MBJ Review: Back Anatomy
List 4 reasons why doing a spinal tap in the lumbar region is most ideal.
1. Because of the presence of a space and fluid-filled lumbar cistern 2. Because the cauda equina with its branches are harder to puncture than the spinal cord at higher levels 3. There is a good amount of space between adjacent vertebrae for access
What are the functions of the intervertebral disc?
1. Flexibility/Mobility 2. Shock Absorption (nucleus pulposus is responsible) 3. Transmits loads through the vertebral column
What are 2 unique features of the atlas?
1. It lacks a vertebral body (and intervertebral disc above and below it) 2. the presence of lateral masses (superior and inferior articular facets, which are pretty large)
What are three unique features of thoracic vertebrae?
1. They possess a transverse costal facet on the transverse process for articulating with the ribs 2. small, heart-shaped vertebral body 3. posteroinferiorly-angled spinous processes
What are five unique features of typical cervical vertebrae?
1. foramen transversarium (for the vertebral arteries) 2. long spinous processes 3. small vertebral bodies 4. large vertebral foramina (region where brachial plexus is) 5. (Sometimes) bifid spinous process
Which muscles are deeper than the transversospinalis muscles?
1. interspinalis 2. intertransversarii 3. levatores costarum
What are three unique features of the lumbar vertebrae?
1. large vertebral bodies 2. shorter, thicker spinous processes 3. slender transverse processes
What forms the vertebral arch?
2 pedicles and 2 laminae (laminae are closer to the spinous process)
How many vertebrae are there in each section of the vertebral column?
7 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal (may vary in number)
What is a Jefferson fracture?
A fracture of the arches of the atlas in which axial loading causes a vertical compression due to a blow to the top of the head.
When would a spinal anesthetic be used, as opposed to an epidural?
During a C-section
Which opening in the skull does the vertebral foramen of the atlas align with?
Foramen magnum
What is the extent of the transversospinalis muscles?
From the transverse process of one vertebra to the spinous process of the adjacent vertebra
Name two actions of the levator scapula
It elevates and rotates the scapula; helps with stabilisation
What is the relevance of the thickness of the anterior longitudinal ligament?
It is the only ligament that resists the backward bending of the spine
What is the significance of the end plate of a vertebra?
It marks the end of the capillary network of the vertebra, which means that oxygen, nutrients etc. have to diffuse to the (avascular) intervertebral disc.
What is the extent of the anterior longitudinal ligament?
It runs from the sacrum to the skull.
What is the significance of the fact that aggrecans are very hydrophilic?
It stores water within intervertebral discs well.
What is the course of the multifidus muscle?
It travels from the transverse process of one vertebra up to the spinous process of a vertebra about 4 vertebrae higher.
Which is the deepest and most superficial muscle of the transversospinalis muscle group?
Most superficial-semispinalis Deepest-rotatores
Where does the splenius cervicis originate and insert?
Origin: spinous processes of the lower vertebrae Insertion: transverse processes of cervical vertebrae (C1 to C4)
What is the origin and insertion of the splenius capitis?
Origin: the ligamentum nuchae and spinous processes of vertebrae (from C7-T6) Insertion: mastoid process and superior nuchal line
What is the origin and insertion of spinalis capitis?
Origin: the nuchal ligament and spinous processes of C7-T4 Insertion: occipital bone
What is the origin and insertion of the iliocostalis cervicis muscle?
Origin: the ribs Insertion: the transverse processes of C4-6
What is the origin and insertion of the semispinalis muscle?
Origin: the spinous processes of some vertebrae Insertion: the transverse processes of other vertebrae (for semispinalis capitis, origin is transverse and articular processes of C4-T6 and insertion is occipital bone)
What is the origin and insertion of the levator scapulae?
Origin: transverse process of cervical vertebrae (C1-C4) Insertion: the medial border (specifically, the superior 1/3) of the scapula
What is the origin and insertion of the longissimus capitis muscle?
Origin:the transverse processes of the upper thoracic vertebrae and lower cervical vertebrae Insertion: the mastoid process
What are the two major parts of the intervertebral disc?
Outer annulus fibrosus and inner nucleus pulposus
Where does the dura mater end?
S2 (covers some of the cauda equina)
Which nerves are anesthetized during the administration of an epidural?
S2-S4 (give rise to the pudendal nerve (supplies sensation to the external genitalia) and vesveral afferents from pelvic viscera
What do the superior and inferior articular surfaces/facets of the atlas articulate with?
Superior-the occipital condyles of the occipital bone Inferior-the superior articular facets of the axis
What is the name of the single filament running down from the conus medullaris to the coccyx?
The filum terminale
What is the difference between levatores costarum longus and levatores costarum brevis?
The former crosses two vertebrae, while the latter crosses two (all crossing is to inferior vertebrae).
In what way are sacral vertebrae different from vertebrae of other regions?
They are fused
What happens to the vertebral arteries as they pass through the foramen magnum?
They become the basilar artery
If the trapezius and the sternocleidomastoid work together, what action do they cause?
They help to bring the chin towards the sternum
How do lumbar articular processes differ from those of the thoracic vertebrae?
They show much overlap, causing limited mobility, while thoracic vertebrae show less overlap and more mobility
What happens to our intervertebral discs as we age?
They stiffen
How do the vertebral arteries enter the skull?
Through the foramen magnum
What is the annulus fibrosus made up of?
