ANAT human reproductive system Flashcards
what are the male sexual development stages?
- descent of the testes
- there is shortening of the gubernaculum (a cord of muscle which allows testes to enter scrotum)
- usually completes by 7th month of gestation - puberty
why is the descent of the testes a significant stage in the sexual development of males?
- spermatogenesis (production of sperm) is temperature sensitive and cannot occur at normal body temperature (37degC)
- temperature of the scrotum is 2 degC lower than body temp (35degC)
hence, males with undescended testes (cryptorchidism) are unable to produce viable sperm
the descent of testes is dependent on which hormone?
testosterone (from fetal testes)
microscopic structures of testes + its functions
- sertoli cells - provide support for spermatogenesis
- leydig cells - produce testosterone
how long does spermatogenesis take?
64 days
does spermatogenesis occur synchronously throughout the seminiferous tubule?
no, different tubules are in different stages of spermatogenesis
what processes occur at puberty in males?
- onset of spermatogenesis
- enlargement of testes and development of secondary characteristics
- hormonal changes. at puberty, hypothalamus secretes Gonadotropin-releasing hormone (GnRH) in a pulsatile fashion every 1-3 hours. GnRH triggers secretion of luteininzing hormone (LH) and follicle stimulating hormone (FSH) from the anterior pituitary (GnRH pulsatility is NECESSARY for proper functioning of the testes because it regulates the secretion of FSH and LH, which are also released in a pulsatile fashion)
why is GnRH secreted at pulsatile fashion?
continuous exposure of gonadotropin releasing hormone results in desensitization of GnRH receptors leading to a decrease in LH and FSH release –> unresponsive to the GnRH hormones
draw the control of testicular function
refer to slide10
list the effects of testosterone (7)
internal male genitalia (differentiation), pubertal growth spurt, penis growth, deepening of voice, spermatogenesis, libido, muscle mass
for the case of taking exogenous testosterone (anabolic androgenic steroids), describe how the HPA works.
as the body receives the synthetic anabolic androgenic steroids, the anterior pituitary is inhibited by androgenic steroids via negative feedback loop as the body senses that there is enough testosterone in the body. testosterone inhibits the hypothalamus to stop producing GnRH and subsequently LH, and FSH. the testes do not receive normal stimulatory input from anterior pituitary to produce testosterone.
what are the side effects of taking anabolic steroids?
testosterone secretion and sperm production decrease and testes shrink
hormone abuse may also set the stage for cancer of the testes and prostate because testosterone enhances proliferation of cells
biosynthesis of dihydrotestosterone (DHT)
(happen in leydig cells) cholesterol –> pregnenolone –> progesterone –> 17-OH progesterone –> androstenedione –> testosterone –> (happen in sertoli cells) dihydrotestosterone formed via 5a-reductase
effects of DHT (5)
external male genitalia (differentiation), sebaceous glands, prostate (growth), male hair pattern, male hair pattern baldness
what are the difference in the effects of testosterone + DHT
male genitalia (internal vs external), penis growth vs prostate growth +++
male pattern baldness pattern is?
horseshoe-shaped ring of hair around the back of the head
how does DHT lead to male pattern baldness
causes shrinkage of overly sensitive follicles making it short and wisper
could also be due to genetic factors where there is androgen receptor gene leading to production of DHT
roles of male reproductive system (3)
- to produce, maintain, transport, and nourish sperm and protective fluid (semen)
- to discharge sperm within the female reproductive tract
- to produce and secrete male sex hormones
roles of female reproductive system (4)
- to release eggs, which can preferentially be fertilised by sperm
- to produce and secrete female sex hormones
- to provide an environment for a fertilised egg to develop during pregnancy
- to facilitate labour and childbirth
what are the properties of an ovary?
- ovum-producing reproductive organ
- analogous to testes in males in that they are both gonads and endocrine glands
- undergoes ovarian cycle
what are the properties of a uterus?
- responsible to for maintenance of fetus during development
- responsible for expelling fetus at end of pregnancy
- major female hormone-responsive reproductive organ
- undergoes uterus cycle
function of ovaries (2)
- produce ova (oogenesis)
- secrete sex hormones (estrogen and progesterone) which act together to promote fertilisation of the ovum (one egg) and to prepare the female reproductive tract for pregnancy
list the 2 ovarian cycle phases
- follicular phase (dominated by presence of maturing follicles)
- luteal phase (characterised by presence of corpus luteum)
properties of ovarian cycle (menstrual cycle) (3)
- around 28 days
- normally interrupted only by pregnancy
- finally terminated by menopause
name the 3 types of follicle in the ovum
- mature follicle
- secondary follicle
- primary follicle
what is primary follicle made up of?
primary oocyte (immature egg cells) + surround granulosa cells (sperm + sertoli cells)
draw the H-P-Ovary axis
refer to slide 28 ic3
how is estrogen produced?
- granulosa cell stimulated by FSH
- THECA CELL stimulated by LH
they both caused secondary messengers and amplification of signals
regulation of ovarian cycle (folllicular phase)
slide 29 & 30
regulation of ovarian cycle (luteal phase)
slide 31 32
what are the 3 phases of menstrual cycle/uterine cycle
- follicular phase
- ovulation
- luteal phase
what are the properties of puberty in a female?
- growth and maturation
- beings at ~10age (lowered due to synthetic BPA estrogen)
- triggered by GnRH (gonadotropin-releasing hormone)
signs of puberty in females:
- thelarche (earliest) - development of breasts
- pubarche - growth of pubic and axillary hair
- menarche - the first menstrual period
other changes: growth of secondary sex organs [fallopian tube ( oviduct), uterus, vagina, cervix and external genitalia (vulva)], fat deposition, rapid increase in height due to growth hormone
what are the properties of menopause?
- decrease in hormone secretion at midlife = occurs in males too but not as drastic as females
- cessation of menstruation
- occurs between the ages of 45-55
- ovaries have fewer remaining follicles - hence less responsive to gonadotropins (GnRH) and secrete less estrogen and progesterone
signs of menopause (7)
cessation of menstrual cycles (12mths after last menstrual period), gradual atrophy genital organs, vasomotor changes, skin changes, psychological/emotional, increase cholesterol level (risk of cardiovascular disease), increase risk of osteoporosis (decrease bone mass due to less E)
treatment of menopause
hormone replacement therapy (HRT) = give external estrogen or progesterone
to reduce the initial negative feedback responses due to the rollercoaster changes in hormone levels
