Embryology (GI, Neuro, Renal) Flashcards
Divisions of gut
Foregut - pharynx to duodenum
Midgut - duodenum to transverse colon
Hindgut - transverse colon to rectum
Anterior abd. wall defect: rostral fold closure
Sternal defects
Anterior abd. wall defect: lateral fold closure
Omphalocele (protrusion with peritoneum), gastroschisis (protrusion without peritoneum)
Anterior abd. wall defect: caudal fold closure
Bladder exstrophy
Duodenal atresia
Failure to recanalize (seen in Trisomy 21)
Jejunal, ileal, colonic atresia
Vascular accident in utero –>apple peel atresia (blind ended prox. jejunum with absence of portion of SB and dorsal mesentery; terminal ileum distal to atresia spiraled around ileocolic vessel)
Tracheoesophageal anomalies
Esophageal atresia with distal TEF is most common –>drooling, choking, vomiting with first feeding
Air in stomach and cyanosis (laryngospasm)
H type - fistula alone
EA type - gasless abdomen
Congenital pyloric stenosis
Hypertrophy of the pylorus (muscularis mucosa) causes obstruction and palpable “olive” mass in epigastric region
Nonbilious projectile vomiting at ~2 weeks
Midgut volvulus
Abnormal rotation and fixation of midgut –>intestinal malrotation –>intestinal obstruction, cecum in RUQ fixed by adhesions (Ladd’s bands)
Mesodermal defects: VACTERL
Vertebral abnormalities, anal atresia, cardiac abnormalities, TEF, renal abnormalities, limb abnormalities
Pancreas embryology
Derived from foregut; ventral pancreatic bud - part of head, uncinate, main pancreatic duct
Dorsal pancreatic bud - rest of head, body, tail, isthmus, accessory pancreatic duct
Annular pancreas
Ventral pancreatic bud abnormally encircles 2nd part of duodenum; forms a ring of pancreas that may cause duodenal narrowing
Pancreas divisum
Ventral and dorsal parts fail to fuse at 8 weeks
Spleen
Arises in mesentery of stomach but is supplied by foregut
Neural plate formation
Notochord induces overlying ectoderm to differentiate into neuroectoderm and form neural plate
Neural tube and neural crest cells
Derived from neural plate
Divisions of neural plate
Alar plate (dorsal): sensory Basal plate (ventral): motor
Three primary vesicles of developing brain
Forebrain (prosencephalon)
Midbrain (mesoencephalon)
Hindbrain (rhombencephalon)
Five secondary vesicles of developing brain: Telencephalon
Telencephalon –>cerebral hemispheres and lateral ventricles
Five secondary vesicles of developing brain: Diencephalon
Thalamus and 3rd ventricle
Five secondary vesicles of developing brain: Mesencephalon
Midbrain and aqueduct
Five secondary vesicles of developing brain: Metencephalon
Pons and cerebellum, upper part of 4th ventricle
Five secondary vesicles of developing brain: Myelencephalon
Medulla and lower part of 4th ventricle
Neural tube defects
Neuropores fail to fuse in 4th week –> persistent connection between amniotic cavity and spinal canal. Associated with low folic acid intake during and prior to pregnancy
Markers for NTDs
Elevated AFP and AChE
Spina bifida occulta
Failure of bony canal closure, but no structural herniation and intact dura
Seen at lower vertebral levels and assoc. with tuft of hair or skin dimple at site of defect
Meningocele
Meninges herniate through spinal canal defect
Meningomyelocele
Meninges and spinal cord herniate through spinal canal defect
Anencephaly
Malformation of anterior NT resulting in no forebrain, open calvarium
Associations: elevated AFP, polyhydramnios, maternal diabetes (type I)
Holoprosencephaly
Failure of left and right hemispheres to separate, usually occurs during weeks 5-6. Complete multifactorial etiology that may present as cleft lip/palate or cyclopia
Arnold Chiari I
Low lying cerebellar tonsils extend beyond foramen magnum; asymptomatic in infant, associated with adult headaches and ataxia
Arnold Chiari II
Significant cerebellar and vermian herniation through foramen magnum with aqueductal stenosis and hydrocephalus. Thoracolumbar myelomeningocele and paralysis below defect.
Dandy-Walker
Agenesis of cerebellar vemis with cystic enlargement of 4th ventricle. Associated with hydrocephalus and spina bifida.
Syringomyelia
Cystic enlargement of central canal of SC –> anterior white commissure damage
Capelike bilateral loss of pain/temp sensation in upper extremities (usu. at C8-T1). Associated with Arnold Chiari I.
Tongue development
1st branchial arch forms anterior 2/3rds – sense via V3, taste via CN VII
3rd branchial arch forms posterior 1/3 – sense and taste via CN IX, X
Motor innervation via CN XII
Muscules are derived from occipital myotomes
Kidney embryology
Pronephros - develops until week 4 then degenerates
Mesonephros - 1st trimester kidney, then contributes to male genital system
Metanephros - permanent; appears in 5th week
Ureteric bud
Derived from caudal end of mesonephros; gives rise to ureter, pelvises, calyces, collecting ducts
Metanephric mesenchyme
Ureteric bud interacts with this tissue; interaction induces differentiation and formation of glomerulus –>DCT
Aberrant interactions may result in congenital kidney malformations
Ureteropelvic junction
Last area to canalize –>most common site of obstruction (hydronephrosis) in fetus
Potter’s syndrome
Compression of fetus –>limb deformities, facial deformities, pulmonary hypoplasia
May be due to ARPKD, posterior urethral valves, bilateral renal agenesis
Horseshoe kidney
Inferior poles of both kidneys fuse and get trapped under IMA during ascent. Associated with Turner syndrome.
Multicystic dysplastic kidney
Due to abnormal interaction between ureteric bud and metanephric mesenchyme.
Nonfunctioning kidney made of cysts and connective tissue
Unilateral –>compensatory hypertrophy of contralateral kidney
