Reproductive Lab

Question 1

spermatogenesis

Answer 1

• spermatogonial stem cells (2n = 46) → mitosis
• some spermatogonia remain near basement membrane and remain undifferentiated
• some spermatogonia lose contact with basement membrane → squeeze through tight junctions of blood-testis barrier → undergo developmental changes → differentiate into primary spermatocytes
• primary spermatocytes (2n = 46) replicate its DNA → meiosis I → secondary spermatocytes
• secondary spermatocytes (n = 23, each chromosome has two chromatids) → meiosis II → spermatids
• spermatids (n = 23, each chromosome has one chromatid)

Question 2

unique process of spermatogenesis

Answer 2

• as spermatogenic cells proliferate, they fail to complete complete cytoplasmic separation (i.e. cytokinesis)
• remain in contact via cytoplasmic bridges
• likely accounts for synchronised production of sperm in any given area of seminiferous tubule
• provides survival value as half of sperm has X chromosome and other half has Y chromosome, larger X chromosome may carry genes needed for spermatogenesis that are lacking on the smaller Y chromosome

Question 3

spermiogenesis

Answer 3

• development of spherical spermatids → elongated, slender sperm
• acrosome forms above the nucleus
• flagellum develops
• mitochondria multiply
• sustentacular cells (i.e. sertoli) dispose of excess cytoplasm
• finally sperm are released from the connections to sustentacular cells (i.e. spermiation)
• sperm enter lumen of seminiferous tubule
• fluid secreted by sustentacular cells push sperm towards the ducts of the testes

Question 4

oogenesis

Answer 4

• begins before female is born
• primordial germ cells migrate from yolk sac → ovaries
• germ cells differentiate → oogonia
• oogonia (stem cells, 2n = 46) → mitosis → millions of germ cells
• most of these germ cells degenerate (i.e. atresia)
• germ cells → primary oocytes
• primary oocytes are surrounded by single layer of follicular cells (i.e. primordial follicle)

Question 5

ovarian cortex

Answer 5

• surrounds primordial follicles
• consists of collagen fibres and stromal cells (fibroblast-like)
• at birth → 200,000~2,000,000 primary oocytes in each ovary
• at puberty → 40,000 primary oocytes in each ovary
• ~400 mature and ovulate during a woman’s reproductive lifetime
• remainder undergo atresia

Question 6

follicular development

Answer 6

• each month after puberty, gonadotropins (i.e. FSH/LH) secreted by anterior pituitary stimulate development of primordial follicles
• primordial follicles -> primary follicles -> secondary follicles -> mature/Graafian follicles

Question 7

primary follicles

Answer 7

• primary oocyte surrounded by several layers of granulosa cells
• outermost granulosa rests on basement membrane
• as it grows, forms a clear glycoprotein layer (i.e. zona pellucida) between primary oocyte and granulosa cells
• stromal cells surrounding basement membrane form layer (i.e. theca folliculi)

Question 8

secondary follicles

Answer 8

• theca differentiated into two layers
• theca interna → highly vascular internal layer, has cuboidal secretory cells that secrete oestrogens
• theca externa → outer layer of stromal cells and collagen fibres
• granulosa cells secrete follicular fluid, build up in cavity (i.e. antrum) in centre of follicle
• innermost layer of granulosa cells become firmly attached to zona pellucida (i.e. corona radiata)

Question 9

mature/graafian follicles

Answer 9

• diploid primary oocyte (2n = 46) → meiosis I → two unequal haploid cells (n = 23, two chromatids in a chromosome)
• smaller cell (i.e. first polar body) is a packet of discarded nuclear material
• larger cell (i.e. secondary oocyte) recieves most of cytoplasm
• meiosis II begins
• rupture of mature follicle releases secondary oocyte (i.e. ovulation)

Question 10

ovulation

Answer 10

• secondary oocyte, first polar body, and corona radiata released into pelvic cavity
• normally are swept into uterine tube
• if fertilisation does not occur → cells degenerate
• if sperm is present → meiosis II continues
• first polar body → splits into two polar bodies → degenerates
• secondary oocyte (n = 23, two chromatids in a chromosome) → two unequal haploid cells (n = 23, one chromatid in a chromosome)
• smaller cell → second polar body → degenerates
• larger cell → ovum

Question 11

difference in gamete production between sexes

Answer 11

• male → one primary spermatocyte produces four gametes (i.e. sperm)
• female → one primary oocyte produces a single gamete (i.e. ovum)

Question 12

oestrogen

Answer 12

• promote development and maintenance of female reproductive structures, secondary sex characteristics
• increase protein anabolism (i.e. building strong bones)
• lower blood cholesterol level
• moderate levels in the blood inhibit GnRH and LH/FSH

Question 13

progesterone

Answer 13

• secreted mainly by corpus luteum
• cooperates with oestrogens to prepare and maintain endometrium and mammary glands for pregnancy
• high levels in the blood inhibit GnRH and LH

Question 14

relaxin

Answer 14

• produced by corpus luteum
• relaxes uterus by inhibiting contractions of myometrium (implantation occurs more readily in relaxed state)
• placenta produces more relaxin in pregnancy → helps to dilate the uterine cervix

Question 15

inhibin

Answer 15

• secreted by granulosa cells of growing follicle and by corpus luteum after ovulation
• inhibits secretion of FSH and LH (to a lesser extent)

