Lecture 8 - The Gonads 1 Flashcards
How do the gonads develop in males and females?
Males - testes Females - ovaries
What differentiates the ovaries from testes in embryogenesis?
The SRY gene on Y chromosome makes gonad develop into testes
When does spermatogenesis begin?
In puberty
When does oogenesis begin?
Reach 6-7 million oogonia at 24 weeks and cells begin deteriorating (atresia) and when puberty is reached 400,000 and by the time menopause is reached, 300-400
What are the functions of the gonads?
Production of gametes - gametogenesis Steroidogenesis - Androgens (MALES, females) and Oestrogens/Progesterones (FEMALES males)
Describe the process of Spermatogenesis:
Germ cell (diploid) > spermatogonia (mitotic, ^ testosterone) > 1ry spermatocytes (1st meiotic) > 2ry spermatocytes (2nd meiotic/HAPLOID) > Spermatids > Spermatozoa
How long does spermatogenesis take?
Around 70 days
How do males retain some spermatogenic capability throughout life?
A pool of spermatogonia remain for subsequent cycles
At what rate is sperm produced?
300-600 sperm/gm in testis/second
Describe the process of oogenesis:
Germ cell (diploid) > Oogonia (mitotic) > 1ry oocyte (1st meiotic) > 2ry oocyte (HAPLOID, 2ry meiotic and takes both cytoplasms, so 1st polar body dies - occurs during ovulation) > Ovum (with 2nd polar body)
What happens to primordial follicles?
They are arrested in development and enter atresia - cell degradation then death
Key features of testes:
Coiled seminiferous tubules - spermatogenesis Rete testis, Vasa efferentia Epididymis - stores sperm and sperm gain motility Vas deferens - surrounded by smooth muscle, propels sperm to urethra and other secretions added
Key features of seminiferous tubules:
Leydig cells - close to ST Sertoli cells - Sperm develop in folds of sertoli cells, where they then move into tubule lumen - connected very tightly leading to blood-testes barrier
What are Sertoli cells?
Form seminiferous tubules Synthesise FSH and androgen receptors (ABG) In response to FSH - INHIBIN produced Associated with developing spermatocytes
What are Leydig cells?
Lie outside ST Synthesise LH receptors In response to LH are the main source of testicular androgens - testosterone (testosterone in testicles is 1000x higher than in blood)