Type I collagen, few proteoglycans
What is the nucleus pulposus?
Type II collagen, many proteoglycans (i.e. aggrecans)
How would you instruct a patient while doing a lumbar puncture?
You would tell the patient to curl/bend over.
What kind of movement does the atlanto-axial joint allow for?
a "no" motion
What is a side effect of administering a spinal anesthetic?
a headache, due to the leakage of CSF from the dura mater
Which feature is present in the axis, but absent in the atlas?
a vertebral body (which forms the dens)
What is the trapezius innervated by?
accessory nerve (CN XI) , (C3,4 etc. spinal nerves also play a role)
What are the names of the joints formed between the occipital bone and the atlas, and between the atlas and axis, respectively?
atlanto-occipital joint and atlanto-axial joint
What structure is found between vertebrae and their adjacent intervertebral discs?
cartilage
What is the end of the spinal cord called?
conus medullaris
What are the main actions of the splenius cervicis?
extension of the head
What is the action of the longissimus capitis?
extension of the head and neck
What action do the semispinalis capitis muscles on both sides have together?
extension of the head/neck
What are the main actions of the splenius capitis individually (each side) and together?
extension of the neck (together), lateral flexion (individually)
What is a hangman's fracture?
fracture of the pedicles/pars articularis of the axis
What is the course of the levatores costarum?
from a transverse process to a rib
What is the span of the supraspinous ligament?
from the sacrum to C7
What is the course of interspinalis?
from the spinous process of one vertebra to the spinous process of the adjacent vertebra
What is the course of the intertransversarii?
from the transverse process of one vertebra to the transverse process of the adjacent vertebra
Which region of the body is anesthetized during the administration of a spinal anesthetic in the lumbar region?
from the waist down
Which muscles make up the erector spinae muscles?
iliocostalis (runs between ilium of pelvis to ribs), longissimus (middle sector), and spinalis (closest to the spine)
Where does the longitudinal membrane superiorly end?
in the cranium
Where is the spinalis muscle found?
in the groove of the spinous process
What is the name of the ligament running between the spinous processes of adjacent vertebrae?
interspinous ligament
Which muscle is deep and lateral to the splenius capitis?
levator scapulae
Which is the last ligament punctured before entering the epidural space, if a needle is used to puncture the muscles of the back?
ligamentum flavum
Which vertebral ligament runs between the laminae of adjacent vertebrae?
ligamentum flavum
What movement does the atlanto-occipital joint allow for?
nodding (flexion and extension of the head)
Where are facets (containing synovial cartilage) found?
on the superior and inferior articular processes of the vertebrae
What is another name for the pedicle of the axis?
pars interarticularis
Which method is easiest for accessing the vertebral canal during a lumbar puncture?
piercing the ligamentum flavum
What does the sternocleidomastoid do independently?
rotation of the head & movement of head from side to side;
What are the main actions of the trapezius?
rotation of the scapula, movement of the neck and head (e.g. elevation)
Which of the rotatores muscles travels from the spinous process to the transverse process, and which travels from the transverse process to the spinous process?
rotatores longus and rotatores brevis, respectively
What lind of joint is the intervertebral joint?
secondary cartilaginous/symphysis joint
Which muscle in the neck is directly deep to the trapezius?
splenius capitis (Clue: splenius means bandage)
Which ligaments link the dens and occipital bone?
the alar ligaments
Which vertebral ligament runs anterior to the vertebral bodies and intervertebral disc?
the anterior longitudinal ligament
What passes through the vertebral foramen of the sacral vertebrae?
the cauda equina
What is the combination of the transverse ligament of the atlas and the longitudinal membrane called?
the cruciate ligament (cruciate means cross)
What is the trapezius attached to medially?
the external occipital protuberance, spinous processes of vertebrae (C7- T12) and the nuchal ligament
What does the supraspinous ligament become as it reaches the neck?
the ligamementum nuchae (nuchal ligament)
Which structure supports the transverse ligament's function in keeping the dens in place?
the longitudinal membrane
What is the subarachnoid space, filled with CSF and nerve roots, within the lumbar region called?
the lumbar cistern
What does the splenius capitis insert into?
the mastoid process
What is the superior boundary of the ligamentum nuchae?
the occipital protuberance
Name one unique feature of the axis
the presence of the dens/odontoid process
Which muscles of the back are directly deep to the erector spinae?
the semispinalis capitis
Which three muscles make up the transversopinalis muscle group?
the semispinalis, the multifidus, rotatores muscles
What does the trapezius attach to laterally/distally?
the spine of the scapula (posteriorly) and the clavicle anteriorly
What is the inferior boundary of the ligamentum nuchae
the spinous process of C7 vertebra
What covers the spinous processes of the vertebrae?
the suprapinous ligament
Which ligament is found anterior to the dens, and what purpose does it serve?
the transverse ligament of the atlas; it holds the dens in place and separates the dens from the spinal cord
What passes though the foramen trasversarium?
the vertebral artery
What is the name of the group of deepest muscles of the back?
transversospinalis
What is the most superficial muscle in the posterior neck?
trapezius
The vertebral column and spinal cord are about the same length up until which point?
~3 months of IUL (vertebral column gets longer thereafter with spinal cord stopping at about the L3 vertebra by birth and L2 by adulthood)
Semispinalis has a course similar to that of the multifidus muscle. However, it crosses a different number of vertrbrae. How many?
~6