Parturition Flashcards
1
Q
__________ a.k.a. bringing forth of young Phases
A
Parturition
2
Q
WHat is the first phase of parturition?
A
: - a prelude to—first phase
3
Q
What is the second phase of parturition?
A
- the preparation for—second phase
4
Q
What is the thrid phase of parturition?
A
- the process of—third phase -
5
Q
What is the fourth phase of parturiotion
A
recovery from—fourth phase
6
Q
____________
- uterus must initiate extensive changes in its size and vascularity to accommodate the pregnancy and prepare for uterine contractions in phase 3 of parturition
A
Uterine Quiescence
7
Q
- some myometrial contractions are noted during the quiescent phase, they do not normally cause cervical dilatation . What type of contraction is this?
A
o unpredictability
o low intensity
o brief duration
8
Q
____________contraction is a discomfort that they produce usually is confined to the lower abdomen and groin
A
- Braxton Hicks
9
Q
Is there a contraction in the first phase of parturition?
A
yes there is but it doesnt lead to dilation
10
Q
What are the function of cervix in pregnancy?
A
Cervix has multiple function in pregnancy
- maintenance of barrier function to protect the reproductive tract from infection,
- maintenance of cervical competence despite the increasing gravitational forces imposed by the expanding uterus
- orchestrating extracellular matrix changes that allow progressive increases in tissue compliance in preparation for birth.
11
Q
What happens at the- End of pregnanc with our cervix? -
A
cervix is easily distensible, and its consistency is similar to the lips of the oral cavity
12
Q
o ____________ - is characterized by an increase in tissue compliance, yet the cervix remains firm and unyielding
A
Softening
13
Q
Structural Changes with Softening
A
- Cervical softening results from
o increased vascularity
o stromal hypertrophy
o glandular hypertrophy and hyperplasia
o compositional or structural changes of the extracellular matrix -
Phase 1 of parturition o cervix begins a slow, progressive increase in turnover of matrix components
o change in collagen processing or a change in the number or type of covalent cross-links between collagen triple helices which are normally required for stable collagen fibril formation
14
Q
Describe phase 1
A
Phase 1
Quiescent
Contraction Unresponsive
Cervical softening
15
Q
Describe phase 2
A
ACtivation
Preparation for labor
Cervical Ripening
16
Q
______________ - process constitutes phase 2 and represents a progression of uterine changes during the last 6 to 8 weeks of pregnancy
A
Uterine awakening or activation
17
Q
The last few hours of human pregnancy are characterized by forceful and painful uterine contractions that effect cervical dilatation and cause the fetus to descend through the birth canal.
There are extensive preparations in both the_________________ long before this.
A
uterus and cervix
18
Q
During the first ____________- of normal gestation, the myometrium is in a preparatory yet unresponsive state.
A
36 to 38 weeks
19
Q
Concurrently, the cervix begins an early stage of remodeling— termed_____________—yet maintains structural integrity.
A
softening
20
Q
Following this prolonged uterine quiescence, there is a transitional phase during which myometrial unresponsiveness is suspended, and the cervix undergoes ___________, _____________ and ______________
A
ripening, effacement, and loss of structural integrity.
21
Q
It is clear, however, that labor onset represents the culmination of a series of biochemical changes in the uterus and cervix. These result from _________________________
Their relative contributions vary between species, and it is these differences that complicate elucidation of the exact factorsthat regulate human parturition.
A
endocrine and paracrine signals emanating from both mother and fetus.
22
Q
When parturition is abnormal,then_________, ____________ and ____________ may result.
A
preterm labor, dystocia, or postterm pregnancy
23
Q
Of these results when partuition is abnormal ,_____________remains the major contributorn to neonatal mortality and morbidity in developed countries.
