fertilization & early development Flashcards
hCg
Human Chorionic Gonadotripin.
Hormone produced by the trophoblasts
Forms the basis of most pregnancy tests
serum vs urine
serum is the most accurate method of measuring hCG
Used when ruling out ectopic pregnancy or other pathology
urine gives false negatives & false positives and is used to determine if there is enough hCG to confirm or deny pregnancy
What happens to the hormones hCG, estrogen, progeterone and HPL (human placental lactogen) throughout pregnancy?
quantitative hCG
measures the amount of hCG actually present in the blood
Rising pattern
Can be correlated w/ sonographic findings.
levels give clues.
Measuring systems for B-hCG
–
IRP (International Research Preparation)
–
SIS (Second International Standard)
–
3IS (3rd International Standard)
embryonic age
Date from when conception occurred
fertilization
Union of an ovum with the spermatozoon
–
Now termed a zygote
Where does fertilzation occur?
ampulla of fallopian tube
Menstrual/Gestational Age
Calculated from the 1st day of LMP to the current date of pregnancy
Embryonic Period
Varies by source
Begins with fertilization and ends the 8th week
Hagen-Ansert uses gestational age = 4-10 weeks of gestation
fetal period
Begins with 9th or 10th week & is until birth (not using LMP method)
Describe the 1st week of human development
fertilize @ oocyte (in ampulla)
enter cell stages
1 = zygote, followed by 2, 4, 8 and finally morula and early/late blastocytes before turning into an embryo by the time it reaches the uterus
What do the sperm need to do to fertilize the egg?
make their way through the corona radiata and zona pellucida
What must occur for the zygote turn into the morula?
duplication of cells in zona pellucida
What and where do blastocysts and trophoblasts form?
early blastocyts get together to begin forming the embryo while trophoblasts move to the edges to replace the “degenerating” zona pellucida
synctiotrophoblast
OUTER LAYER of trophoblast
Results in a primitive utero-placental circulation
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Produce human chorionic gonadotrophin (hCG)
–
Syncytiotrophoblasts are erosive and invasive*
later look like they become chorionic villi in basalis
cytotrophoblasts
INNER LAYER of trophoblast
Thin layer that forms new cells
–
Cytotrophoblast proliferate and will eventually form the chorion and chorionic cavity
blastocyst implantation
day 6 and 7 in the endometrial lining
Ebryonic Development
cavity growth in uterus pt 1
cavity growth in uterus pt 2
decidua & 3 layers
term applied to gravid endometrium – the functional reaction of the endometrial lining ot pregnancy.
layers: decidua basalis, capsularis, parietalis
decidua basalis
capsularis
parietalis
The villi on the myometrial side of the placenta or embryo; unites with the chorion to form the placenta.
Thin, surrounds the gestational sac
The endometrium during pregnancy except at the site of the implantation.
double decidual sac sign
Interface between the decidua capsularis and the echogenic, highly vascular endometrium (decidua parietalis)
yolk sac (aka coelom) & functions (4)
Primary & Secondary
Functions: Hemopoiesis (production of RBC in bone marrow), Development of sex glands, Formation of digestive tract, Transfer of nutrients
when is it seen on TA/’TV?
what is its max diatmeter?
secondary yolk sac
Earliest structure seen inside gestational sac
TV at 5 weeks gestation
TA at 6-7 weeks gestation
Max. diameter of yolk sac is 5.0 mm – 6.0 mm
embryo 26-27 days
neuralation
Week 5 (Days 31-42)
Formation of the neural plate, neural tube & somites
Fusion begins in the middle of the embryo and proceeds in both cephalic & caudal directions
The embryonic disk become trilaminar at beginning of 5th week forms these 3 germ layers
Ectoderm
Central & peripheral nervous systems
Endoderm (epithelial lining)
GI & respiratory tracts
Liver, pancreas, urinary bladder etc.
Mesoderm
Connective tissue, cartilage, bone, smooth muscle, heart, kidneys, ovaries & testes, blood & lymphatics etc.
When is embryonic heart motion detected and ~ what will the CRL measure at this time?
TV at ~ 5.5 weeks (menstrual age)
CRL ~ 2mm
When does the neural tube begin to develop?
What are its parts?
