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Phys II Unit III > 4 Fertilization, Pregnancy, Parturition, & Lactation > Flashcards

4 Fertilization, Pregnancy, Parturition, & Lactation Flashcards

1
Q

What are the four stages of pregnancy?

A
  1. Initiation (Fertilization—>Implantation—>Secretion of hCG to rescue the corpus luteum)
  2. Gestation
  3. Parturition
  4. Lactation
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2
Q

________ is the usual site of fertilization

A

Oviduct, usually in the upper third (ampulla)

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3
Q

When must fertilization occur?

A

Within 24 hours of ovulation

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4
Q

Sperm usually survive about _______ but can survive up to _______ in the female reproductive tract

A

48 hours

5 days

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5
Q

How do sperm deposited in the vagina reach the ovum for fertilization?

A

Travel through cervical canal, uterus, and oviduct to the ampulla (upper third)

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6
Q

How does the female reproductive tract aid sperm in their migration?

A

Contractions of the myometrium

Upward contractions of oviduct smooth muscle

Allurin released by mature eggs

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7
Q

Chemoattractant for sperms to reach egg in ampulla of oviduct

A

Allurin

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8
Q

Upon sperm passage through female reproductive tract, the process of __________ occurs

A

Capacitation or “activation”

Surface characteristics of the sperm are altered

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9
Q

Sperm motility in the cervical canal requires _________ pH

A

Alkaline

Alkaline secretions from prostate gland elevate pH

Estrogen makes mucus watery, facilitating sperm motility

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10
Q

How does the uterus assist with sperm transport?

A

Myometrial contractions
• Prostaglandins in the ejaculate
• Estrogen-primed tissue

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11
Q

Sperm capacitation involves what processes?

A

Cholesterol withdrawal
Redistribution of surface proteins
Calcium influx to increase motility (whiplashing)

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12
Q

Once a capacitated sperm reaches an ovum, what has to happen in order for fertilization to occur?

A

Penetration of the corona radiate —> binding of membrane head to ZP3 proteins of the zona pellucida

Acrosome hydrolytic enzymes digest zona pellucida, creating pathway to the ovum membrane

When the sperm reaches the ovum, the two membranes fuse and the sperm head with its DNA enters the cytoplasm

ZP3 proteins are inactivated and harden the zona pellucida to block polyspermy

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13
Q

Sperm contains receptors that bind to _________ in the zona pellucida

A

Protein ZP3

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14
Q

An enzyme released from the sperm to allow it to penetrate the zona pellucida

A

Acrosin

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15
Q

Fusion of the sperm to the ovum’s membrane is mediated by….

A

Binding of fertilin on the sperm head to integrin receptor on ovum’s membrane

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16
Q

How is polyspermy prevented?

A

Structural changes in zona pellucida following sperm’s fusion with the ovum’s membrane

Release of cortical granules containing enzymes that degrade ZP3 proteins and harden glycoproteins on the zona pellucida

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17
Q

The zona reaction signals the ovum to do what?

A

Complete 2nd meoitic division and extrusion of 2nd polar body

Allows for formation of female pronucleus and its fusion to male pronucleus

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18
Q

The fertilized ovum divides in what manner?

A

Mitotically

Within a week it grows and differentiates into blastocyst capable of implantation

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19
Q

Blastocyst implants into endometrial lining by means of…

A

Enzymes that digest endometrial tissue

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20
Q

Due to progesterone action days ______ of a regular 28-day cycle are the optimal period for implantation

A

20-24

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21
Q

When is hCG detectable in maternal serum?

A

Only after implantation is completed, 8-11 days after conception

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22
Q

Placenetal hCG will rescue the ________.

A

Corpus luteum

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23
Q

When the free-floating blastocyst adheres to the endometrial lining, ______________ begin to penetrate the endometrium.

A

Cords of trophoblastic cells

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24
Q

What happens as advancing cords of trophoblastic cells tunnel deeper into the endometrium?

A

They carve out a hole for the blastocyst —> boundaries between the cells in the advancing trophoblastic tissue disintegrate

When implantation is finished, the blastocyst is completely buried in the endometrium

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25
Q

The placenta is well established and operational by ________

A

5 weeks after implantation

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26
Q

Organ of exchange between maternal and fetal blood that performs the functions of the digestive system, the respiratory system, and the kidneys for the fetus

A

Placenta!!!!

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27
Q

The placenta prevents….

A

Immunologic rejection

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28
Q

The placenta acts as a transient endocrine organ that secretes what essential pregnancy hormones?

