Chapter 17: The Use of Ultrasound in the First Trimester Flashcards
minimizing the risk of ultrasound induced bioeffects by controlling acoustic output, scan modes, machine settings, and duration of exposure
ALARA
the membrane enclosing the amniotic cavity and embryo or fetus
amnion
An early gestation consisting of a thin outer layer of cells (trophoblast), a fluid-filled cavity, and an inner cell mass (embryoblast)
Blastocyst
the membrane around the chorionic cavity, made up of trophoblast cells and extraembryonic mesoderm
chorion
Bud-like outward growths from the trophoblast, some of which will give rise to fetal portion of placentra
chorionic villi
the duration of pregnancy, counted from fertilization (conception), expressed in hours or days; also called embryonic age or postovulatory age
conceptual age
The product of fertilization, including all stages from zygote fetus
conceptus
the progesterone-secreting structure formed by a follicle after releasing its oocyte
corpus luteum
measurement of the long-axis of an embryo; used to determine the gestational age
crown-rump length
changes in the endometrium to allow implantation of a blastocyst
decidualization
due date calculated by adding 280 days to the first day of the last menstrual period; also called estimated date of confinement
estimated date of delivery
a group of hormones, primarily produced in the ovaries, which affect secondary sex characteristics and the menstrual cycle
estrogen
penetration of an oocyte by a sperm to form a diploid zygote
fertilization
0th day (the first day of LMP) to the end of the 13th week
first trimester
A hormone produced in the anterior pituitary which stimulates the maturation of ovarian follicles
follicle-stimulating hormone (FSH)
haploid cell that, when merged with a gamete from the opposite sex, creates a diploid xygote
gamete
the duration of pregnancy counted from the first day of the LMP, expressed in weeks and days or fractions weeks.
gestational age
the first sonographic evidence of an intrauterine pregnancy, the fluid-filled blastocyst
gestational sac
the number of times a woman has been pregnant
gravidity
a hormone produced by trophoblast cells of the blastocyst, which extends the life of the corpus luteum in the ovary; most pregnancy tests are based on the detection of hCG
human chorionic gonadotropin
the first day of the last menstrual period
LMP
A hormone produced in the anterior pituitary, which triggers ovulation in females
luteinizing hormone
an average diameter of the gestational sac used to determine the gestational sac
mean sac diameter
the solid cluster of undifferentiated cells formed by repeated cleavages of the single cell that resulted from the fusion of two gametes
morula
calculation to find a patient’s EDD. (1) take LMP (2) add 1 year (3) subtract 3 months (4) add 7 days
Naegeles Rule
subcuteaneous fluid in the posterior region of the neck of embryos and fetuses up to 14 weeks gestational age.
Nuchal translucency
female gamete (also called ovum or egg)
oocyte
a summary of a woman’s pregnancy outcomes
parity
a protein produced by the trophoblasts, abnormal levels of which may be associated with an increased risk of chromosomal abnormalitites
Pregnancy-associated plasma protein
a hormone produced by the corpus luteum and the placenta
progesterone
14th week to the end of the 27th week
second trimester
male gamete
spermatozoa
28th week to delivery
third trimester
a structure within the cavity of the blastocyst, which provides nourishment to the embryo and produces its first blood cells; the secondary umbilical vesicle (yolk sac) is the first structure to be sonographically identified within the gestational sac
umbilical vesicle
a single cell resulting from the fusion of two gametes
zygote
a small gestational sac (2-5 mm) is seen within the endometrium, adjacent to the uterine cavity interface
4 weeks 3 days - 5 weeks 0 days
umbilical vesicle (yolk sac) can be seen within the chorionic cavity
5 weeks 1 day - 5 weeks 5 days
an embryonic pole measuring 2-4 mm may be identified adjacent to the yolk sac
5 weeks 6 days - 6 weeks 0 days
The yolk sac is clearly separate from the embryo. cardiac activity is visualized by the time the embryonic pole measures 5mm. It may be possible to distinguish the head from the body.
6 weeks 1 day - 6 weeks 6 days
the yolk sac is seen in the chorionic cavity, whereas the amniotic membrane clearly encloses the embryo in the amniotic cavity
7 weeks 0 days - 7 weeks 6 days
The crown rump length is between 17-23 mm. The embryonic forebrain, midbrain, and hindbrain can be identified, and limbs become evident. The physiologic herniation of the midgut may also be visible.
