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Phsyiology 210 B > Reproduction 3 - fertilization, pregenancy, lactation > Flashcards

Reproduction 3 - fertilization, pregenancy, lactation Flashcards

1
Q

What is Fertilization?

A

Fusion of the male and female gametes to form a zygote

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2
Q

After fertilization: duration of hours pregnancy or gestation

A
  • First two months: embryo
  • After 8 weeks (two months): fetus
  • About nine months (40 weeks) of gestation • parturition or birth
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3
Q

Site of Fertilization

A

• Female oviduct

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4
Q

Timing for fertilization is limited how?

A
  • Sperm viable for 5 days

* Oocyte viable for 12-24

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5
Q

Sperm initially incapable of fertilization

Why?

A

• Requires capacitation

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6
Q

Sperm Movement in the Uterine Tube, only ~100 make it there, why?

A
  • Damage due to acidic pH of the female tract

* Some loss due to leakage from cervix

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7
Q

How long do sperm survive in female tract?

A

5 days

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8
Q

Why is polyspermy not favored?

A

Because only one sperm cell carrying n # of chromosomes is allowed in the egg to maintain the diploid zygote.

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9
Q

How is polyspermy prevented?

A

To prevent polyspermy:

  • Change in membrane potential
  • Release of contents from cortical granules
  • Enzymes enter and harden zona pellucida
  • Enzymes inactivate sperm binding receptor
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10
Q

Events of fertilization

A

1) sperm heads bind to receptor of zona pellucida = acrosome rxn
2) sperm move through zona pellucida
3) one sperm binds to egg plasma membrane

4) 3 simultaneous events:
- Egg blocks polyspermy (secretory vesicles and enzymes enter zona pellucida).

  • Meiosis II = zygote = embryogenesis
  • egg enzyme activated - embryogenesis
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11
Q

What happens to the oocyte during fertilization?

A

• oocyte —> ovum (meiosis II)
– Sperm plasma membrane degrades
– Chromosomes from sperm and ovum migrate to centre
– DNA replicated —> zygote

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12
Q

Early Embryonic Development and Implantation

A

Mitotic divisions —> morula

• Cell cleavage
(4 cells stage, no increase in overall size)
——>
• Morula contains 16-32 Totipotent cells cell
(3-4 days post fertilization)
—-> Moves to uterus

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13
Q

Division of totipotent morula cells results in

A

identical twins

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14
Q

Fertilization of two oocytes (released during the same cycle) results in

A

non-identical (fraternal) twins

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15
Q

3-4 days after fertilization, the morula loses its

A

Zona pellucida

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16
Q

What does the morula become?

A

Blastocyst

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17
Q

Blastocyst

A

Lost zona pellucida = lost totipotency

– Outer cell layer = trophoblast = becomes fetal placenta

– Inner cell mass = becomes embryo

– Fluid-filled cavity = blastocoele

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18
Q

The trophoblast, inner cell mass, and fluid filled cavity of the blastocyst becomes

A

Trophoblast becomes placenta

Inner cell mass becomes embryo

Fluid filled cavity becomes blastoceole

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19
Q

Early Embryonic Development and Implantation

A

Zygote —> early cleavage (4 cell)

—> morula (totipotent) —-> blastocyst (totipotency lost)

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20
Q

Why does the blastocyst lose its totipotency ?

A

Because the inner cell mass has all the info required to make embryo

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21
Q

embryo is in the first

A

2 months of growth

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22
Q

When does implantation occur and what phase does it occur in menstrual cycle?

A
  • 6-7 days after fertilization.

- within the Luteal phase of the menstrual cycle = lots of progesterone

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23
Q

During implantation what hormone is very high and what does it cause?

A

lots of progesterone = decreases constracility and keeps env calm = prevents miscarriage or early abortion of implanted embryo.

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24
Q

Implantation

A

The blastocyst implants via sticky trophoblast cells (become placenta) 6-7 days after fertilization
( ~day 21 of ovulation cycle)

  • disidual response
  • Syncytiotrophoblast
  • cytotrophoblast
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25
Q

What are Syncytiotrophoblast and cytotrophoblast during implantation

A

Syncytiotrophoblast: fused trophoblast cell layer, outlayer of trophoblast

cytotrophoblast: inner layer of trophoblast, its the interior of the Syncytiotrophoblast.

