reproduction Flashcards
what gene on the Y chromosome determines the male sex?
SRY gene - means testes develop
what are the 3 stages of gametogenesis?
- mitosis
- meiosis 1
- meiosis 2
what happens in the mitosis stage of gametogenesis?
proliferation of the primordial germ cells
each mitotic division produces 2 genetically identical daughter cells
what happens just before meioses 1?
interphase
- homologous chromosome pairs are duplicated
what happens in the meiosis 1 stage of gametogenesis?
- separates the homologous chromosome pairs in the diploid
- producing 2 haploids
what happens in the meiosis 2 stage of gametogenesis?
- Sister chromatids separated
- produces 4 haploids
how in genetic variation introduced into gametes?
- cross over in prophase 1
- independent assortment
where does spermatogenesis happen?
testes (seminiferous tubules)
what is the name of the germ cell that undergoes spermatogenesis?
and oogenesis?
spermatogonium (a spermatogonia)
oogonia ( an oogonium)
what does mitosis of a spermatogonia/oogonia produce?
a primary spermatocyte
a primary oocyte
what does meiosis 1 of a primary spermatocyte/oocyte produce?
secondary spermatocytes/oocytes
2 haploids
what does meiosis 2 of a secondary spermatocyte produce?
4 spermatids, these then differentiate into sperm
fertilised oocyte
what is the blood testses barrier?
Sertoli cells forming a ring around circumference of tubule stopping movement into lumen
what is the purpose of the blood testes barrier?
- retains luminal fluid
- proper conditions for germ cell development
what are the 2 compartments of the blood testes barrier?
basal (BM to tight junctions of Sertoli cells)
central (tight junctions to lumen)
what stage of spermatogenesis happens in the basal compartment?
differentiate into primary spermatocytes
what stage of spermatogenesis happens in the central compartment?
meiosis 1 and 2
what gonadotrophin stimulates Sertoli cells?
FSH
what gonadotrophin stimulates Leydig cells?
LH
what do sertoli cells do in the HPG axis?
FSH stimulates Sertoli cells to release inhibit and initiate spermatogenesis
what do Leydig cells do in the HPG axis?
LH stimulates Leydig cells to secrete testosterone.
what are the local and general affects of testosterone (HPG axis)
local : diffuses into Sertoli cells and stimulates spermatogenesis
general: reproductive tract
what hormones of the HPG axis increase during puberty?
GnRH,GHRH, FSH, LH,GH
physical changes for males in puberty
- 9-14
- testicular enlargement
- facial hair growth
- spermatogenesis begins
- growth spurt
- body odour
- mood changes
- acne
physical changes for females in puberty
- 8-14
- menarche (2.5 yrs into puberty)
- growth spurt
- hair growth (pubic an axillary)
- breast enlargement
- body odour and mood changes
- acne
what is menopause? when does it happen?
The cessation of menstruation, when the ovaries STOP releasing eggs because of a reduction in circulating oestrogen
when does menopause happen?
usually occurring between 48-52 years,
give 3 short term signs of menopause?
hot flushes
shorter menstruation cycle
skin dryness
give 3 long term symptoms of menopause?
vagina dryness
hair loss
general aches and pains
what can menopause put women more at risk of developing ?
Osteoporosis
oestrogen is essential for bone density
drops
menstrual cycle can be split into 2 phases of equal length, seperated by ovulation:
follicular - development of mature follicle and secondary oocyte
luteal - post ovulation and death of corpus callosum
what does FSH do in the female HPG axis? (4)
- binds ot granulosa cells
-stimulates follicle growth
-permit the conversion of androgens (from theca cells) to oestrogens
stimulate inhibin secretion
what does LH do in the female HPG axis?
acts on theca cells
stimulates production and secretion of androgens
how does moderate oestrogen levels affect HPG axis?
negative feedback
how does high oestrogen levels affect HPG axis?
positive effect
how does progesterone + oestrogen present affect HPG axis?
negative feedback
what does inhibin do?
secreted by granulosa cells
selectively inhibits ant.pituitiary release of FSH
how many follicles mature during the follicular phase of menstrual cycle (day 1-13)?
only 1 dominant follicle reaches maturity
what is the impact of the LH surge on granulosa cells?
- increases inhibin so stops FSH production
- Granulosa cells become luteinised and express receptors for LH.
when does ovulation happen in menstrual cycle?
day 14
what triggers ovulation?
LH surge causes dominant follicle to rupture and release mature oocyte
what does it mean if cells have been luteinised?
proliferation ceases, terminal differentiation, produces high levels of progesterone
eg. follicle post rupture
how is the cycle stalled after ovulation?
- the follicle remains luteinised after the LH surge
- therefore it is now secreting oestrogen + progesterone
- this causes negative feedback on the HPG axis.
- cycle is stalled in anticipation of fertilisation
what is the corpus luteum?
tissue of the collapsed mature follicle after ovulation
becomes glandular and secretes oestrogen, progesterone and inhibin
what happens in the luteal phase of menstrual cycle?
day 14-28
- corpus luteum secretes steroids to create conditions for fertilisation
- if no fertilisation by day 28, it regresses
- hormones fall and HPG resets
- menstruation occurs
what happens to the corpus leteum if fertilisation occurs?
- it doesn’t regress, its maintained
- due to placental HcG
- it produces progesterone and oestrogen for first 2 months of pregnancy
what are the 2 layers of the uterus?
myometrium - smooth muscle, external
endometrium - internal
3 layers of the endometrium:
- stratum compactum
- stratum spongiosum
- stratum basalis
what are the 3 phases of the uterine cycle?
- menses
- proliferative
- secretory
what happens in menses?
- the endometrium degenerates
- corpus luteum brakes down
- there’s menstrual flow when the spinal arteries rupture
what happens in proliferative phase of uterine cycle?
alongside follicular phase
OESTROGEN:
- endometrium thickens
- increased growth and mobility of myometrium
- thin alkaline cervical mucous
- renews glandular structures
- initiates fallopian tibe formation
what happens in secretory phase of uterine cycle?
alongside the luteal phase
PROGESTRONE
- endometrium thickens to glandular form
- reduction of mobility of myometrium
- thick acidic cervical mucous
- increases spiral arteries
how is the egg transported to site of fertilisation?
- after ovulation, emerges on surface of ovary
- fimbriae move towards it
- fimbrae cilia sweep egg into fallopian tube
- fallopian cilia beat it close to uterus