8 weeks 0 days - 8 weeks 6 days
cerebral hemispheres become more distinct, and echogenic choroid plexus can be seen within the lateral ventricles, hands and feet can be visualized
9 weeks 0 days -10 weeks 0 days
mean sac diameter equation
MSD = (length x width x height)/3
gestational age in days equation
menstrual age in days = MSD + 30
CRL gestational age equation
CRL in cm + 6
EDD Naegele’s Rule equation
EDD = LMP - 3 months + 7 days
The fetus must be in the _______ plane for NT measurement.
midsagittal
The ____ must be seen as separate from the NT line.
amnion
single cell with genetic components derived from its mother and father will develop into a complex organism
first trimester
period in which most spontaneous losses occur
first trimester
contain two sets of cells 23 from mom and 23 from dad
diploid cells
new cells form through a process of duplication and division
results in two cells with same number of chromosomes as the cell from which they derive
mitosis
reduces the number of chromosomes, resulting in haploid cells containing a single set of 23 chromosomes
meiosis
male gamete; sperm
spematozoa
female gamete; oocyte
ova
Where does sperm development occur?
seminiferous tubules of the tests
Where is the haploid sperm stored?
epididymis
Each mature sperm contains a ____ and a _____.
head, tail
contains cell nucleus, topped with a hat-like acrosome with enzymes capable of penetrating the outer layer of an ovum
head
contains mitochondria to power the whip-like motion that creates sperm motility
tail
spermatozoa and fluid produced in seminal vesicles, prostate, and bulbourethral glands are pumped through the urethra of the penis and deposited in the vagina at the external os of the cervix
ejaculation
Where is FSH produced at?
pituitary gland
Rising levels of ______ causes pituitary gland to release LH.
estrogen
What hormone triggers ovulation?
LH
membrane surrounding haploid cell
zona pellucida
corona radiata
usually occurs in ampullary portion of fallopian tube 24-36 hours after ovulation
fertilization
single diploid cell
conceptus or zygote
rapid division of cells; begins 24-30 hours after fertilization
cleavage
solid cluster of cells; reaches uterine cavity about 4 days after fertilization
morula
3 parts of blastocyst
trophoblast
blastocele
embryoblast
thin outer layer of cells, part of which will give rise to embryonic potion of placenta
trophoblast
fluid-filled blastocystic cavity
blastocele
inner cell mass, will develop into embryo
embryoblast
two layers of endometrium
thin basal layer adjacent to myometrium
functional layer of connective tissue (stroma), glands, and capillaries, which are covered by a thin layer of epithelial cells
After ovulation, the corpus luteum produces progesterone which causes _______ of endometrial cells, allowing implantation to occur
decidualization
the period during which the endometrium is able to receive the blastocyst, begins 6-8 days after ovulation, lasts approximately 4 days
implantation window
two layers of trophoblast cells
inner cytotrophoblast, outer mass synctiotrophoblast
Three distinct layers of decidualized endometrium
decidua basalis
decidua capsularis
decidua parietalis or decidua vera
point of attachment by blastocyst, contributes maternal portion of placenta
decidua basalis
closes over and surounds burrowing blastocyst
decidua capsularis
lines remainder of endometrial cavity
decidua parietalis
formed by cells of the hypoblast and adjoining cells lining exocoelmic cavity ; commonly known as the yolk sac
primary umbiclic vesicle
first structure sonographically visualized within the gestational sac
secondary yolk sac
slender connection eventually connects umbilical vesicle to embryonic midgut; provides nourishment to conceptus and produces embryos first blood cells
vitelline duct
Blood cells are carried to and from the embryo via ______.
vitteline veins and arteries
extension of umbilical vesicle; protrudes into connecting stalk forming urachus
allantois
membrane around chorion cavity
chorion
chorionic sac
gestational sac
3 germ cell layers of embryonic disc
embryonic mesoderm
embryonic endoderm
embryonic ectoderm
flows into spaces between villi via endometrial spiral arteries; drained by endometrial veins
maternal blood
from branches of umbilical veins and arteries extend into villi
fetal capillaries
urine pregnancy tests
qualitative
blood pregnancy tests
quantitative
round anechoic structure surrounded by a highly reflective echogenic ring
gestational sac
The gestational sac measures ___ mm in diameter at 5 weeks.
2.3
appearance of small sonolucent amniotic sac, yolk sac, and developing embryo
“double bleb sign”
first organ to function in embryo
heart
The primitive heart begins to beat about ____ days after conception.
23
The most cranial section of neural tube forms:
brain and rest of neural tube forms spinal cord
embryonic brain develops three vesicles:
prosencephalon
mesencephalon
rhombencephalon
also known as embryonic forebrain; gives rise to telencephalon and diecephalon
prosencephalon
