Embryonic Development, Pregnancy Dating, Maternal Adaptations to Pregnancy Flashcards
process of gametogenesis
development of gametes (when haploid male or female germ cell is able to unite with another of the opposite sex in sexual reproductive to form a zygote); oogenesis or spermatogenesis
meiosis vs mitosis
meiosis: a process of two successive cell divisions, producing cells, egg, or sperm that contain half the number of chromosomes found in somatic cells
mitosis: type of cell division of somatic cells in which each daughter cell contains the same number of chromosomes as the parent cell
oogenesis vs spermatogenesis
OOGENESIS: developmental process by which the mature human ovum is formed; haploid number of chromosomes
SPERMATOGENESIS: formation of mature functional spermatozoa; haploid number of chromosomes
haploid = how many chromosomes?
23 (i.e. half of 46)
what is the definition of fertilization?
union of ovum and spermatozoan; usually occurs in the fallopian tube within minutes or no more than a few hours of ovulation
most pregnancies occur when intercourse occurs within how many days of ovulation?
2 days
the stages of development
1. zygote
2. blastomeres
3. morula
4. blastocyst
5. embryo
6. fetus
7. conceptus
- zygote: diploid cell with 46 chromosomes; results from the fertilization of the ovum by the spermatozoan
- blastomeres: mitotic division of the zygote (cleavage) yields daughter cells called blastomeres
- morula: the solid ball of cells formed by 16 or so blastomeres; mulberry-like ball of cells that enters the uterine cavity 3 days after fertilization
- blastocyst: after the morula reaches the uterus, a fluid accumulates between blastomeres, converting the morula to a blastocyst; the inner cell mass at one pole becomes the embryo, the outer cell mass becomes a trophoblast
- embryo: stage in prenatal development between the fertilized ovum and the fetus (i.e., between second and eighth weeks inclusive)
- fetus: the developing conceptus after the embryonic stage
- conceptus: all tissue products of cepception: embryo (fetus), fetal membranes, and placenta
physiology of implantation of the blastocyst
-definition
-how many days after fertilization does implantation occur?
-definition: blastocyst adheres to the endometrial epithelium by gently eroding between the epithelial cells of the surface endometrium; invading trophoblasts burrow into the endometrium; the blastocyst becomes encased and covered by the endometrium
-implantation occurs 6-7 days after fertilization and is usually in the upper, posterior wall of the uterus
-provides physiologic exchange between maternal and embryonic environment prior to full placental function
differentiate between
1. the chorion
2. the chorion frondosum
3. chorion laeve
- chorion- an extra-embryonic membrane that, in early development, forms the outer wall of the blastocyst
- chorion frondosum- outer surface of the chorion whose villi contact the decidua basalis; the placental portion of the chorion
- chorion laeve- smooth, non villous portion of the chorion
what develops from the chorion?
- chorionic villi- which establishes an intimate connection with the endometrium
what does the chorionic villi give rise to?
the placenta
what is the synctriotrophoblasts of the chorionic villi of the placenta doing?
making contact with maternal blood or decidua
decidua capsularias vs decidua basalis vs decidua parientalis (vera)
-capsularias: part of the decidua that surround the chorionic sac
-basalis: part of the uterine decidua that unites with the chorion to form the placenta
-parientalis (vera): the endometrium during pregnancy, except at the site of the implanted blastocyst
amnion is defined as…
the innermost fetal membrane; a thin, transparent sac that holds the fetus suspended in the amniotic fluid; it grows rapidly at the expense of the extra-embryonic coelom; by the end of the third month, it fuses with the chorion, forming the amniochorionic sac, commonly called the “bag of waters”
placental function…
- serves as fetal lungs, liver, and kidneys until birth while growing and maintaining the conceptus in a balanced, healthy environment
anatomy of the placenta includes…
a. trophoblasts
b. chorionic villi
c. intervillous spaces
d. chorion
e. amnion
f. decidual plate
trophoblasts of the placenta produce what 5 steroid hormones? what is each steroids function in pregnancy?
