Embryology Flashcards
Ectoderm
Becomes the skin (epidermis) and NS (CNS)
These cells are on the neural plate
Yolk sac
Early nutrition to embryo (tissue)
Neural plate
Invaginates into the neural groove (at 20 days)
Piece of thickened ectoderm (thus becomes skin and CNS)
Neural groove
Fuses at the dorsal aspect to become the neural tube
Middle step
Neural tube
Turns into the brain and SC
The folding over into its formation creates the HOLLOW nature of the brain and SC
Neural crest cells (pre neural tube)
Purple ridges on lateral and dorsal aspect of the neural plate
Turn into sensory Ns (most of the sensation for the skin) because they are right next to the ectoderm cells that become skin cells
Sit more dorsally once plate invaginates - why dorsal cord is sensory
Neural crest cells (post neural tube)
Grow out to become the dorsal roots
12-15 rootlets at each level that come together as single sensory dorsal root
Turns into spinal N
Ventral N roots
From ventral part of neural tube
First as many rootlets into one N root, joins with dorsal N root to make spinal N
80% motor function - to specific myotomes
Dorsal roots
Have swelling where cell bodies live
Enter directly into posterior gray matter
Somite + dermal cells = dermatomes
Mesoderm
Becomes cardiovascular system, MSK system and dermal layer of the skin
Notochord
Ventral to SC and therefore ectoderm cells
Where the vertebral column and annulus pulposus of the discs develop
Remnant of the notochord is the discs
Dermatome
Each level of Somites ( specific dorsal root level) that innervate a specific piece of dermis
N testing based on area of skin innervated
Affiliated with mesoderm and ectoderm - a relationship that will always be maintained
Myotomes
Piece of mm that develops and is innervated by specific ventral n root
Central canal
Of SC in the middle (potential space In adults)
Can have CSF or be closed
Gray matter in inside
White matter on outside
White matter
Outer myelinated fibers of SC
High conduction speed
Information travels long distances
Sensory or motor
Spins bifida
Failure of neural tube / VC to close. SC exits thru opening - can cause paralysis
Clinical implication
Prosencephalon
Forebrain
Divides into telencephalon and diencephalon
Mesencephalon
Mid brain
Rhombencephalon
Hindbrain; most caudal
Divides into metencephalon and myelencephalon
Telencephalon
Anterior portion of primitive forebrain
Includes cerebral hemispheres which develop into:
Cerebral cortex, olfactory bulbs, basal ganglia
2 lateral ventricles
Diencephalon
Posterior part of forebrain
Hypothalamus, thalamus, metathalamus, epithalamus
3rd ventricle
Mesencephalon
Midbrain
Tectum and cerebral peduncles
1st brainstem segment
Metencephalon
Anterior part of hindbrain
Cerebellum (motor coordination) and pons
4th ventricle
Myelencephalon
Posterior part of hindbrain
Medulla oblongata
Ventricular system
Hollow spaces within the brain; CSF filled
R and L lateral spaces –> 3rd ventricle –> cerebral aqueduct –> 4th –> outside brain
Central canal exits the 4th ventricle
Thalamus
Relay center for sensory info to cortex, all 6 sensory pathways will synapses in thalamus
Hypothalamus
Major integrating center for endocrine function and ANS
Choroid plexus
Blood vessels in the ventricles that filter blood and produce CSF
Gray matter
Inner butterfly shape, not myelinated
Processes info, reflexes: inhibiting/facilitating either reflex activity or information
Outer layer of of brain
Somites
Small bodies within skin, mm, and bone Located at each level of the SC and turn into mm, and dermal layer of skin Show segmentation of NS Covered c ectoderm Become myotomes/dermatomes Located within the dorsal root ganglion
