3 Embryology

q123456's version from 2016-05-30 16:35


Question Answer
Surface ectoderm derivativesepidermis(touch)
lens and cornea(vision)
olfactory epithelium(smell)
oral cavity epithelium(taste)
hearing (sensory organs of ear)
glands (salivary, sweat, mammary gland and anterior pituary)
Neural crest derivativesParafollicular cells of thyroid
Laryngeal cartilage
Aorticopulmonary septum
adrenal medulla (Chromaffin cells)
Schwann cells KA36-22
Celiac ganglion
Arachnoid and pia mater
Cranial nerves
Skull bones
Endoderm derivativesGI epithelium
pharyngeal pouches (thymus, parathyroid)
thyroid follicular cells
Mesoderm derivativesMuscle
cardiovascular structures
urogenital structure
adrenal cortex.
notochordnucleus pulposus of the intervertebral disk


Question Answer
Cytotrophoblastinner layer of chorionic villi, Cyto makes cells
Syncytiotrophoblastouter layer of chorionic villi; secretes hCG (structurally similar to LH; stimulates corpus luteum to secrete progesterone during first trimester)
Umbilical arteriesdeoxygenated
from fetal internal iliac arteries to placenta
Derived from allantois
Umbilical veinoxygenated
from placenta to fetus
Derived from allantois
Urachal ductallantois duct=urachus
urachus=median umbilical ligament: bladder<--->umbilicus
***medial umbilical ligament: umbilical artery
failure to obliterate:
1. Patent urachus - urine discharge from umbilicus
2. Vesicourachal diverticulum - outpouching of bladder
omphalomesenteric duct
Viteline duct
connects the terminal ileum to the umbilicus in utero.
meconium discharge from umbilicus (s.a Meckel’s)
processus vaginalistotal failure to fuse: persistent processus vaginalis>>>congenital inguinal hernias
incomplete fusion>>>hydrocele of the spermatic cord
annular pancreaspresent from birth
narrow at the mid duodenum
CT a mass lesion surrounding the duodenum
*congenital pyloric stenosis: 2-3 weeks after birth
**tracheoesophageal fistula: copious salivation, choking or cyanosis with feeding

teratogenic effects

Question Answer
drug's teratogenic effectstrimethoprim/sulfamethoxazole: jaundice
alkylating agent: absence of digits, multiple anomalies
Folate: Neural tube defects
Lithium: Ebstein’s anomaly (atrialized right ventricle)
Tetracycline: Discolored teeth
Valproate:Inhibition of intestinal folate absorption
Vitamin A: spontaneous abortions and birth defects (cleft palate, cardiac abnormalities)
Warfarin: Bone deformities, fetal hemorrhage and abortion
Fetal alcohol syndrome KA32-28Mental retardation
small teeth
ear deformities
small palpebral fissures
chromosomal abnormality (robertsonian translocation)miscarriage occurred in the first trimester
Neonate, greenish yellow vomiting, absence of a large segment of small bowelvascular occlusion
polyhydramniosdecreased fetal swallowing or increased fetal urination, gastrointestnal abstruciton and anencephaly,
increased level of acetylcholonesterase in the amniotic fluidfailed fusion, neural tube defects
malformationintrinsic, embryonic period
deformationextrinsic, after embryonic period


Question Answer
Truncus arteriosusAscending aorta and pulmonary trunk
Bulbus cordissmooth parts of ventricle
Left horn of sinus venosus (SV)Coronary sinus
Right horn of Sinus venosusSmooth part of right atrium
Neural crest migrationascending aorta and pulmonary trunk
Truncus arteriosus pathologytransposition of great vessels + tetralogy of Fallot
Fetal erythropoiesis1. Yolk sac (3-8 weeks)
2. Liver (6-30 weeks)
3. Spleen (9-28weeks)
4. Bone marrow (28 week onward)
Shunts in fetal circulation1. Ductus venosus - diverts from umbilical vein into IVC to bypass hepatic circulation
2. Foramen ovale - bypass lungs
3. Ductus arteriosus - pulm artery to lower body of fetus.
O2 sat in umbilical vein80% saturated
Change in infant circulation at birthinfant takes breath and ↓ resistance in pulmonary vasculature causes ↑ left atrial pressure vs right atrial pressure closing the foramen ovale - ↑ in O2 ↓ prostaglandins, causing closure of ductus arteriosus.
PDAindomethacin helps close PDA, prostaglandins keep PDA open
Pulmonary artery to the systemic circulation
Kid, continuous murmur
Umbilical vein ligamentum teres hepatis
Umbilical arteriesmedial umbilical ligament
Ductus arteriosusligamenhlm arteriosum
Ductus venosusligamentum venosum
Foramen ovale post natal derivativefossa ovalis
Allantois/urachusmedian umbilical ligament
atrial septal defectsostium secundum (most common)
ostium primum (atrioventricular septal defects, AV canal defects, endocardial cushion defects) ***Heart defect of Down syndrome belongs this type KA35-26
sinus venosus>>>located at the junction of the right atrium and superior vena cava
Ventricular septal defectKA37-10


