Week 1 CNS & Skull Embryology- Ach

Question 1

What three embryonic sources does the entire nervous system derive from?

Answer 1

Neural tube
Neural Crest
Placodes
(all ECTODERM) in origin

Question 2

Describe development of neural tube

Answer 2

• Notochord stimulates ectoderm differentiation into neural plate
• Neural folds
• Neural groove
• Week 4 fusion of neural tube, begins centrally and moves both directions

Question 3

What are neuropores?

Answer 3

Located on each end of the neural tube

-communicated with amniotic fluid

Question 4

What is the space with in the neural tube called?

Answer 4

Neural canal

Question 5

What does the neural tube form?

Answer 5

Brain AND spinal cord

Question 6

What are neural crest cells and what do they form?

Answer 6

• they are motile neuroectodermal cells
• migrate through out embryo
• Forms PNS, and a wide variety of non-neuronal structures

Question 7

What does the neural canal form?

Answer 7

Ventricles of the brain and Central canal of the spinal cord

Question 8

What are the layers of the neural tube?

Answer 8

• Ventricular layer
• Intermediate layer
• Marginal layer

Question 9

What does the ventricular layer of the neural tube become?

Answer 9

• Rapidly dividing neuroepithelial cells
• Differentiate into neurons and glial cells
• Become ependyma (single layer of cells lining the central canal of the spinal cord)

Question 10

What does the intermediate layer of the neural tube become?

Answer 10

• Will become GRAY MATTER of the spinal cord (dorsal, ventral and lateral horns)
• NOTE: CONTAINS ALL SPINAL CORD NERVE CELL BODIES

Question 11

What does the marginal layer of the neural tube become?

Answer 11

Becomes the WHITE matter of the spinal cord

Question 12

What is the difference between the mitotic ability of Neurons and glial cells?

Answer 12

• Glial cells can divide

- Neurons loose their ability when they develop processes (some rare examples they do)

Question 13

What plates form with-in the intermediate layer of the neural tube?

Answer 13

Alar and basal plates

Question 14

What divides the alar and basal plates?

Answer 14

Sulcus limitans

-longitudinal groove in the lumen

Question 15

What does the alar plate form and where is it located?

Answer 15

Alar is dorsal

• forms second order neurons
• SENSORY/AFFERENT neurons (primarily of the dorsal horn)

Question 16

What does the basal plate form and where is it located?

Answer 16

Basal is ventral
-Forms motor neurons of the VENTRAL (large motor neurons tha innervate skeletal muscle) and LATERAL horns (pre-ganglionic neurons of the sympathetic nervous system)

Question 17

Why are the roof and floor plates of the neural tube important?

Answer 17

Contain NO neuroblasts

-Become routes for axons to cross the midline of the spinal cord!!!

Question 18

Where would you find the cell bodies of motor neurons in the ventral horn? (embryonically)

Answer 18

BASAL PLATE

-will send out neurites (multiple cytoplasmic processses) that become axon/dendrites

Question 19

Where would you find the cell bodies of sensory neurons in the dorsal horn? (embryonically)

Answer 19

ALAR PLATE

Question 20

Where are the dorsal root ganglia derived from?

Answer 20

Neural crest

Note: the neurons are PRIMARY afferents

Question 21

What cell myelinate the CNS and PNS

Answer 21

CNS- Oligodendrocytes

PNS- Schwann cells

Question 22

When does myelination begin?

Answer 22

4 months of prenatal development

Question 23

Why do you see a positive Babinski sign in infants?

Answer 23

Toes extend due to incomplete myelination. (if present in adults indicated CNS pathology)

Question 24

At birth where is the end of the spinal cord located?

Answer 24

L2 or L3

Question 25

In the adult where does the spinal cord terminate?

Answer 25

inferior border of L1

Question 26

What are the three primary brain vesicles?

Answer 26

Prosencephalon (Forebrain) Mesencephalon (Midbrain) Rhombencephalon (Hindbrain)

Question 27

What are the primary brain vesicles?

Answer 27

Prosensephalon Mesensephalon Rhombensephalon

Question 28

What are the secondary vesicles of the proensephalon? And what adult structures do they become?

Answer 28

Telencephalon- cerebral hemispheres | Dienceophalon- Thalmus

Question 29

What are the secondary vesicles of the mesencephalon? And what adult structures do they become?

Answer 29

Does not divide again | Becomes the midbrain

Question 30

What are the secondary vesicles of the Rhombencephalon? And what adult structures do they become?

