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Repro Exam 2 > Meiosis > Flashcards

Meiosis Flashcards

1
Q

What is meiosis?

A

single round of DNA replication followed by 2 consecutive rounds of cell division

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2
Q

Cytokinesis in females is uneven, what is the result of this?

A

each original 2N oogonia entering meiosis gives rise to only one 1N oocyte at the conclusion of the two meiotic divisions

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3
Q

What are polar bodies?

A

remnant cells left over after most of the cytoplasm goes to one of the cells during female meiotic division

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4
Q

Describe the first polar body

A

arises from the first meiotic division in females

1N2C cell

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5
Q

Describe the second polar body

A

arises from the second meiotic division

1N1C cell

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6
Q

When does meiotic division stop in females?

A

first meiotic division is arrested at about the time of birth in most animals

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7
Q

When does reinitiation of the first meiotic division occur in females?

A

sometime after puberty and is a result of the preovulatory LH surge

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8
Q

What happens when the first meiotic division is reinitiated in females?

A
  • oocyte completes meiosis and first polar body is expelled
  • immediately enters the 2nd meiotic division and is arrested
  • oocyte arrested in meiotic division is ovulated
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9
Q

When does the 2nd meiotic division occur in females?

A

when the oocyte is reactivated by a penetrating sperm at time of fertilization

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10
Q

What does the corpus luteum form from?

A

remnants of the ovulated follicle

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11
Q

Definition of leutinization

A

CL formation

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12
Q

When does leutinization occur?

A

following the LH surge but prior to ovulation, when the follicles begin to secrete less estrogen and more progesterone

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13
Q

What happens to the follicle after ovulation?

A
  • collapsed follicle reorganizes
  • granulosa cells form the large luteal cells
  • theca cells form the small luteal cells
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14
Q

Function of large luteal cells

A
  • baseline progesterone secretion

- do not respond to LH by increasing progesterone secretion

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15
Q

Function of small luteal cells

A

-respond to LH by increasing progesterone secretion

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16
Q

What are luteotropins?

A

hormones that support the CL

17
Q

Name some luteotropins and their effects (4)

A
  1. LH - responsible for the early changes of luteinization
  2. Prolactin - important luteotropin in carnivores, mice, rats, and hamsters
  3. Estradiol - luteotropin in rabbits, may be lutolytic in other animals
  4. PGI2 and PGE2 - luteotropic in cattle and women
18
Q

Function of the CL

A

inhibits the hypothalamo-pituitary axis by its secretion of progesterone

19
Q

How can a new estrus cycle commence in animals?

A

CL must be removed (luteolysis)

20
Q

How does luteolysis occur?

A
  • decreased progesterone influence and increased estrogen influence allows increased oxytocin secretion
  • increased oxytocin secretion causes PGFalpha2 release
  • PGFalpha2 causes luteolysis of CL
21
Q

How does luteolysis occur in animals with a closely applied ovarian artery and uterine vein?

A

prostaglandin from uterine endometrium passes up uterine vein and a portion is transferred across vessel wall into ovarian artery where it can directly access the CL

(sheep and guinea pig)

22
Q

How does luteolysis occur in animals where the ovarian artery and uterine vein are not closely applied?

A

prostaglandin is transferred via the systemic circulation, which results in a much less active metabolism in the lungs

(horses and rabbits)

23
Q

Explain luteolysis in ruminants

A

prostaglandin release from the uterine endometrium causes oxytocin release from the CL, which causes more prostaglandin release from the uterine endometrium, etc. etc.

24
Q

Explain luteolysis in primates

A

central oxytocin release acts on luteal oxytocin receptors which gives local formation of prostaglandins within the CL

25
Q

What is pseudomenstruation?

A

blood coming from the vagina without destruction and sloughing of the endometrium at the end of the luteal phase

26
Q

Why is there bleeding from the bitch during proestrus?

A

blood cells are lost into the uterine lumen by diapedesis and following rupture of small capillaries

27
Q

Why is there bleeding from the cow during metestrus?

A

caruncular capillaries hemorrhage following the rapid decline in estrogen after ovulation

28
Q

What two animals have real menstruation (sloughing of the endometrium)?

A

bats and elephant shrews

Repro Exam 2 (9 decks)

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