Embryology Flashcards
What does the Notochord induce?
Overlying ectoderm to differentiate into neuroectoderm & form the neural plate
What does the Neural plate give rise to?
Neural tube & neural crest cells
What does the Notochord become?
Nucleus pulposus of the intervertebral disc in adults
What is the Alar plate?
Dorsal & Sensory
What is the Basal plate?
Ventral & Motor
What is the forebrain?
Prosencephalon
What is the Midbrain?
Mesencephalon
What is the Hindbrain?
Rhomobenchephalon
Which secondary vesicles does the Prosencephalon become?
Telencephalon & Diencephalon
Which 2° vesicles does the Mesencephalon become?
Mesencephalon
Which 2° vesicles does the Rhombencephalon become?
Metencephalon & Myelencephalon
What are the adult derivatives of Telencephalon?
Walls: Cerebral hemisphere
Cavities: Lateral ventricles
What are the adult derivatives of Diencephalon?
Walls: Thalamus
Cavities: Third ventricle
What are the adult derivatives of Mesencephalon?
Walls: Midbrain
Cavities: Aqueduct
What are the adult derivatives of the Metencephalon?
Walls: Pons & Cerebellum
Cavities: Upper part of 4th ventricle
What are the adult derivatives of the Myelencephalon?
Walls: Medulla
Cavities: Lower part of 4th ventricle
When do Neural Tube Defects occur?
Neuropores fail to fuse in the 4th week
What is a Neural Tube Defect?
Persistent connection b/w amniotic cavity & spinal canal
What are Neural Tube Defects assoc w/?
Low folic acid intake before conception & during pregnancy
What labs indicate a Neural Tube Defect?
- Inc AFP in amniotic fluid & maternal serum
- Inc AChE in amniotic fluid (confirmatory test)
What is Spina bifida occulta?
Failure of bony spinal canal to close, but no structural herniation. Dura is intact
Where is Spina bifida usually located?
Lower vertebral levels
What is Spina bifida assoc w/?
Tuft of hair or skin dimple at level of bony defect
What is Menigeocele?
Meninges (but not SC) herniate through spinal canal defect
What is Meningomyelocele?
Meninges & SC hernicate through spinal canal defect
What are the forebrain anomalies?
Anencephaly & Holoprosencephaly
What is Anencephaly?
Malformation of anterior neural tube resulting in no forebrain, open calvarium (“frog-like appearance”)
What are the clinical findings in Anencephaly?
- Inc AFP
- Polyhydraminos (no swallowing center in brain)
What is Holoprosencephaly?
Failure of left & right hemispheres to separate
When does Holoprosencephaly occur?
Weeks 5-6
What causes Holoprosencephaly?
Complex multifactorial etiology that may be related to mutations in sonic hedgehop signaling pathway
What is the moderate form of Holoprosencephaly?
cleft lip/palate
What is the most severe form of Holoprosencephaly?
Cyclopia
What is Anencephaly assoc w/?
Maternal Type I diabetes
What dec the risk of Anencephaly?
Maternal folate supplementation
What are the Posterior fossa malformations?
Chiari II (Arnold-Chiari malformation) & Dandy-Walker
What is Chiari II (Arnold-Chiari malformation)?
Significant cerebellar tonsillar & vermian herniation through foramen magnum w/ aqueductal stenosis & hydrocephalus
How does Chiari II (Arnold-Chiari malformation) present?
Thoraco-lumbar myelomeningocele & paralysis below the defect
What is Dandy-Walker malformation?
Agenesis of cerebellar vermis w/ cystic enlargement of 4th ventricle (fills the enlarged posterior fossa)
What are Dandy-Walker malformations assoc w/?
Hydrocephalus & spina bifida
What is Syringomyelia?
Cystic enlargement of central canal of spinal cord
What is usually damaged first in Syringomyelia?
Crossing fibers of spinothalamic tract
What does Syringomyelia result in?
“Cape-like” bilateral loss of pain & temp senstation in UE (fine touch sensation is perserved)
What is Syrinx?
Tube as in syringe
What is Syringomyelia assoc w/?
Chiari I malformation (>3-5mm cerebellar tonsillar ectopia)
What location is Syringomyelia MC in?
C8-T1
Which brachial arch form the anterior 2/3 of the tongue?
1st brachial arch
Which cranial nerve does sensation for anterior 2/3 of the tongue?
CN V3
Which cranial nerve does taste for anterior 2/3 of the tongue?
CN VII
Which brachial arches form the posterior 1/3 of the tongue?
3rd & 4th brachial arches
Which cranial nerve controls sensation & taste of the posterior tongue?
CN IX
(extreme posterior CN X)
Which cranial nerve controls motor innervation of the tongue?
CN XII
What are the muscles of the tongue derived from?
Occipital myotomes