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25 Cards in this Set

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What are two main processes that must occur in female repro tract to promote natural birth?
Uterine contractions and cervical dilatio.
What is regarded as a "term" delivery?
Around 40 weeks. anywhere between 37 weeks and 41 weeks and 6 days
What are the three important OB planes for childbirth?

Why are they important?
1) Pelvic inlet

2) Pelvic outlet

3) Midplane

These outlet sizes are important so that doctors can evaluate how easy passage through canal will be.
What inlet is the SHORTEST distance through which the head must pass?
Pelvic inlet
What is the importance of the ischeal spines as reference points?
Ischeal spines are called "STATION 0"

Once certain point of baby's head has reached the ischeal spines, this term is called "ENGAGEMENT"
What is the cervix made up of?
MOSTLY collagen, with some smooth muscle. Also contains glycosaminoglycans (which are present in both hydrophobic and hydrophilic forms)
What changes does the cervix undergo during labor?
Cervix begins to dilate.

Collagenase begins to break down the cervical collagen (beginning in third trimester)

The GAG's shift from predominantly HYDROPHOBIC to predominantly HYDROPHILIC. This makes dilation and effacement easier.

The smooth muscle also contracts to pull the cervix apart into the other tissues.
Are UTERINE CONTRACTIONS under neural or hormonal control?
Smooth muscle is predominantly HORMONALLY CONTROLLED.

Same is true in uterine contractions. Muscles communicate via GAP JXNS.
How do uterine contractions contract?

What is the MAIN ION INVOLVED IN MUSCLE CONTRACTION?
Contractile protein in ALL MUSCLES is ACTOMYOSIN.

When myosin binds to actin, an ATPase cross-links into actomyosin.

Ca2+ is the MAIN ION.
What is the principal enzyme responsible for muscle contractions?

In what state is MLCK activated?
MLCK - phosphorylates the myosin light chain.

MLCK is ACTIVATED UPON DEPHOSPHORYLATION.
What is the general pathway for muscle contraction?
1) Ca2+ enters cell

2) Ca2+ complexes with calmodulin

3) Ca2+ - calmodulin complex DEPHOSPHORYLATES MLCK, in turn activating it.

4) MLC - K then phosphorylates myosin light chain.

5) Myosin light chain MUST BE PHOSPHORYLATED for myosin and actin to bind together to then form ACTOMYOSIN via an ATPase
What pathways can cause Ca2+ increases?
1) Receptor agonists (oxytocin, PG's)

DAG + IP3 reaction --> Ca2+
If one wants to HALT PRE-TERM LABOR, what is the metabolic target?
CALCIUM!
What hormonal fluxes are generally observed in labor?
ESTROGEN INCREASE (BIG)

Progesterone decrease (importance debated)

Cortisol increase.
What is the difference between cortisol's effect on CRH release in adults vs. fetuses
Cortisol acts as POSITIVE FEEDBACK on CRH in fetus, activating HPA.

in ADULTS, cortisol is a NEGATIVE FEEDBACK.
In the placenta, why isn't cortisol activated by 17a-hydroxylase to convert progesterone into estrogen?
17a-hydroxylase IS NOT FOUND IN THE PLACENTA.

As a result, there is a shuttle system that must obtain estrogen some other way.
What are key points to this estrogen synthesis pathway?
Progesterone and pregnenolone in the placenta are

2) Transported to fetal adrenal, where they form cortisol AND DHEA.

3) DHEA is an important precursor for androgens

4) Fetus can produce DHEA in adrenal. DHEA is then converted to 16-OH-DHEA in the liver.

5) 16-OH-DHEA CAN BE METABOLIZED INTO ESTRIOL IN THE PLACENTA!!
Does estrogen DIRECTLY induce uterine contractions?
NO! Estrogen causes an increase in PG and oxytocin and their receptors.

PG's and oxytocin are DIRECT contractors. CORTISOL increases oxytocin levels. Also increases PG levels.
How many stages of delivery are there?
3 STAGES

Stage 1: Latent and active phases. Runs from cervix being closed to fully dilated

Stage 2: Runs from full dilation until delivery

Stage 3: Passage of placenta
What are cardinal movements?
Movements made by the fetus to pass through pelvis
A positive score relative to "0 station" means reference point is ABOVE or BELOW ischeal spines (0 station)
BELOW. Positive is good.
TRUE/FALSE

Labor is faster in women with prior pregnancies?
TRUE
What are the THREE POTENTIAL PROBLEM SPOTS with abnormal labor?
1) Push power is low

2) Passenger position/size

3) Passage (pelvis) size/shape
What is a pudendal nerve block?
Pudendal nerve innervates the perineal region via S2,3,4.

Injection of local anesthetic is made just inferior to sacrospinous ligament.
In C-sections, where are you looking to make incision?

What are two indications for C-section?
1) Make incision in lower uterine segment

2) Abnormal delivery. Placenta previa (placenta has implanted on top of cerxic (rather than mid post uterus)