Embryos - Pregnancy Flashcards
how does the uterus change during pregnancy
- myometrium grows markedly
- muscle fibres hypertrophy and increase in number
- 3 LAYERS OF MUSCLE
outer longitudinal
middle interlacing
inner circular
- CT becomes more vascular
uterus and pelvic floor changes
what is the upper uterine segment attached to
peritoneum is intimately attached to upper uterine segment
loose and mobile all over the segment
uterus supports hypertrophy
broad ligaments show hypertrophy of all their content
levatores anii muscles hypertrophy and become softer ⇒ pelvic floor becomes progressively more distensible, thereby facilitating passage of the foetus
change in uterine blood supply
blood supply increases
uterine and ovarian arteries become large and very tortuous
PROTECTIVE FUNCTION:
lymphatics, like BVs, increase in size and number
large lymph spaces beneath the decidua and a well developed plexus under the enveloping peritoneum
what happens from 2nd month onwards
describe blood supply by 9th month
hypertrophy of BVs and lymphatics produces progressive softening of whole body
by 9th month, the whole of uterus and outer pelvic viscera are so engorged with the blood and lymph that the outlines of the various organs become vague and difficult to define
size and position of uterus
how does the position of uterus change throughout pregnancy
non-pregnant uterus = 2.5x5.7.5cm
full term = 23x25x30cm
uterus lies in true pelvis at 1st but by week 12 the fundus is level with the top of the symphysis pubis
by week 16 it lies mid way between the symphysis pubis and the umbilicus
What might a woman experience towards the end of a pregnancy
lightening as the baby moves down
position of uterus @ 20 weeks and 24 weeks
change in position throughout pregnancy
20 weeks - below umbilicus
24 weeks - just above it
⇒ fundus rises 2 fingerbreadths every 4 weeks until 36 weeks when it lies @ xiphisternum
between 36 and 40 weeks it drops by 1 fingerbreadth per week and @ week 40 it lies at the same level that it had reached @ week 32
what causes the lightening in the last month
due to descent of foetal head into cavity of true pelvis
although the woman may feel more comfortable and may breathe more easily after lightening has occurred, she may notice frequency of micturition due to lack of space in the pelvis
role of cervix
passive role
cervical blood vessels and lymphatics hypertrophy thereby causing progressive softening which may be detected very early in pregnancy
connective and muscular tissues, although they both become more vascular and softer, they do not undergo hyperplasia
change in cervical mucosa
hypertrophies markedly until it constitutes nearly half of cervix @ full term
eventually, complex of glands resembles a honeycomb full of sticky tenacious mucus
when this protective mucus plug is expelled at onset of labour, it carries most of honeycombed mucosa with it
external os comes to have anterior and posterior lip, especially in multiparae
deep purple - engorged with blood
how does the isthmus and lower uterine segment change
approx upper 1/3 of cervix = isthmus
unaffected in 1st month of pregnancy
dilates and is taken up into body of uterus to form the lower uterine segment
the foetal membranes are less firmly blended with the mucosa in the isthmus than elsewhere
the endometrium lining the lower segment does not undergo a full decidual change
changes in vagina
similar to uterus
blood supply increases enormously - deep violet colour
hypertrophy of wall increases both length and width of vaginal canal
changes in vulva
undergoes similar changes - increased blood and lymphatic supply
progressive softening
changes in breasts
what happens at week 8
during the 1st 6 months - duct system proliferates
during the last 3 months - alveoli proliferate
also in alveoli, there is hypertrophy of BVs and lymphatics which supply them
WEEK 8 - Montgomery’s tubercles (mouths of enlarged sebaceous glands) become prominent in areola
WEEK 12 - darkening of primary areola occurs
WEEK 16 - a paler, secondary areola forms (more noticeable in dark-haired women)
abdominal viscera changes
what is a common complication of pregnancy
stomach is displaced upwards during the 2nd half of pregnancy
diaphragmatic herniation is a common complication of pregnancy
change in pelvis during pregnancy
symphyseal, sacroiliac and sacrococcygeal joint capsules soften and relax
reaches a maximum about week 28 and may cause sacroiliac back ache
may be accompanied by pain and tenderness in the symphysis
changes in skin
deposition of melanin occurs in certain areas in the body - particularly dark haired women
in midline of abdominal wall - linea nigra
chloasma uterinum
melanin deposition on forehead and cheeks
moulding
fetal cranium is relatively deformable
bones of calvaria are thin and elastic and can alter their shape to some extent
they are attached to 1 another by relatively loose fibrous sutures
they can override one another somewhat in response to compression forces as the head is squeezed down through the pelvis
this is limited
must be sufficient prior congruity to permit first engagement and then passage of foetus through the pelvic cavity
boundaries of pelvic inlet
angle it makes with pelvic floor
heart-shaped - bounded posteriorly by sacral promontory, laterally by iliopectineal line and anteriorly by symphysis pubis
plane of pelvic inlet makes an angle of 60° with that of pelvic floor
true conjugate diameter
measured from top of symphysis pubis to sacral promontory and averages about 4.5 inches
oblique diameter of pelvis
measured from sacroiliac joint to obturator foramen of opposite side and averages 4.75 inches
transverse diameter of pelvis
widest measurement from side to side and averages 5.25 inches
boundaries of pelvic cavity
measurement of diameters
bounded anterioly by symphysis pubis and posteriorly by sacrum and coccyx
diameter is usually taken at the level of junction of 2nd and 3rd sacral vertebrae posteriorly and middle of symphysis anteriorly
