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OBYGNE > [PF] Physiology of Labor > Flashcards

[PF] Physiology of Labor Flashcards

1
Q

_____ is the last few hours of human pregnancy.

A

Labor

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2
Q

It is characterized by forceful and painful uterine contractions that effect cervical dilation and cause the fetus to descend through the birth canal.

A

Labor

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3
Q

During the first _______ of normal gestation, the myometrium is in a preparatory yet unresponsive state.

A

36 to 38 weeks

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4
Q

Following this prolonged uterine quiescence, a _________ follows during which myometrial unresponsiveness is suspended and the cervix undergoes ripening, effacement, and loss of structural
cohesion.

A

transitional phase

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5
Q

The physiological processes that regulate ________ -the bringing forth of young-and the onset of labor continue to be defined.

A

parturition

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6
Q

Three general contemporaneous theories describe labor initiation.

A
  1. functional loss of pregnancy maintenance factors
  2. synthesis of factors that induce parturition
  3. signal or parturition commencement (mature fetus is the source of the initial)
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7
Q

________ remains the major contributor to neonatal mortality and morbidity.

A

Preterm labor

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8
Q

The __________ of the uterus is composed of bundles of smooth muscle cells surrounded by connective tissue.

A

myometrial layer

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9
Q

In contrast to skeletal or cardiac muscle, the __________ is not terminally differentiated and therefore is readily adaptable to environmental changes

A

smooth muscle cell

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10
Q

Lining the thick muscular uterine walls, the endometrium is transformed by pregnancy hormones and is then termed _________

A

decidua

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11
Q

Composed of stromal cells and maternal immune cells,
the _______ serves to maintain the pregnancy via unique immunoregulatory functions that suppress inflammatory signals during gestation.

A

decidua

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12
Q

Maintenance of barrier function to protect the

reproductive tract from infection

A

Cervix

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13
Q

maintenance of cervical competence despite greater gravitational forces as the fetus grows

A

Cervix

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14
Q

orchestration of extracellular matrix changes that allow progressively greater tissue compliance

A

Cervix

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15
Q

In nonpregnant women, the cervix is ______ and ______ and its consistency is similar to nasal cartilage.

A

closed and firm

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16
Q

By the end of pregnancy, the cervix is easily _________, and its consistency is similar to the lips of the oral cavity

A

distensible

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17
Q

Concurrent with expansion of the stroma, the ____________ proliferate and exert a pregnancy-specific immunoprotection.

A

cervical epithelia

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18
Q

In addition to providing the exchange of nutrients and waste between mother and fetus, the _________ is a key source of steroid hormones, growth factors, and other mediators that maintain pregnancy and potentially aid the transition to parturition.

A

placenta

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19
Q

The fetal membranes ______, _______ and _______ make up an important tissue shell around the fetus that serves as a physiological, immunological, and metabolic shield to protect against untimely parturition initiation.

A

amnion
chorion
adjacent decidua

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20
Q

The _______ provides virtually all of the fetal membranes’ tensile strength to resist membrane tearing and rupture.

A

amnion

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21
Q

This avascular tissue is highly resistant to penetration

by leukocytes, microorganisms, and neoplastic cells.

A

amnion

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22
Q

It also constitutes a selective filter to prevent fetal particulate-bound lung and skin secretions from reaching the maternal compartment.

A

amnion

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23
Q

The ______ is a primarily protective tissue layer and provides immunological acceptance. It is also enriched with enzymes that inactivate _______, which are agents that stimulate contractions.

A

chorion

uterotonins

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24
Q

Inactivating enzymes include:

A

Prostaglandin dehydrogenase
Oxytocinase
Enkephalinase

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25
Q

In many species, the role of sex steroid hormones is clear- _________ promotes and __________ inhibits the events leading to parturition.

A

estrogen

progesterone

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26
Q

The removal of progesterone, that is ______________ directly precedes progression of parturition

A

progesterone withdrawal

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27
Q

In addition, providing progesterone to some species will delay parturition via a decline in _____________ and continued _________.

A

myometrial activity

cervical competency

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28
Q

In all species studied including humans, administration of the progesterone-receptor antagonists ________ or _______ will promote some or all key features of parturition. These include cervical ripening, greater cervical distensibility, and augmented uterine sensitivity to uterotonins.

A

mifepristone (RU-48) or onapristone

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29
Q

Estrogen can advance progesterone responsiveness

and in doing so promote _____________.

