Reproduction Flashcards
Draw a labelled diagram of the adult female reproductive system.
4 marks
ovary – shown adjacent to but not joined to oviduct/fallopian tube;
oviduct/fallopian tube – shown as a tube leading into a uterus;
uterus – shown with a thicker wall than oviduct/fallopian tube;
vagina – shown leading from the uterus, connected to the cervix;
cervix – shown as a constriction between the vagina and uterus;
endometrium – shown as inner lining of uterus;
Draw a labeled diagram of an adult male reproductive system.
6 marks
penis
scrotum
prostate gland
sperm duct
urethra / urinary tract
seminal vesicle
bladder
testes
epididymis
sperm duct / Vas deferens
Cowper’s gland
seminiferous tubules
erectile tissue
Explain the processes involved in oogenesis in humans.
9 marks
- Oogenesis describes the production of female gametes (ova) within the ovaries (and, to a lesser extent, the oviduct)
- The process begins during foetal development, when a large number of primordial cells are formed by mitosis (~40,000)
- These cells (oogonia) undergo cell growth until they are large enough to undergo meiosis (becoming primary oocytes)
- The primary oocytes begin meiosis but are arrested in prophase I when granulosa cells surround them to form follicles
- The primary oocytes remain arrested in prophase I until puberty, when a girl begins her menstrual cycle
- Each month, hormones (FSH) will trigger the continued division of some of the primary oocytes
- These cells will complete the first meiotic division to form two cells of unequal size
One cell retains the entirety of the cytoplasm to form a secondary oocyte, while the other cell forms a polar body
The polar body remains trapped within the follicle until it eventually degenerates - The secondary oocyte begins the second meiotic division but is arrested in metaphase II
- The secondary oocyte is released from the ovary (ovulation) and enters into the oviduct (or fallopian tube)
- The follicular cells surrounding the oocyte form a corona radiata and function to nourish the secondary oocyte
- If the oocyte is fertilised by a sperm, chemical changes will trigger the completion of meiosis II and the formation of another polar body (the first polar body may also undergo a second division to form a third polar body)
- Once meiosis II is complete the mature egg forms a ovum, before fusing its nucleus with the sperm nucleus to form a zygote
Draw the structure of a mature human egg.
4 marks
haploid nucleus
centrioles
cytoplasm (must show large volume relative to nucleus: minimum 4:1 diameter)
polar body (must be drawn outside of egg cell)
plasma membrane
follicle cells / corona radiata
cortical granules (must be drawn in vicinity of plasma membrane)
zona pellucida
Explain the role of hormones in the regulation of the menstrual cycle in human females.
8 marks
FSH and LH are produced by the pituitary
estrogen and progesterone are produced by the ovary
FSH stimulates the ovary to produce a follicle
developing follicles secrete estrogen
estrogen inhibits FSH / negative feedback
estrogen stimulates growth of endometrium / uterine lining
estrogen stimulates LH secretion / positive feedback
LH stimulates ovulation
follicle becomes corpus luteum
corpus luteum secretes estrogen and progesterone
estrogen and progesterone maintain the lining of the uterus / endometrium
estrogen and progesterone inhibit LH and FSH / negative feedback
after two weeks corpus luteum degenerates
ovarian hormone levels / progesterone / estrogen fall
menstrual bleeding begins / lining of uterine wall / endometrium lost
Outline the levels of each of the hormones that control the menstrual cycle immediately before ovulation.
3 marks
LH levels very high / LH surge
FSH levels are high
estrogen levels are high
progesterone levels are very low
Explain the roles of LH and FSH in the menstrual cycle, including the timing of their secretion during the cycle.
6 marks
FSH is secreted at the start of the cycle / early in the cycle / days 1 to 5 / when progesterone / estrogen is low
FSH stimulates follicle development
FSH stimulates secretion of estrogen (by the follicle / ovary)
LH is secreted in the middle of the cycle / before ovulation / days 10 to 14
LH stimulates ovulation
LH stimulates the development of the corpus luteum
LH stimulates less estrogen
more progesterone secretion / high progesterone / estrogen inhibits FSH and LH release
Outline the roles of progesterone and estrogen in the human menstrual cycle.
