Vertebral Column and Back 1-5-17
What is the purpose of the intervertebral disks, and what are they responsible for?
"Shock absorbers" in between each vertebrae *Discs are responsible for ~1/4 of the height of the column* Allow some flexion of the vertebral bodies between each other
All mammals have _____ cervical vertibrae.
7
List the kinds of human vertebrae and number of each kind (cranial to caudal)
7 Cervical 12 Thoracic 5 Lumbar 5 Sacral (fused) 4 Coxygeal (fused)
Where is flexion-extension greatest in the spine?
Cervical, lumbar (not thoracic)
What restricts the mobility of vertebrae in different regions of the body?
Change in direction of the facet joints (angle of facet joints)
What forms the "H" shaped pattern in cross section of the spinal cord, and what are they topographically divided into?
Collections of nerve cell bodies (grey matter) *Dorsal (sensory) and ventral (motor) horns*
Describe the pia mater.
Composed of 2 fused layers of loose connective tissue, which encloses the network of blood vessels which supply the spinal cord.
Which spinal arteries are supplied by the medullary artery?
Anterior spinal artery (longitudinal, runs all the way down) *Posterior spinal artery (longitudinal, pairs runs all the way down)*
Where is the body of the vertebra located in relation to the spinal cord?
Anteriorly
What is the epidural space surrounded by?
Anteriorly: posterior longitudinal ligament, and intervertebral discs and bodies of vertebrae *Laterally: periosteum on the pedicles and 38 intervertebral foramen* Posteriorly: laminae and ligamentum flavum
What is located inside the dura mater?
Arachnoid mater and denticulate ligament.
Which nerves innervate the spinal canal?
Articular nerve *Recurrent meningeal nerve*
Where do vertebral body compression fractures typically happen?
Because weight of the body is largely anterior to the spinal column, compression fractures most commonly occur first within the anterior portion of the vertebral body.
Describe the pattern of body size from C3 to L5.
Becomes progressively larger caudally
Where is rotation greatest in the spine?
Between C1 and C2 = most *Cervical and thoracic, NOT lumbar*
Where is there no lateral flexion in the spine (cervical to lumbar)?
Between atlas (C1) and axis (C2)
Where is the epidural space located?
Between the dura mater of the spinal cord and the periosteum of the vertebra (and ligaments).
What are the parts of a "typical" (lumbar) vertebra (and how many of each exists)?
Body *Vertebral arch (2 pedicles, 2 laminae)* 4 articular processes *2 transverse processes* 1 spinous process
What is the response of intervertebral disks to increased load?
Bulge into the intervertebral foramen
What is the sacrum?
Called sacred because last bone of body to deteriorate in the soil *5 fused vertebrae, wedge shaped bone supporting vertebral column, forming the posterior of bony pelvis.
Describe the special features of C1.
Called the "atlas" *Superior articular facets receive occipital condyles of the occipital bone of the skull* No body and no spinous process, but does have a posterior arch and posterior tubercle. *The posterior arch has groove (or sulcus) for each vertebral artery, just behind the superior articular facets*
Describe the special features of C2.
Called the "axis" *Has a body and spinous process* Two large superior articular facets *one large dens/odontoid process formed during embryonic development from body of the first cervical vertebra.*
Where is the largest spinal subarachnoid space located?
Caudal to the conus medullaris (L2) and prior to termination of the dura mater at about S2, called the lumbar cistern.
Describe the location of the spinal somatic motor nerve cell body, its axon, and what it innervates.
Cell body lies in the ventral horn of the spinal cord and sends its axon throughout the body to innervate muscle as far as a meter away *Multipolar motor neuron*
Where is lateral flexion greatest in the spine?
Cervical and lumbar only slightly better than thoracic
In what direction does the spinous process extend from the body? What is it connected by?
Posteriorly and inferiorly *Connected by interspinous ligaments and supraspinous ligaments*
What is the preganglionic neurotransmitter for the sympathetic nervous system? Postganglionic?
Pre = acetylcholine *Post = norepinephrine*
Compare where the spinal cord ends vs where the dura mater and subarachnoid space ends.
