months of age. Those that do not are corrected surgically at 4-6 months. Associated with increased risk of testicular cancer and infertility.
Describe the descent of the ovaries.
Only descend to pelvic brim. Gubernaculum passes through inguinal canal and inserts into labia majora. Persists in adult as the ovarian ligament proper and the round ligament of the uterus.
