Comparative anatomy of the spinal cord Flashcards
What are the three general functions of the spinal cord?
Conducts info to and from the brain through a system of axonal tracts,
Connects with spinal nerves
The spinal cord also acts as a reflex centre, producing subconscious muscle responses
Where does the spinal cord end?
the 6th/7th lumbar vertebrae
Where do the axons of each root bind?
they bind laterally to form spinal nerves
What do dorsal roots convey?
Dorsal roots convey sensory input to the spinal cord
What do ventral roots convey?
Ventral roots carry motor input to muscles and glands
Where is the spinal ganglion present?
spiral ganglion are present on each dorsal root
Where do paired spinal nerves emerge from?
spaces formed between vertebrae
What nerve do the first seven spinal segment rootlets join to form?
spinal roots of the accessory nerve
At what point in the spinal cord is the diameter increased?
the two locations where nerves to the limbs arise
Which parts does the cervical enlargement innervate?
innervates the thoracic limb
What is the conus medullaris?
the terminal end of the spinal cord
What is the nerve plexus?
complex, interwoven network of nerves
What forms the nerve plexus?
The ventral branches of spinal nerves
What tissues do the dorsal roots innervate?
epaxial tissues
What tissues do the ventral roots innervate?
hypaxial tissues
Where is the majority of growth after birth?
more growth occurs in the vertebral column than in the spinal cord
What is the cauda equina?
thick bundle of elongated nerve roots within the lower vertebral canal
What is the function of the filum terminale?
glial continuation that persists beyond the functional end of the spinal cord, it stabilises it
Where are spinal arteries suspended?
within small strands of tissue called arachnoid trabecula
What are denticulate ligaments?
fibrous structures that help anchor the spinal cord in place
What is the filum terminale?
fibrous band that extends from the conus medullaris to the periosteum of the coccyx
What is grey matter?
consists of neurons and a neuronal blood supply, it is grey due to perikaryal
What is white matter?
Myelinated and non-myelinated axons, it is white due to the lipid composition of myelin
What is the spinal cord divided into?
symmetric left and right halves by a ventral and dorsal median fissure
What are interneurons?
interposed between a particular input and the resulting output from the spinal cord, can either have long or short axons
Where in the skull does the spinal cord leave?
It exits through the foramen magnum and then runs through the vertebral column
Where does the spinal cord exit?
The level of the 6th/7th lumbar vertebrae
What does the centre of the spinal cord contain?
a central canal filled with CSF and lined with ependymal cells
What parts of the body does the spinal cord innervate?
neck, trunk, tail, limbs and the caudal/dorsal surfaces of the head
What are ependymal cells?
Cells that form the lining of the fluid-filled spaces in the brain and spinal cord
What nerves supply the brachial plexus/ front portion of the animal?
Ventral portion of spinal nerves C6-C8 and T1-T2
What nerves supply the back-end of the animal?
Ventral portion of spinal nerves L4-L7 and S1-S3
Where do remaining spinal nerves exit?
sacral foramina
Where does the C8 spinal nerve exit and why?
It exits through the T1 vertebrae because there isn’t sufficient cranial vertebrae
Where does the first cranial nerve exit?
Through the arch of the atlas in the head
Where does the functional spinal cord terminate?
at L6-L7
Where are spinal cord arteries suspended?
within small strand of tissue called arachnoid trabecula that connects to the pia mater
What is the subarachnoid space in the spinal cord continuous with in the brain?
The foramen magnum
Why is white matter white?
Due to the lipid composition of the myelinated neurons
What is the dorsolateral sulcus?
Where dorsal roots enter the spinal cord
What is the function of the dorsal horn?
contains cell bodies of interneurons where the afferent neurons terminate
What is the function of the ventral horn?
contains cell bodies of the efferent motor neurons supplying skeletal muscles
What is the function of the lateral horns?
Where autonomic nerve fibres that supply cardiac and smooth muscle originate from
What are the ventral branches of spinal nerves that form the brachial plexus?
C6, C7, C8, T1 and T2
What spinal nerves form the nerve plexus?
L4, L5, L6, L7, S1, S2 and S3
How many segments are usually in the spinal cord of dogs?
36
Where is the cervical enlargement of the spinal cord?
C6-C7 intervertebral disc
What kind of cells produce CSF?
Ependymal cells
What are dorsal/ventral roots made up of?
Thousands of axons
What root are spinal ganglion present on?
The dorsal root
How many cervical vertebrae and cervical segments/ nerves are there, and what is the significance of this?
There are 7 cervical vertebrae and 8 cervical segments/ nerves, the first cervical nerve exits through the arch of atlas and cervical nerve C8 exits between vertebrae C7 and T1