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26
Q

Late Embryonic and Fetal Development

A

3 weeks:
- endometrium secretes glycogen rich fluid for growth & implantation of blastocyst.

5 weeks:

  • heart beat begins
  • early placenta development
  • amnion and chorion

8 weeks:

  • amnion and chorion
  • embryo —-> fetus
  • placenta fully developed
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27
Q

By 5 weeks,

A

placenta functioning, heart beating

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28
Q

Chorion

A

Trophoblast cell layer closest to amniotic cavity. As fetus grows, surrounds fetus inside.

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29
Q

Amnion

A

Forms amniotic sac that Contains amniotic fluid, protect fetus

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30
Q

Placental development form what kind of cells

A

The endothelial cells in the chorionic villus and the endothelial cells

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31
Q

What do the The endothelial cells in the chorionic villus and the endothelial cells create?

A

creates a barrier between mother blood and fetus blood (cell barrier)

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32
Q

Is there ever mixing of blood between mother and fetus ?

A

NO NEVER

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33
Q

Placenta function as:

A
  • exchange tissue: Respiratory gases, nutrients and waste products
  • Temporary endocrine gland
  • blood barrier
34
Q

Chorionic villus

A

Projections Implanting into the endometrial tissue, surrounded by blood filled space.

35
Q

Umbilical cord contains

A

Umbilical vein (blood in) and umbilical artery (blood out)

36
Q

Why is the barrier created by the placenta to speerate the bloods important?

A

Filter/Immunological protection: protect form mother antibodies or lymphocyte, so mothers bodies doesn’t reject fetus.

37
Q

Major Hormones in pregnancy

A
  • human chorionic gonadotropin (HCG) (glycoproteins)
  • human placenta lactogen (HPL) (protein)
  • estrogen
  • progesterone (steroid)
38
Q

Where is HCG released from?

A

Trophoblast cells that make up the corionic tissue

39
Q

HCG is released when

A

released as blastocysts being implanted.

40
Q

HCG acts as a detector for ______? How?

A

pregnancy

HCG peak secretion found around 60-80 days (~2months) after the last menstrual cycle and then drops sharply and remains low for the remainder of pregnancy.

41
Q

What is the indicator for pregnancy?

A

A sharp drop in HCG after 2 months of pregnancy indicates pregnancy

42
Q

HCG peak secretion found around

A

60-80 days (~2months) after the last menstrual cycle and then drops sharply and remains low for the remainder of pregnancy.

43
Q

Early in pregnancy, what levels are E and P?

A

They are low,

44
Q

Do the low levels of E and P go back up during early pregnancy? How?

A

Slowly rise as the placenta develops and begins to act as n endocrine gland, secreting a lot of E and P. This continues until birth (placenta expelled)

45
Q

Human chorionic gonadotropin ( hCG)

Function:

A

(glycoprotein)

  • Maintains corpus luteum functions in early pregnancy
46
Q

Human chorionic
somatomammotropin (hCS)
or human placental lactogen
(hPL)

Function:

A

(protein)

– GH-like and anti-insulin like actions in the mother (prevents sugar uptake by muscle cells/adipose cells of liver, hyperglycaemia)

  • helps the fetus to avail more glucose
47
Q

Is the hyperglycaemia caused by HPL good for the fetus

A

Yes cuz more sugar in blood available to help with baby growth

48
Q

Progesterone

function:

A

(steroid)

  • decreases uterine contractions
  • inhibits LH and FSH
  • growth of mammary glands and alveolar glands
  • secretes sperm unfriendly mucus
49
Q

Estrogen

Function:

A
  • growth of uterus (myometrium)
  • growth of mammary glands
  • inhibits LH and FSH
50
Q

How is the secretion of E and P stimulates and where is it from?

A

Placenta (HCG) —-> corpus luteum

= (E and P)

51
Q

Effects of Estrogen on the uterus

A
  • nor’easter contractile activity

- increase responsiveness to OXY

52
Q

Effects of Estrogen on the ant pit

A
  • PRL sec

- grow breast tissue

53
Q

Effects of Estrogen on the breast

A
  • grow duct tissues
  • fat deposition
  • suppression of lactation
54
Q

Effects of progesterone on the uterus

A
  • Suppress contrails activity
    (counter to E and OXY)
  • maintains secretory phase conditions
55
Q

Effects of progesterone on the breast

A
  • brow glandular tissue

- suppression of lactation

56
Q

• The highly developed breast tissue where milk lactation is suppressed is caused by the

A

high levels of both estrogen and progesterone that are secreted by the placenta.

