Anatomy/Physiology of Labor & Birth Flashcards
primary cause is collagen rearrangement. Modulated by inflammatory and hormonal influences accompanied by increase in water content. Triggered by increase in inflammation, oxytocin, and prostaglandin activity. Traction on the cervix from uterine contractions may contribute prior to onset of labor.
cervical ripening
“cephalic, breech, shoulder” are fetal __________
presentations
flexion of fetal head in labor results in:
the presentation of a smaller diameter
restitution occurs as a result of:
untwisting of the neck
An inlet with a short anteroposterior diameter and a wide transverse diameter is characteristic of which pelvic type?
plattypeloid
The positional changes the fetus undergoes to accommodate itself to the maternal pelvis
mechanisms of labor
- ->lowest level of the presenting part has reached the level of the ischial spines
- ->Biparietal diameter has reached the inlet
engagement
The sagittal suture of the fetal head lies between:
the parietal bones
to deterimine position of the fetus, the midwife identifies:
the sagittal suture
to determine the attitude of the fetus, the midwife identifies:
the cephalic prominence
to determine station of the fetus, the midwife would:
palpate the ischial spines
flexion is a fetal __________
attitude
Extension of the fetal head during labor results in:
Pivoting of the head under the symphysis pubis
Pivoting of the head under the symphysis pubis
effacement
Cervical os widens. Force of contraction plus hydrostatic action of amniotic fluid or pressure from presenting fetal part promotes dilation on the softened/low resistance cervix
dilatation
hormone that inhibits contractions
progesterone
Uterotropin that causes uterine myometrial cells to express receptors for prostaglandins and oxytocin and develop gap junctions
estrogen
Uterotropin and uterotonin that facilitate contractions, increase myometrial sensitivity to oxytocin, and stimulates formation of gap junctions.
prostaglandins
Uterotonin that is released in pulsatile fashion, peaks with fetal ejection reflex.
oxytocin
receptors in the myometrium that stimulate smooth muscle contractions. The binding of these receptors results in Prostaglandin production in decidua
oxytocin receptors
transmembrane proteins that create a line of communication between two adjacent myocytes. Action potentials that initiate contractions travel through these to create a synchronized contraction
gap junctions
middle layer of the uterine wall, consisting mainly of uterine smooth muscle cells (also called uterine myocytes), but also of supporting stromal and vascular tissue. Its main function is to induce uterine contractions.
Myometrium
phase with increased myometrial excitability and responsiveness to substances that stimulate ctx due to estrogen influence, cells express receptors for prostaglandin and oxytocin and develop gap junctions.
activation phase
Changes in oxytocin receptor _____________ (rather than production and release of oxytocin) is the primary influence on the strength and frequency of contractions. Prolonged or repeated stimulation of receptors contribute to downregulation, reducing number of receptors available -> less forceful/less frequent contractions
number and sensitivity
contractions start in the __________
fundus
contractions 1) start in the fundus, 2) last longer in the fundus, 3) progress from fundus to isthmus. Muscle bundles in fundus shorten w/ contractions, upper portion of uterus thickens. Reduced fundal capacity promotes descent of the fetus. Lower segment muscles become longer and more flexible to accommodate the fetus.
Triple descending gradient
contractions last longer in the __________
fundus
contractions progress from _________ to ________
fundus to isthmus
period in late pregnancy of uterine inactivity. Inhibitors of uterine contractions include progesterone, prostacyclin, relaxin, nitric oxide, and other hormones
Quiescence
period of pregnancy where uterotropins (estrogen) stimulate upregulation of myometrial receptors for oxytocin and prostaglandins, and turning on of gap junctions between myometrial cells
activation
period of pregnancy where uterotonins (oxytocin and prostaglandins) promote labor progression
stimulation
during labor, maternal BP:
increases during ctx and returns to baseline in between
_______ increases an additional 10-15% in first stage labor and as much as 50% in secod stage
cardiac output
____________ decreases as contraction intensity and duration increases
placental blood flow
Increase in _____________ in second stage due to pushing, prompting PNS stimulation during Valsalva.
