Ch. 17 Spinal Cord & Spinal Nerves Flashcards Preview

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Flashcards in Ch. 17 Spinal Cord & Spinal Nerves Deck (10):
1

Intro

- contains neural circuits that control quickest reactions to environmental changes
- site for integration of neuronal stimulation
- relay sensory nerve impulses
- continuous with brain and together constitute the CNS

2

Spinal Cord Anatomy

spinal meninges: cover spinal nerves up to the point of exit from spinal column through the intervertebral foramina
cerebrospinal fluid: serves as shock absorber and suspension system for spinal cord and brain
denticulate ligaments: thickenings of pia mater that project and fuse with arachnoid mater and inner surface of dura mater between anterior and posterior nerve roots of spinal nerves on either side

3

Meninges

Dura mater: most superifical, composed of dense, irregular connective tissue
- also protected by cushion of fat and connective tissue in epidural space
Arachnoid mater: middle layer and avascular covering; delicate collagen fibres and some elastic fibres
- betweendura mater and arachnoid mater is thin subdural space which contains interstitial fluid
Pia mater: innermost connective tissue layer that adheres to surface of spinal cord and brain

4

External Anatomy

cervical enlargement: extends from fourth cervical vertebra to first thoracic vertebra
lumbar enlargement: inferior enlargement, extends from ninth to twelfth thoracic vertebra
- inferior to lumbar enlargment, spinal cord terminates as a tapering, conical structure called conus medullaris
- conus modulars ends at level of intervertebral disc between first and second lumbar vertebra in adults
- arising from concur modulars is hilum terminal

5

Internal Anatomy

- 2 grooves penetrate white matter of spinal cord and divide into right and left sides
- anterior median fissure is a wide groove on anterior side
- posterior median sulcus is narrow groove on posterior side
- gray matter of spinal cord is shaped like latter H and surrounded by white matter
- gray matter consists of cell bodies of neutrons, neuroglia, unmyelinated axons, and dendrites of interneurons and motor neurone
- white matter consists of bundles of myelinated axons of sensory neutrons, interneurons and motor neurons

6

Gray Horns

- gray commissure forms crossbar of H; in centre is small space called central canal, extends entire length of spinal cord and contains CSF
- gray matter on each side of spinal cord is subdivided into horns
1. anterior (ventral) gray horn: contain somatic motor nuclei; clusters of cell bodies of somatic motor neurone that provide skeletal muscles
2. posterior (dorsal) gray horns: contain cell bodies and axons of interneurons as well as axons of incoming sensory neutrons
3. lateral gray horns: present only in thoracic, upper lumbar, and sacral segments of spinal cord; lateral horns contain cell bodies of autonomic motor nuclei that regulate activity of smooth muscle, cardiac muscle and glands

7

White Matter

- anterior and posterior gray horns divide white matter
- anterior to gray commissure is anterior white commissure, which connects white matter of right and left sides of spinal cord

8

Spinal Nerves

- part of PNS
- connect CNS to sensory receptors, muscles, and glands
- 31 pairs of spinal nerves
- 8 pairs of cervical, 12 pairs of thoracic, 5 pairs of lumbar, 5 pairs of sacral, 1 pair of coccygeal

9

Branches of Spinal Nerve

- sensory posterior root and motor anterior root project laterally; converge to form a mixed nerve and spinal nerve trunk
- spinal nerve trunk runs for a short distance before branching into two large branches and a a variable series of smaller branches
- large branch is called a ramus

10

Ramus

anterior ramus and posterior rams are somatic branches that run in musculoskeletal system
- posterior ramus serves: deep muscles and skin of posterior
- anterior ramus: serves muscles and structures of upper and lower limbs and muscles and skin of lateral and anterior regions of trunk
- smaller visceral branches, such as meningeal branch and communicating rami, form autonomic pathways to smooth muscles and glandular tissue