Spinal cord = conus medullaris at L2 (or higher) *Dura/subarachnoid = S2*
What is the impact of a bulging intervertebral disc on the spinal nerves?
Spinal nerves can be compressed against the ligamentum flavum and boney elements.
What is the cauda equina?
Spinal nerves distal to the conus medullaris
What is spondylolisthesis often caused by, and what does it result in?
Spondylolysis of the L5 vertebra, allowing the vertebral column to slide forward on top of the sacrum, resulting in compression of sacral spinal nerves and thus, leg pain.
What is the filum terminale?
Strand of connective tissue from the end of the conus medullaris (L2) to inferiorly attach to the dural sac (S2) *Inferiorly, below the dural sac the filum terminale externa (central ligament) attaches to the periosteum of the coccyx* Upon flexion, pulls the spinal cord anteriorly.
Describe the location, orientation, and function of the anterior longitudinal ligament.
Strong, broad, fibrous band running anterior to the vertebral bodies and discs from base of skull to sacrum *Limits hyperextension*
What is the role of the great ventral medullary artery of Adamkiewicz?
Supplies spinal cord blood between T8 and L3, arises from inferior intercostals or superior lumbar arteries (off of aorta) *Left-sided in 70-80% of people*
Which division of the autonomic nervous system is thoracolumbar? Craniosacral?
Sympathetic = thoracolumbar *Para = craniosacral*
What is the name of the posterior longitudinal ligament at the base of the skull?
Tectorial membrane (as it crosses C1 and the occipital bone and on to the clivus region of the occipital bone)
What is the lumbar cisterna?
The area between L2 to S2 that contains the cauda equina, filum terminale, and cerebral spinal fluid
As you run your fingers down the back of your neck the first "bump" in the midline you feel is what?
The vertebral prominence (extra long spinous process of C7).
What is supplied by the radicular arteries?
Vertebrae
For the thorax, lumbar, and sacral regions, the spinal nerve exits ________ the corresponding vertebra.
below
Cervical spinal processes of C2-C6 are normally _________, but not _____ nor _____.
bifid C1 C7
The spinal cord has ________ ______ curvature in uterio, whereas the adult spine develops _____ curvature.
concave anterior *Secondary*
What is the ala of the sacrum?
lateral mass of the sacrum that articulates with the pelvis.
Spinal tap: Typically, ~____ml of CSF is removed in a series of 4 collecting tubes, which should become progressively _______ _______.
4 less bloody
What is scoliosis?
Abnormal lateral and/or rotational curvature of the vertebral column within the coronal or frontal plane.
If subluxation is greater than ______, it is considered unstable and immediate surgery is recommended.
3.5mm
Preganglionic fibers may synapse on up to _________ postganglionic fibers. What does this mean for the sympathetic response?
30 Sympathetic response is generalized
The spinal cord contains _______ pairs of spinal nerves made up of _________ ________ __________ and ________ __________ __________.
31 ventral motor roots dorsal sensory roots
Describe spina bifida occulta.
*Occurs in 2-10% of population* Generally a tuft of hair develops over a region of spine which lack a portion of the bony coverings (e.g. lamina defect, spinous process) *Typically lower lumbar or sacral, but also can be cervical*
The depth of the spinal tap needle penetration until it gets into CSF is about _______ in in a child and up to ______ in in an obese adult.
1 4
What is the order of structures that a midline spinal tap needle will penetrate?
1. Skin 2. Subcutaneous tissue 3. Suraspoinous ligament (toughest) 4. Interspinous ligament 5. Ligamentum flavum (tough; in some patients this structure may not be present in the midline) 6. Fatty tissue (and venous blood) within the extra dural space 7. Dura mater (tough) 8. Arachnoid mater; and into the subarachnoid space
What is the normal volume of CSF, and how much is produced each day?
120-150 ml (95 around/in brain, 35-55 around spinal cord) *450-500 ml daily*
How many nerves are involved in an autonomic signal pathway?
2
How many cervical spinal levels are there? Why?