Question Answer
1st Aortic archmaxillary artery (branch of external carotid)
2nd aortic archStapedial artery and hyoid artery
3rd Aortic archcommon Carotid artery and proximal part of internal carotid artery
4th aortic archon left, aortic arch; on right, proximal part of right subclavian artery
6th Aortic archpulmonary arteries and ductus arteriosus
ARCHartery and muscle from medoderm
bone from neural crests

first aortic arch: maxillary A
second aortic arch:stapedial A/ Hyoid A
third aortic arch;common carotid A/proximal part of internal carotid A
fourth aortic arch:aortic arch/Right subclavian A
sixth aortic arch:pulmonary arteries and ductus arteriosus
First pouch:tympanic cavity
second pouch:epithelial lining of palatine tonsil
Third pouch: Inferior parathyroid gland/Thymus
Fourth pouch: superior parathyroid gland
B: Malleus incus

B: stapes/hyoid bone
M: facial expression, stapedius, stylohyoid

M: stylopharyngeus
B:hyoid bone (greater)


Question Answer
neuron tube defectsNeuropores fail to fuse (4th week) → persistent connection between amniotic cavity and spinal canal. Associated with low folic acid intake during pregnancy. Elevated a-fetoprotein (AFP) in amniotic fluid and maternal serum. ↑ AFP + acetylcholinesterase in CSF.
Spina bifida occultafailure of bony spinal canal to close, but no structural herniation. Usually seen at lower vertebral levels. Dura is intact.
Meningocelemeninges herniate through spinal canal defect.
Myelomeningocelemeninges and spinal cord herniate through spinal canal defect
AnencephalyMalformation of anterior end of neural tube
no brain
elevated AFP
polyhydramnios (no swallowing center in brain ).
Holoprosencephaly↓ separation of hemispheres across midline
severe fetal alcohol syndrome
prosencephalontelencephalon:cerebral hemispheres and lateral v
diencephalon:thalami and 3rd v
Rhombencephalonmetencephalon:pons, cerebellum, aqueduct (KA34-7) and 4th v
Chiari II malformationcerebellar tonsillar herniation through foramen magnum with aqueductal stenosis and hydrocephaly. Often presents with syringomyelia, thoraco-lumbar myelomeningocele.
Dandy-walker malformationlarge posterior fossa; absent cerebellar vermis with cystic enlargement of 4th ventricle. Can lead to hydrocephalus and spina bifida.
SyringomeliaEnlargement of the central canal of spinal cord. Crossing fibers of spinothalamic tract are typically damaged first. "Cape-like," bilateral loss of pain and temperature sensation In upper extremities With preservation of touch sensation - most common C8-T1


Question Answer
reproductive system embryologyUrethral folds: labia minora (F) or ventral aspect of penis (M)

Genital tubercle: penis

Genital swellings: Scrotam(M) labia majora (F)

mesonephric ducts: Male genital ducts

urogenital sinus of male: Bladder, prostate gland and urethra

mesonephric ducts of female: Trigone of bladder

paramesonephric ducts: Oviduct, uterus, upper vagina
Hypospadias Failure of urethral folds to close
EpispadiasFaulty positioning of genital tubercle


Question Answer
rache's pouchectoderm
anterior pituitary
the optic chiasm>>>bitemporal hemianopsia
compress the pituitary gland>>>diabetes insipidus, obesity, growth failure and hypothyroidism
Craniopharyngioma:benign rathke’s pouch tumor with cholesterol crystals, calcifications and dark brow, oily fluid
pancreasannular pancreas
abnormal migration of the ventral pancreatic bud
pancreatic tissue encircling the duodenum

pancreas divisum:unfinished fusion of the ventral and dorsal pancreatic buds
maxillary prominence with the medial nasal prominence cleft lip
meiosis1) oogonium:
46=23 from mother, 23 from father
2n=Duplicate, homologous chromosomes

2) primary oocyte 46, 4n.
46=23 from mother, 23 from father
4n= 2 homologous chromosomes, 2 sister chromatids each homologous chromosome
5th month of fetal life
arrests in prophase I until puberty

3) secondary oocyte:
23=from mother or father
2n=2 sister chromatids
arrested at metaphaseII

e.g. oocyte:isolated from the fallopian tube after ovulation. arrest in metaphase II

random fertilization, crossover and independent assortment fertilization(prophase I)
diploidsomatic cells(2n)
Haploidsex cells (n)
meiosis Iproduced 2 haploid cells, 2 sister chromatids, each cell contains 23 chromosomes but each of these consists of two chromatids.
meiosis II2 haploid cells-->4 haploid cells, 1 chromatid, no sister chromatids