A

uterine quiescence

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30
Q

At the end of pregnancy, __________ aids processes that mediate uterine activation and cervical ripening.

A

estrogen

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31
Q

Two nuclear receptors for estrogen are:

A

estrogen receptor a (ERa)

estrogen receptor 3 (ER3)

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32
Q

Nuclear receptor isoforms of the progesterone receptor _______ and ______ are encoded by differing transcripts from a single gene.

A

(PR-A and PR-B)

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33
Q

_________ are lipid molecules with varied hormone-like actions.

A

Prostaglandins

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34
Q

In parturition, they play a prominent role in myometrial contractility, relaxation, and inflammation.

A

Prostaglandins

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35
Q

Prostaglandins interact with a family of ____ different G-protein-coupled receptors several of which are expressed in myometrium and cervix.

A

eight

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36
Q

Prostaglandins are produced using plasma membrane-derived _________, which usually is released by the action of ___________.

A

arachidonic acid

phospholipase A2 or C

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37
Q

Arachidonic acid can then act as substrate for both type 1 and 2 prostaglandin H synthase (PGHS-l and -2), which are also called ___________.

A

cyclooxygenase -l and -2 (COX-l and -2)

38
Q

Both PGHS isoforms convert arachidonic acid to the unstable ________ and then to prostaglandin H2. These enzymes are the target of many ______.

A

prostaglandin G2

nonsteroidal anti-inflammatory drugs (NSAIDs)

39
Q

Through prostaglandin isomerases, __________ is converted to active prostaglandins. These include prostaglandins E2 (PGEJ, F2x (PGF2x), and 12 (PGI2
).

A

prostaglandin H2

40
Q

Another important control point for prostaglandin activity is its metabolism, which most often is through the action of _____________.

A

15-hydroxyprostaglandin dehydrogenase

PGDH

41
Q

Expression of this enzyme is up regulated during pregnancy in the uterus and cervix, which provides the important ability to rapidly inactivate prostaglandins.

A

15-hydroxyprostaglandin dehydrogenase

PGDH

42
Q

It is entirely possible that __________ contribute to myometrial relaxation at one stage of pregnancy and to myometrial contractions after parturition initiation.

A

prostanoids

43
Q

The _______ is likely the major source for amnionic fluid prostaglandins, and their role in the activation of cascades that promote membrane rupture is clear.

A

amnion

44
Q

PHASE 1:

A

UTERINE QUIESCENCE AND CERVICAL SOFTENING

45
Q

Parturition can be arbitrarily divided into four overlapping phases that correspond to the major
physiological transitions of the myometrium and cervix during pregnancy. These phases of parturition include:

A

(1) a prelude to it
(2) the preparation for it
(3) the process itself
(4) recovery

46
Q

Importantly, the phases of parturition should not be confused with the ____________, that is, the first, second, and third stages-which make up phase 3 of parturition.

A

clinical stages of labor

47
Q

The myometrial cells undergo a phenotypic modification to a noncontractile state, and uterine muscle is rendered unresponsive to natural stimuli.

A

Phase 1

48
Q

That said, some low-intensity myometrial contractions are felt during the quiescent phase but they do not normally cause cervical dilation. These contractions
are common toward the end of pregnancy, especially in multiparas, and are referred to as ________.

A

Braxton Hicks contractions or false labor.

49
Q

The quiescence of phase 1 likely stems from:

A

(1) actions of estrogen and progesterone via intracellular receptors
(2) myometrial-cell plasma membrane receptor-mediated increases in cyclic adenosine monophosphate (cMIP)
(3) generation of cyclic guanosine monophosphate (cGMP)
(4) other systems, including modification of myometrial-cell ion channels.

50
Q

diminished intracellular crosstalk and reduced intracellular Ca2+ ([Ca2 +)] levels

A

Quiescence

51
Q

ion channel regulation of cell membrane potential

A

Quiescence

52
Q

enhanced interactions between the actin and myosin proteins

A

Contractility

53
Q

heightened excitability of individual myometrial cells

A

Contractility

54
Q

activation of the uterine endoplasmic reticulum stress-unfolded protein response

A

Quiescence

55
Q

promotion of intracellular crosstalk that allows synchronous contractions to develop

A

Contractility

56
Q

uterotonin degradation

A

Quiescence

57
Q

Indeed, a potential mechanism for maintenance of

_______ is the promotion of actin into a globular form rather than into fibrils, which are required for _______.

A

relaxation

contraction

58
Q

Moreover, ______ must be attached to the cytoskeleton at focal points in the cell membrane to allow tension to develop.