Answer 30

Metenecephalon-pons and cerebellum Myelencephalon- Medulla

Question 31

What does the telencephalon become?

Answer 31

Cerebral hemispheres

Question 32

What does the diencephalon become

Answer 32

Thalmus

Question 33

What does the mesencephalon become?

Answer 33

Midbrain

Question 34

What does the Metencephalon become?

Answer 34

Pons and cerebellum

Question 35

What does the myelencephalon become?

Answer 35

Medulla

Question 36

What constitutes the brain stem?

Answer 36

Midbrain Pons Medulla

Question 37

What is the hypophysis? And where does it come from?

Answer 37

PITUITARY gland!! | -dual ectodermal origin (neuro and oral ectoderm)

Question 38

What is the infundibulum?

Answer 38

Neuroectoderm that becomes the neurohypophysis (posterior lobe of the pituitary gland)

Question 39

What is Rathke's Pouch?

Answer 39

Oral ectoderm that becomes the adenophypophysis (anterior lobe of the pituitary gland)

Question 40

What is the choroid plexus?

Answer 40

Produces CSF | forms in all ventricles

Question 41

Craniorachischisis

Answer 41

complete failure of the neural tube to close resulting in exposure of the malformed tissue to the outside of the head and body

Question 42

Congenital Megacolon (Hirschsprung's Disease)

Answer 42

Neural crest cells fail to migrate into the colon - fecal retention - ballooning of colon

Question 43

Waardenburg Syndrome

Answer 43

occures with diffuse disruption of migration of neural crest cells - abnormall appearance of face, deafness - lack of pigmentation - Digestive problems

Question 44

Anencephaly and meroanencepaly

Answer 44

Failure of the rostral neuropore to close and subsequent failure of the cranial vault to form

Question 45

Occipital encephalocele

Answer 45

Defect in occipital bone, brain and meninges protrude through

Question 46

Spina Bifida (Myelomeningocele)

Answer 46

Failure of CUADAL neuropore to close

Question 47

Syringomyelia

Answer 47

Formation of "empty tube" in the spinal cord | -pathogenesis unknown

Question 48

Holoprosencephaly

Answer 48

forebrain does not divide into two hemispheres

Question 49

Hydrocephalus

Answer 49

dilations of the ventricles due to CSF overproduction, obstruction of flow, or failure to reabsorb

Question 50

Prenatal- alcohol exposure

Answer 50

Teratogenic at all times of gestation, effects depend on time of exposre

Question 51

Carniosynostosis

Answer 51

PREMATURE closure of one of more sutures that produces a misshapen skull.

Question 52

Brachycephaly

Answer 52

fusion of coronal suture | flat-head

Question 53

Oxycephaly, turricephaly or acrocephaly

Answer 53

Fusion of coronal and lamboidial sutures produces "tower skull"

Question 54

Plagiocephaly

Answer 54

fusion of coronal and lamboidal sutures unilaterally | -produces an asymmetrical skull

Question 55

Scaphocephaly

Answer 55

fusion of the sagittal suture produces a long front-to-back diameter skull

Question 56

Microcephaly

Answer 56

is a small head due to brain that fails to grow

Question 57

Cranioschisis

Answer 57

- failure of rostral neuropore to close | - skull defect through which the meninges and/or brain herniate

Question 58

Apert Syndrome

Answer 58

Autosomal dominant genetic disorder characterized by craniosynostosis and other congenital abnormalities (syndactylyl of hands and feet, mental retardation)

Question 59

Acrania

Answer 59

No skull

Question 60

Where are the bones of the skull derived from?

Answer 60

Paraxial mesoderm | Neural crest

Question 61

What type of ossification occurs in the skull base?

Answer 61

Endochondrial ossification

Question 62

What type of ossificaiton occurs in the cranial vault

Answer 62

Membranous ossification

Question 63

What is special about the occipitial bone?

Answer 63

- Part of bone is intramembranous ossificaiton | - Part of bone is endochonrial ossification

Question 64

What is the neurocranium?

Answer 64

brain case, base of skull

Question 65

What is the viscerocranium

Answer 65

Face, contains taste, sight and smell organs

Question 66

What contributes to mesenchyme of the neurocranium?

Answer 66

BOTH somites (paraxial mesoderm) and NEURAL CREST contribue to mesenchyme

Question 67

What contributes to mesenchyme of the viscerocranium?

Answer 67

- forms around the gut tube, rostral to the notocord - Neural crest cells migrate into the paryngeal arches where they form mesenchyme to form the bones of the face, hyoid and middle ear bones.