- estradiol-17B: responsible for the growth of the uterus, fallopian tubes, vagina, and breast development
- estriol- estrogen metabolite excreted by the placenta during pregnancy; found in urine of pregnant women
- progesterone- secreted by corpus luteum; essential in preparing the uterus for implantation of the fertilized ovum and maintaining the pregnancy
- aldosterone- responsible for regulation of the body’s salt and water balance
- cortisol- plays a role in the metabolism of fats, glucose, and proteins
there are 9 protein and peptide hormones produced by the placenta including…
- Human placental lactogen (hPL): placental hormone that inhibits maternal insulin activity during pregnancy; decreases to undetectable levels after delivery of placenta
- Human chorionic gonadotropin (hCG): hormone secreted by the placenta to help maintain corpus luteum function and production of progesterone; found in serum and urine as early as a week after conception
- placental adrenocorticotropin hormone (ACTH): plays a role in regulation of the secretion of glucocorticoids
- Pro-opiomelanocortin: precursor polypeptide
- chorionic thyrotropin: a type of hormone similar to TSH that has the ability increase metabolism
- growth hormone variant: plays vital role in growth control
- parathyroid hormone: related protein (PTH-rP)- essential for bone differentiation and formation/development of mammary glands
- Calcitonin: hormone responsible for calcium balance
- Relaxin: produced in placenta and corpus luteum; believed to help with relaxing the uterine myometrium during pregnancy
placental hypothalamic-like releasing and inhibiting hormones
1. TRH
2. GnRH
3. CRH
4. Somatostatin
- TRH/Thyrotropin-releasing hormone: responsible for TSH regulation
- GnRH: controls secretion of LH and FSH
- CRH/Coricotropin-releasing hormone: works with vasopressin hormone to regulate release of ACTH
- Somatostatin: inhibits release of growth hormone, prolactin, and thyrotropin
how are oxygen and glucose transported across the placenta
via facilitated diffusion (protein channels help sugars pass through!) oxygen is small and nonpolar so can easily cross membrane
umbilical cord anatomy
-size in cm
2 arteries, 1 vein
arteries: carry fetal deoxygenated blood to the placenta
one vein: carries oxygenated blood from the placenta to the fetus
.8 - 2 cm in diameter, 55 cm on avg in length; with range of 30-100 cm
what is Wharton’s jelly
extracellular matrix consisting of specialized connective tissue that serves as protection for the umbilical cord
extremely short umbilical cord is associated with…
abruptio placentae or uterine inversion
abnormally long umbilical cord is associated with
vascular occlusion by thrombi and true knots
polyhydramnios
-AFI>
-s/sx
-excess amniotic fluid
-50-60% are idiopathic
-an AFI > 24 cm or max vertical pocket > 8 cm
-SX: uterine size > EGA, difficulty auscultating fetal HR
how is amniotic fluid produced? how is it maintained?
-production: by amniotic epithelium; water transfers across amnion and through fetal skin; in second trimester fetus starts to swallow, urinate, and inspire amniotic fluid
-maintenance: fetal swallowing is critical; polyhydramnios is consistently present when fetal swallowing is INHIBITED;
diagnosis of polyhydramnios
-physical findings
-u/s findings
-fundal height measurements that are 3-4 cm greater than normal (warrants u/s)
-u/s: AFI > 24 cmw
what has hydramnios been linked to… (many things)
-fetal macrosomia
-PTL
-risk for PP hemorrhage (higher given the uterus is enlarged)
-increased risk for cord prolapse w/ ROM
management of polyhydramnios is only indicated if…
monitoring includes…
symptomatic and benefits outweigh the risks
-monitor with serial NSTs and BPPS starting at 34 weeks
- amniocentesis
- indomethacin: impairs production of lung liquid
oligohydramnios defined as…
decreased AFV, defined as AFI < 5 cm or a maximum deepest vertical pocket of fluid < 2 cm
conditions associated with oligohydramnios
1. fetal
2. placental
3. maternal
4. drugs
- fetal: chromosomal abnormalities, congenital anomalies, growth restriction, demise, post-term pregnancy, ROM, PROM
- placental: abruption, twin to twin transfusion syndrome
- maternal: uteroplacental insufficiency, hypertensive disorders (chronic, gestational), diabetes
- drugs: prostaglandin synthesis inhibitors, ACE-inhibitors
fetal surveillance with oligohydramnios…
once or twice weekly surveillance upon diagnosis
embryonic development
-organogenesis begins…. and lasts about…
-what week is the heart fully formed?
begins in the third week after fertilization and spans 8 weeks
fourth week- partitioning of heart begins; arm and leg buds form; amnion begins to unsheathe the body stalk that becomes the umbilical cord
sixth week: head is much larger than body; heart is completely formed; fingers and toes present
***all major organ systems are formed except for lungs
fetal development
-begins how many weeks after fertilization?
