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Bioscience for Midwifery > Week 3 > Flashcards

Week 3 Flashcards

1
Q

At what gestation can a fetus survive independently outside the uterus?

A

From 32 - 34 weeks.

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2
Q

At what gestation is the sex of the fetus able to be distinguished externally?

A

12 weeks.

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3
Q

From when is the placenta fully established?

A

From 8 - 10 weeks. It will be full size by 4 months.

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4
Q

What is the purpose of maternal lacunae?

A

It allows primitive transfer of nutrients etc from mother to fetus from the endometrial glands.

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5
Q

How are maternal lacunae developed?

A

The syncytiotrophoblast errodes the glands and blood vessels of the endometrial tissue to form lacunae (spaces) where nutrients can pass. It is present by day 13.

By the end of the first trimester, these spaces develop into intervillous spaces of the placenta, where blood enters providing fluid with a higher o2 content for fetal exchange.

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6
Q

What are the chorionic villi?

A

Finger-like projections that develop due to the cytotrophoblast invading areas of syncytiotrophoblast between the lacunae. Blood vessels develop in the chorionic villi by 18 - 21 days.
There are two types, anchoring or branch. Branch villi facilitate diffusion, while anchoring villi attach the placenta to the decidua.

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7
Q

What are the chorion and the amnion?

A

The two layers of the chorioamniotic membrane which are separated by 200ml of amniotic fluid and mucous produced by the amnion.

The Amnion is the membrane around the embryo/fetus, the inner membrane.

The chorion is the membrane closest to the decidua, or the outer membrane.

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8
Q

Where does the amnion attach to the fetus?

A

At the site of the umbilical cord.

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9
Q

Which membrane contains blood vessels. The amnion or the chorion?

A

The Chorion.

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10
Q

What are the functions of amniotic fluid?

A

Allow fetal movement;
Protect fetus from changes in pressure and temperature;
Protection from infection (through antibacterial factors).

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11
Q

How is amniotic fluid produced/formed?

A

Initially by secretion by amniotic cells;
Then by diffusion of fluid from the interstitial fluid of the decidua parietalis and from the blood in the intervillous spaces of the placenta - across the amniochorionic membrane to the amniotic cavity.

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12
Q

What is amniotic fluid comprised of?

A

98 - 99% water;

Remaining is electrolytes, creatinine, urea, bile, renin, glucose, hormones, fetal cells, lanugo and vernix.

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13
Q

What is the other name for the primary yolk sac?

A

The umbilical vesicle.

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14
Q

What are the four roles of the placenta?

A
  1. Transport: of respiratory gases O2 and CO2, nutrients, hormones, waste products, electrolytes;
  2. Immunological: provides an effective barrier against most large bacterial microorganisms, but not most viruses or smaller bacteria. Protection is instead provided by the transport of maternal antibodies;
  3. Endocrine: hormones that help maintain pregnancy are synthesised by the placenta such as oestrogen, progesterone, hPL and hCG;
  4. Metabolic: the placenta synthesises glycogen, cholesterol, fatty acids and enzymes which are used by the embryo/fetus and the placenta. This is mostly important in early pregnancy before the fetal/maternal circulation is established.
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15
Q

What is wharton’s jelly?

A

It is a jelly like substance in the umbilical cord that suspends and protects the umbilical blood vessels.

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16
Q

What is the approximate size of a placenta at full term?

A

20 cm in diameter and 2.5cm thick at the centre.

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17
Q

What is the name given to the lobes of the placenta on the maternal side and how many are there in a normal placenta?

A

There are 15 - 20 cotyledons in a normal placenta.

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18
Q

What are the two “plates” of the placenta?

A

Basal plate: maternal tissue along the wall of the uterus that contains maternal blood vessels.

Chorionic plate: fetal tissue containing umbilical blood vessels that push into lacunae to allow diffusion of nutrients/waste products and gas exchange from the maternal blood to the fetal circulation.

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19
Q

True or False: The umbilical cord is wrapped in amnion membrane?

A

TRUE.

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20
Q

How many blood vessels are contained in the umbilical cord?

A

There are three: one vein, and two arteries.

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21
Q

What is calcification and how is it identified?

A

Calcification of the placenta is where deposits of lime salts occur on the surface of the maternal side and they appear as whitish/grey spots and are “gritty” to the touch.

They’re associated with maternal smoking and high blood pressure.

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22
Q

True or False: Heart shaped placentas are associated with fetal abnormality.

A

False. This is simply a variation in presentation, and is not associated with fetal abnormality.

23
Q

What is a circumvallate placenta?

A

Where the membranes have overlapped and fused together, creating a dense white ring around the edge. This occurs where the chorionic plate is small (underdeveloped) and is associated with IUGR.

24
Q

What are the four ways in which twins can grow within the uterus?

