Unit 1.L3-Late Organogenetic & Fetal Periods of Human Embryo Flashcards
What is the size of 3 week embryo, 5 week embryo and 8 week embryo>
3: 3mm
5: 10mm
9: 22mm
How does the structure change in week 5?
- Head grows rapidly & becomes large
- The facial prominences develop so much that they
contact the heart prominence. - The maxillary and mandibular prominences of the first arch are delineated.
- Cranially: A large stomodeum, brain folding & 4th ventricle are prominent
- Caudally: Neural tube primordium -> spinal cord
- The mesonephric ridge emerges as a site of the primordial kidney and urogenital system.
What is inferior to all the pharyngeal arches?
pharynx
What is the mesonephric ridge?
Primidal kidney
What is a very key thing that happens in week 6
Embryo moves:
- Embryo show spontaneous movements in trunk & limbs.->Body arches & curls
Embryo have what due early neural connections?
Reflex action to touch
Early in 6th week: Regional differentiation of the upper & lower limbs:
– Elbows
– Large hand plates (starting to have digits)
– Digit primordia
– Foot plate (no digits)
- Auricular hillocks (primordial pinna),
- External acoustic meatus (external ear canal)
What does the auricular hillocks form?
auricle of external ear
When does umbilical herniation happen?
Late sixth week
Lower limbs develop _ into the sixth
week
5 days late
What happens in late sixth week?
- The eye become pigmented & prominent as
pigment retina is formed. - Head is large & bent over & touching the heart.
- The intestines enter the extraembryonic coelom in the proximal part of the umbilical cord, showing umbilical herniation to accommodate the large gut tube.
What happens to accommodate large gut tube?
the intestines enter the extraembryonic coelom in the proximal part of the umbilical cord, showing umbilical herniation to accommodate the large gut tube.
What happens in week 7?
What signifying digits (fingers or toes) & wrist?
The limbs show notches between the digital rays on hand and foot plates, signifying digits (fingers or toes) & wrist.
During 7th week, what is reduced?
Reduced communication between the primordial gut & umbilical vesicle.
What happens to the bones during the 7th week
Bones of the upper limbs undergo endochondral ossification
What accounts for the large size of the abdomen in week 7?
The liver prominence
Week 7
What stops with the enlargement of liver?
Stops descent of heart and lungs
only liver periotum
What happens in week 8
What does the scalp vascular plexus form in week 8?
band across the head-> capillaries are formed
What becomes more prominent in week eight?
A stubby nose and heavily pigmented eye (retina), with eye-lids become prominent.
What rotates, separate and lengthen in week 8?
Upper limb rotate ventrally and fingers separate & lengthen, and the toes begin to separate
What can virtually cut the embryo?
Magnetic Resonance Microscopy (MRM)
What happens happen in week8?
What does the embryo develop and what does it begin in week 8?
- The embryo develops distinct human appearance.
- Purposeful limb movement begins-> limbs can touch each other
What occurs to the bones in week 8?
Femoral bone (thigh) ossification occurs and both hands and feet elongate and touch each other.
What is going on with the eyes in week 8?
The eye-lids fuse by epithelialization.
– Urine formed->amniotic fluid caustic
* Closed because of urine
How to measure the length of embryo
Embryo 8-9 weeks:
On the brink of becoming a fetus.
What happens in ninth week to birth?
grow, grow, grow
What is the size of week 9 fetus?
38mm
From the 9th week to birth (38th week), the developing human is called a _
fetus
The fetal period is characterized by three features:
(1) Rapid growth of the body (increase in size and cell number), barring head (not growing as much)
(2) Tissue & organ differentiation (functional specialization of cells)
(3) Slow head-growth, while other organs and the body grows fast.
What is formed during the embryonic period?
Refinement of the organ primordia
How does growth occurs?
spurts at intermittent intervals
When does phenomenal weight gain in fetus occur?
Phenomenal weight gain in the Fetus during the 3rd trimester
What is viability?
is defined as the ability of fetuses to survive in the extrauterine environment
Most fetuses weighing _ at birth do not survive, therefore, are not called viable
<500g
What are immature infants?
