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Genetics Exam 2 > Exam 2 > Flashcards

Exam 2 Flashcards

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1
Q

How much does a placenta usually weigh?

A

450 gms

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2
Q

What are the functions of the placenta?

PREMIES

A

PREMIES

Provide all necessary nutrients for fetal development and growth
Remove wastes
Exchange of oxygen and CO2
Metabolism of glycogen, cholesterol and fatty acids
Immune barrier that protects the growing fetus from antigen attack from the maternal system.
Endocrine organ: hormones and growth factors that regulate pregnancy, support and promote fetal growth, and initiate parturition
Sources of nutrients and energy for embryo

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3
Q

What are the two separate circulations for the placenta? Think FM

A

Fetal-placental (fetoplacental) blood circulation
Maternal-placental (uteroplacental) blood circulation

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4
Q

How does the exchange of gases and nutrients happen?

A

Passive diffusion
Facilitated diffusion
Active transport
Endocytosis/exocytosis

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5
Q

Does the blood from the mother and baby circulations mix in the placenta?

A

No.

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6
Q

How is the blood separated in the placenta?

A

Separated by trophoblastic tissue and fetal endothelial cells

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7
Q

What can cause abnormalities in the transport of nutrients to the placenta?

A

Concentration gradient
Maternal hypoxia or hypercarbia
Diffusing distance
Edema of villi secondary to maternal diabetes, infection,
erythroblastosis fetalis, twin –twin transfusion, fetal congestive
heart failure
Vasoconstriction
Smoking, hypertension, diabetes

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8
Q

What endocrines are made and secreted? Think 4HP

A

hCG
Human chorionic somatomammotropin or human placental
lactogen
Human chorionic thyrotropin
Human chorionic corticotropin
Progesterone and estrogens
Chorionic refers to placenta

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9
Q

What occurs during maternal circulation?

A

Uteroplacental circulation starts with the maternal blood flow into
the intervillous space through decidual spiral arteries.
Exchange of oxygen and nutrients take place as the maternal blood
flows around terminal villi in the intervillous space.
The in-flowing maternal arterial blood pushes deoxygenated blood
into the endometrial and then uterine veins back to the maternal
circulation.

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10
Q

What occurs during fetal circulation?

A

The fetal-placental circulation allows the umbilical arteries to carry
deoxygenated and nutrient-depleted fetal blood from the fetus to
the villous core fetal vessels.
**Artery carries deoxygenated blood away from fetal circulation
After the exchange of oxygen and nutrients, the umbilical vein
carries fresh oxygenated and nutrient-rich blood circulating back to
the fetal systemic circulation
**Veins carry oxygenated blood back into fetal circulation

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11
Q

Discuss placental blood flow. Think PURE.

A

Placenta adversely affected by hypo or hypertension, decreased
blood volume, affects how much blood flow to placenta
Uterine blood flow supplies the myometrium, endometrium and the
placenta (90% of total uterine blood flow at term)
Requires a doubling of maternal cardiac output and 40% increase of
blood volume
Estrogen induced vasodilatation of uterine vasculature

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12
Q

Discuss cord blood flow.

A

Through umbilical vein to the fetus
Large, thin walled vessel
More easily occluded with cord compression
-Decrease blood flow from placenta to baby, umbilical vein easily compressed, not true for umbilical artery (hard to compress), baby at risk for hypovolemic because baby is still sending out blood to placenta through umbilical artery
May result in fetal/newborn hypovolemia
Back through umbilical arteries to the placenta

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13
Q

Concerning doppler studies, what is the flow through the umbilical arteries dependent on?

A

-strength of the fetal heart contraction
-health of the placenta

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14
Q

How is the blood flow through the umbilical arteries evaluated?

A

-evaluated by measuring the blood flow velocity at peak systole and peak diastole
-Ratio:
peak of systole and then dividing it by the sum of measurements at
peak systole and diastole.
RI= systole/(systole+diastole)

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15
Q

As the duration of the pregnancy increases, what also increases?

A

the amount of blood flowing in the umbilical artery increases during diastole

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16
Q

What does it mean when the amount of blood flowing in the umbilical artery increases during diastole?

A

Means that the placenta is less resistant to blood flow, thus providing more blood to flow from the fetus to the placenta.
**Doppler high (too much blood flow)? Baby possibly anemic
**Doppler low (not enough blood flow)? Placenta not functioning

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17
Q

What are doppler findings that are indicative of needing an emergency delivery?

A

Absent end diastolic flow- marked decreased blood flow from the fetus to placenta

Reversed diastolic velocities- blood not flowing to and from baby, blood is also backing up

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18
Q

What are maternal indications to have a placenta evaluated?

A

Diabetes or glucose intolerance
Hypertension (essential or pregnancy induced)
Pre-maturity (? <34, <36, <38 wga) less than 38 weeks
Post-maturity (? >41, >42 wga) greater that 41 weeks
Previous pregnancy loss (spontaneous AB, stillbirth, neonatal)
Oligohydramnios
Fever or signs of infection
Substance abuse (? tobacco)
Abruption, previa, or repetitive bleeding
Therapeutic or diagnostic intervention
Trauma during pregnancy

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19
Q

What are neonatal indications to have a placenta evaluated?

A

Stillbirth or neonatal death
Multiple gestations
Congenital abnormalities
Growth restriction or excess
Prematurity
Evidence of infection
Hydrops
Meconium
Admission or transfer to NICU
Central nervous system depression or seizures, HIE

20
Q

Why should the placenta be evaluated? Legally?