A
preterm labo
24
Q
The bringing forth of young—_____________—requires wellorchestrated transformations in both uterine and cervical function. As shown in Figure 21-1,
A
parturition
25
parturition can be arbitrarily divided into **four overlapping phases** that **correspond to the major physiological transitions** of the **myometrium and cervix** during pregnancy (Casey, 1993, 1997; Challis, 2000; Word, 2007). These phases of parturition include:
(1) a prelude to it,
(2) the preparation for it,
(3) the process itself, and (
4) recovery.
Note: Importantly, the phases of parturition should not be confused with the clinical stages of labor, that is, the first, second, and third stages—which comprise the third phase of parturition
26
Beginning even before implantation, a remarkably effective period of myometrial ________________ is imposed. This phase normally comprises **95 percent of pregnancy** and is **characterized by uterine smooth muscle tranquility with maintenance of cervical structural integrity.**
The inherent propensity of the **myometrium to contract is held in abeyance,** and **uterine muscle is rendered unresponsive to natural stimuli.**
Concurrently, the uterus must initiate extensive changes in its size and vascularity to accommodate the pregnancy and the pregnancy and prepare for uterine contractions
in phase 3 of parturition. The myometrial unresponsiveness
of phase 1 continues until near the end of pregnancy.
Uterine Quiescence
27
Although some myometrial contractions are noted during the quiescent phase, they do not normally cause cervical dilatation. They are characterized by their unpredictability, low intensity, and brief duration. Any discomfort that they produce usually is confined to the lower abdomen and groin. Near the end of pregnancy,contractions of this type become more common, especially in **multipaous women**. They are sometimes referred to as\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
Braxton Hicks contractions or false labor
28
The cervix has multiple functions during pregnancy that include: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
In nonpregnant women, the cervix is closed and firm, and its consistency is similar to nasal cartilage.
(1) **maintenance of barrier function** to **protect** the reproductive tract from infection
, (2) maintenance of cervical competence despite the increasing gravitational forces imposed by the expanding uterus, and
(3) **orchestrating extracellular matrix changes t**hat allow progressive increases in tissue compliance in preparation for birth.
29
By the end of pregnancy, the cervix is easily distensible, and its consistency is similar to the lips of the oral cavity. Thus, the **first stage of this remodeling**— termed\_\_\_\_\_\_\_\_\_\_\_\_\_\_—is characterized by an **increase in tissue compliance, yet the cervix remains firm and unyielding.** Hegar (1895) first described **palpable softening of the lower uterine segment at 4 to 6 weeks’** gestation, and this sign was once used to diagnose pregnancy.
softening
30
Clinically, the maintenance of cervical anatomical and structural integrity is essential for continuation of pregnancy to term. Preterm cervical dilatation, structural incompetence, or both may forecast an unfavorable pregnancy outcome that ends most often in preterm delivery (see Chap. 36, p. 814). Indeed, **cervical shortening between \_\_\_\_\_\_\_\_\_\_\_\_ **has been associated with an increased risk of preterm delivery (Hibbard and associates, 2000; Iams and colleagues, 1996).
**16 and 24 weeks**
31
Structural Changes with Softening.
Cervical softening results from \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_(Danforth and colleagues, 1974; Leppert, 1995; Liggins, 1978 ; Word and associates, 2007). Specifically, **during phase 1 of parturitio**n, the cervix **begins a slow, progressive increase in turnover of matrix components**. For example, in mouse models with deficiency of the extracellular matrix protein, thrombospondin 2, collagen fibril morphology is altered and there is premature cervical softening (Kokenyesi and co-workers, 2004).
increased vascularity, stromal hypertrophy, glandular hypertrophy and hyperplasia, and compositional or structural changes of the extracellular matrix
Note: Another change found in **animal model**s is that **physiological
softening**is**preceded by an increase in collagen solubility** (Read
and associates, 2007). This reflects a change in collagen processing
or a change in the number or type of covalent cross-links between
collagen triple helices which are normally required for
stable collagen fibril formation (Fig. 6-3) (Canty and Kadler,
2005). A reduction in cross-linking of newly synthesized collagen
may aid cervical softening because decreased transcripts and
activity of the cross-linking enzyme, lysyl oxidase, have been reported
in the mouse cervix during pregnancy (Drewes and associates,
2007; Ozasa and colleagues, 1981).