anteroposterior, oblique and transverse = 12cm
pelvic outlet boundaries
outlet is bounded by pubic arch anteriorly, by ischial tuberosities and sacroiliac ligaments laterally and tip of coccyx posteriorly
anteroposterior diameter of pelvic outlet
measured from lower border of symphysis pubis to the sacroiliac joint
5.25 inches
transverse diameter of pelvic outlet
bituberous
taken between the lower borders of ischial tuberosities
4.25 inches
subpubic angle - pelvic outlet
bounded by the pubic rami and symphysis
86°
how is the inlet divided
into forepelvis and hindpelvis by the widest transverse diameter
walls of hindpelvis include that portion of the ilium overlying the sacroiliac notch - one of the most variable sections in the pelvis and this region is most affected by sexual and evolutionary differences
how is the outlet divided
anterior and posterior segments by intertuberous diameter
what influences the capacity of anterior segment (of pelvic outlet)
subpubic arch
either wide, moderate or narrow
its shape depends on the curve of the inferior pubic rami and is usually well curved in the female pelvis and straight-edged in male pelvis
side walls
may incline toward or away from one another or may be parallel as they pass downward
depth of pelvis
taken from iliopectineal line along the back of the obturator foramen to ischial tuberosity
what influences the capacity of posterior segment of pelvic outlet
width of greater sciatic notch
sacral curve and inclination
the greater the upward and backward tilt of the lower end of the sacrum, the more room there is in the lower pelvis for passage of the foetal head
the degree to which the ischial spines project inward
anatomical changes during normal labour - primigravida (first pregnancy)
head normally becomes engaged in pelvic inlet by week 37 or 38 of pregnancy
anatomical changes during normal labour - multipara
engagement may not occur until the membranes rupture at the end of 1st stage of labour
first stage of labour
rhythmic uterine contractions increase markedly in strength, freq and duration
typically experienced as pain, beginning in sacral region and passing around to the front of the abdomen, rising to a climax and then fading way
Associated with the success of contraction and retraction of the upper uterine segment, the lower uterine segment becomes progressively thinner and the cervix dilates
This leads to detachment of the mucosa lining the lower uterine segment with rupture of the small blood vessels attaching it to the uterine wall
Forewaters are formed
SHOW = the blood that has been shed mixes with the mucosa of the cervical plug, which separates at the same time, to form this blood-stained mucous discharge
Effacement
cervical dilation
internal os of the cervix and the cervical canal are gradually “taken up” - merge with the cavity of the lower uterine segment
this process is completed by dilation of external os
where are the pacemakers and what do they do
one on each side at the uterine end of each uterine tube
drive uterine contractions
sequence of uterine contractions
Increasing strength
maximum
quick decline
period of rest
some of the shortening of a muscular contraction is permanently maintained
retraction
progressive process
occurs throughout upper uterine segment but mainly at the fundus
with each contraction, traction is applied to the relatively passive lower segments and through it to the cervix
at the same time the forewaters and the presenting part are forced downwards
retraction and the upper segment
retraction causes the upper segment to progressively thicken and the lower segment to stretch
Bandi’s ring
junction of upper segment (which is progressively thickening)
and the lower segment (which is stretching)
how is the birth canal formed
stretching and expansion of lower segment
effacement and dilation of cervix
all converts the cavities of the uterus, cervix and vagina into a single unit
when is formation of birth canal complete
by the end of the 1st stage
a low resistance pathway down which the foetus may be driven by the upper uterine segment
what contributes to membrane rupture
membranes begin to degenerate
increasing pressure exerted by retraction of upper segment
removal of support from below as a result of cervical dilation
difference between effacement with primigravida vs multigravida
2nd stage of labour
expulsion of foetus from full dilation of foetus until the child has been delivered
force is provided by the contraction and retraction of the upper uterine segment
After the membrane ruptures, uterine contractions become stronger, more frequent and more sustained
As the liquid drains away, the force of the uterine contractions is applied directly to the fetal breech
from the breech the force is transmitted to the foetal spinal column and from there to the foetal head
change in position of uterus during 2nd stage
uterus rears forward, straightening out the curve of the foetal spine, resulting in elongation of the foetus which is an additional aid to its descent
what happens to the anterior pelvic structures in the 2nd stage of labour
e.g. urethra, bladder and anterior vaginal wall
drawn upward out of the path of the descending foetus by contraction and retraction of the upper uterine segment -transmitted by the elastic tissues of the lower segment and intervening connective tissue
movement is facilitated by extensive softening of pelvic tissues late in pregnancy
posterior pelvic structures in the 2nd stage of labour
posterior vaginal wall, rectum, anal canal, levator ani muscles
forced downward and backward
foetal head during descent
rotates
3rd stage of labour
separation and expulsion of placenta and membranes
transverse caesarean incision
indications for caesarean section
ectopic pregnancies
implantation does not occur in upper part of uterine wall (which is usual)
epithelium of foetal lungs @ 24 weeks
cuboidal
gases cannot diffuse across
cells that produce surfactant
type I pneumocytes
type II pneumocytes
