1.3

Question 1

Embryology

Answer 1

An egg is fertilized, then develops into an embryo as cells divide.
As the embryo grows, 3 tissue layers develop. These layers then develop into specific adult structures.
- ectoderm: skin and nervous system
- mesoderm: muscles and skeleton
- endoderm: viscera

Ectoderm becomes brain and spinal cord. As the embryo grows, it folds in to form the nervous tissue (neural tube).

The mesoderm is thickening next to the neural tube. It begins to show the segmental form we see in mature humans, like skin, muscles, and vertebral bodies.

segments = somites

Question 2

Dermatome and Myotome

Answer 2

Both refer to structures that are innervated by the nerves of a single spinal nerve.

Dermatome:
- area of skin
- some overlap
- responsible for coordination of sense
- unilateral

Myotome:
- group of muscles
- some innervated by more than one spinal nerve
- responsible for coordination of voluntary muscle movement

Question 3

Landmarks of the spinal cord

Answer 3

Cervical (C4-T1) and lumbosacral (L1-S3) enlargement: enlargements are due to more nervous input and output in the region for the upper and lower extremities

Conus medullaris: L1-L2

Cauda equina: bundle of nerve roots running inferior to the spinal cord through the lumbar cistern

Filum terminale: end of the meninges

Question 4

Cross sectional anatomy of the spinal cord

Answer 4

Grey matter: horns, made up of cell bodies
White matter: made up of axons; signals travel quickly
Dorsal: sensory
Ventral: motor
Central canal: empty space from nerual tube development
Ventral median fissure: gap by central canal separating ventral horns
Spinal tracts

Question 5

Gross anatomy of spinal cord and spinal nerves

Answer 5

8 cervical nerves, but 7 cervical bodies because C1 nerve comes out on top

All other nerves come out below the vertebral body

Question 6

Spinal meninges

Answer 6

From superficial to deep:
1. Dura mater: protective, tough, fibrous
2. Arachnoid mater: delicate, fibrous, elastic, web-like appearance
3. Pia mater: thin, adherent

Question 7

Cerebrospinal fluid

Answer 7

Flows in meningeal spaces surrounding the brain and down into spinal canal
Clear, colorless, protein-free, some electrolytes
Functions:
- protection
- nourishment
- waste removal

Question 8

Neurovasculature of Spinal Cord

Answer 8

Cervical region of spinal cord receives blood from:
- branches of subclavian a.
• ascending and deep cervical arteries
- vertebral aa that travel up the neck in the transverse foramina of the cervical vertebrae
• anterior spinal a. (single) and posterior spinal aa. (paired)

Thoracic region: intercostal aa

Lumbar region cauda equina: lumbar aa

Sacral: medial and lateral sacral arteries

Great anterior segmental medullary a.