Question 16

phases of female reproductive cycle

Answer 16

• menstrual cycle -> first 5 days
• preovulatory phase -> days 6-13
• ovulation -> day 14
• postovulatory phase -> days 15-28

Question 17

events in uterus during menstrual phase

Answer 17

• declining levels of progesterone and oestrogens → stimulate release of prostaglandins → cause uterine spiral arterioles to constrict
• cells of stratum functionalis become oxygen deprived, die, and sloughs off
• only stratum basalis remains

Question 18

events in ovaries during menstrual phase

Answer 18

• FSH initiates development of primordial follicles → primary follicles → secondary follicles
• may take several months to occur
• therefore follicle that develops at beginning of menstrual cycle may not ovulate until several menstrual cycles later

Question 19

events in ovaries during preovulatory phase

Answer 19

• secondary follicles begin to secrete oestrogens and inhibin
• a single secondary follicle in one ovary has outgrown all of the others (i.e. dominant follicle)
• oestrogen and inhibin secreted by dominant follicle → decreases secretion of FSH → causes less dominant follicles to stop growing, undergo atresia
• dominant follicle → develops into mature follicle → increases its production of oestrogens

Question 20

events in uterus during preovulatory phase

Answer 20

• oestrogens released by follicles in the blood → stimulate repair of endometrium
• cells of stratum basalis → mitosis → produce new stratum functionalis
• endometrial glands develop, arterioles coil and penetrate stratum functionalis
• thickness of endometrium doubles

Question 21

events during ovulation

Answer 21

• high levels of oestrogens during last part of preovulatory phase → positive feedback on LH and GnRH → LH surge causes rupture of mature follicle
• mature follicle ruptures → secondary oocyte (surrounded by corona radiata and zona pellucida) is released into pelvic cavity → swept in to uterine tube

Question 22

events in ovary during postovulatory phase

Answer 22

• mature follicle collapses → basement membrane between granulosa cells and theca interna breaks down → blood clot forms → corpus hameorrhagicum
• theca interna cells mix with granulosa cells under influence of LH → corpus luteum
• corpus luteum is stimulated by LH → secretes progesterone, oestrogens, relaxin, and inhibin, and absorb the blood clot
• if oocyte is not fertilised → corpus luteum has a life span of 2 weeks → secretory activity declines → degenerates into corpus albicans → decreased progesterone, oestrogen, inhibin → release of GnRH, FSH, LH rises → follicular growth resumes → new ovarian cycle begins
• if oocyte is fertilised → hCG released by chorion of embryo → stimulates secretory activity of corpus luteum → persists past its lifespan of 2 weeks

Question 23

events in uterus during postovulatory phase

Answer 23

• corpus luteum secretes progesterone and oestrogen → promotes growth and coiling of endometrial glands, vascularisation of stratum functionalis
• prepatory activity peaks ~1 week after ovulation, around the time that a fertilised ovum might arrive in the uterus
• if fertilisation does not occur → levels of progesterone and estrogens decline due to degeneration of corpus luteum

Question 24

ovarian cycle

Answer 24

• follicular phase -> - menstrual phase + preovulatory phase, ovarian follicles are growing and developing
• luteal phase -> postovulatory phase, corpus luteum is formed

Question 25

uterine cycle

Answer 25

• proliferative phase -> preovulatory phase, endometrium is proliferating
• secretory phase -> postovulatory phase, secretory activity of endometrial glands

Question 26

female athlete triad

Answer 26

• disordered eating, amenorrhea, premature osteoporosis
• athletes experience pressure to lose weight → develop disordered eating behaviours
• low levels of leptin produced by adipose cells → reduced secretion of GnRH → decreased release of LH/FSH → ovarian follicles fail to develop, ovulation does not occur, synthesis of oestrogen/progesterone wanes → absence of menstruation (i.e. amenorrhea)
• low levels of oestrogens → loss of bone mineral density → osteoporosis

Question 27

what could be the cause of decreased concentrations of FSH, LH, oestrogen and progesterone?

Answer 27

• delayed puberty
• lower body fat due to female athlete triad

Question 28

area of relevance and mechanism of action of male condom

Answer 28

• area of relevance -> penis/penile urethra
• mechanism of action -> barrier

Question 29

area of relevance and mechanism of action of vasectomy/tubal ligation

Answer 29

• area of relevance -> ductus deferens/uterine tubes
• mechanism of action -> surgical

Question 30

area of relevance and mechanism of action of diaphragm

Answer 30

• area of relevance -> cervix
• mechanism of action -> barrier
• more effective when used with spermicide

Question 31

mechanism of action of oral contraception

Answer 31

• hormonal
• combined oral contraceptives → contain progestin and oestrogens → suppress FSH/LH → prevents development of dominant follicle
• progestin only pills → thicken cervical mucous → make it more difficult for sperm to enter uterus, does not consistently inhibit ovulation

Question 32

area of relevance and mechanism of action of IUD

Answer 32

• area of relevance -> uterine tubes
• mechanism of action -> chemical (i.e. basic/copper material messes up sperm motility)

Question 33

label diagram of male reproductive system

Question 34

label diagram of female reproductive system

Question 35

label image of rat testis

Question 36

label diagram of female reproductive cycle

Question 37

label diagrams of ovary histology