~6 weeks
Prosencephalon (#3)
Forebrain
Mesencephalon (#6)
Midbrain
Rhombencephalon (#4)
Hindbrain (cystic)
brain development 25-100 days
embryonic cavities
Membranes at 4 weeks gestation
Cavity growth w/ gestational age
Notice yolk sac and decidua capularis are degenerating
chorionic and amnioti cavities
- Morula
- 8 cell
- 4 cell
- 2 cell
- oocyte
- early blastocyst
- zygote
- late blastocyst
a. decidua pareitalis
b. decidua capsularis
c. gestational sac
d. myometrium
e. uterine cavity
f. decidua basalis
a. umbilical cord
b. amniochoronic membrane
c. amnion
d. smooth chorion
e. decidua parietalis
f. yolk sac
g. fetal pole
Anatomy of Embryo days 28-30
- Amnion
- Arm bud
- Branchial arches
- Chorion
- Head
- Heart bulge
- Leg bud
- Lens formation
- Somites- Gives rise to muscle mass supplied by a spinal nerve and vertebra
- Tail
- Umbilical cord
Cardiovascular System Development 6, 8, 10 weeks.
6 Weeks
Unidirectional blood flow
8 Weeks
Formation of the heart is complete
10 Weeks
Formation of the peripheral vascular system is complete.
Urogenital System 8, 11, 14 weeks
8 Weeks
Formation of metanephros (primitive kidney) in the pelvis and ascension into the abdomen
11 Weeks
Kidneys in adult position, external genitalia similar in males and females
14 Weeks
Genitalia differentiate
embryo in uterus diagram
embryo day 40-42
- Arm
- Ear
- Elbow
- Eye
- Forebrain 6. Heart bulge
- Hindbrain 8. Liver bulge
- Midbrain bulge
- Midgut herniation
- Mouth
- Notched hand plate
- Umbilical cord
embryo in uterus diagram
Muskuloskeletal Development 5, 6, 8, 9, 11 weeks
5.5 -6 Weeks
Formation of limb buds
7.5-8 Weeks
Digital rays develop: arms bent at elbow
8 Weeks
Clavicle begins to ossify
9 Weeks
Mandible, palate, vertebral bodies and neural arches begin to ossify
11 Weeks
Long bones begin to ossify
gastrointestinal devleopment 6, 8 weeks
6 Weeks
Formation of the primitive gut
8-12 Weeks
Herniation of the midgut into the umbilical cord
midgut herniation
The bowel normally migrates into the base of the umbilical cord between 8-12 gestational weeks or menstrual ( 6-10 embryonic weeks)
The bowel returns to the abdominal cavity by 12 weeks gestation undergoing an additional 180- degree rotation along the axis of the SMA
*Note the tail is gone because the bladder & rectum formation is now complete
head anatomy
At 9 weeks the head is almost half of the fetus. With the rapid growth of the body length the CRL doubles by week 12)
CRL is 20 mm
–Approx. 8.5 weeks gest. age Day 40- 42
trans of lateral ventricles @ 12 weeks
Para
Parity describes the outcome of each gravid experience P0000
1st 0 Place = Number of full term pregnancies
2nd 0 Place = Number of premature births
3rd 0 Place = Number of abortions
4th 0 Place = Number of living children
Nagele’s Rule
Predicts the estimated day of confinement (EDC) or date of delivery
Count back or subtract 3 months from 1st day of LMP & add 7 days
Examples Numerical
LMP Oct 13 10/13
- 3 months July 13 - 3 months
+ 7 days July 20 is EDC 7/13
+ 7days
7/ 20 = EDC
types of monozygotic twins (3)
3 Types based on day of division
25% –> Type 1 Prior to day 4: Dichorionic-diamniotic (When the zygote divides between the 2-cell stage and the morula state)
75% –> Type 2 Between 4-8 days
Monochorionic-diamniotic
~1% –> Type 3 After 8 days
Monochorionic-monoamniotic
Rare division after more than 13 days
Conjoined or Siamese twins
what does the “twin peak” sign of a membrane represent with regards to twins?
dichorionic membrane is thicker than monochorionic. you will see a twin peak in the dichorionic
what do u see?
what happens to the decidua capularis w/ increased gestational age?
it degenerates
is the decidua pareitalis more deep or superficial to the uterine cavity?
superficial. it surrounds the uterine cavity.
What is another name that means “to fertilize”?
fectundate