32
In humans, the clinical importance of these matrix changes is shown by the **greater prevalence of cervical incompetence** in women with inherited defects in collagen and elastin synthesis or assembly—for example,\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ and \_\_\_\_\_\_\_\_\_\_\_\_\_
Ehlers-Danlos and Marfan syndromes
33
To prepare for labor, the myometrial tranquility of phase 1 of parturition must be suspended through what has been called \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_. This process constitutes phase 2 and **represents a progression of uterine changes during the last 6 to 8 weeks of pregnancy.** Importantly, shifting events associated with phase 2 can cause either preterm or delayed labor. Thus, understanding myometrial and cervical modifications during phase 2 provides a better understanding of events leading to normal and abnormal labor..
Phase 2 of Parturition: Preparation for Labor
uterine awakening or activation
34
Myometrial Changes During Phase 2
Most myometrial changes during phase 2 prepare it for labor contractions. This shift probably results from **alterations in the expression of key proteins that control contractility.** These contraction- associated proteins (CAPs) include the ____________ (Smith, 2007).
oxytocin receptor, prostaglandin F receptor, and connexin 43
Note: Thus, myometrial oxytocin receptors markedly increase along with increased numbers and surface areas of gap junction proteins such as connexin 43. Together these lead to increased uterine irritability and responsiveness to uterotonins—agents that stimulate contractions.
35
Another critical change in phase 2 is
formation of the lower uterine segment from the isthmus. With this development, the fetal head often descends to or even through the pelvic inlet— so-called\_\_\_\_\_\_\_\_\_\_\_ The abdomen commonly undergoes a change in shape, sometimes described as “the baby dropped.” It is also likely that the lower segment myometrium is unique from that in the upper uterine segment, resulting in distinct roles for each during labor.
Note:This is supported by baboon studies that demonstrate differential expression of prostaglandin receptors within myometrial regions. There are also human studies that report an expression gradient of oxytocin receptors, with higher expression in fundal myometrial cells (Fuchs, 1984; Havelock, 2005; Smith, 2001, and all their colleagues).
lightening.
36
Cervical Ripening During Phase 2
Prior to the initiation of contractions, the cervix must undergo more extensive remodeling. This eventually results in cervical yielding and dilatation upon initiation of forceful uterine contractions in the third phase of parturition. Cervical modifications during this second phase principally involve **connective tissue changes**—so-called\_\_\_\_\_\_\_\_\_\_\_\_.
cervical ripening.
37
The transition from the softening to the ripening phase begins ___________ before onset of contractions. During this transformation, the total amount and composition of **proteoglycans and glycosaminoglycans** within the matrix are altered.
Many of the processes that aid cervical remodeling are controlled by the **same hormones regulating uterine function.** That said, the molecular events of each are varied because of differences in cellular composition and physiological requirements.
weeks or days
38
The uterine corpus is predominantly \_\_\_\_\_\_\_\_\_\_\_\_\_, whereas the cervix is primarily \_\_\_\_\_\_\_\_\_\_\_\_. Cellular components of the cervix include smooth muscle, fibroblasts, and epithelia.
smooth muscle
connective tissue.
Note: Because from the uterine, mucles will contract to push the baby and the cervix needs to dilate thats why it is primarily composed of collagen"
39
. During pregnancy, \_\_\_\_\_\_\_\_\_\_\_cells proliferate such that **endocervical glands** occupy a significant percentage of cervical mass by the end of pregnancy.
Endocervical Epithelia
40
The endocervical canal is lined with \_\_\_\_\_\_\_\_\_\_\_\_\_and \_\_\_\_\_\_\_\_\_\_\_\_\_, which protect against microbial invasion.
mucus-secreting columnar and stratified squamous epithelia
41
\_\_\_\_\_\_\_\_\_\_\_\_ function as sentinels that recognize antigens, respond in ways that lead to bacterial and viral killing, and signal to underlying immune cells when pathogenic challenge exceeds their protective capacity (Wira and co-workers, 2005).
