Anatomy Lecture 3: Spinal Cord Flashcards
Structures of the central nervous system
Brain and spinal cord
What are the major subdivisions of the nervous system?
Central nervous system (CNS)
Peripheral nervous system (PNS)
Structures of the peripheral nervous system
All parts external to the CNS:
12 pairs of cranial nerves,
31 Paris of spinal nerves,
Peripheral portions of autonomic nervous system (ANS)
What are the functional divisions of year nervous system and their definitions?
- Somatic: innervates structures in body wall (skeletal m., skin, bones)
- Autonomic: innervates viscera (smooth m., cardiac m., glands)
What are 4 characteristics of the spinal cord?
- Solid structure with hollow central canal containing cerebrospinal fluid (CNF)
- Two types of tissue: grey and white matter
- Diameter varies along length of cord
- Has 31 segments, 1 segment per pair of spinal nerves
What are characteristics of spinal cord grey matter?
- Includes neuron cell bodies
- Centrally situated in spinal cord
- Cross-section shaped like H (or butterfly), with 2 dorsal horns and 2 ventral horns
What are characteristics of spinal cord white matter?
- Consists if axons and glial cells, no neuron cell bodies
2. Surrounds grey matter
What are the spinal enlargements called and what do honey relate to?
- Cervical enlargement - relates to upper limbs
2. Lumbar enlargement - relates to lower limbs
Define conus medullaris
Tapered inferior end of spinal cord below lumbar enlargement.
What are the spinal cord segments and how many segments correspond to them?
- Cervical segments: 8
- Thoracic segments: 12
- Lumbar segments: 5
- Sacral segments: 5
- Coccygeal segments: 1
What are the constituents of each spinal nerve?
- Rootlets emerge from spinal cord and unite to form dorsal and ventral roots
- Spinal nerve proper (mixed spinal nerve) formed from Union of dorsal and ventral roots
- Spinal nerve proper divides to form dorsal and ventral rami
- Recurrent meningeal (sinuvertebral) nerve
What are characteristics of the dorsal (posterior) root?
- Carries sensory (afferent) fibers toward spinal cord
2. Dorsal root ganglion: swelling at distal end of root, contains sensory fiber cell bodies
Where are dorsal root ganglion found throughout the segments of the spine?
- Cervical: ganglia extend lateral to intervertebral foramina
- Thoracic/Lumbar: ganglia within foramina, but usually don’t extend beyond
- Sacral: ganglia with in sacral canal medial to intervertebral foramina
Usually the first cervical nerve has no dorsal root, which nerve takes over?
C2
What are the characteristics of the ventral root?
- Carries motor (efferent) fibers away from the spinal cord
- Cell bodies of these motor fibers are in spinal cord grey matter
- Two types: somatic and visceral (autonomic) motor fibers
What are somatic motor fibers and where are they found?
Control voluntary (skeletal, striated) muscle fibers. Present in every ventral root.
What are visceral (autonomic) motor fibers, what are the different types, and where are they found?
Control involuntary muscle fibers and certain glands.
Two types: sympathetic and parasympathetic, both preganglionic
Sympathetic motor fibers carried in T1-L2 ventral roots only
Parasympathetic motor fibers carried in S2-S4 ventral roots only
What types of fibers do spinal nerve proper (mixed spinal nerve) carry?
Carry somatic motor, sympathetic, and sensory fibers irrespective of spinal cord level.
What are the characteristics of the dorsal ramus?
- Supplies both motor and sensory innervation to deep back muscles
- Gives off posterior cutaneous nerve to skin of back
What are the characteristics of the ventral ramus?
- Supplies both motor and sensory innervation to muscles of lateral and anterior body wall, and limbs
- Has branches to skin: Lateral and Anterior cutaneous nerve
- Ventral rami that supply limbs and neck for a plexus
In the sacral region, where do the rami exit through?
Dorsal rami emerge through dorsal sacral foramina and ventral rami emerge through ventral sacral foramina.
Which rami has a larger diameter?
The ventral ramus has a larger diameter except the 1st and 2nd cervical spinal nerves.
What is the C2 dorsal ramus called?
The greater occipital nerve.
What connects the sympathetic trunk to the ventral rami?
Rami communicantes
