Embryology 5 Flashcards
embryonic vs fetal development?
-embryonic= 1-8 week s fetal= 8 weeks and beyond
what happens by end of the embryonic period?
- major organ systems have begun to develop
- Initially head growth exceeds that of other regions
- Rostral (cranial/anterior) parts develop sooner/earlier than caudal
What does “wave of development” mean?
-that the rostral (cranial/anterior) parts develop sooner than the caudal parts
When do women realize they are pregnant? why is this potentially problematic?
-know ~5-6 weeks pregnant
1-2 weeksafter missed period
-embryonic period is very delicate, most crucial time for development (first 6 weeks) women can not know & be harming the baby
Pregnancy diagnostic tests?
1) Amniocentesis
2) Chorionic villi sampling
3) Ultrasonography
4) Umbilical cord blood sample
5) Computed tomography & MRI
6) Fetal monitoring
Amniocentesis
- initially risky could damage embryo , process now due to ultrasound guided probe
- remove sample of amniotic fluid; test for specific mutations, risk factors, enzymes(see if have metabolic defects)
ultrasound
- used to ID gender & fetal progression
- have made incredible advances (HD 3D ultrasounds)
- no deleterious effect on human embryos yet; but research is unclear
ultrasound & deleterious effects
- ultrasound radiations dosages similar to what humans get have shown cellular effects in rats
- stimulation increases bone tissue proliferation, decreases normal cell proliferation
difficulties in estimating fetal age?
- sperm can last in the uterus for 5-6 days, so fertilization day could be off
- a lot of times base on last menstrual cycle, which add 1-2 weeks until ovulation& fertilization
What happens in gestation?
-divided into three 3-month periods (trimesters)
What happens in the fetal period?
- increases in length & weight
- progressive nerve & muscle wiring create vital functions required immediately after birth
- Lungs mature in last trimester
when did growth and maturation of organs & structures developed?
the embryonic period
3 ways to estimate how long you’ve been pregnant?
1) Lab/Embryologists count from fertilization: 38 weeks:~266 days or 38 weeks since the time of conception (8 ¾ calendar)
2) MDs count from last menstrual period: 40 weeks. ~280 days, 40 weeks since last normal menstrual period (9 ¼ calendar)
3) Estimating Fetal Age Based on Weight and Crown-rump Length
why call estimation and not calculate ?
-hard to estimate, is not a guarantee a lot of factors could effect the accuracy
Estimating Fetal Age Based on Weight and Crown-rump Length (CRL)?
size of baby from top of head to bottom of butt
-easier than basing it on weight since hard to weight a fetus
average at term birth size (CRL and weight)?
- weight 3400 grams (7.5 lb)
- crown-to-rump length 360 mm (~14 in)
fetal period rate of growth in embryonic vs fetal period ?
- in the embryonic development, head grew disproportionately fast
- in fetal period; body grows disproportionally fast compared to head cuz is trying to catch up to it
other ways to determine fetal age?
1) Biparietal diameter
2) Head circumference
3) Abdominal circumference
4) Femur length
5) Foot Length
not infallible…our estimates kinda suck ass
why weight not best way to determine the fetal age?
- because there a lot of variation due to maternal factors
- can often lead to overestimating size of baby
suspected macrosomia?
-when doctors conclude from various tests that the baby is too large for the mama
-often misdiagnosed (4 in 5)
which is bad cuz leads to unnecessary intervention (induction, epidural, and C-section)
when estimating fetal age with crown-rump length? How gather info?
-when date of conception is in doubt
-method of choice for late 1st trimester
-do with ultrasound
-
How analyze crown-rump length?
- based on ethnicity
- correlates length w/ specificed age/week (either after fertilzition or last menstrual period) on a chart
9 weeks
- (CRL 50)
- Head is almost half of the CRL of fetus.
- Face broad, eyes widely separated, eyelids fused, ears low-set. Androgynous external genitalia.
- Portions of Intestine in umbilical cord
10-11 Week
- (CRL 61)
- Intestine to abdomen
- Early fingernail development
12 weeks
- (CRL 87)
- Primary oscification centers appear in cranium, long bones.