A

Human chorionic gonadotropin (hCG) - maintains corpus luteum until placenta takes over function in last two trimesters

Estrogen

Progesterone

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29
Q

______ is what most pregnancy tests detect

A

hCG

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30
Q

______ may be the causative agent of morning sickness

A

hCG

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31
Q

The action of hCG is similar to LH in that it…

A

Stimulates the corpus luteum to secrete progesterone and estrogen

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32
Q

Once the placenta secretes estrogen and progesterone, the hCG levels _______ and the corpus luteum _______

A

Decline
Regresses

hCG levels in maternal plasma peak between 9 and 12 weeks gestation and then decline to a stable plateau

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33
Q

Describe normal levels of hCG in pregnancy

A

Steep rise in hCG starting after implantation, with peak around 9-12 weeks, plateauing at ~10^3 or 10^4

34
Q

If there is fetal death, what happens to hCG levels?

A

Levels rise normally, then fall with a half-life of 24 hours after death of the fetus

35
Q

In cases of ectopic pregnancy, what happens to hCG levels?

A

Rise more slowly

36
Q

When hCG levels rise slowly but continue to rise after week 9-12, this is called…

A

Hydatidiform mole

37
Q

______ levels increase during pregnancy and require __________ for synthesis

A

Increase

Both fetus and placenta

38
Q

What is the most important estrogen of pregnancy

A

Estriol

Levels in maternal urine may be used as an index of fetal health

39
Q

What are the functions of estrogen during pregnancy?

A

Increased growth of myometrium (muscles for labor)

Development of ductile system of breasts

Stimulates prolactin release by anterior pituitary

Relax and soften pelvic ligaments

Inhibits lactation by antagonizing prolactin effect on the best and inhibiting lactalbumin (required for lactose synthesis)

40
Q

For the first 6-12 weeks of pregnancy, progesterone is secreted by ________, but after 12 weeks, the major source is ________

A

Corpus luteum —> placenta

41
Q

Synthesis of progesterone requires…

A

Maternal cholesterol

42
Q

What are the functions of progesterone in pregnancy?

A

Conversion of uterus to secretory gland, readying it for implantation

FOrmation of cervical plug

Inhibition of myometrial contraction

Inhibition of prostaglandin synthesis from uterus

Development of alveolus and lobule in breast

Inhibition of lactose synthesis

43
Q

How long is gestation?

A

About 38 weeks from conception

44
Q

What are the physical changes within the mother to meet the demands of pregnancy?

A 
Uterine enlargement
Breasts enlarge and develop ability to produce milk
Volume of blood increases 30%
Weight gain
Respiratory activity increases about 20%
Urinary output increases
Kidneys excrete added wastes from fetus
Nutritional requirements increase
45
Q

During the first two trimesters, the uterus remains quiet due to …

A

Inhibitory effects of high levels of progesterone

46
Q

During the last trimester, uterus becomes progressively __________

A

More excitable (Braxton-Hicks contractions)

47
Q

Throughout gestation, the uterus remains sealed by …

A

The rigid, tightly closed cervix

48
Q

What hormone, produced by corpus luteum of pregnancy and by the placenta, relaxes pelvic ligaments and softens the uterine cervix by loosening the connective tissue between pelvic bones

A

Relaxin

49
Q

What are the three parts of parturition?

A

Labor, delivery, and birth

50
Q

What changes are required in order for parturition to occur?

A

Dilation of cervical canal to accommodate passage of fetus from uterus through vagina and to the outside

Contraction of uterine myometrium that are sufficiently strong to expel fetus

51
Q

Exact factors triggering increase in uterine contract ability and initiation of parturition are…

A

Not fully established

52
Q

What is the role of high estrogen levels in parturition?

A

Promotes synthesis of connexons for gap junctions within uterine smooth muscle cells —> coordinated uterine contraction

Increased concentration of myometrial receptors for oxytocin —> increased responsiveness to oxytocin

Increased production of prostaglandins —> stimulates enzymes to degrade collagen fibers (cervical softening) and increases oxytocin receptors in myometrium

53
Q

What is the role of Oxytocin during labor?