6 marks
follicles secrete estrogen / FSH stimulates secretion of estrogen;
(rapid) increase in estrogen stimulates FSH/LH production;
estrogen also stimulates repair/thickening of endometrium/uterus lining;
LH causes follicle to produce less estrogen/more progesterone;
corpus luteum secretes more estrogen/progesterone;
progesterone maintains/stimulates thickening of endometrium/uterus lining;
estrogen/progesterone inhibit FSH/LH secretion;
estrogen/progesterone levels fall after day 21–24 if no embryo/fertilization;
lower concentration of estrogen/progesterone allows disintegration of endometrium/uterus lining / menstruation occurs;
Draw the structure of the human female reproductive system immediately before ovulation. (Only the ovaries, oviducts and uterus need to be shown.)
6 marks
two ovaries shown with oval shape
follicle containing oocyte in one ovary (or both ovaries)
Graafian follicle
funnel of oviduct close to follicle
oviduct shown as a narrow tube connecting ovary and uterus
uterus shown either in side or front view
thickened uterus lining / endometrium shown
Draw a labelled diagram of a mature sperm.
5 marks
head and midpiece/mid-section/body;
tail/flagellum; (at least four times length of the head and containing fibres)
acrosome; (shown as distinct structure near front of head)
nucleus; (occupying more than half the width or length of head)
mitochondria; (as repetitive structures inside membrane of mid piece)
centriole; (between head and midpiece)
(plasma) membrane; (shown as single line covering whole cell)
microtubules; (in 9 plus 2 array)
Outline the process of spermatogenesis in humans.
5 marks
production of sperm/spermatozoa in the testes/seminiferous tubules;
first stage of sperm production requires divisions by mitosis;
germline epithelium of the seminiferous tubules divides by mitosis;
cells then undergo a period of growth;
future sperm cells then undergo two meiotic divisions;
cells then differentiate to form sperm cells;
nourished by Sertoli cells
number becomes haploid / chromosome number halved / 46 to 23 chromosomes;
Production of semen involves a series of processes, which in total take many weeks to carry out. Outline the processes involved in semen production from the start of sperm formation (spermatogenesis) to ejaculation.
8 marks
cell division by mitosis to form more cells / spermatogonia
growth of cells / spermatogonia to form larger calls / primary spermatocytes
cells / primary spermatogonia divide by meiosis
haploid cells / spermatids formed
differentiation of haploid cells / spermatids into sperm
growth of tail / other feature of differentiation
FSH, testosterone and LH all needed for spermatogenesis
sperm stored / maturation in epididymis / gain motility
fluid added to sperm by seminal vesicle (during ejaculation)
fluid from seminal vesicle contains nutrients / mucus
fluid added to sperm by prostate gland (during ejaculation) / fluid from prostate gland contains alkali / minerals
Compare the process of spermatogenesis and oogenesis.
7 marks
both involve meiosis
both involve cell proliferation / mitosis (before meiosis)
both involve cell growth /enlargement (before meiosis)
LH /FSH involved in both
spermatogenesis starts at puberty versus oogenesis starts in the fetus
spermatogenesis until death versus oogenesis until menopause
millions of sperm versus one egg per month
ejaculation of sperm any time versus ovulation in middle of menstrual cycle
four sperm per meiosis / spermatogenesis versus 2 or 3 polar bodies in oogenesis
spermatogenesis involves equal divisions versus oogenesis involves unequal cell / cytoplasm divisions
no polar bodies in spermatogenesis versus 2 or 3 polar bodies in oogenesis
spermatogenesis involves Sertoli / nurse cells versus oogenesis does not
meiosis II completed before fertilization in spermatogenesis versus after in oogenesis
testosterone needed for spermatogenesis versus not needed for oogenesis
Discuss how, in humans, a larger number of sperms are produced than eggs.
4 marks
more germ cells in testes than ovary / more germinal epithelium
all four products of meiosis become sperm versus one only becoming an egg
continuous sperm production versus monthly egg production
early stages of oogenesis only in the fetus so finite number of cells for oogenesis
reference to progesterone inhibiting FSH secretion and thus egg production
no eggs produced during pregnancy
eggs not produced after menopause
Describe the process of fertilization in humans.
8 marks
sperm approaches ovum in oviduct
sperm attaches to receptors in zona pellucida
acrosome reaction /release of enzymes by exocytosis
hyaluronidase / other named enzyme
zona pellucida enzymatically broken down
many sperm needed to allow one to penetrate
membrane of sperm fuses with oocyte membrane
fast block to polyspermy / depolarization of oocyte / sodium gates open
head / sperm nucleus / sperm penetrates the egg membrane
cortical reaction / cortical granules released / lysosomes release enzymes
slow block to polyspermy / zona pellucida glycoproteins cross-link / harden
so additional sperm can’t enter
male nucleus swells
secondary oocyte completes meiosis II
