Reproductive Physiology Flashcards
What do testis contain and what do they do?
Seminiferous tubules
• produce sperm
Leydig cells
• produce testosterone
Explain what the Epididymis is
One within each scrotal sac
• sperm stored here
During ejaculation, sperm is released
• passes through the vas deferens
• mixes with fluid from the seminal vesicles
• fluid leaves duct and passes into urethra to mix w. prostate secretions
What stimulates the male regulatory system
Leydig cells
• produce testosterone
• LH stimulates
Sertoli cells
• produce inhibin
• FSH stimualted
• support stermatogenesis
Spermatogenesis of males?
- Germ cells
• mitotic division
• 44+XY (diploid) - 1o spermatocyte
• 1st meiotic division
• 44+XY (diploid) - 2o spermatocyte
• 2nd meiotic division
• 22+X ; 22+Y (haploid) - Spermatids
• 22+X ; 22+Y (haploid) - Spermatozoa
• 22+X ; 22+Y (haploid)
Explain the ovary, fallopian tubes and uterus
Ovary
• produce gametes & steroids
Fallopian tubes
• sustains oocyte OR conceptus
Uterus
• conceptus implants here
Explain the different cells found in the female ovary
Thecal cells
• oestrogen & androgen
• LH stimulated
Granulosa cells
• androgens –> oestradiol (produce progesterone in 2nd-half of cycle)
• FSH stimulated
Main role of PG and O?
PG
• maintains endometrium
O
• stimulate proliferation of the endometrium
Changes in the female HPO axis?
Follicular phase
• estradiol -VE feedbacks
Midcycle
• estradiol +VE feedback
• stimulates ++ FSH & LH release
Luteal phase
• Progesterone -VE feedbacks
Explain the menstrual cycle
Composed of the endometrial & ovarian cycles:
• Endometrial – menstrual, repair & proliferative, secretory phases
• Ovarian – follicular, luteal phase
- FSH & LH stimulate the follicular phase which results in oestradiol production
• = stimulates the endometrial proliferation - Oestradiol (E2) production continues at a greater pace
• and –ve feedback switches to +ve and ovulation occurs - Corpus luteum produces progesterone and E2 and the endometrium enters the secretory phase
(Ludley picture!)
Terminology used regarding menstrual cycle depends upon what is being described…..
Endometrium/Uterine
• proliferative/secretory
Ovarian
• follicular/luteal
Explain the Menstrual Cycle graph (with the hormones)
Note basal body temperature raises around ovulation
- Gradual rise of oestradiol by developing follicle (FSH)
- Follicles grow and –ve feedback on LH and FSH
- Dominant follicle selected and produces lots of E2 = –ve feedback switch to +ve feedback = LH surge
- Ovulation
- Corpus luteum produces E2 and progesterone = -ve feedback on LH and FSH
- No fertilisation = E2 and progesterone fall and endometrium enters secretory phase.
Folliculogenesis?
INSIDE OVUM
- Oogonia
• mitotic division - 1o oocyte
• 1st meiotic division - 2o oocyte (+ polar body)
• 2nd meiotic division - Ovum (+ polar body)
2nd polar body generated AFTER the 2nd meiotic division (occurs in the fertilised cell)
Important point regarding folliculogenesis
Time taken from primordial follice –> 2o oocyte is >1month
• dominant (Graafian) follicle is released at any one time
Human ovaries contain 2m primordial follicles @ birth
• only 400 released at ovulation in a lifetime
During meiosis, both 1st & 2nd vision if paused during follicular development
• meiosis 1 starts during embryonic development BUT halts at 1o follice stage until puberty
• 2nd follicles then undergo a 2nd arrest
Define sexual reproduction, sexual intercourse & biological sex
Sexual reproduction – produce genetically different offspring
Sexual intercourse – required for – sexual reproduction, sexual activity, sexual pleasure, human bonding
Biological sex – identifies gender, a result of chromosomes, produces different gametes.
Explain the brain pathway linked with fertility and the penile erection pathway
Neuro-endocrine pathways
• regulating fertility & parenting
Penile erection pathways:
1. EITHER sexy thoughts in brain OR tactile stimulus to penis
• Brain - limbic system
- Spinal cord - efferent to penis, afferent back
• via. pudendal nerve
Explain the changes seen during penile & clitoral erection
- (ESEED) increased PNS to SM of pudendal artery.
- Increase activity of NOS and thus NO release.
- NO stimulates cGMP = vasodilation.
• cGMP inactivated by phosphodiesterase - Counteracts SNS-maintained myogenic tone.
- Increases blood flow in corpus cavernosum.
• Compress dorsal vein restricting outflow of blood
• Urethra not compressed due to corpus spongiosum
Clitoral - SAME mechanism
How does viagra work?
Inhibits phosphodiesterase = potentiating effects of cyclic GMP
Explain the process and main events of fertilisation
- Deposition of sperm near the cervix
• Cervical mucous is hostile to sperm which forms a physical barrier
• Cervical mucous changes at mid-cycle to permit sperm to enter the uterus - Passage of sperm through uterus and then fallopian tubes
- Sperm moves to fallopian tube ampulla
• 2mm/min, 12cm/hour
• Survival of the fittest
• Capacitation takes place (within the uterus) which matures the spermatozoa - Egg meets sperm fusion of egg with sperm (24 hours post ovulation)
• Acrosome reaction – penetration of zona pellucida (& Coronal cells)
• Calcium flux
• Resumption of meiosis, release of 2nd polar body
• Alignment of maternal and paternal chromosomes to generate zygote - Change in Zona Pellucida to stop additional sperm fusing
- Initiation of mitotic divisions in embryo.
What happens after the 2nd polar body forms and the paternal head undergoes decondensation & expands?
- Metaphase of cleavage division 1
• chromosomes on spindle - Separation of chromosomes
- 2-cell stage (2n chromosomes of both origins)