- Gender-specific external genitalia distinguishable
- Well-defined neck.
Weeks 13-16 broadly what happens?
Rapid growth, limbs, body relatively faster than head
14 weeks
- (CRL 120)
- Head erect. Eyes face anteriorly, slow movement.
- Lower limbs well developed,
- initial light movement.
16 weeks
- (CRL 140)
- External ears stand out from head
- Differentiated Ovaries.
- ultrasound signal
Weeks 17-20 generally?
Relative growth rate slows
18 Weeks
- (CRL 160)
- Vernix caseosa
- Quickening (first movements) felt by mother.
Vernix caseosa
(dead cells and lipids “cheese wax”) covers skin & protects fetus
21 weeks
- (CRL 200)
- Skin wrinkled, translucent and pink (blood)
- Rapid eye movement
21 weeks
- (CRL 200)
- Skin wrinkled, translucent and pink (blood)
- Rapid eye movement
22-23 Weeks?
startle responses
-surfactant in lungs
surfactant indicate?
-develop around weeks 22-23; if baby has surfactant indicates that it can potentially survive birth in the NICU
24 week
- (CRL 230)
- fingernails
- lean body
What is viability weight & week cut off?
- weigh higher than 500 g
- 22-25 week may survive in (NICU)
- high neurodevelopment risk up to week 26
26 weeks
- (CRL 250)
- Lungs & pulmunory vasculature sufficiently developed
- CNS has matured
- can direct rithmic breathing&movements
- Subcutaneous white fat fills wrinkles skin
- Erythropoiesis in Spleen
28 Weeks
- (CRL 270)
- Erythropoiesis in Bone Marrow
What displays highest neonatal mortality?
very low birth weight indicates high levels of mortality more so than week of birth
Weeks 30-34?
- Normal weight fetuses born by the end of this period usually survive
- Skin is smooth, limbs have chubby appearance
30 weeks
- (CRL 280)
- Body filling out. Testes descending
32 Week
- (CRL 300):
- fingernails reach fingertips
- skin smooth
Weeks 35-38?
- Nervous system mature to execute integrative functions.
- Despite body growth, head still big
36 weeks
- (CRL 340)
- Body usually plump.
- Flexed limbs
- firm grasp.
Factors Affecting Fetal Growth (x7):
1) Maternal Nutrition
2) Smoking
3) Multiple Pregnancy
4) Social Drugs
5) Infection
6) Environmental Factors
7) Impaired uteroplacental blood flow
Factors Affecting Fetal Growth (x7):
1) Maternal Nutrition
2) Smoking
3) Multiple Pregnancy
4) Social Drugs
5) Infection
6) Environmental Factors
7) Impaired uteroplacental blood flow
Maternal Nutrition
- leads to underweight infants (normal head size and body)
Smoking
decreased O2 leads to small infants w/ low birth weight & structural changes
Multiple Pregnancy
- increased demand on limited resources
- infants weigh less; typically develop normally in life
Birth Defects In the United States per year? What can affect this %?
- Birth defects affect one in 33 babies (~ 3%) born
- Birth defects are the leading cause of infant deaths
- Socioeconomic factors:
Frequency of occurrence of major and minor congenital anomalies?
Major: 3% of live births; by 2 years of age, is ~6% (later detection)
Minor: 15%
what kind of congenital anomalies are more common in early embryos?
-Major anomalies
~15%
-most severely malformed results in abortion
Teratogens; ex?
-agents that cause
congenital anomalies following maternal exposure
-Congenital rubella syndrome: when mama gets infected w/ rubella and give to baby
-b4 this thought birth defects were hereditary
Jim Wilson’s Six Principles of Teratogenicity (Susceptibility to teratogenesis depends on)?
1) Genotype of the conceptus
2) Timing of the exposure
3) Dose of exposure
4) Duration or access of exposure
5) Specific cellular mechanism in which it acts
6) Four Manifestations of abnormal development:
a) death
b) malformation
c) growth retardation
d) functional disorder.
