Development of the Nervous System, Dermatomes & myotomes

Question 1

CNS & motor neurons

Answer 1

develop from the neural tube

Question 2

Sensory & autonomic ganglia

Answer 2

develop from the neural crest cells.

Question 3

The musculoskeletal system and dermis

Answer 3

develops from segments of mesoderm.

Question 4

The nervous system

Answer 4

is somatotopically organised.

Question 5

0 to 8 weeks

Answer 5

embryo:
initial development of each organ system
3-8wks period of greatest sensitivity

Question 6

9-38 weeks

Answer 6

fetus:

period of functional maturation

Question 7

week 3

Answer 7

• trilaminar germ disc
• craniocaudal axis
• bilateral symmetry

Question 8

Trilaminar germ disc

Answer 8

superficial > deep
ectoderm - forms NS - is the outer surface
mesoderm - connective and muscle tissues
endoderm

Question 9

Neurulation

Answer 9

Development of the neural tube & neural crest cells

Question 10

somites

Answer 10

segments of mesoderm
- the mesodermally derived somites, adjacent to the neural tube, go on to form most of the vertebral column, as well as segmental structures such as skeletal muscle and dermis corresponding to spinal cord segments

Question 11

Neurulation timeline

Answer 11

The neural plate and beginning neural groove at about 18 days of development > 2 days later development of neural groove > Neural tube closure during the fourth week > Neural folds begin to fuse at the cervical level of the future spinal cord at about day 21 > By about day 24, the rostral end of the neural tube has closed; the caudal end will close 2 to 3 days later

Question 12

notochord

Answer 12

forerunner of the skeletal axis, helping to form the vertebral column
- comes from mesoderm; important in inducing development of neural tube

Question 13

Neurulation timeline simple

Answer 13

Notochord forms from mesoderm (inductive)
Neural plate > Neural groove > Neural tube > Neural tube
…. CNS (brain/spinal cord)

Question 14

Rostral neural tube develops into the brain - 3 weeks

Answer 14

3 primary vesicles:
encephalon = brain
1. Prosencephalon
2. Mesencephalon
3. Rhombencephalon

Question 15

Rostral neural tube develops into the brain - 5 weeks

Answer 15

5 secondary vesicles:
Prosencephalon:
1.telencephalon
2.diencephalon
3. Mesencephalon
Rhombencephalon:
4.metencephalon 
5.myelencephalon

Question 16

neural tube tissue

Answer 16

tissue in wall of neural tube becomes brain tissue and Remaining neural tube develops into the spinal cord

Question 17

1.Telencephalon

Answer 17

cerebrum (cerebral lobes & basal nuclei)

Question 18

2.Diencephalon

Answer 18

thalamus, hypothalamus, epithalamus & subthalamus

Question 19

3.Mesencephalon

Answer 19

midbrain

Question 20

4.Metencephalon

Answer 20

pons & cerebellum

Question 21

5.Myelencephalon

Answer 21

medulla oblongata

Question 22

Neural tube lumen

Answer 22

• develops into the ventricular system of the brain & the central canal of the spinal cord
• neural tube distorts along with the development of the brain
• filled with CSF

Question 23

Ventricular system

Answer 23

1 lateral ventricle in each cerebral hemisphere (with anterior, posterior & inferior horns)
• interventricular foramen
• 3rd ventricle (in midline between L & R diencephalon)
• cerebral aqueduct in midbrain
• 4th ventricle between pons & medulla oblongata anteriorly & cerebellum posteriorly
• central canal of spinal cord

Question 24

CSF movement

Answer 24

flows from 4th ventricle into subarachnoid space > superior sagittal sinus

Question 25

Neural tube walls

Answer 25

develop into the CNS neurons & glial cells

Question 26

Neural tube cavity

Answer 26

becomes the ventricular system of the brain

Question 27

Neural crest cells develop into:

Answer 27

- pia & arachnoid mater - sensory ganglion cells (CN V, VII, VIII, IX & X & DRG) -autonomic ganglion cells (CN III, VII, IX, X & spinal) -Schwann cells - adrenal medulla

Question 28

Dorsal-ventral organisation within the spinal cord

Answer 28

4th week: Neural tube > 6th week: Embryonic spinal cord > Adult spinal cord. spinal ganglion (SG = DRG) cells, derived from the neural crest, send their central processes into the spinal cord to terminate mainly on alar plate (AP) cells many basal plate (BP) cells become motor neurons, whose axons exit in the anterior roots

Question 29

Medial–lateral organisation within the brainstem

Answer 29

with development of the 4th ventricle the walls of the neural tube spread out - Lateral alar plate - Medial basal plate

Question 30

Lateral alar plate

Answer 30

sensory neurons located laterally

Question 31

Medial basal plate

Answer 31

motor neurons located medially

Question 32

4th ventricle

Answer 32

opens out like a book because of peduncles and cerebellum

Question 33

Mesoderm gives rise to the musculoskeletal system

Answer 33

``` most of the axial skeleton • appendicular skeleton • skeletal muscles of the neck, trunk & limbs • tendons & ligaments • dermis on the back & limbs ```