- Full-term, low-birth-weight infants resulting from IntraUterine Growth Restriction (IUGR)
- With expert postnatal care, some fetuses do survive; called extremely low-birth- weight infants, or immature infants at full-term.
Not premature
What are preterm infants
Fetuses (750 -1500 g) that usually survive, but complications may occur; such as BPD (bronchopulmonary dysplasia) or RDS (respiratory distress syndrome), and are called preterm infants
- BPD: alvoli do not align therefore cannot consume as much O2
- RDS: comp. lung fxn, growth not good
_ births/year in US, some with severe morbidity and mortality.
500,000 preterm infants
What is used to have reduced acute and long-term morbidity
The use of antenatal steroids and postnatal administration of endotracheal surfactant
Prematurity remains the most common causes
morbidity and perinatal death.
Clinical gestation: has 3 periods (3-trimesters = ~9-months), each lasting 3 months
(1) At First trimester: Major organ systems continues to develop.
(2) At second trimester: The fetus grows & anatomical detail are visualized by ultrasonography.
* Major birth defects are detected by high-resolution real-time ultrasonography or MRM.
(3) At third trimester (after 6 months): The fetus may survive if born prematurely
What happens in third trimester?
– At 35 weeks the fetus weighs 2,500 g (5.5 lb) and is a measure of fetal maturity.
– At 35 weeks, fetuses usually survive if born prematurely
–Normal gestation period is 40 weeks (1st day of the woman’s last menstrual period)
What is the clinical term (due date)
Estimated Date of Confinement (EDC)
Actual in utero growth is what?
2 weeks less (fertilization to birth=38 weeks)
What is the Nägele’s rule?
What determines the fetus the size, age and date of delievery of 9 week old fetus?
Ultrasound measurements of the Crown−Rump Length (CRL) of the fetus determines size, age & date of delivery
What is the CRL of 9 week old fetus?
4.2 cm
9-Week-old Fetus: Ex vivo Structures
Fetus with Chorionic Sac removed:
– cartilaginous ribs
– large head
– intestinal growth is fast & descend in the umbilical cord
– the face is broad
– eyes are widely separated, eye-lids fused
– ears are low set
What happens from 9 to 12 weeks
What happens to the intestines during 9th to 12th week
The intestines go back in the abdomen & are not in the umbilical cord
What is establised 9-12th week
Primary Ossification Centers are established (Cranium (skull) & Long Bones)
What is fully grown at 9 to 12 week?
Upper limbs are fully grown compared to the lower limbs
What develops and visible in 12th week
External male & female Genitalia develop & are visible by 12 weeks, but remain small
What is 12 week old fetal physiology?
At 9 weeks what happens to the liver?
At 9-weeks, Liver initiates erythropoiesis (making of RBCs: Red blood cells)
At 12-weeks, erythropoiesis switches to _
Spleen
What happens in 9th-12th with urine?
Urine formation begins & is discharged via urethra into the amniotic fluid in the amniotic cavity
What happens to swallowing amniotic fluid?
- the fetus reabsorbs amniotic fluid in the gut after swallowing it bc so salty
- fetal waste products goes into maternal circulation via the placenta
12-Week Fetus Imaging Modalities:
Look for Cranio-facial defects
16th week
- When is the fetal growth the most?
- What is smaller?
- What contines to lengthen?
- Fetal growth is greatest (9-16th week); 25-fold by weight
- While the growth is very rapid the head is
- smaller.
- Lower limbs continue to lengthen.
What happens to the limbs in 16 week fetus?
- Limb movements are well-coordinated, but too slight to be felt by the mother. (because of muscle and leran how to use them)
- Limb movements are visible during ultrasonographic examination.
What is the size of 12 week old fetus, 38 week?
- 2.5 inch
- 20 inch
What is happening 16th week?
What is the fetal development of 17 week fetus
Relationship between age and egg quality
Deterioration after age 30
What happens during 17th to 20th week (5 months)
T/f: during 17th - 20th week of fetus is growing super fast
FALSE: super slow
What happens to featal movements during 17th to 20th week?