central venous pressure
joint that connects the sacrum with the coccyx
sacrococcygeal symphysis
the bony passageway through which the fetus must maneuver to be born vaginally…below the linea terminalis
true pelvis
above the linea terminalis, includes iliac fossa and iliac crests
false pelvis
invisible line that runs along the pelvic brim from the top of the symphysis pubis around to the sacral promontory
linea terminalis
primary portion of the levantor ani. Originates at posterior border of the symphysis pubis and sweeps back to insert on lateral margins of coccyx.
pubococcoygeus
Attach posteriorly to central tendinous point on perineum, anteriorily inters to corpus cavernous of the clitoris, laterally surround orifice of the vagina and cover vestibular bulbs and Bartholin glands on either side
Bulbocavernosus (2)
Arise from inner and anterior surfaces of the ischial tuberosity of the superior ramus of the ischium by a small tendon. They insert into the central tendinous point of the perineum.
Superficial transverse perineal (2)
Midline between vagina and anus. Point of fusion for both superior and inferior fascia of the urogenital diaphragm. Common point of attachment for Bulbocavernosus, superficial transverse perineal, and pubococcoygeus.
Central tendinous point of the perineum (a fibromuscular structure)
Perineal innervation occurs via the _____________ and its branches
pudendal nerve
pudendal nerve originates from:
S2, S3, and S4.
__________ nerve also innervates the levator ani, rectal sphincter, skin of the vulva and lower portion of the vagina, and muscles of the urogenital diaphragm
pudendal nerve
obstetric conjugate (what the fetus must pass through) is 11 cm
pelvic inlet
least amount of room, where arrest of labor usually occurs. Extends from apex of suprapubic arch, through ischial spines, to the junction of the 4th and 5th sacral vertebrae.
midplane
obstetric diameter is 11.5 cm. Flexibility of the coccyx allows it to be pushed out of the way by the presenting part.
pelvic outlet
type of pelvis that is commonly known as the “female pelvis” because inlet and midplane are adeqate in all diameters, the posterior segment is broad and roomy, forepelvis is well-rounded, AP is long, transverse is adequate, pelvic arch is 90 degrees, and capacity is adequate
gynecoid
type of pelvis inlet:
Android Adequate anterorposterior and transverse diameters. Very short and inadequate posterior sagittal diameter. Long anterior sagittal diameter. Shallow posterior segment w/ reduced capacity. Narrow, sharply angled forepelvis. Reduced in all diameters. Short AP, narrow transeverse. 70 degree pelvic arch. Reduced capacity.
android
type of pelvis inlet:
Long anteroposterior, posterior sagittal, and anterior sagittal diameters. Adequate but short transverse. Deep posterior and anterior segments.
anthropoid
type of pelvis midplane:
Long AP diameter, all other adequate. Overall capacity adequate.
anthropoid
type of pelvis midplane:
Reduced in all diameters.
android
type of pelvis midplane:
Adequate in all diameters.
gynecoid
type of pelvis inlet:
Short anteropsterior, posterior and anterior sagittal diameters. Long transverse. Shallow posterior and anterior segments.
platypelloid
type of pelvis midplane:
Short AP, AS, and AS diameters. Wide transverse. Overall capacity reduced
platypelloid
type of pelvis outlet:
Short AP, wide transverse. Very wide arch. Inadequate capacity.
platypelloid
type of pelvis outlet:
Short AP, narrow transeverse. 70 degree pelvic arch. Reduced capacity.
android
type of pelvis outlet:
Long AP, adequate transverse. Normal or narrow arch. Adequate capacity.
anthropoid
two types of pelvis that are adequate for vaginal birth
gynecoid, anthropoid
relationship of the long axis on the fetus to the long axis of the pregnant person.
“longitudinal, transverse, oblique”
lie
The part of the fetus that lies over the pelvic inlet
- cephalic or head first
- breech or pelvis first
- shoulder.
presentation
the posture of the fetus, specifically the degree of flexion or extension of the head.
attitude
relationship of the denominator to the front, back, or sides of the pregnant pelvis
position
sagittal suture is located midway between the symphysis pubis and the sacral promontory
synclitism
fetal neck is tilted so that so that the fetal head leans laterally toward the fetal shoulder
asynclitism
when the anterior parietal bone (the one closest to the symphysis) becomes the lowest/leading part due to the flexion of the head toward the sacral promontory
anterior asynclitism
when the posterior parietal bone (the one closest to the sacral promontory) becomes the lowest/leading part as a result of lateral flexion toward the symphysis
posterior asynclitism
Ways that ___________ assists in labor:
during normal labor, the head enters the pelvis with a moderate degree of posterior asynclitism and then changes to anterior as it descends farther into the pelvis before the mechanism of internal rotation occurs. This is an accommodation by the fetus to take advantage of the roomiest parts of the true pelvis.