Recent studies in mice suggest that cervical epithelia may also aid cervical remodeling by regulating tissue hydration and maintenance of barrier function. Hydration may be regulated by expression of **aquaporins**—water channel proteins, whereas paracellular transport of ion and solutes and maintenance of barrier function is regulated by tight junction proteins, such as claudins 1 and 2 (Anderson and colleagues, 2006; Timmons and Mahendroo, 2007).
Mucosal epithelia
42
Cervical Connective Tissue. The **cervix** is made up of only ___________ **percent smooth muscle** with the remaining tissue comprised **primarily of extracellular connective tissue. **
10 to 15
43
Cervical Connective Tissue. The cervix is made up of only 10 to 15 % percent smooth muscle with the remaining tissue comprised primarily of extracellular connective tissue. Constituents of the latter include\_\_\_\_\_\_\_\_\_\_\_\_\_.
type **I, III, and IV collagen,**
NMEM: 143 ILY
**glycosaminoglycans, proteoglycans, and elastin**
44
. This material is the **major component of the cervix** and it is largely responsible for its structural disposition.
Collagen
Collagen is the most abundant mammalian protein, and it has a complex biosynthesis pathway including at least six enzymes and chaperones to accomplish maturation (see Fig. 6-3). Each collagen molecule is composed of **three alpha chains**, which wind around each other to form **procollagen**. Multiple collagen triple-helical molecules are cross-linked to one another by the actions of lysyl oxidase to form long **fibrils.**
45
Collagen fibrils **interact with small proteoglycans** such as \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_. These interactions determine fibril size, packing, and organization so collagen fibrils are of uniform diameter and are packed together in a regular and highly organized pattern (Canty and associates, 2005).
**decorin or biglycan**, as well as matricellular proteins such as **thrombospondin 2**
46
During cervical ripening, collagen fibrils are\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
These changesmay result in part **from accumulation of poorly cross-linked
collagen**and**reduced expression of matricellular proteins.**
**Dispersion of collagen fibrils** leads to a **loss of tissue integrity **and **increased tissue compliance**.
disorganized, and there is increased spacing between fibrils.
47
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ are proteases capable of degrading extracellular matrix proteins. Of thes :e, collagenase members of the** thse family degrade collagen**.
NoteSome studies support a role of this in cervical ripening. But, others suggest that the biomechanical changes are not consistent solely with collagenase activation and loss of collagen. For example, Buhmschi and colleagues (2004)
performed tissue biomechanical studies in the rat and suggest
that ripening correlates with changes in the three-dimensional
structure of collagen rather than its degradation by collagenases.
Moreover, mouse and human studies document no changes in
collagen content between nonpregnancy and term pregnancy
(Akins, 2011; Myers, 2008; Read, 2007).
**Thus, it is likely that dynamic changes in collagen *structure*
rather than collagen content may regulate remodeling.**
This point is well illustrated in specialized microscopy images
of mouse and human cervical collagen (Zhang, 2012). In further
support, polymorphisms or mutations in genes required
for collagen assembly are associated with an increased incidence
of cervical insufficiency (Anum, 2009; Paternoster, 1998;
Rahman, 2003; Warren, 2007).
Matrix metalloproteases (MMPs
48
. These are **high-molecularweight polysaccharides** that complex with proteins to form proteoglycans. One glycosaminoglycan is \_\_\_\_\_\_\_\_\_\_\_, a carbohydrate polymer whose synthesis is carried out by hyaluronan synthase isoenzymes. **Expression of these enzymes is increased in the cervix during ripening** (Akgul, 2012; Osmers, 1993; Straach, 2005).