57
Q

Which hormones increases contractile activity and which suppresses it ?

A

E = increases contractile activity

P = decreases contractile activity

58
Q

In the placenta can cholesterol be turned to androgens (E) ?
Why or why not?

A

No because there are no enzymes there to convert C —> P —> A —> E

59
Q

How is E produced if placenta cannot produced it?

A

C and P inside the mothers blood are transferred to the placenta where:
C ——> P

Then P moves to the fetus where:
P—-> A

Then A move back to the placenta where:
A —> E (E then moves back to the mother)

60
Q

Control of Parturition

A

OXY secretion from posterior pituitary (strengthen uterine contractions) = pressure of fetus against cervix ((+)feedback to produce more OXY) = partition / birth

61
Q

Myometrial contractions are increased by:

A
  • E
  • Prostaglandins
  • OXY
  • stretch
62
Q

Myometrial contractions are inhibited by:

A
  • Progesterone

- Relaxin

63
Q

Cervical ripening is increased by:

A
  • prostaglandins

- relaxin

64
Q

Cervical ripening is inhibited by:

A

-progesterone

65
Q

Source of Relaxin in human:

A

Corpus luteum, placenta

66
Q

Cervical ripening:

A

At end of pregnancy, cervix goes through enzymatic action = collagen fibres get loosened and area gets more relaxed = fetus can push itself upwards and out.

67
Q

Relaxin:

A

It has vasodilatory effects = increases blood flow to uterus and towards fetus.

Helps manage the renal capacity for mother to accommodate the increase in blood volume.

68
Q

When is relaxin important?

A

important effects during the middle to end of pregnancy.

69
Q

Partition

A

1) cervix ripens
2) beginning of partition, cervix dilates = labour (uterine contractions)
3) baby leave head first
4) expulsion of placenta (after birth)

70
Q

The Mammary gland

  1. Birth to puberty
A

• Rudimentary ducts, few if any alveoli

71
Q

The Mammary gland

  1. At puberty
A
  • Ducts grow and branch out (E)
  • Some alveolar growth (P)
  • Deposition of fat and alveolar tissue
72
Q

The Mammary gland

During Pregnancy and lactation:

A

Full development (E, P, PRL, hPL and growth factors needed)

• Prolactin: lactogenesis 
(initiation of milk synthesis - low E + P)
• hPL, growth factors
• Oxytocin  
(milk ejection = lactation)
73
Q

Breasts filled with lobular structures called

A

alveoli which are connected to several ducts that end up to the outside of the breast tissue, through the nipple area.

74
Q

Alveolar structure of a mammary gland

A
  • myoepithelial cells

- alveolar cells

75
Q

Alveolar cells

A

secretory epithelial cells, site where milk protein is synthesized and is released into the lumen within the alveolus

  • Have brush border enzymes
76
Q

Stored milk protein within the

A

alveolus can be let out through the small ducts.

77
Q

myoepithelial cells located

A

outside the alveolus

78
Q

Myoepithelial cells

A

Contract in response to OXY that increased by E.

79
Q

Suckling stimulates the tactile receptors of nipple which is then carried to

A

hypothalamus = oxytocin produced further = Post. Pit to be released into the blood stream = taken to myoepithelial cells. Increased recpetors = contraction of myoepithelial cells.

80
Q

once epithelial cells contract under oxytocin =

A

contract milk secreting epitheialel cells of the alveolar cells = milk proteins made and released out the lumen = let out the ducts of nipples = excreted

81
Q

Suckling Reflex

A

Receptor in nipples —> hypothalamus—>

1) Ant. Pit. = increase PRL = milk secretion by alveoli

2) increase activity of neurosecretory cells
—-> Post. Pit. = OXY = contraction of myepthial cells = milk ejection

82
Q

Suckling causes stimulation where?

A

Hypo —> both Ant. Pit (PRL) and Post. Pit. (OXY)

Phsyiology 210 B (24 decks)

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