A
  1. Monochorionic/monoamniotic: Both fetus’ grow within a single chorion and single amnion, and share the same placenta. They are likely identical twins.
  2. Monochorioni/diamniotic: One chorion, surrounding two placenta and two amnion.
  3. Dichorionic/diamniotic (fused placenta): Separate amniotic sacs for each twin, and separate placenta that have fused together.
  4. Dichorionic/diamniotic: completely separate placentas and sacs, which have implanted in separated locations within the uterine wall.
25
Q

What is a succenturiate lobe?

A

This is where a lobe of the placenta grows separately from the body of the placenta and blood vessels will travel to it. It can often be left behind in the uterus after the third stage. You can identify the missing lobe from a hole in the membranes with vessels leading to it.

26
Q

What is bipartite placenta?

A

This where the placenta forms in two separate parts and vessels separate to both parts.

27
Q

What is meant by velamentous insertion of the cord?

A

This where the cord inserts into the membranes rather than directly into the placenta, with blood vessels running through the membranes. This increases the risk of hemmorage, and these vessels can sometimes run across the internal cervical os. They can rupture during labour causing signification fetal blood loss, and potentially fetal death.

28
Q

What is meant by battledore insertion of the cord?

A

The cord inserts on the edge of the placenta, rather than the middle. This is NOT associated with abnormalities of the fetus.

29
Q

If the cord, membranes and/or fetal skin are a yellowy colour on birth, what might this indicate?

A

The fetus has passed meconium inutero some time ago, and this has stained the cord/membranes.

30
Q

When does ossification fetal bones begin?

A

Around weeks 13 - 16.

31
Q

When are fetal movements normally felt by the mother?

A

Weeks 16 - 20

32
Q

What is lanugo?

A

Fine hairs over the body of the fetus. It develops around Weeks 17 - 20 and disappears around weeks 30 - 34.

33
Q

When does the production of surfactant begin in the fetus?

A

Weeks 21 - 25.

34
Q

When are the fetal lungs capable of breathing and exchanging gas?

A

Weeks 26 - 29.

35
Q

When do intrauterine respiratory movements begin?

A

Weeks 26 - 29.

36
Q

When does the fetus begin to store iron?

A

Weeks 30 - 34.

37
Q

Where is the vault, face and base of the fetal skull?

A

Vault: from the nape of the neck to the orbital ridge.

Face: From the orbital ridge to the chin.

Base: from the chin back to the nape. (this does not have obstetric significance).

38
Q

Name the main bones of the fetal skull relevant to obstetrics?

A

Occipital
Parietals
Frontal

39
Q

Name the four sutures of the fetal skull relevant to obstetrics?

A

Lambdoidal: between the occipito and parietal bones.
Sagittal: runs between the parietal bones.
Coronal: separates the parietals from the frontal.
Frontal: divides the frontal bones.

40
Q

What is the posteriod fontanelle?

A

It is the area where the lambdoidal and sagittal sutures meet, it is triangular in shape and will allow the tip of a finger to fit. This is used to determine fetal position during labour, and will close at 6 weeks postpartum.

41
Q

What is the anterior fontanelle?

A

The area where the sagittal, frontal and coronal sutures meet, forming a kite/diamond shape. It closes at approximately 18 months old.

42
Q

What are the landmarks of the fetal skull?

A 
Glabella:  bridge of nose;
Sinciput:  brow;
Bregma:  anterior fontanelle
Vertex: between the anterior and posterior fontanelles and the parietal eminence;
Lambda: the posterior fontanelle
Occiput: bone at the back of the skull;
Subocciput: below the occipital protruberance;
Mentum:  chin.
43
Q

Which part of the fetal skull is the ideal presentation and why?

A

The subocccipito-bregmatic (vertex presentation) as it is a round shape and is the smallest diameter of 9.5cm.

44
Q

Which presentation of the fetal skull gives the largest diameter?

A

The mento-vertical diameter (brow presentation) which is approximately 13 - 13.5cm and is usually too large to engage.

45
Q

What is the diameter of the occipito-frontal?

A

11.5cm. This is presented when the baby is in the posterior position.

46
Q

If you have a vertex presentation with deflexion, which diameter would you have?

A

The Occipito-frontal which is approximately 11.5cm.

47
Q

What are the three types of abnormal moulding?

A
  1. Excessive - if it moulds too far it can put too much pressure/stretch on the brain tissue;
  2. Upward moulding - this can occur particularly in the posterior position;
  3. Rapid moulding: when the baby’s head is pushed through the birth canal very quickly (as in breech birth), it can occur rapidly and cause damage.
48
Q

What best describes the placenta?

A

Round in appearance, defined edge, bright red, membranes clear and shiny.

49
Q

Placenta calcification is a result of …?

A

Maternal smoking and high blood pressure

50
Q

True or False: The bipartite placenta is one with two separate parts with vessels that separate into two.

A

True.

51
Q

At what gestational age is the sex of the fetus able to be determined?

A

12 Weeks

52
Q

When does the fetus begin to store iron?

A

30 - 34 weeks

53
Q

By 38 weeks how much of the fetus’ body weight is comprised of body fat?

A

16%

54
Q

What is a fontanelle?

A

The area where two or more sutures meet.

Bioscience for Midwifery (4 decks)

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