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HUBS192 2024 > Lecture 37 > Flashcards

Lecture 37 Flashcards

1
Q

What are the stem cells that produce oocytes?

A

oogonia

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2
Q

Is an oogonia cell haploid or diploid?

A

Diploid (2n = 46)

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3
Q

What does oogenesis require?

A

mitosis and meiosis

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4
Q

When is oogenesis initiated?

A

Before birth

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5
Q

What does oogenesis supply?

A

A life time supply of gametes produced before birth

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6
Q

Where do the oocytes develop?

A

Within ovarian follicles

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7
Q

How does the population of oogonia cells increase?

A

Via mitosis which stops before birth

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8
Q

What do oogonia differentiate into?

A

Primary oocytes

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9
Q

Are primary oocytes haploid or diploid?

A

Diploid (2n = 46)

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10
Q

What is the primary oocyte encased by?

A

The primary follicle

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11
Q

What happens to many of the primary oocytes?

A

They undergo atresia, a form of apoptosis

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12
Q

What do primary oocytes initiate?

A

Meiosis

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13
Q

Where does meiosis halt?

A

Prophase 1

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14
Q

When does meiosis procede?

A

At the beginning of puberty

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15
Q

What is menarche?

A

The first menstrual cycle

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16
Q

When puberty is reached, how many oocytes do females have?

A

~300,000

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17
Q

What happens in meiosis 1 after puberty has begun?

A

The primary oocyte will divide into a secondary oocyte and the first polar body

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18
Q

Is the secondary oocyte haploid or diploid?

A

Haploid (n)

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19
Q

What is a polar body?

A

A small haploid cell that cannot be fertilised and dies

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20
Q

What starts meiosis 2?

A

The secondary oocyte

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21
Q

Where does meiosis 2 halt?

A

At metaphase 2

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22
Q

When does meiosis 2 procede?

A

When fertilised - when the sperm penetrates the plasma membrane of the ovum

23
Q

What happens to the secondary oocyte if fertilisation does not occur?

A

It will degenerate and undergo atresia, not completing meiosis

24
Q

What does one primary oocyte ultimately form?

A

One ova and three polar bodies

25
Q

Where does oogenesis occur?

A

Within the developing follicle

26
Q

What are follicles?

A

Multilayered cell systems containing oocyte

27
Q

What are the two types of cells within the follicle?

A

Granulosa and theca cells

28
Q

What do granulosa cells produce?

A

Estradiol which surrounds oocyte

29
Q

What is ovulaition?

A

When the oocyte and corona radiata are released into the peritoneal cavity

30
Q

What is the female reproductive hormone released from the hypothalamus?

A

Gonadotropin-releasing hormone (GnRH)

31
Q

What does GnRH do?

A

Stimulates release of follicle simulating (FSH) and luteinising hormone (LH)

32
Q

Where is FSH and LH released from?

A

The anterior pituitary gland

33
Q

What does FSH do?

A

Stimulates the growth of ovarian follicles

34
Q

What does LH do?

A

Is involved in ovulation; the formation of the corpus luteum

35
Q

What hormones do the ovary follicles secrete?

A

Estradiol (an estrogen) and inhibin

36
Q

What hormones do the ovary corpus luteum secrete?

A

Inhibin and progesterone

37
Q

What does estradiol do?

A

Assists follicle growth, bone and muscle growth, endometrial growth and secondary sex characteristics

Feeds back to anterior pituitary

38
Q

What does inhibin do?

A

Negative feedback to anterior pituitary to suppress FSH

39
Q

What does progesterone do?

A

Negatively feeds back to hypothalamus to suppress GnRH (therefore LH and FSH too). Also involved in endometrial maturation and maintains the pregnant state

40
Q

What is the purpose of the ovarian cycle?

A

To prepare an oocyte for fertilisation and the endometrium for embryo implantation

41
Q

When does menarche occur?

A

Around 12-13 years old

42
Q

What is one part of puberty orchestrated by?

A

The increase in sex steroid production (estrogens) by the gonads

43
Q

What happens in menopause?

A

The reduction of estradiol and progesterone due to the absence of or lack of response by follicles. The anterior pituitary feedback is no longer active and therefore FSH and LH are high

44
Q

What is the follicular phase?

A

The preovulatory phase; day 1 - 14

45
Q

What is the luteal phase?

A

The postovulatory phase; day 15 - 28

46
Q

What happens during the follicular phase?

A

Increase FSH stimulates follicular growth, which secretes estradiol and inhibin in turn reducing FSH from negative feedback. Growing follicles undergo atresia, except dominant. High estradiol stimulates a surge of LH from positive feedback, the follicle ruptures and ovulation occurs - oocyte enters the peritoneal space

47
Q

What happens during the luteal phase?

A

Ovulated follicle collapses and forms corpus luteum which secretes progesterone, estradiol and inhibin. These all negatively feedback to the hypothalamus, decreasing FSH and LH secretion.

48
Q

What happens in the luteal phase if fertilisation and implantation do not occur?

A

The corpus luteum involutes (luteolysis), there is a fall in progesterone and estradiol and the negative feedback on the hypothalamus is removed. FSH and LH increase again for the cycle to begin again.

49
Q

What is the menstrual and proliferative phase?

A

Day 1-14 for the endometrium

50
Q

What is the secretory / premenstrual phase?

A

Day 15 - 28 for the endometrium

51
Q

What happens in the menstrual and proliferative phase?

A

Endometrium breaks down and bleeds during menstruation. Estradiol stimulates endometrial growth from days 6-14and rapid tissue growth occurs including the growth of glands and vasculature

52
Q

What happens in the secretory phase?

A

After ovulation (day 14) corpus luteum secreted progesterone which promotes endometrial maturation. Glands become secretory and spiral arterioles grow and coil

53
Q

What happens at the end of the secretory phase if fertilisation does not occur?

A

Corpus luteum atrophies, progesterone levels fall and spiral arteries contract. Endometrial tissue breaks down and bleeding occurs. Shed tissue and blood removed via cervix and vagina

HUBS192 2024 (38 decks)

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