Glycosaminoglycans (GAGs)
hyaluronan (HA)
49
The functions of hyaluronans are dependent on size, and the breakdown of large- to small-molecularweight molecules is carried out by a family of hyaluronidase enzymes.
**Hyaluronidase** genes are expressed in both the mouse and **human cervix,** and increased hyaluronidase activity is reported in the mouse cervix at term (Akgul, 2012).
\_\_\_\_\_\_\_\_\_\_ predominates in the **mouse cervix during ripening** and has a **dynamic role to increase viscoelasticity and matrix disorganization**.
\_\_\_\_\_\_\_\_\_\_ has **proinflammatory properties**, and studies in mice and women reveal increased concentrations **during labor and in the puerperium**
Largemolecular- weight HA
Low-molecular-weight HA
50
The importance of regulated changes in HA size during cervical ripening and dilatation is supported by a study reporting hyaluronidase administration to the cervix for ripening in term pregnant women (Spallicci, 2007). Activation of intracellular signaling cascades and other **biological functions requires interactions with cell-associated HA-binding proteins such as \_\_\_\_\_\_\_\_\_\_\_\_** (Ruscheinsky, 2008).
**versican**
51
Expression of these enzymes is increased in the cervix during ripening (Akgul, 2012; Osmers, 1993; Straach, 2005).
The functions of hyaluronans are **dependent on size**, and the **breakdown of large- to small-molecularweight molecules is carried out by a family of hyaluronidase enzymes.**
Glycosaminoglycans
52
Hyaluronidase genes are expressed in both the mouse and **human cervix**, and **increased hyaluronidas**e activity is reported in the **mouse cervix at term** (Akgul, 2012). ____________ predominates in the mouse cervix during **ripening and has a dynamic role to increase viscoelasticity and matrix disorganization**.
Largemolecular- weight HA
53
\_\_\_\_\_\_\_\_\_\_\_ has proinflammatory properties, and studies in mice and women reveal **increased concentrations during labor and in the puerperium**
Low-molecular-weight HA
54
These glycoproteins are composed of a protein core and GAG chains.
Changes in the amount of core protein or in the number, length, or degree of sulfation of GAG chains can influence proteoglycan function. Although not well-defined, changes in proteoglycan composition are thought to **accompany cervical ripening**. At least three small leucine-rich proteoglycans are expressed in the cervix-----\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
—decorin, biglycan, and fibromodulin
55
In addition to the cervix, these proteoglycans are expressed in the ______ and ___________ Changes in expression levels may **regulate fetal membrane tensile strength** and **uterine function** (Meiner, 2007; Wu, 2012).
fetal membranes and uterus.
56
The marked changes within the extracellular matrix during cervical ripening in phase 2 are accompanied by **stromal invasion with inflammatory cells**. This has led to a model in which ____________ is considered an **inflammatory process.** As such, cervical chemoattractants attract inflammatory cells, which in turn **release proteases** that may aid **degradation of collagen and other matrix components**.
In phase 3 or 4 of parturition, there is increased cervical expression of chemokines and collagenase/ protease activity. It was assumed that processes **regulating phases 3 and 4 of dilation and postpartum recovery of the cervix were similar to those in phase 2 of cervical ripening** (Bokström, 1997; Osman, 2003; Sennström, 2000; Young, 2002).
NOTE :
This has been challenged by observations from both human and animal studies. Sakamoto and associates (2004, 2005) found no correlation between the degree of clinical cervical ripening and the tissue concentrations of cervical neutrophil-chemoattractant interleukin 8 (IL-8). Microarray studies comparing gene expression patterns at term before and after cervical ripening report little increase in expression of proinflammatory genes. In contrast, there is a robust increase in proinflammatory and immunosuppressive genes in the cervix after delivery compared with during cervical ripening (Bollapragada, 2009; Hassan, 2006, 2009).
cervical ripening
57
Induction and Prevention of Cervical Ripening
There are **no therapies to prevent premature cervical ripening.**
58
\_\_\_\_\_\_\_\_\_\_\_\_\_ is used to circumvent cervical insufficiency, although success appears limited.
