lolernie's version from 2015-11-02 05:10


Embryology (by desaisa)
Embryology for the boards (by desaisa)
Embryology - structures (by cbutler)
Congenital cardiac defect associations (by cbutler)
Heart embryology (by cbutler)

Fetal landmarks

Question Answer
3 daysmorula enters uterus
5 daysblastocyst forms
1 wkblastocyst implantation and hCG secretion
2 wksbilaminar disk (epiblast, hypoblast)
2 wks2 cavities (amnionic cavity, yolk sac)
2 wks2 layers of placenta - cytotrophoblast (inner), syncytiotrophoblast (outer)
3 wksgastrulation (3 germ layers - ectoderm, mesoderm, endoderm)
3 wksprimitive streak, notochord, neural plate begin to form
4 wksheart beats
4 wks4 limb buds form
4 wksneural tube (from neuroectoderm) closes
3-8 wksembryonic period - organogenesis, very susceptible to terotagens
8 wksfetal period - movement, fetus looks like a baby
10 wksmale/female genital characteristics

Embryologic derivatives

Neuroectoderm - think CNS and brain
Neural crest - think PNS and non-neural structures nearby, odonto = Crest toothpaste
Mesodermal defects - VACTERL - Vertebral defects, Anal atresia, Cardiac defects, Tracheo-Esophageal fistula, Renal defects, Limb defects (bone and muscle).


Embryologic originAdult tissue
Surface ectodermlens
Surface ectodermoral cavity epithelial lining
Surface ectodermsensory organs of ear
Surface ectodermolfactory epithelium
Surface ectodermepidermis
Surface ectodermsalivary glands
Surface ectodermsweat glands
Surface ectodermmammary glands
NeuroectodermCNS neurons
Neuroectodermspinal cord
Neural crestANS
Neural crestdorsal root ganglia
Neural crestcranial nerves
Neural crestceliac ganglion
Neural crestmelanocytes
Neural crestSchwann cells
Neural crestpia mater
Neural crestarachnoid mater
Neural crestbones of skull
Neural crestodontoblasts
Neural crestlaryngeal cartilage
Neural crestaorticopulmonary septum
Endodermgut tube epithelium
Endodermthyroid follicular cells
Mesodermconnective tissue
Mesodermserous linings of body cavities (ex. peritoneum)
Mesodermcardiovascular structures
Mesodermurogenital structures
Mesodermadrenal cortex

Developmental derivatives of brain

My own mnemonic - The Dirty Mess Met My Sponge
Region during developmentAdult derivatives (walls + cavities)
Prosencephalon (Telencephalon)cerebral hemispheres, lateral ventricles
Prosencephalon (Diencephalon)thalami, 3rd ventricle
Mesencephalonmidbrain, aqueduct
Rhombencephalon (Metencephalon)pons, cerebellum, aqueduct, 4th ventricle
Rhombencephalon (Myelencephalon)medulla, 4th ventricle
Spinal cord-

Gut tube derivatives

Foregut = esophagus to proximal duodenum just after opening of common bile duct, supplied by celiac artery
Midgut = distal duodenum to proximal 2/3 of transverse colon, supplied by superior mesenteric artery
Hindgut = distal 1/3 transverse colon to upper anal canal, supplied by inferior mesenteric artery


Part of gutAdult derivative
Foregutgallbladder & bile ducts
Foregutupper duodenum
Midgutlower duodenum
Midgutascending colon
Midgutproximal 2/3 of transverse colon
Hindgutdistal 1/3 of transverse colon
Hindgutdescending colon
Hindgutsigmoid colon
Hindgutupper anal canal


What is itKey pointExplanation
Arnold-Chiari type II malformationcerebellar tonsillar herniation thru foramen magnum (posterior fossa malformation)aqueductal stenosis and hydrocephaly, syringomyelia, thoracolumbar myelomeningocele
Dandy-Walker malformationlarge posterior fossa, absent cerebellar vermis and cystic enlargement of 4th ventriclecan lead to hydrocephalus and spina bifida
Syringomyeliaenlargement of central canal of spinal cordcape-like bilateral loss of pain and temp sensation in upper extremities with preservation of touch (damages crossing spinothalamic fibers), most common at C8-T1, seen in Arnold-Chiari II. (My mnemonic is a superhero wearing a cape, and holding a syringe, with a big X on his chest representing the affecting of crossing spinothalamic fibers in central canal).
Treacher Collins syndrom1st branchial arch neural crest fails to migratemandibular hypoplasia, facial abnormalities
Congenital pharyngocutaneous fistulapersistence of cleft & pouch of 3rd branchial archflistula between tonsillar area, cleft in lateral neck
DiGeorge syndromeaberrant development of 3rd and 4th branchial pouchesT-cell deficiency (thymic aplasia) and hypocalcemia (no parathyroid development)
Persistent cervical sinusbranchial cleft cystlocated in lateral neck, does not move with swallowing
Persistent thyroglossal ductthryoglossal duct cystlocated in midline of neck, moves with swallowing
Cleft lipdefect in formation of 1o palatefailure of fusion of maxillary and medial nasal processes
Cleft palatedefect in formation of 2o palatefailure of fusion of lateral palatine processes, nasal septum, and/or median palatine process
Gastroschisisfailure of lateral body folds to fuseextrusion of abdominal contents thru abdominal folds
Omphalocelepersistent herniation of abdominal contentsherniates into umbilical cord, covered by peritoneum
Duodenal atresiafailure to recanalizecommon in trisomy 21 (Down syndrome)
Jejunal, ileal, colonic atresiavascular accidentaka "apple peel atresia"
Volvulustwisting of bowels around SMAdue to problem in rotation of bowels when returning to body cavity at 10th week
Tracheoesophageal fistulaconnection btw trachea & esophagusmost common is blind upper esophagus with lower esophagus connected to trachea - get cyanosis, choking & vomiting with feeding, air bubble on CXR, poly hydramnios
Potter's syndromebilateral renal agenesisoligohydramnios, due to malformation of ureteric bud
Hypospadiasopening on ventral penisfailure of urethral folds to close (most common)
Epispadiasopening on dorsal penisfaulty positioning of genital tubercle, associated with exstrophy of bladder