asynclitism
How ___________ impedes labor;
if the head remains asynclitic as it continues to descend in the pelvis internal rotation may be prevented.
asynclitism
portion of the fetal head that is first encountered on 4th leopold maneuver
cephalic prominence
engagement descent flexion internal rotation extension restitution external rotation
mechanisms of labor for birth in the occiput anterior position
engagement descent flexion internal rotation 8flexion followed by extension* restitution external rotation
mechanisms of labor for birth in the occiput posterior position
long arc from LOP to ROP/ OA=
135 deg
short arc from LOP to ROP/ OP=
45 deg
occurs when the biparietal diameter passes through the pelvic inlet
engagement
Allows the smaller suboccipitobregmatic diameter to be the widest fetal head diameter that transverses the pelvis
flexion
brings anteroposterior diameterof the fetal head into alignment with the anteroposterior diameter of the pelvis
internal rotation
allows the head to follow the curve of Carus and move under the symphysis pubis
extension
neck turns back so head is at a right angle with shoulders. Sagittal suture is in one oblique diameter of pelvis, shoulders in the other
restitution
shoulders rotate 45 degrees, bringing shoulders into alignment with AP diameter of pelvic outlet
external rotation
birth of shoulders by lateral flexion
expulsion
change in shape of the fetal head d/t the soft skull bones overriding/overlapping one another so that movement is possible at the location of the sutures
molding
formation of an edematous swelling over the most dependent portion of the presenting fetal head. Crosses sutures lines as generalized swelling (different than hematoma)
caput succadaneum
bleeding beneath the periosteum. May occur over more than one cranial bone but is limited to each individual bone and does not cross sutures.
Cephalohematoma
how to determine ____________:
2nd leopold maneuver. Firm, convex, continuously smooth and resistant mass extending from breech to neck.
fetal back
a neutral fetal head and spine. The head is neither extended nor flexed, and the spine is neither arched nor curved (This is a fetus with excellent posture!). This attitude features the top of the head, the middle part of the vertex, as the presenting part.
military attitude
cardinal movement that occurs at the mid-plane of the pelvis
internal rotation
corresponds with the internal rotation of the shoulders
external rotation
plane of the pelvis where engagement occurs
inlet
the head negotiates this during extension
outlet
when the sagittal suture is closer to the sacrum
anterior asynclitism
when the posterior parietal bone enters the pelvis first
posterior asynclitism
when the sagittal suture is closer to the symphysis pubis
posterior asynclitism
asynclitism interferes with this cardinal movement
internal rotation
this makes the diameter of the fetal head smaller at the inlet
asynclitism
central hormone leading to uterine quiescence. When progesterone dominates, labor onset it prevented.
progesterone
Plays a central role in activation of labor (phase 1). It is a uterotropin-a hormone that facilitates initiation of labor.
estrogen
under influence of this, uterine myometrial cells express receptors for prostaglandins and oxytocin and is necessary for development of gap junctions.
estrogen
Plays a role in labor activitation and acts as a uterotropin by increasing myometrial sensitivity to oxytocin and stimulating the formation of gap junctions
prostaglandins
Promotes decreased collagen content in the cervix leading to cervical softening and effacement
prostaglandins
produces by uterine decidua and promotes uterine contractions
prostaglandins
when bound to receptors in the uterus causes contractions. It also leads to production of prostaglandins in the uterine decidua
oxytocin
Increase dramatically in last weeks of pregnancy. Changes in number and sensitivity are the primary influence on the strength and frequency of contractions in active labor-not the production and release of oxytocin
oxytocin receptors
allow communication between muscle fibers that allows for effective coordination of contractions
Gap junctions
thing needed for both onset of labor and effective progress of labor
Gap junctions
quiescence active hormones
progesterone, nitric oxide, relaxin, prostacyclin
activation phase hormones
estrogen, prostaglandins
stimulation phase hormones
oxytocin, prostaglandins
