Reproductive system Flashcards
What are the key sex steroids?
Androgens, progestagens and oestrogens
What are the key androgens and what are their function?
Testosterone and 5a dihydrotestosterone, used for male sex development, spermatogenesis, sexual behaviour, muscle development
What are the key oestrogens and what are their function?
Oetradiol, oestrone, oestriol. Used for female sex development, endometrial growth, menstrual cycle regulation, bone growth
What is the function of progestagens?
Preparation and maintenance of the female body for preganancy
Describe the pathway of the hypothalamic-pituitary-gonadal axis?
Hypothalamus releases GnRH (gonadotropin releasing hormone) along neurosecretory neurons, anterior pituitary releases FSH (follicle stimulating hormone) and LH (luteinising hormone), gonads release sex hormones
Describe the stages involved in follicular development?
Primordial follicle, primary follicle, secondary follicle, mature follicle, ovulation, corpus luteum, fertilisation
Describe the primordial follicle stage?
Oocyte surrounded by granulose cells formed from single layer flat follicular cells
Describe the primary follicle stage?
More layers of granulosa cells as they grow in response to FSH
Describe the secondary follicle stage?
Proliferating granulosa cells produce viscous follicular fluid which forms follicular antrum, theca develops into inner glandula, theca interna and theca externa
Describe the mature follicle stage?
Follicular antrum grows, oocyte becomes suspended in fluid, connected to rim of peripheral granulosa cells by a stalk of cells
Describe the ovulation stage?
Follicle bulges from ovarian surface and ruptures, carrying oocyte and surrounding cumulus cells, collected by cilia on fimbriae which push cumulus mass into the uterine tube
Describe the corpus luteum stage?
Antrum breaks down, basement membrane between granulosa and thecal layers breaks down, blood vessels invade, granulosa form large yellow lutein cells (luteinisation), progestagens are secreted, remaining white scar tissue (corpus albicans) is absorbed back into ovary and reused
Describe the fertilisation stage?
If oocyte is fertilised corpus luteum persists past its usual 14 day lifespan rescued from degradation by human chorionic gonadotrophin (hCG) produced by embryonic chorion approximately 8 days after fertilisation
Name the two stages of the menstrual cycle?
Follicular stage and luteal stage
When does the follicular stage occur?
Day 1 until ovulation
When does the luteal stage occur?
Ovulation until menstruation
Describe the hormonal changes over the course of the menstrual cycle?
1 - corpus lutem regresses, oestrogen and progesterone levels low, high FSH
2 - FSH stimulation leads to increased follicular growth
3 - selection of dominant follicle, increased oestrogen
4 - oestradiol suppresses FSH and LH production in pituitary
5 - oestrogen levels rise, threshold level of oestradiol reached and if maintained there is a temporary switch from negative to positive feedback
6 - oestrogen-mediated positive feedback leads to increased GnRH secretion leading to LH surge
7 - LH surge induces ovulation
8 - Corpus luteum develops, increased progesterone
9 - high progesterone inhibits GnRH leads to decreased LH and FSH
10 - demise of corpus luteum
What genetic factor affects sex determination?
The presence or absence of the sex determining region of the Y chromosome (SRY gene)
What does the SRY gene do?
Allows the testes to develop, in it’s absence the embryo will automatically be female
Describe the process of sex differentiation in males?
Mesoderm > bipotential gland > testis >
1 - sertoli cells > anti-Mullerian hormone (AMH) > Mullerian duct regression
2 - Leydig cells > testosterone > Wolffian duct development > internal male genitalia
Describe the process of sex differentiation in females?
Mesoderm > bipotential gland > ovary > oestrogens and progestagens >
1 - Wolffian duct regression
2 - Mullerian duct development > internal female genitalia
What do the Wolffian ducts develop into?
Epididymus, vas deferens, seminal vesicles
What happens to the testis?
Approximately month 7, testis descends from internal position to scrotum
What do the Mullerian ducts develop into?
Fallopian tubes, uterus, cervix, upper vagina
Describe the differentiation of external male genitalia?
Fusion of urethral folds enclosing the urethral tube forms the shaft of the penis, labioscrotal swellings fuse in midline to form the scrotum, genital tubercle (glans area) expands to form glans penis
Describe the differentiation of external female genitalia?
Urethral folds and labioscrotal swellings remain separate forming labia minora and majora, genital tubercle (glans area) forms the clitoris
What hormonal changes occur during puberty?
An increase in plasma LH as a result of increased GnRH release, both LH and FSH release occurs at night in early puberty
Describe the order of physical changes in male puberty?
Testis, pubic hair, penis, height spurt
Describe the order of physical changes in female puberty?
Breasts, pubic hair, height spurt, menarche
Describe the process of spermatogenesis?
Spermatogonium (stem cell), primary spermatocyte, secondary spermatocyte, spermatid, sperm cell (spermatozoon)
Describe the physical features of a sperm cell?
Acrosome, nucleus, neck, mitochondria, middle piece, principal piece, end piece
Describe the hormonal control of testicular function?
Hypothalamus releases GnRH > anterior pituitary releases LH to Leydig cells and FSH to Sertoli cells > Leydig cells release testosterone > secondary sexual characteristics > negative feedback loop to inhibit LH and GnRH > Sertoli cells release androgen binding protein (ABP) which maintains testosterone levels > releases inhibin which inhibits FSH release
Describe the movement of sperm through the male reproductive tract?
Seminiferous tubules > rete testis > pushed along epididymus (muscular tube) into vas deferens (storage) > past prostate > into penis
What do the seminal vesicles secrete?
Alkaline fluid
What does the prostate secrete?
Acidic fluid
