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Cell biology > the reproductive system (lecture 29) > Flashcards

the reproductive system (lecture 29) Flashcards

1
Q

what are the gonads?

A

males have testes
females have ovaries
these are gonads

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2
Q

wha are the reproductive tracts for?

A

responsible for carrying gametes through the reproductive system

females are responsible for carrying the gametes - reproductive tract is important for implantation, gestational growth and labour

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3
Q

what are the 2 functions of the gonads?

A

to secrete sex hormones

gametogenesis

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4
Q

what sex hormones do the testes secrete?

A

secrete large amounts of androgens and small amounts of oestrogens

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5
Q

what sex hormones do the ovaries secrete?

A

secrete large amounts of oestrogen and small amounts of androgens

secrete progesterone - prepares uterus for pregnancy

secrete relaxin during pregnancy - loosens ligaments in the pubic symphysis and softens the cervix to facilitate delivery

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6
Q

what is gametogenisis?

A

production of gametes for sexual reproduction

spermatogenesis
oogenesis

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7
Q

whats in the ovary?

A

many follicles containing eggs

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8
Q

what happens each month?

A

1) egg is selected from either ovary and released into the peritoneal cavity
2) oviducts have fimbriae that overhang the ovary and catch the egg being released and carry it towards the uterus
4) fertilised egg will be in the oviduct at fertilisation

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9
Q

what happens after fertilisation?

A

will be in the oviduct

after 5-6 days it will enter the uterus and implant itself

vagina is a copulatory organ but also important in delivery

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10
Q

what happens if the egg isn’t fertilised?

A

the lining sheds its endometrium resulting in a menstrual period

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11
Q

what is the myometrium?

A

muscle layer to support the uterus

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12
Q

what is oogenesis?

A

oocytes are formed in the developing ovary

they arrest in prophase of meiosis 1 and exist within primordial follicles

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13
Q

what are primordial follicles?

A

egg cell surrounded by follicular cells

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14
Q

how many primordial follicles are present at birth?

A

7 million

most die before puberty
at menarche = 300,000
most die by atresia

500 are realised by ovulation

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15
Q

what is menarche?

A

first menstruation

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16
Q

what is the ovarian cycle?

A

occurs in line with the menstrual cycle and uterine cycle

has 3 phases

1) follicular phase
2) ovulation
3) luteal phase

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17
Q

what is the uterine cycle?

A

cycle of the uterus preparing for implantation

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18
Q

outline of follicular phase

A

lasts several months

maturation of follicles

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19
Q

outline of ovulation

A

lasts a few hours

release of ovum from ovary into Fallopian tube

20
Q

outline of luteal phase

A

lasts 12-15 days
after ovulation
formation of the corpus luteum and its fate

21
Q

what is the corpus luteum?

A

the bit of the follicle that is left inside the ovary that starts to release hormones

supports the development of the embryo/foetus

22
Q

what happens in the pre-antral phase of the follicular phase?

A

primordial follicle to primary follicle to mature pre-antral follicle

23
Q

how does the primordial follicle develop into the primary follicle?

A

follicular cells around the oocyte send signals (paracrine factors) that cause the egg to mature

antimullerian hormone limits no. developing at the same time

egg releases factors that cause follicular cells to grow

primary follicle is slightly bigger than the primordial follicle

24
Q

how does the primary follicle develop into the mature pre-antral follicle?

A

zona pellucida (layer of glycoproteins) contains receptors that give species selectivity

granulose cells start to divide and form layers - express FSH receptors

layer of thecal cells develop around the outside - start to express LH receptors

LH and FSH released by anterior pituitary in response to gonad release

25
what is species selectivity?
human eggs will only except human sperm as they have to get through the protein layer
26
what happens in the antral phase of the follicular phase?
formation of the Antrum begins - fluid filled atria increased layers of zona granulosa thicker zona pellucida theca interns more apparent growth dependent of FSH dominant follicle selected and becomes a significant steroidogenic gland - starts to produce hormones
27
what do theca and granulosa cells do in the antral phase of the follicular phase?
theca cells catalyse androgen production from cholesterol granulosa cells contain aromatase so they can convert the androgen to oestrogen
28
what happens in the pre-ovulatory phase of the follicular phase?
dominant follicle responds to a surge in LH by completing the first meiotic division and arresting in metaphase of meiosis II becomes secondary oocyte with a polar body progesterone production inflammatory cytokines and hydrolytic enzymes released by theca and granulosa cells
29
what are the 3 stages of the follicular phase?
pre-antral phase antral phase pre-ovulatory phase
30
what happens during ovulation?
inflammatory event that erodes the wall of the follicle and releases the ovary oocyte, zona pellucida and corona radiate released into peritoneal cavity before being captured by the oviduct remnants of the follicle in the ovary form the corpus luteum
31
what happens in the luteal phase?
corpus luteum develops - produces hormones to help support the growth of the embryo granulosa cells filled with lipid manly progesterone produced oestrogen initially but decrease due to LH surge but then rebounds
32
what happens in the luteal phase if no pregnancy?
corpus luteum degenerates into corpus albicans and will gradually fade into scar tissue oestrogen and progesterone levels fall allowing FSH and LH levels to rise
33
what happens in the luteal phase if pregnancy?
placenta releases human chorionic gonadotrophin which enables the corpus luteum to persist
34
what are the important hypothalamic and pituitary hormones in hormonal control of the ovarian cycle?
gonadotrophin releasing hormone (GnRH) follicle stimulating hormone (FSH) luteinising hormone (LH)
35
what does gonadotrophin releasing hormone (GnRH) do?
release is pulsatile
36
what does follicle stimulating hormone (FSH) do?
stimulates recruitment and growth of immature follicles up regulates CYP19 (aromatase) gene expression and activity induces expression of LH receptors in granulosa cells in late follicular phase prevents apoptosis of antral follicles
37
what does luteinising hormone (LH) do?
acts on thecal cells to promote androgen production surge lasts 1-2 days in the follicular phase and triggers ovulation stimulates granulosa cells to secrete progesterone in late follicle and corpus luteum maintains the corpus luteum
38
what are the 3 important ovarian hormones?
oestrogen progesterone inhibin A and B
39
what does oestrogen do?
prepares reproductive tract for potential fertilisation and pregnancy dominant hormone secreted pre-ovulation (follicular phase)
40
what does progesterone do?
promotes uterine and uterine tube secretions to maintain and support potential fertilisation and implantation of an egg dominant hormone secreted post-ovulation (luteal phase)
41
what do inhibin A and B do?
secreted by granulosa cells represses FSH secretion
42
what happens at the end of the previous cycle?
* demise of the corpus luteum * decrease in oestrogen and progesterone production * release of negative feedback and FSH increases * crop of antral follicles recruited and start to grow
43
what happens in the early follicular phase? (in terms of hormones)
* follicles produce low levels of oestrogen * oestrogen negatively feedbacks on FSH * loss of progesterone and high oestrogen increases frequency of GnRH pulses * LH to FSH ratio increases * decreased FSH leads to follicular atresia leaving 1 dominant one
44
what happens in the late follicular phase? (in terms of hormones)
* dominant follicle produces more oestrogen * high oestrogen levels positively feedback on LH * LH surge enhanced by progesterone * oocytes complete meiosis 1 * ovulation is triggered * transient drop in oestrogen ends surge
45
what happens in the luteal phase? (in terms of hormones)
* corpus leteum forms * high progesterone levels negatively feedback on FSH and LH * corpus luteum begins to regress * progesterone and oestrogen levels fall * FSH rises again

Cell biology (14 decks)

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