8 weeks after fertilization! 10 weeks after onset of LMP
@ 12 weeks: uterus palpable at the symphysis; fetus begins to make spontaneous movements
@ 16 weeks: experienced observes can determine sex on u/s
@ 20 weeks: uterus @ belly button; weight begins to increase
@ 24 weeks: fat deposition, terminal sacs in the lungs still not completely formed
@ 28 weeks: fetus weight 1100 g; papillary membrane has just disappearance from eyes; 90% chance of survival if otherwise normal
@ 32-36 weeks: fetus continues to increase in weight as more subcutaneous fat accumulates
diagnosis of pregnancy
-signs of pregnancy
a. presumptive
b. probable
c. positive
a. presumptive
(subjective)
-amenorrhea
-N/V
-urinary frequency
-fatigue
-breast tenderness
(objective)
-Chadwick’s sign (bluish discoloration of vagina/cervix)
-expression of colostrum
-appearance of Montgomery’s tubercles
b. probable
-enlargement of abdomen, uterus
-change in shape of uterus
-positive pregnancy test
c. positive
-FHTs (heard with doppler starting at 10 weeks)
-sonographic evidence
-palpation of fetal movement
methods for determining EDD
-Naegle’s rule
subtract 3 months, add 7 days to the first day of the LMP, then add 1 year
first trimester u/s are the most…
accurate! That is why we always use the earliest dating ultrasounds (w/ first day of LMP) to determine EDD
discrepancies only go up as baby grows
Maternal physiologic adaptations to pregnancy!
so many!
uterus
-first trimester
-early second trimester
-after 20 weeks
-by term
-first: 6 weeks uterus is soft, globular, and asymmetric (Piskacek’s sign); at 12 weeks, it is 8-10 cm and its moving out of the pelvis
-early second: 16 wks uterus is half way to belly button and at 20 weeks, the fundus is @ umbilicus
-after 20 weeks: number of cm with tape measure equals number of weeks of gestation within 2 cm
by term: uterus weighs about 1100 grams with a 5-L volume
cervix in pregnancy
-Hegar’s sign
-Chadwick’s sign
-Goodell’s sign
-increased vascularity, thick mucus plug forms secondary to glandular proliferation
-Hegar’s sign: softening of the isthmus
-Chadwick’s sign: bluish color of the cervix
-Goodell’s sign: softening of the cervix
how long is the corpus luteum under the influence of hCG?
until about 12 weeks
-corpus luteum secretes progesterone which maintains the endometrium and pregnancy until the placenta takes over
vagina in pregnancy
a. chadwick’s sign: bluish color
b. thickening of vaginal mucosa
c. increase in vaginal secretions
breasts in pregnancy
-increase in size secondary to mammary hyperplasia
-areola becomes more deeply pigmented and increases in size
-colostrum may be expressed after the first several months of pregnancy
-vascularity increases
four types of pelvis
a. anthropoid
b. android
c. gynecoid
d. patylpelloid
a. anthropoid
-shape favors posterior position of fetus
-adequate for vaginal birth due to large size
b. android
-commonly known as male pelvis
-heavy, heart shaped pelvis leads to increased posterior positions, dystocia, operative births
c. gynecoid
-commonly known as female pelvis
-41-42% of women
-good prognosis for vaginal birth
d. patylpelloid
-rare, vaginal delivery is poor secondary to short anterior-posterior diameter
pregnancy and the GI system
-mouth and pharynx
-esophagus
-stomach
-large and small intestines
-gallbladder
-liver
-mouth and pharynx: gingivitis, bleeding gums, increased salivation
-esophagus: decreased LES pressure and tone; heartburn is common
-stomach: decreased gastric emptying time, decreased gastric acidity and histamine output
-large and small intestines: decreased tone and motility; displaced by growing uterus
-gallbladder: decreased tone and motility
-liver: altered production of liver enzymes, plasma proteins, and serum lipids
pregnancy and its impact on the genitourinary/renal system
-decreased bladder tone
-renal blood flow increases by 35-60%
-GFR increases
-RAAS system increases: more sodium and water retention
increased risk of UTI in pregnancy is a result of…
dilation of renal calyces, pelvis, and ureters