Cervical cerclage
59
en, 2012). In contrast, treatment to **promote cervical ripening for labor induction includes direct application of** \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
prostaglandins **E2 (PGE2**) and **F2α (PGF2α).**
Note : Prostaglandins likely modify extracellular matrix structure to aid ripening. Although the role of prostaglandins in the normal physiology of cervical ripening remains unclear, this property is useful **clinically to assist labor induction** (Chap. 26, p. 526). In some nonhuman species, the cascades of events that **allow cervical ripening are induced by decreasing serum progesterone concentrations.** And in humans, **administration of progesterone antagonists causes cervical ripening.** As discussed later, humans may have developed unique mechanisms to localize decreases in progesterone action in the cervix and myometrium.
60
This phase is synonymous with **active labor**, which is customarily divided into **three stages**. These compose the commonly used labor graph shown in Figure 21-2.
Phase 3 of Parturition: Labor
61
The clinical stages of labor may be summarized as follows.
The first stage is the stage of **cervical effacement and dilatation.**
The second stage is the
stage of **fetal expulsion**.
third stage of labor is the stage of **placental
separation and expulsion.**
62
The first stage begins **when spaced uterine contractions of sufficient frequency, intensity, and duration are attained to bring about cervical thinning, or effacement.**
This labor stage ends when the cervix is fully dilated—about 10 cm—to allow passage of the term-sized fetus. The first stage of labor, therefore, is the stage of\_\_\_\_\_\_\_\_\_\_\_\_\_.
cervical effacement and dilatation.
63
64
The first stage begins when spaced uterine contractions of sufficient frequency, intensity, and duration are attained to bring about cervical thinning, or effacement.
. The first stage of labor, therefore, is the stage of cervical effacement and dilatation his labor ends [Next](https://www.brainscape.com/decks/3016798/cards/120372205/edit#)when\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
the cervix is fully dilated—**about 10 cm**—to allow passage of the term-sized fetus
65
The second stage begins when cervical dilatation is complete and ends with delivery. Thus, the second stage of labor is the stage of \_\_\_\_\_\_\_\_\_\_\_.
fetal expulsion
66
The second stage begins when cervical dilatation is _________ and \_\_\_\_\_\_\_\_\_\_\_. Thus, the second stage of labor is the stage fetal expulsion.
complete and ends with delivery
67
. Last, the third stage begins\_\_\_\_\_\_\_\_\_\_\_\_\_ Thus, the third stage of labor is the stage of placental separation and expulsion.
immediately after delivery of the fetus and ends with the delivery of the placenta.
68
. Last, the third stage begins immediately after delivery of the fetus and ends with the delivery of the placenta. Thus, the third stage of labor is the stage of\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
placental separation and expulsion.
69
First Stage of Labor: Clinical Onset of Labor
In some women, forceful uterine contractions that effect delivery begin suddenly
. In others, labor initiation is heralded by spontaneous release of a small amount of blood-tinged mucus from the vagina. This extrusion of the mucus plug that had previously filled the cervical canal during pregnancy is referred to as\_\_\_\_\_\_\_\_\_\_\_\_\_\_
“show” or “bloody show.”
70
There is very little blood with the \_\_\_\_\_\_\_\_\_\_\_, and its passage **indicates that labo**r is already in progress or likely will ensue in hours to days.
mucous plug
71
Uterine Labor Contractions
**Unique** among physiological muscular contractions, those of uterine smooth muscle during labor are \_\_\_\_\_\_\_\_\_.
painful
72
Uterine Labor Contractions Unique among physiological muscular contractions, those of uterine smooth muscle during labor are pain.
The cause of this is not known definitely, but several possibilities have been suggested:
(1) hypoxia of the contracted myometrium— such as that with angina pectoris;
(2) compression of nerve ganglia in the cervix and lower uterus by contracted interlocking muscle bundles
; (3) cervical stretching during dilatation; and
(4) stretching of the peritoneum overlying the fundus.