Fetal movements quicken; felt by the mother very often.
Eyebrows and head hair are well-developed & properly visible When
20 week of age
What happens to fat during 17th to 20th week?
Brown fat (root of the neck) for heat production at birth.
What is formed during 17th to 20th week
Fetal uterus is formed and canalization of the vagina begins
- What is visible for female fetus at 17 to 20 weeks?
- What happens in male fetuses?
- Primordial ovarian follicles containing oogonia are visible.
- In males, the testes descends, but remains in the posterior abdominal wall.
By 20th week what happens to the skin?
the skin has greasy /waxy white substance, which has a cheese-like consistency, called the “vernix caseosa”
- What does the vernix do?
- What is made up of?
- The vernix protects the fetal skin from abrasions, chapping, and hardening as it is exposed to the salty amniotic fluid.
- Vernix is made of dead epidermal cells& fatty sebaceous exudate from fetal sebaceous glands.
What does the fetus have for the vernix to stick?
Fetus has fine downy hair(called lanugo), for vernix to stick.
What occurs during 21-25th week?
What happens to weight and what is detected in 21-25 weeks
Substantial weight gain; body proportions are well defined and fingernails are detected
Wrinkled & translucent skin; pink to red because of blood
capillaries develop by what?
24 weeks
What happens to eyes at 21-25 weeks
- Rapid eye movements/blink−startle responses.
What happens to lungs at 21-25 weeks
Lungs begin maturation: the secretory epithelial cells (type II pneumocytes) in the lung alveoli secrete surfactants
What is surfactant?
Surfactants (lipoproteins) maintain patency ( i.e. keeps the lung open for air breathing and does not allow its membranes to stick) of the developing alveoli of the lung
- A 25 week old fetus bone prematurely may survive in NICU if what?
- What is there a risk for?
- if surfactant therapy is given endotracheally; a standard of care in the NICU.
- Risk for neurodevelopmental disability remains high.
- Risk of BPD (bronchopulmonary dysplasia) is high
What happens during 26-29 weeks?
What happens to Fetal Lung Development and Maturation: Week 26 onwards
What happens at 30-38th week ?
World Health Organization (WHO) Statistics on Premature Births
Complications in Pregnancy: Maternal Mortality
Last trimester
At full term, CRL = _ mm and Weight = _ g ( _ lb.)
At full term, CRL = 360 mm and Weight = 3400 g (7.5 lb.)
What is happens in the last trimester?
What are low birth weight causes?
Major causes of IUGR (Intrauterine Growth Restriction):
- What is preterm neonates
- What is postmaturity syndrome?
- What are signs of fetal dysmaturity?
What are some causes in low birth weight and high birth weight?
What are other factors that influence fetal growth?
Assessment of fetal status (26 weeks to 4 weeks after birth) is done by what?
perinatologists
Methods employed for assessment:
- (1) Diagnostic Ultrasonography
– (2) Diagnostic Amniocentesis
– (3) Chorionic Villus Sampling (CVS)
What is dianostic ultrasonography?
What is diagnostic amniocentesis?
What is the Diagnostic Value of Amniocentesis
What is Chorionic Villus Sampling (CVS)
What is congential malformations (birth defects)
developmental anomalies or disorders that show anatomical/strucural or mental abnormality at birth
What are is the leading casue of infact mortality?
birth defects
What are some birth defects (5)
What is Teratology
Principles of [Embryology + Pathology + Toxicology] to understand & classify developmental defects of malformed embryos and fetuses.
What is Teratology (concept)”
Certain stages of embryonic development are more sensitive to “factors” that disrupt normal growth.
Effect of Teratogens depend on:
- Critical periods of development
– Dose of the drug or chemical
– Genetic background of the embryo
What is a earlier medical belief?
Baby’s are protected in the womb by sterile environment. This concept changed in 1941: Rubella Virus infection in pregnant mothers caused German measles, which lead to “congenital rubella syndrome”.
What is Congenital Rubella Syndrome
Congenital Rubella Syndrome: Eye anomalies:
What is the background of thalidomide?
What is spina bifida cystica?
What are the Classification of the causes of birth defects
