ANA 303 Spinal Cord Flashcards
The spinal cord is located________and extends from _______ to __________?
Where does it occupy?
The spinal cord is located within the vertebral canal and extends from the foramen magnum
(medullary spinal junction) to the first or second lumbar vertebra.
It occupies the upper two thirds of the vertebral
column. The rest of the cord is occupied by cauda equina
The conical-shaped caudal end of the spinal
cord, known as the_____________
conus medullaris
What is the filum terminale internum?
A thin filament enclosed in pia and consisting of glial cells, ependymal cells, and astrocytes emerges from the conus medullaris. This filament is called the filum terminale internum.
What is the filum terminale externum?
At this level, a caudal thin extension
of the spinal dura, called the coccygeal ligament (filum terminale externum) surrounds the filum terminale.
What anchors the spinal cord?
Filum terminale
Why is it that in an adult, the spinal cord occupies only the upper two-thirds of the vertebral column?
The spinal cord occupies the whole length of the vertebral canal up to the third month of fetal life. Then it lengthens at a slower rate than the vertebral column
What is the cauda equina?
The lumbosacral nerve roots surround the filum terminale and form a cluster that resembles the tail of a horse and that is called the cauda equina
What is the lumbar cistern?
The subarachnoid space is the widest from the caudal end, L1. of the spinal cord to S2 and contains no CNS structures except the filum terminale and the nerve roots of cauda equina. This space is known as the lumbar cistern
Clinical significance of lumbar cistern
Because of this anatomic feature, this space is most suitable for the withdrawal of cerebrospinal fluid (CSF) by lumbar puncture. The site for performing a lumbar puncture changes with age in childhood. For example, in children, the caudal end of the spinal
cord is usually located at the third lumbar vertebra (L3); therefore, the needle for lumbar puncture is inserted at the L4–L5 level
How many segments does the spinal cord have?
31
How many pairs of nerves does the spinal cord have? How many does each segment have?
31 pairs
Cervical 8 pairs
Thoracic 12 pairs
Lumbar 5 pairs
Sacral 5 pairs
Caudal 1 pairs
At each level, the spinal nerves exit through the ____________
intervertebral foramina
Each spinal nerve consists of a______________
dorsal root (containing afferent fibers) and a ventral root (containing efferent fibers).
Function of the dorsal root ganglion
The spinal ganglion (dorsal root ganglion) is located within the intervertebral foramen and contains the neurons that give rise to afferent fibres entering dorsal horn of the spinal cord.
The dorsal and ventral roots are joined distal to the spinal ganglion and form the___________
common spinal nerve
Describe the cervical enlargement
The nerve roots emerging from this enlargement form the brachial plexus and innervate the upper extremities.
Describe the lumbar enlargement
The lumbar plexus (comprising the nerve roots from L1–L4) and sacral plexus ( consisting of nerve roots from L4–S2) emerge from the lumbar enlargement. The lumbar
plexus innervates the lower extremities.
The sacral spinal nerves contain and innervate____________
The sacral spinal nerves emerging from the conus medullaris contain parasympathetic fibres and motor fibres innervating the bladder
and its sphincters, respectively.
Describe the internal structure of the spinal cord with reference to the matter
The inner core of the spinal cord is formed by grey matter, and it is surrounded by white matter at the periphery consisting of ascending and descending bundles of myelinated and unmyelinated axons that are called tracts or fasciculi.
A tiny central canal filled with CSF at its center.
Surrounding the canal is a single layer of cells, the ependymal layer.
What is a funiculus?
A bundle containing one or more tracts or fasciculi is called a funiculus
What are the 3 funiculi?
In each half of the spinal cord, there are
three funiculi: (1) the dorsal (posterior) funiculus, which is located between the dorsal horn and a midline structure called the dorsal (posterior) median septum;
(2) the lateral funiculus, which is located between the sites where the dorsal roots enter and ventral roots exit from the spinal cord; and
(3) the ventral (anterior) funiculus, which is located between the anterior (ventral) median fissure and the site where the ventral roots exit
The anterior white commissure,
consisting of____________and located___________
decussating axons of nerve cells, is located
ventral to the gray commissure
The two sides of the gray matter are connected by a band of gray matter called the _____________
gray commissure (lamina X).
Where is the central canal located
in the grey commissure
The general senses are classified as follows:
- Exteroception: Sensations perceived by the body, arising from the external world and including touch, pressure, vibration, pain, thermal sensation, itch, tickle, etc.
- Proprioception: Sensations perceived by the body, generated by the own tissues and include perception of posture, joint position and movement, muscle contraction and stretch.
- Interoception: Sensations perceived by the body, arising from the internal world and including sensations