73
Of these, compression of nerve ganglia in the cervix and lower uterine segment by the contracting myometrium is an especially attractive hypothesis.
**Paracervical infiltration** with **local anesthetic** usually produces **appreciable pain relief with contractions** (Chap. 25, p. 509).
Uterine contractions are ________ and, for the most part, \_\_\_\_\_\_\_\_\_\_\_.
involuntary
independent of extrauterine control
74
Neural blockade from epidural analgesia **does not diminish their** **frequency or intensity**. In other examples, myometrial contractions in paraplegic women and in women after bilateral lumbar sympathectomy are normal but painless.
:)
" KHIT Sa PARALYZE NORMAL ANG CONTRACTION PERO PAINLESS
75
Mechanical stretching of the cervix enhances uterine activity
in several species, including humans. This phenomenon
has been referred to as the ___________ (Ferguson, 1941).
Its exact mechanism is not clear, and **release of oxytocin has
been suggested but not proven.**
Manipulation of the cervix and
“stripping” the fetal membranes is associated with an **increase
in blood levels of prostaglandin F2α metabolite (PGFM).**
Ferguson refleX
76
The interval between contractions diminishes gradually from approximately ____________ at the **onset of first-stage labor** to as little as\_\_\_\_\_\_\_\_\_\_ in the second stage.
10 minutes
1 minute or less
77
Periods of relaxation between contractions, however, are **essential for fetal welfare**.
Unremitting contractions compromise uteroplacental blood flow sufficiently to cause **\_\_\_\_\_\_\_\_\_\_\_\_\_**
**fetal hypoxemia.**
78
In \_\_\_\_\_\_\_\_\_\_\_\_\_, the duration of each contraction ranges from **30 to 90 seconds,** averaging about **1 minute**.
activephase laboR
79
There is appreciable variability in contraction intensity during normal labor. Specifically, **amnionic fluid pressures** generated by contractions during **spontaneous labor** average \_\_\_\_\_\_\_\_\_, but vary from \_\_\_\_\_\_\_\_\_\_\_
40 mm Hg
20 to 60 mm Hg
80
Distinct Lower and Upper Uterine Segments.
During active labor, the anatomical uterine divisions that were initiated in phase 2 of parturition become increasingly evident (Figs. 21-4 and 21-5). By abdominal palpation, even before membrane rupture, the **two segments can sometimes be differentiated.**
The ___________ is **firm** during contractions, whereas the \_\_\_\_\_\_\_\_\_\_\_\_\_\_ is **softer, distended, and more passive**.
upper segment
Lower segment
81
This mechanism is imperative because **if** the entire myometrium, including the lower uterine segment and cervix, were to contract simultaneously and with equal intensity, the **net expulsive force would be markedly decreased**
**.** Thus, the upper segment ___________ the fetus. In response to these contractions, the\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
**contracts, retracts, and expels**** **
**softened** lower uterine segment and **cervix dilate** and thereby form a **greatly expanded**, thinned-out tube through which the fetus can pass.
82
The myometrium of the\_\_\_\_\_\_\_\_\_\_\_ **does not relax to its original length after contractions**. Instead, **it becomes relatively fixed at a shorter length**. The upper active uterine segment contracts down on its diminishing contents, but **myometrial tension remains constant**. The net effect is to take up slack, thus **maintaining the advantage gained in expulsion of the fetus. **
Concurrently, the uterine musculature is kept in firm contact
with the uterine contents. As the consequence of retraction,
each successive contraction commences where its predecessor Left off.
Thus, the **upper part of the uterine cavity becomes slightly smaller with each successive contraction.** Because of the** successive shortening** of the muscular fibers, the **upper active segment becomes** **progressively thickened throughout first- and second-stage labor** (see Fig. 21-4). This process continues and** results in a tremendously thickened upper uterine segment immediately after delivery.**
upper segment
83