A

actin

59
Q

The coupling of myosin and actin activates ____________, hydrolyzes adenosine triphosphate, and generates force.

A

adenosine triphosphatase (ATPase)

60
Q

This interaction is brought about by ___________ of the 20-kDa light chain of myosin

A

enzymatic phosphorylation

61
Q

This is catalyzed by the enzyme __________, which is activated by calcium.

A

myosin light-chain kinase

62
Q

Calcium binds to _______, a calcium-binding regulatory protein, which in turn binds to and activates myosin light-chain kinase.

A

calmodulin

63
Q

Thus, logically, uterine relaxation ordinarily is promoted by conditions that _______ concentrations of (Ca2+)i.

A

lower

64
Q

But, contractions can be prolonged by inhibition of ___________, an enzyme which dephosphorylates myosin.

A

myosin phosphatase

65
Q

In normal physiology, the myometrial ________ plays dual and opposing roles to maintain a balance between uterine quiescence and contractility.

A

BKca channel

66
Q

The Bca channel is abundantly expressed in the _________.

A

myometrium

67
Q

Enhancing Bca channel opening results in myometrial ________ whereas inhibition of the Bca channel augments myometrial _________.

A

relaxation

contractility

68
Q

Communication is established between myocytes by ________ which aid the passage of electrical or ionic coupling currents as well as metabolite coupling.

A

gap junctions

69
Q

The transmembrane channels that make up the gap

junctions consist of two protein ___________.

A

“hemi-channels”

70
Q

These ________ are each composed of six connexin subunit proteins.

A

connexons

71
Q

___________ is expressed in myometrium, and concentrations rise near labor onset.

A

Connexin-43

72
Q

Optimal numbers and types of gap junctions are believed to be important for electrical ___________.

A

myometrial synchrony

73
Q

_________ maintains uterine quiescence in part by mechanisms that lower expression of various key proteins needed for contractility.

A

Progesterone

74
Q

These ___________ include the oxytocin receptor, prostaglandin F receptor, and connexin-43.

A

contraction-associated proteins (CAPs)

75
Q

As another potential mechanism, progesterone maintains uterine quiescence through support of myometrial ______ which is an anticontractile agent

A

caspase 3

76
Q

This protein degrades both actin and the specific gap junction protein, connexin-4.

A

caspase 3

77
Q

In mice, myometrial caspase 3 activation is regulated by a pregnancy-induced _______________. Prolonged ERSR promotes caspase 3
activation to preserve quiescence despite these stimuli.

A

endoplasmic reticulum stress response (ERSR)

78
Q

As background, the __________ aids protein folding and transport.

A

endoplasmic reticulum

79
Q

_____________ cause misfolded proteins to accumulate and trigger the ERSR.

A

Functional irregularities

80
Q

The ERSR and its ______________ are cellular mechanisms that work to maintain homeostasis in the face of stimuli, such as stretch and inflammation.

A

unfolded-protein response (UPR)

81
Q

Prolonged ERSR promotes _________ to preserve quiescence despite these stimuli.

A

caspase 3 activation

82
Q

___________ are prototypical examples of cAMP signaling causing myometrium relaxation.

A

B-Adrenoreceptors

83
Q

Levels of myometrial _____ receptors during pregnancy are greater before than during labor.

A

LH-hCG

84
Q

_________ acts to activate adenylyl cyclase by way of a plasma membrane receptor
G’s-linked system.

A

Chorionic gonadotropin

85
Q

Thus, high circulating levels of hCG may be one mechanism of ________.

A

uterine quiescence

86
Q

_________ mediates its diverse cellular effects through four G-protein-coupled receptors.

A

Prostaglandin E2

87
Q

Specifically, __________ are expressed in the myometrium during pregnancy and with labor onset.

A

prostaglandin E receptors 1 through 4 (EP1,-EP 4)

88
Q

___________ act through G’s to raise cAMP levels and maintain myometrial cell quiescence but switch to a G’alpha/ 1 1 calcium-activating pathway during labor.

A

EP2 and EP4

89
Q

_______ receptors act through G’alpha q and G’alpha i to augment intracellular Ca2+ and contractility.

A

EP1 and EP3

90
Q

The peptide hormone _______ binds to the G-protein coupled receptor named relaxin famiy peptide receptor 1 (FP 1).

A

relaxin

OBYGNE (4 decks)

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