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Renal and Endocrine Biology > REB 16. Pregnancy > Flashcards

REB 16. Pregnancy Flashcards

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1
Q

What is the common site of fertilization?

A

Ampulla

- the upper 1/3rd of the oviduct

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2
Q

What are the ends of the fallopian tubes called?

A

Fimbria - because they are fimbriated ends

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3
Q

When must fertilization occur by (in regards to the ovum)? How is this different to how long the sperm may survive in female reproductive tract?

A
  • must occur within 24 hours after the ovulation

- sperm can survive about 48 hours, but may live up to 5 days in female reproductive tract

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4
Q

When released from the ovary, the oocyte is surrounded by 2 layers:

A

[1] Corona Radiata (outer)
- layer of follicular cells
[2] Zona Pellucida (inner)
- matrix of glycoproteins

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5
Q

When does human fertilization begin?

A

when sperm breaks through corona radiata to bind to SUGAR GROUP on zona pellucida

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6
Q

What are the 3 parts of the sperm?

A

[1] Head
[2] Midpiece
[3] Tail

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7
Q

What is special about the head of the sperm?

A

it contains enzymes to break through the Corona Radiata and Zona Pellucida

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8
Q

Explain how the sperm breaks through the outer layers of the ovum/oocyte to fertilize it.

A

[1] sperm breaks through Corona Radiata via the enzymes of its head

[2] sperm binds to ZP3 receptors on Zona Pellucida

[3] binding of sperm leads to triggering the acrosome reaction in which hydrolytic enzymes in the acrosome are released onto Zona Pellucida

[4] acrosomal enzymes digest Zona Pellucida creating a path for the sperm

[5] sperm and oocyte fuse

[6] sperm nucleus enters the ovum cytoplasm

[7] the sperm stimulates release of Ca2+ stored in cortical granules of ovum

[8] Ca2+ inactivates ZP3 receptors leading to the blockage of polyspermy

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9
Q

What happens 1 hour after fertilization?

A

the sperm and egg nuclei fuse

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10
Q

What happens 3 to 4 days after fertilization?

A

zygote remains within ampulla (of oviduct) and undergoes mitotic cell divisions
- morula is created!

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11
Q

After fertilization, there is a rising level of progesterone from the corpus luteum which stimulates…?

A

release of glycogen from the endometrium

  • used as energy by the early embryo
  • after 3 to 4 days, the morula is allowed to enter the uterus because enough nutrients were allowed to accumulate
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12
Q

What happens 6 to 7 days after ovulation/fertilization under the influence of progesterone?

A
  • uterine lining being prepared for implantation
  • uterus is in its secretory, progestational phase
  • stores up glycogen + becomes righly vascularized (builds up wall)
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13
Q

The endometrium is suitable for implantation after how long?

A

1 week after ovulation

- at this stage, morula has descended into uterus and differentiated into blastocyst

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14
Q

What are the layers of the blastocyst? What are the functions of each layer?

A

[1] Inner Cell Mass
- becomes the embryo

[2] Trophoblast

  • becomes the placenta
  • makes fuel + raw materials available for embryo
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15
Q

During implantation, what happens to trophoblastic cells?

A

[1] release enzymes permitting trophoblastic cells to penetrate endometrium
[2] cells degenerate - becoming fetal portion of placenta

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16
Q

At the area of implantation, what changes does the endometrial tissue undergo?

A
  • it enhances its ability to support the embryo

- now called the decidua

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17
Q

What is the relationship between the decidua and the blastocyst?

A
  • the blastocyst burrows into the decidua
  • a layer of endometrial cells covers over the surface of the hole
  • the trophoblastic layer continues to digest surrounding decidual (endometrial) cells providing energy for the embryo
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18
Q

On what day is the embryo embedded in the decidua?

A

day 12

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19
Q

On day 12 after fertilization, the trophoblastic layer is 2 cell layers thick and is called…?

A

Chorion

20
Q

What does the Chorion do? (general overview)

A
  • it releases enzymes and expands and forms a network of cavities within decidua
  • maternal blood leaks from capillaries to fill the cavities
  • chorionic tissue extend into the pools of maternal blood
  • developing embryo sends capillaries into these chorionic projections to form placental villi
  • maternal + fetal blood do not mingle (but we know this sometimes may not be the case)
21
Q

The placenta is made up of 2 tissues which are:

A

[1] Trophoblastic Tissue (Tissue from Blastocyst)

[2] Decidual Tissue (Endometrial Tissue)

22
Q

What type of organ does the placenta temporarily become during pregnancy?

A

a temporary endocrine organ

23
Q

Why is the placenta unique among endocrine tissues?

A

[1] composed of tissues of 2 organisms (mom + baby)
[2] transient tissue
[3] secretion of its hormones is not subject to extrinsic control
- depends on the stage of pregnancy

24
Q

What are the 4 main hormones that the placenta secretes?

A

[1] Estrogens
[2] Progesterone
[3] Human Chorionic Gonadotropin (hCG)
[4] Human Placental Lactogen (hPL)

25
Q

What is the source of secretion for hCG?

