10 - Gonads 1 Flashcards
How long does the process of spermatogenesis take place?
70 days
How do spermatogonia pass through the Sertoli cell barrier?
- move into Sertoli cells and enclosed in cytoplasm
- Sertoli cells provide structural and metabolic support for spermatogonia
- helps spermatogonia develop
- spermatogonia then enter lumen
What enzyme in the testes converts androstenedione to testosterone?
17 hydroxysteroid dehydrogenase
What is the process of spermatogenesis?
- germ cells multiply and differentiate into spermatogonia (2n)
- at puberty: spermatogonia divide into more spermatogonia or primary spermatocytes (2n); FSH starts to be released
- primary spermatocytes undergo first meiotic division to give secondary spermatocytes (n)
- secondary spermatocytes undergo second meiotic division to give spermatids (n)
- spermatids mature and differentiate into spermatozoa
What are the labels of the seminiferous tubules?
- lumen
- spermatogonia
- spermatozoa
- spermatid
- sertoli cells
- leydig cells
- tight junctions
- primary and secondary spermatocytes
What is the proceess of oogenesis?
- germ cells divide into oogonia (2n)
- oogonia multiply to give primary oocytes (2n)
- primary oocytes immediately enter first meiotic division but stop at prophase i
- layer of cells form around oocyte before birth (forms primary follicle)
- at puberty: FSH continues development
- first meiotic division completes around ovulation to give secondary oocyte (n) and polar body
- secondary oocyte enters second meiotic division that doesn’t complete until fertilisation (second polar body and ovum formed on completion)
What are the labels of the testes?
- coiled seminiferous tubules
- rete testis
- vasa efferentia
- epididymis
- vas deferens (surrounded by smooth muscle)
What are the labels of the ovaries?
- follicles undergoing atresia
- graafian follicle
- ovum
- granulosa cells
- thecal cells
- follicular fluid
- remnants of last corpus luteum
- ovarian stroma
What are the features of the follicles in the ovaries?
- contain follicles at all stages of development
- some follciles undergo atresia
- largest follicle (graafian) ready for ovulation
- all follicles embedded in ovarian stroma
- graafian follicle becomes corpus luteum when oocyte released
What are the cells and tubes of the testes and their functions?
- seminiferous tubules: site of spermatogenesis, lined by layers of spermatogonia and sertoli cells
- sertoli cells: synthesise FSH and androgen receptors; produce inhibin in response to FSH
- leydig cells: produce androgens (testosterone) in response to LH; lie outside seminiferous tubules
- rete testis: collect and concentrate spermatozoa
- vasa efferentia: tube connecting rete testis and epidiymis
- epididymis: stores spermatozoa
- vas deferens: tube connecting epidiymis and urethra
What are the features of the testes?
- develop in abdomen and descend to scrotum before birth
- if no descent then infertility may result
- scrotum 2-3C cooler than body temperature (important for spermatogenesis)
What is gametogenesis?
the production of gametes
What are the processes of steroidogenesis in the adrenals and gonads?
- cholesterol converted into pregnenolone
- pregnenolone converted into progesterone
- progesterone converted into 17-OH progesterone
- 17-OH progesterone converted into androstenedione
What are the processes of steroidogenesis in the adrenals only?
- progesterone converted into deoxycorticosterone
- deoxycorticosterone converted into corticosterone
- corticosterone converted into aldosterone
- 17-OH progesterone converted into 11-deoxycortisol
- 11-deoxycortisol converted into cortisol
What are the processes of steroidogenesis in the gonads only?
- androstenedione converted into testosterone or oestrone (5-α reductase)
- testosterone converted into dihydrotestosterone or 17β-oestradiol (aromatase)
- oestrone converted into 7β-oestradiol