A

Produced in the hypothalamus and stored in posterior pituitary

Circulating blood levels of oxytocin remains constant prior to onset of labor

Uterine responsiveness to oxytocin is 100x greater at term than in nonpregnant women

Profound effect of oxytocin at term due to INCREASED CONCENTRATION of RECEPTORS in MYOMETRIUM

54
Q

Labor is initiated when the _____________ concentration reaches a critical threshold

A

Oxytocin receptor concentration

Permits the onset of strong, coordinated contractions in response to ordinary levels of circulating oxytocin

55
Q

________ levels in _____________ act as a “placental clock” for parturition

A

CRH levels in maternal plasma (corticotrophin-releasing hormone)

56
Q

What is the role of CRH in induction of labor?

A

Fetal portion of placenta secretes CRH into fetal circulation —> increased fetal ACTH

Increased ACTH —> DHEA from fetal adrenal cortex —> increases availability for placental conversion into estrogen

Increased ACTH stimulates fetal cortisol production —> fetal lung maturation (ensures infant is ready to live outside the womb)

57
Q

High CRH levels are associated with ….

A

Premature deliveries

58
Q

Low CRH levels are associated with…

A

Late deliveries

59
Q

What is the role of inflammation in labor?

A

Activation of nuclear factor (NF-kB) in the uterus (caused by uterine stretching and increased production of macrophages as a result of increased pulmonary surfactant)

NF-kB stimulates production of inflammatory cytokines (IL-8) and prostaglandins —> promotes cervical softening

60
Q

What else could activate NF-kB and result in premature labor?

A

Bacterial infections
Allergic reactions
Multiple fetus pregnancy (due to increased uterine stretching)

61
Q

Labor is a _________ cycle that progressively increases until….

A

Positive-feedback cycle

Until cervical dilation and delivery are complete

62
Q

_______ is a pharmacological synthetic form of oxytoxin

A

Pitocin

63
Q

What are the three stages of labor?

A

Cervical dilation - lasts from several hours to as long as 24 hours in a first pregnancy

Delivery of baby - begins when cervical dilation is complete (usually 30 to 90 minutes)

Delivery of placenta - second series of uterine contractions separates placenta from uterus (usually 15-30 min)

64
Q

Which stage of labor is the longest?

A

Cervical dilation

65
Q

Which stage of labor is the shortest?

A

Delivery of placenta

66
Q

What is involution?

A

After delivery, shrinkage of uterus to presentational size

67
Q

________ and ________ promote development of mammary glands during gestation

A

Estrogen and progesterone

68
Q

During gestation, ______ stimulates synthesis of milk enzymes

A

Prolactin

69
Q

Lactation does not occur during pregnancy due to ….

A

Inhibition from estrogen and progesterone

Withdrawal of placental steroids at parturition initiates lactation

70
Q

Lactation is sustained by _______.

A

Suckling

Oxytocin —> milk ejection
Prolactin —> secretion (production) of more milk

71
Q

What are the hormones of lactation?

A

ESTROGENS stimulate ductal growth

PROGESTERONE, PROLACTIN, and hCS (human chorionic somatomammotropin) stimulate development of lobules and alveoli

PROLACTIN and hCS stimulate milk enzymes

INSULIN and CORTISOL also promote lactation

72
Q

After parturition, estrogen and progesterone ______, so lactation can occur

A

Decrease

73
Q

How does the sucking reflex occur?

A

(+) signal = infant’s cry or smell
(-) signal = psychological stress

(+) signal to POSTERIOR pituitary —> increased Oxytocin release —> contraction of myoepithelial cells surrounding alveoli —> milk ejection

Suckling of infant —> mechanoreceptors in nipple —> signal hypothalamus to release prolactin from ANTERIOR pituitary —> secretion by alveolar epithelial cells —> increased milk synthesis

74
Q

Major hormone responsible for lactogenesis

A

Prolactin

Synthesized/secreted by lactotrophs in pituitary

75
Q

Release of prolactin is controlled by what two hormones?

A

Thyrotropin-releasing hormone (stimulatory)

Dopamine (inhibitory)

76
Q

Prolactin inhibits _______ release, preventing ________.

A

GnRH

Ovulation

77
Q

Ovulation is suppressed as long as _______ continues

A

Lactation

Because prolactin inhibits GnRH —> inhibition of LH and FSH release
It also antagonizes the action of LH and FSH on ovaries

78
Q

In non-lactating women, ovulation resumes in ________ postpartum

A

7-10 weeks

79
Q

In lactating women, ovulation resumes within _______ postpartum

A

27 weeks (7 months)

80
Q

In order to get full ovulation suppression, you must…

A

Breast feed regularly

BUT not recommended as a contraceptive method

Phys II Unit III (5 decks)

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