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FA: Embryology


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when: fertilization by sperm, embryogenesis starts
day 1
when: implantation as a blastocyst
during week 1
when: bilaminar disk
during week 2
when: gastrulation
during week 3
when: primitive streak, notochord and neural plate start to form
during week 3
when: neural tube formed, organogenesis, and high risk to teratogens
weeks 3-8
when: heart beats, upper and lower limb buds start forming
week 4
when: genitalia have male/female characteristics
week 10
what's the right order?

blastocyst, morula, gastrula...?
morula: ball of cells
blastocyst: hollow
gastrulation: infolding
what development happens right over the notochord?
neural plate
-> neural crest
-> neural tube
surface ectoderm ->

Lens of eye
Epithelial linings
neuroectoderm ->

Pineal gland
CNS neurons
neural crest cells ->

Celiac gangion
DRG (dorsal root ganglion)
Schwann cells

C cells of thyroid
Laryngeal cartilage

Chromaffin cells (adrenal medulla)
Enterochromaffin cells
mesoderm ->
Serous linings of body cavities (eg. peritoneal)

Dura connective tissue

CV structures

Urogenital structures
Adrenal cortex
endoderm ->
Gut tube epithelium and derivatives:


notochord ->
induces ectoderm to form neuroectoderm (ie. neural plate)

only postnatal derivative is the nucleus pulposus of the intervertebral disk
what is the rule of 2's for the 2nd week?
2 germ layers
2 cavities: amniotic cavity, yolk sac
2 placenta components: cytotrophoblast, syncytiotrophoblast
what is the rule of 3's for the 3rd week?
3 germ layers (gastrula):
how is the primitive streak formed? what is developed from the primitive streak?
epiblast (ectoderm precursor) invaginates to form the primitive streak

primitive streak becomes the intraembryonic mesoderm and endoderm
teratogen: ACE inhibitor
renal damage
teratogen: cocaine
abnormal fetal development and fetal addiction
teratogen: DES
vaginal clear cell adenocarcinoma
teratogen: iodide
congenital goiter or hypothyroidism
teratogen: 13-cis-retinoic acid
extremely high risk for birth defects
teratogen: thalidomide
limb defects ("flipper" limbs)
teratogen: warfarin, x-rays
multiple anomalies
monozygotic twins
2 amniotic sacs
1 chorion
1 placenta
dizygotic (fraternal)
2 amniotic sacs
2 chorions
2 placentas

sometimes the monozygote can present this way
order of fetal hematopoiesis?
1. Yolk sac (3-8 wks)
2. Liver (6-30 wks)
3. Spleen (9-28 wks)
4. Bone marrow (28- wks)

Young Liver Synthesizes Blood
what are the structures in the umbilical cord?
2 arteries
1 vein
1 alantoic duct

Wharton's jelly
amniotic epithelium

(if there's only 1 artery, there are congenital and chromosomal anomalies)
truncus arteriosus becomes...
ascending aorta and pulmonary trunk
bulbus cordis becomes...
smooth parts of left and right ventricle
primitive ventricle becomes..
trabeculated parts of L and R ventricle
primitive atria become...
trabeculated L and R atrium
L horn of sinus venosus becomes...
coronary sinus
R horn of sinus venosus becomes...
smooth part of R atrium
R common cardinal vein and R anterior cardinal vein become...
superior vena cava
how saturated is blood in umbilical vein?
how does blood get to fetal heart and then where does it go?
umbilical vein
ductus venosus
most goes through foramen ovale
head circulation
how does the deoxygenated blood from the SVC travel?
pulm artery
ductus arteriosus
descending aorta
umbilical arteries
at birth, increased oxygen at the ductus arteriosus causes what to happen?
inhibit prostaglanding release and the ductus closes
1st aortic arch derivative...
part of MAXillary artery
2nd aortic arch derivative...
Stapedial artery and hyoid artery

Stapedial is Second
3rd aortic arch derivative...
Common Carotid and proximal part of internal Carotid

C is third letter of alphabet
4th aortic arch derivative...(L and R sides!)
L: aortic arch

R: proximal part of subclavian artery

4th -> 4 limbs (systemic circ)
6th aortic arch derivative...
proximal part of pulm arteries and the ductus arteriosus (on L)
umbilical vein becomes...
ligamentum teres hepatis
umbilical arteries become...
medial umbilical ligaments
ductus arteriosus becomes...
ligamentum arteriosum
ductus venosus becomes...
ligamentum venosum
foramen ovale becomes...
fossa ovalis
allaNtois becomes...
urachus or mediaN umbilical ligament
notochord becomes...
nucleus pulposus
branchial apparatus: what are the origins of the clefts, arches and pouches?

C: Cleft -> ectoderm
A: Arch -> mesoderm and neural crests
P: Pouch -> endoderm
does arch 5 make any major developmental contributions?
branchial arch 1 derivatives?
Meckel's cartilage: Mandible, Malleus, incus, sphenoMandibular ligament

Muscles: Muscles of Mastication (temporalis, Masseter, lateral and Medial pterygoids), Mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatani

Nerve: CN V3
branchial arch 2 derivatives?
Reichert's cartilage: Stapes, Styloid process, lesser horn of hyoid, Stylohyoid ligament

Muscles: muscles of facial expression, Stapedius, Stylohyoid, posterior belly of digastric

Nerve: VII
branchial arch 3 derivatives?
cartilage: greater horn of hyoid

Muscle: stylopharyngeus

Nerve: CN IX

glossoPHARYNGEAL nerve supplies the styloPHARYNGEUS
branchial arches 4 and 6 derivatives?
Cartilage: thyroid, cricoid, arytenoids, corniculate, cuneiform

Muscles of 4th arch: most pharyngeal constrictors, cricothyroid, levator veli palatani

Muscles of 6th arch: all intrinsic muscles of larynx except cricothyroid

Nerve: 4th arch (CN X) and 6th arch (CN X, recurrent laryngeal branch)
arch 1 derivative innervation?
CN V2 and V3
arch 2 innervation?
arch 3 innervation?
arch 4 and 6 innervation?
1st brachial cleft develops into...
external auditory meatus
2nd through 4th clefts develop into...
temporary cervical sinuses which are obliterated by 2nd arch mesenchyme
what can a persistent cervical sinus lead to?
branchial cyst in the neck
anterior 2/3 of tongue is formed by what branchial arch? innervation?
1st arch

sensation: V3
taste: VII
posterior 1/3 of tongue is formed by what branchial arch? innervation?
3rd and 4th arches

sensation and taste mostly: IX

extreme posterior: X
motor innervation of the tongue?
what 3 nerves contribute to tongues ability to taste?
VII, IX, X (solitary nucleus)

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