A

Clarification of cause of adverse outcome.
Differentiation between acute and chronic insults.
Who is at fault: poor management before or after delivery
See calcifications? Chronic
Acute? Anything to do with delivery

21
Q

Why should the placenta be evaluated? Medically? Think CIA

A

Medical:
Clarification of cause of adverse outcome
Improvement of risk assessment for future pregnancies.
Assessment of risk for abnormal neurologic outcome.

22
Q

What happens with a placenta previa?

A

Placenta presents before baby, cut off baby’s blood flow

23
Q

What is the intervention for complete previa?

A

c-section

24
Q

What are baby considerations when mommy has a placenta previa?

A

Has kidney or gut seen blood flow: Increased risk for renal failure and nec
Considerations: feeds and urine output, BP

25
Q

What happens with a placenta accreta?

A

Invasion of the myometrium (grows into thickness of the muscle, invades into uterine wall), does not penetrate the entire thickness of the muscle.
Can have a d&c
75% of all cases.

26
Q

What happens with a placenta increta?

A

placenta further extends into the myometrium (muscle of the uterus), penetrating the muscle.
17%
Postpartum hemorrhage, may need a hysterectomy, depends on degree of attachment to wall

27
Q

What happens with placenta percreta?

A

placenta penetrates the entire myometrium to the uterine serosa (invades through entire uterine wall).
Can lead to the placenta attaching to other organs such as the rectum or bladder
5-7% (Maternal mortality rate 10%)
Mom needs a hysterectomy, may need reconstructive surgery to detach organs from placenta

28
Q

What increases the risk of placenta accretas, incretas, and percretas? Think PUR

A

Placenta previa
Uterine scar tissue
Repeated C/S or D & C

1 in 2500 pregnancies (1 in 30,000 in 1950)

29
Q

What is Trisomy 21?

A

Trisomy 21, also known as Down syndrome, is a genetic disorder caused by the presence of an extra chromosome 21.

30
Q

What are the three types of Trisomy 21?

A
  1. Full Trisomy 21 (Nondisjunction)
  2. Mosaic Trisomy 21 (Post-Zygotic Nondisjunction)
  3. Translocation Trisomy 21 (Robertsonian Translocation)
31
Q

How does Full Trisomy 21 occur?

A

It results from nondisjunction during meiosis, leading to a gamete with an extra chromosome 21, which combines with a normal gamete to produce a zygote with three copies of chromosome 21.

32
Q

What is Mosaic Trisomy 21?

A

It occurs due to a nondisjunction event after fertilization, leading to a mix of cells—some with two copies and others with three copies of chromosome 21.

33
Q

What causes Translocation Trisomy 21?

A

A structural rearrangement where a piece of chromosome 21 attaches to another chromosome, most commonly chromosome 14.

34
Q

What is a Robertsonian translocation?

A

A Robertsonian translocation is a chromosomal rearrangement where the long arms of two acrocentric chromosomes fuse at the centromere, forming a single chromosome. This can result in a balanced carrier state or disorders like Translocation Trisomy 21 if extra genetic material is inherited.

35
Q

What increases the risk of Trisomy 21?

A

Advanced maternal age, due to the accumulation of errors in oocytes that remain paused in meiosis I for decades.

36
Q

What are common phenotypic features of Trisomy 21?

A

Intellectual disability, hypotonia, low set eyes, palelbral fissures, sigle palmar crease, an increased risk for cardiac anomalies, leukemia.

37
Q

What is the role of nondisjunction in chromosomal abnormalities?

A

Nondisjunction occurs when chromosomes fail to separate properly during meiosis or mitosis, leading to an abnormal chromosome number.

38
Q

What are some structural chromosomal abnormalities?

A

Deletions (e.g., Cri du Chat), translocations, inversions, and ring chromosomes.

39
Q

What are balanced and unbalanced translocations?

A

Balanced Translocation: Chromosomal segments are exchanged without loss or gain of genetic material.
Unbalanced Translocation: Results in extra or missing genetic material, potentially leading to disorders.

40
Q

What is mosaicism?

A

A condition where different cells in the same individual have different genetic makeups, such as some with and some without Trisomy 21.

41
Q

What is the most common cause of chromosomal abnormalities?

A

Non-disjunction during meiosis.

42
Q

What are common cardiac defects associated with Trisomy 21?

A

Congenital heart disease affects 40-50% of individuals with Trisomy 21, with common defects including atrioventricular septal defect (AVSD), ventricular septal defect (VSD), patent ductus arteriosus (PDA), and less commonly, Tetralogy of Fallot (TOF).

43
Q

What are common gastrointestinal defects associated with Trisomy 21?

A

Gastrointestinal defects include duodenal atresia (“double bubble” sign), Hirschsprung disease, and esophageal atresia with or without tracheoesophageal fistula.

44
Q

What is the Median Plane?

A

Vertical plane of section that passes longitudinally through the body.
Median sections divide the body into right and left halves

45
Q

What is the Coronal Plane?

A

A coronal plane is any vertical plane that intersects the median plane at a right angle and divides the body into anterior (ventral) and posterior (dorsal) parts.

46
Q

When does the completion of implantation occur?

A

Day 8- Blastocyte is partially embedded in the endometrium.

47
Q

What are the 2 cell layers of the blastocyst?

A

Trophoblast (outer layer) and Embryoblast (inner layer)

Genetics Exam 2 (5 decks)

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