ANAT human reproductive system

Question 1

what are the male sexual development stages?

Answer 1

1. 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
2. puberty

Question 2

why is the descent of the testes a significant stage in the sexual development of males?

Answer 2

• 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

Question 3

the descent of testes is dependent on which hormone?

Answer 3

testosterone (from fetal testes)

Question 4

microscopic structures of testes + its functions

Answer 4

1. sertoli cells - provide support for spermatogenesis
2. leydig cells - produce testosterone

Question 5

how long does spermatogenesis take?

Answer 5

64 days

Question 6

does spermatogenesis occur synchronously throughout the seminiferous tubule?

Answer 6

no, different tubules are in different stages of spermatogenesis

Question 7

what processes occur at puberty in males?

Answer 7

1. onset of spermatogenesis
2. enlargement of testes and development of secondary characteristics
3. 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)

Question 8

why is GnRH secreted at pulsatile fashion?

Answer 8

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

Question 9

draw the control of testicular function

Answer 9

refer to slide10

Question 10

list the effects of testosterone (7)

Answer 10

internal male genitalia (differentiation), pubertal growth spurt, penis growth, deepening of voice, spermatogenesis, libido, muscle mass

Question 11

for the case of taking exogenous testosterone (anabolic androgenic steroids), describe how the HPA works.

Answer 11

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.

Question 12

what are the side effects of taking anabolic steroids?

Answer 12

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

Question 13

biosynthesis of dihydrotestosterone (DHT)

Answer 13

(happen in leydig cells) cholesterol –> pregnenolone –> progesterone –> 17-OH progesterone –> androstenedione –> testosterone –> (happen in sertoli cells) dihydrotestosterone formed via 5a-reductase

Question 14

effects of DHT (5)

Answer 14

external male genitalia (differentiation), sebaceous glands, prostate (growth), male hair pattern, male hair pattern baldness

Question 15

what are the difference in the effects of testosterone + DHT

Answer 15

male genitalia (internal vs external), penis growth vs prostate growth +++

Question 16

male pattern baldness pattern is?

Answer 16

horseshoe-shaped ring of hair around the back of the head

Question 17

how does DHT lead to male pattern baldness

Answer 17

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

Question 18

roles of male reproductive system (3)

Answer 18

1. to produce, maintain, transport, and nourish sperm and protective fluid (semen)
2. to discharge sperm within the female reproductive tract
3. to produce and secrete male sex hormones

Question 19

roles of female reproductive system (4)

Answer 19

1. to release eggs, which can preferentially be fertilised by sperm
2. to produce and secrete female sex hormones
3. to provide an environment for a fertilised egg to develop during pregnancy
4. to facilitate labour and childbirth

Question 20

what are the properties of an ovary?

Answer 20

• ovum-producing reproductive organ
• analogous to testes in males in that they are both gonads and endocrine glands
• undergoes ovarian cycle

Question 21

what are the properties of a uterus?

Answer 21

• 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

Question 22

function of ovaries (2)

Answer 22

1. produce ova (oogenesis)
2. 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

Question 23

list the 2 ovarian cycle phases

Answer 23

1. follicular phase (dominated by presence of maturing follicles)
2. luteal phase (characterised by presence of corpus luteum)

Question 24

properties of ovarian cycle (menstrual cycle) (3)

Answer 24

1. around 28 days
2. normally interrupted only by pregnancy
3. finally terminated by menopause

Question 25

name the 3 types of follicle in the ovum

Answer 25

1. mature follicle 2. secondary follicle 3. primary follicle

Question 26

what is primary follicle made up of?

Answer 26

primary oocyte (immature egg cells) + surround granulosa cells (sperm + sertoli cells)

Question 27

draw the H-P-Ovary axis

Answer 27

refer to slide 28 ic3

Question 28

how is estrogen produced?

Answer 28

1. granulosa cell stimulated by FSH 2. THECA CELL stimulated by LH they both caused secondary messengers and amplification of signals

Question 29

regulation of ovarian cycle (folllicular phase)

Answer 29

slide 29 & 30

Question 30

regulation of ovarian cycle (luteal phase)

Answer 30

slide 31 32

Question 31

what are the 3 phases of menstrual cycle/uterine cycle

Answer 31

1. follicular phase 2. ovulation 3. luteal phase

Question 32

what are the properties of puberty in a female?

Answer 32

1. growth and maturation 2. beings at ~10age (lowered due to synthetic BPA estrogen) 3. triggered by GnRH (gonadotropin-releasing hormone)

Question 33

signs of puberty in females:

Answer 33

1. thelarche (earliest) - development of breasts 2. pubarche - growth of pubic and axillary hair 3. 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

Question 34

what are the properties of menopause?

Answer 34

1. decrease in hormone secretion at midlife = occurs in males too but not as drastic as females 2. cessation of menstruation 3. occurs between the ages of 45-55 4. ovaries have fewer remaining follicles - hence less responsive to gonadotropins (GnRH) and secrete less estrogen and progesterone

Question 35

signs of menopause (7)

Answer 35

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)

Question 36

treatment of menopause

Answer 36

hormone replacement therapy (HRT) = give external estrogen or progesterone to reduce the initial negative feedback responses due to the rollercoaster changes in hormone levels