A

chorion, then the placenta

26
Q

What are the functions of hCG?

A

[1] stimulates + maintains corpus luteum so it does not degenerate
- progesterone is produced leading to thicmening of endometrial lining + produces energy

[2] in male fetus, stimulates precursor of Leydig cells so that testosterone may be secreted
- masculinizes the reproductive tract

27
Q

How is hCG excreted from the body and why is this important?

A
  • excreted in urine

- pregnancy tests detect hCG in urine as early as the 1st month

28
Q

What is the source of secretion for hPL?

A

initially trophoblast, then later the placenta

29
Q

What are the functions of hPL?

A

[1] lactogenic (breast feeding) + growth hormone like actions

[2] promotes cell specialization in mammary gland

  • BUT is less potent than PRL is stimulating milk production
  • BUT is less potent than GH in stimulating growth

[3] ensure adequate fuel supplies for fetus

  • effects on carbs, protein and fat metabolism are simialr to those of GH
  • conserves carbs, builds protein and uses fat
30
Q

What is the MAIN function of hPL? [1]

A

ensure adequate fuel supplies for fetus

  • effects on carbs, protein and fat metabolism are simialr to those of GH
  • conserves carbs, builds protein and uses fat
31
Q

When is there a peak of hCG? When is there a peak in hPL?

A

hCG: maximal at week 10

hPL: maximal at around week 35

32
Q

What are the sources of progesterone?

A

initially corpus luteum, but then the placenta

same as estrogen

33
Q

What are the functions of progesterone?

A

[1] essential for maintaining uterus + early embryo
[2] inhibits myometrial contractions (prevents miscarriage!)
[3] promotes formation of a mucus plug in cervical canal to prevent vaginal contaminants from reaching uterus
[4] suppresses maternal immunological responses to fetal antigens
[5] precursor for steroid production by fetal adrenal glands
[6] stimulates development of milk glands in breasts in preparation for lactation
[7] role in onset of parturition

34
Q

What are the sources of progesterone?

A

initially corpus luteum, but then the placenta

same as progesterone

35
Q

What are the functions of estrogen?

A

[1] increase size of uterus
[2] increase uterine blood flow
[3] critical in timing of implantation
[4] induce formation of uterine receptors
[5] enhance fetal organ development
[6] promote development of the ducts within mammary glands

36
Q

When is hCG the highest? Why does it drop?

A
  • hCG is the highest at the beginning of pregnancy
  • then there is a sharp drop in hCG
  • hCG is kind of like the precursor for estrogen + progesterone
  • as hCG decreases, both estrogen and progesterone increase
37
Q

What are the 3 stages of labour?

A

[1] Cervical Dilation

  • longest stage
  • 10 cm
  • last from several hours to 24 hours

[2] Delivery of Baby
- usually lasts 30 to 90 minutes

[3] Delivery of Placenta

  • second series of uterine contractions
  • separates placenta from myometrium + expels it
  • shortest stage
38
Q

What is the longest stage of labour?

A

Cervical Dilation

39
Q

What is the name for when the uterus shrinks after delivery?

A

Involution

40
Q

What are the 2 main triggers that lead to the onset of labour?

A

[1] Hormones
- progesterone, estrogen, prostaglandins, oxytocin + relaxin

[2] Mechanical Factors
- distension of uterine muscle + softening of cervix

41
Q

How does progesterone lead to the onset of parturition (labour)?

A
  • typically inhibits uterine contraction
  • prevents premature delivery
  • rise in placental progesterone-binding protein or a decline in the number of receptos alters its effective concentration
42
Q

How does estrogen lead to the onset of parturition (labour)?

A
  • soaring levels of estrogen
  • promotes the synthesis of connexons within uterine smooth muscle cells
  • contract as coordinated unit
  • increase concentration of myometrial receptors for oxytocin
  • promotes production of local prostaglandins
    (contributes to cervical ripening - dilation of cervix - and increase the uterine responsiveness to oxytocin)
43
Q

How does oxytocin lead to the onset of parturition (labour)?

A
  • circulating levels of oxytocin remains constant prior to onset of labour
  • BUT the uterine responsiveness to oxytocin is 100x greater in women at term
  • labour is initated when myometrial responsiveness to oxytocin reaches CRITICAL THRESHOLD
  • side note: used to clinically induce labour
44
Q

How does relaxin lead to the onset of parturition (labour)?

A
  • relaxin is large polypeptide produced by corpus luteum + decidua
  • softens the cervix, permitting passage of fetus
  • increases oxytocin receptors!
45
Q

How is labour maintained through a positive feedback loop?

A
  • the cervical stretch stimulates release of oxytocin
  • additional oxytocin stimulates release of oxytocin from the posterior pituitary
  • this leads to more stretch and more oxytocin being released
  • oxytocin stimulates prostaglanding production by decidua
  • porstaglandin softenst the cervix allowing for head of baby to move through

this is the Ferguson Reflex!!

46
Q

What is the NAME of the positive feedback loop that maintains labour?

A

Ferguson Reflex

Renal and Endocrine Biology (25 decks)

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