Neural Development

Question 1

Embryonic tissues

Answer 1

-3 layers of specialized tissues

Question 2

Endoderm

Answer 2

Inner layer; primarily becomes internal organs

Question 3

Mesoderm

Answer 3

Middle layer; primarily becomes connective tissues, blood vessels & connective tissue

Question 4

Ectoderm

Answer 4

Outermost layer; become outer layer of the skin (epidermis) and NS

Question 5

3rd week of development

Answer 5

-Ectoderm thickens and begins to invaginate
-Neural groove

Question 6

By the end of the 3rd week, edges (neural folds) meet and form the neural tube

Answer 6

-Begins near (what will become) the cervical spinal cord
-Will become the brain and spinal cord
-Cavity within tube will become ventricles (and central canal of spinal cord)

Question 7

Neural crest cells are left behind as the tube separates fully from the overlying ectoderm

Answer 7

These cells form much of peripheral NS (dorsal root ganglion cells, autonomic ganglia, Schwann cells)

Question 8

4th week of development

Answer 8

-Sulcus limitans: longitudinal groove in lateral wall of neural tube; present from spinal cord through brainstem
-Separates the tube into a dorsal (alar plate) and ventral (basal plate)
-Alar plate is primarily sensory (dorsal horn of SC)
-Basal plate is primarily motor (lateral & ventral horns of SC)
-At 4th ventricle, alar plate is pushed apart so that it ends up lateral to the basal plate
-Lateral regions of brainstem are more sensory & medial areas more motor

Question 9

Bulges and bends

Answer 9

Primary @ 4th week, secondary @ 5th week

Question 10

Primary vesicles

Answer 10

Become secondary vesicles become adult structures
From rostral to caudal in following cards

Question 11

Prosencephalon (forebrain) –>

Answer 11

Telencephalon–> cerebral hemispheres
–>diencephalon–> thalamus, hypothalamus, retina

Question 12

Mesencephalon (midbrain)–>

Answer 12

Mesencephalon–> midbrain

Question 13

Rhombencephalon (hindbrain)–>

Answer 13

Metencephalon–> pons, cerebellum
–>myelencephalon–> medulla

Question 14

Flexures

Answer 14

-Cervical & pontine flexures - do not persist
-Cephalic flexure - persists as bend between brainstem and cerebrum

Question 15

Spina bifida

Answer 15

-Failure of caudal end of neural tube to close/fuse
-Cause unknown, but sufficient folic acid reduces incidence significantly
-Myelomeningocele: no vertebrae form; neural tissue continuous with skin
-Spina bifida often accompanied by Arnold-Chiari malformation (unknown why 2 occur together)
-Cerebellum & brainstem pushed down into foramen magnum; results in hydrocephalus

Question 16

Anencephaly

Answer 16

-Failure of rostral end of neural tube to close/ fuse
-Much/all of cerebral hemispheres fail to form

Question 17

Holoprosencephaly (spectrum of disorders)

Answer 17

-Failure of prosencephalon to separate into the diencephalon & telencephalon
-Usually fatal
-Usually accompanied by facial abnormalities