Reproductive system

Question 1

What are the key sex steroids?

Answer 1

Androgens, progestagens and oestrogens

Question 2

What are the key androgens and what are their function?

Answer 2

Testosterone and 5a dihydrotestosterone, used for male sex development, spermatogenesis, sexual behaviour, muscle development

Question 3

What are the key oestrogens and what are their function?

Answer 3

Oetradiol, oestrone, oestriol. Used for female sex development, endometrial growth, menstrual cycle regulation, bone growth

Question 4

What is the function of progestagens?

Answer 4

Preparation and maintenance of the female body for preganancy

Question 5

Describe the pathway of the hypothalamic-pituitary-gonadal axis?

Answer 5

Hypothalamus releases GnRH (gonadotropin releasing hormone) along neurosecretory neurons, anterior pituitary releases FSH (follicle stimulating hormone) and LH (luteinising hormone), gonads release sex hormones

Question 6

Describe the stages involved in follicular development?

Answer 6

Primordial follicle, primary follicle, secondary follicle, mature follicle, ovulation, corpus luteum, fertilisation

Question 7

Describe the primordial follicle stage?

Answer 7

Oocyte surrounded by granulose cells formed from single layer flat follicular cells

Question 8

Describe the primary follicle stage?

Answer 8

More layers of granulosa cells as they grow in response to FSH

Question 9

Describe the secondary follicle stage?

Answer 9

Proliferating granulosa cells produce viscous follicular fluid which forms follicular antrum, theca develops into inner glandula, theca interna and theca externa

Question 10

Describe the mature follicle stage?

Answer 10

Follicular antrum grows, oocyte becomes suspended in fluid, connected to rim of peripheral granulosa cells by a stalk of cells

Question 11

Describe the ovulation stage?

Answer 11

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

Question 12

Describe the corpus luteum stage?

Answer 12

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

Question 13

Describe the fertilisation stage?

Answer 13

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

Question 14

Name the two stages of the menstrual cycle?

Answer 14

Follicular stage and luteal stage

Question 15

When does the follicular stage occur?

Answer 15

Day 1 until ovulation

Question 16

When does the luteal stage occur?

Answer 16

Ovulation until menstruation

Question 17

Describe the hormonal changes over the course of the menstrual cycle?

Answer 17

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

Question 18

What genetic factor affects sex determination?

Answer 18

The presence or absence of the sex determining region of the Y chromosome (SRY gene)

Question 19

What does the SRY gene do?

Answer 19

Allows the testes to develop, in it’s absence the embryo will automatically be female

Question 20

Describe the process of sex differentiation in males?

Answer 20

Mesoderm > bipotential gland > testis >
1 - sertoli cells > anti-Mullerian hormone (AMH) > Mullerian duct regression
2 - Leydig cells > testosterone > Wolffian duct development > internal male genitalia

Question 21

Describe the process of sex differentiation in females?

Answer 21

Mesoderm > bipotential gland > ovary > oestrogens and progestagens >
1 - Wolffian duct regression
2 - Mullerian duct development > internal female genitalia

Question 22

What do the Wolffian ducts develop into?

Answer 22

Epididymus, vas deferens, seminal vesicles

Question 23

What happens to the testis?

Answer 23

Approximately month 7, testis descends from internal position to scrotum

Question 24

What do the Mullerian ducts develop into?

Answer 24

Fallopian tubes, uterus, cervix, upper vagina

Question 25

Describe the differentiation of external male genitalia?

Answer 25

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

Question 26

Describe the differentiation of external female genitalia?

Answer 26

Urethral folds and labioscrotal swellings remain separate forming labia minora and majora, genital tubercle (glans area) forms the clitoris

Question 27

What hormonal changes occur during puberty?

Answer 27

An increase in plasma LH as a result of increased GnRH release, both LH and FSH release occurs at night in early puberty

Question 28

Describe the order of physical changes in male puberty?

Answer 28

Testis, pubic hair, penis, height spurt

Question 29

Describe the order of physical changes in female puberty?

Answer 29

Breasts, pubic hair, height spurt, menarche

Question 30

Describe the process of spermatogenesis?

Answer 30

Spermatogonium (stem cell), primary spermatocyte, secondary spermatocyte, spermatid, sperm cell (spermatozoon)

Question 31

Describe the physical features of a sperm cell?

Answer 31

Acrosome, nucleus, neck, mitochondria, middle piece, principal piece, end piece

Question 32

Describe the hormonal control of testicular function?

Answer 32

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

Question 33

Describe the movement of sperm through the male reproductive tract?

Answer 33

Seminiferous tubules > rete testis > pushed along epididymus (muscular tube) into vas deferens (storage) > past prostate > into penis

Question 34

What do the seminal vesicles secrete?

Answer 34

Alkaline fluid

Question 35

What does the prostate secrete?

Answer 35

Acidic fluid