8 (despite 7 cervical vertebrae) *C1 nerve (only motor components) exits above the atlas, and C2 nerve exits below the atlas. Thus, C8 nerve exits below C7 vertebra.*
Compare the matching of spinal cord and vertebral canal in week 8 of fetal development vs adulthood.
8 weeks: spinal cord fills the vertebral spinal canal, spinal level matches vertebral level *Adulthood: vertebral column outgrows spinal cord, and some spinal nerves have to travel long distances to their respective vertebra (lower lumbar and sacral)*
Describe the peripheral nervous system.
A collection of nerve fibers and cell bodies outside the central nervous system, made up of either spinal or cranial nerves. *Peripheral nerves carry info (sensory or afferent) to the spinal cord and brain, or controls movements and functions of the body (motor or efferent) from the brain and spinal cord to the body*
What is spondylolisthesis?
Aka subluxation *Slipping of vertebra in relation to the adjacent inferior vertebra or sacrum.*
Describe the dura mater.
Aka theca or capsule *Tough fibroelastic connective tissue sheath* Free within the vertebral canal *Continuous with the cranial dura at the foramen magnum* Ends at the inferior border of S2 in most adults *Dura mater is continuous with epineurium of peripheral nerves*
Describe facet joints.
Aka zygapophyseal joints *Paired facets* Synovial joints between hyaline cartilage *Surrounded by an articular capsule* Facet joints are between adjacent superior and inferior articular processes *Limit movement between adjacent vertebrae*
What is the coccyx?
Also called the laymen's tailbone, 3 or 4 fused vertebrae.
Describe the 2 parts of the intervertebral disk.
Annulus fibrosis = concentric layers of oblique fibers running around and between vertebral bodies *Nucleus pulposus = an avascular gelatinous mass, derived from the notochord. Acts as a shock absorber and semifluid ball bearing*
What is kyphosis?
Anterior concave curvature of the vertebral column. *In adults, excessive or pathologic anterior curvature of the spine, most frequently in the upper thoracic region in the elderly*
What is lordosis?
Anterior convex curvature of the vertebral column *Normal lordosis of the lumbar and cervical regions occurs upon holding ones head up and standing* Most frequent lordosis in adults is within the lumbar spine (can occur with pregnancy)
What can cause pain in osteoporosis?
Compression fractures that trap spinal nerves as they pass out the intervertebral foramen, leading to pain or loss of function as the spinal nerves exit out the intervertebral foramen. *Vertebral compression fracture affect up to 25% of postmenopausal women in the U.S.*
Describe the path of the spinal cord.
Cylindrical structure beginning at the medulla *Exits from the foramen magnum and ends at L1 or 2 in ~90% of adults*
What are the 3 parts of the meninges of the spinal cord?
Dura mater *Arachnoid mater* Pia mater
When does scoliosis most frequently initiate?
During adolescence
Where does the dura mater end, and what does this mean for extradural space?
Ends at ~S2 within the sacrum *There is a large extradural space (15-45 ml) filled with fat and mainly venous blood*
What occupies much of the sacarl canal after the dural sac ends below S2?
Epidural space
What is between the dura mater and periostium? What is it filled with?
Extradural or epidural space *Filled with fat and venous blood vessels that generally lack valves*
What is outside the spinal dura mater?
Fat, arteries, veins, then periosteum
What is the epidural space occupied by?
Fat, loose connective tissue, and internal vertebral venous plexus.
What is a symphysis, and what is an example of one?
Fibrocartilaginous articulation between hyaline cartilage *Intervertebral discs*
What is the function of the intervertebral foramen? What is it formed by?
Formed by the inferior and superior vertebral notches *Contains dorsal root ganglion and spinal nerves*
What is the function of the vertebral foramen?
Forms the vertebral canal containing the spinal cord.
From where does the transverse process originate, and what is its function?
From the junction of the pedicles and laminae *Site of muscle attachment*
Describe the special features of thoracic vertebrae.
Have at least one or sometimes two facets for the heads of ribs on each side of each body *Have an additional facet for tubercle of rib on the transverse process* Very stable, all articulate with ribs *Look like a giraffe's head*
What are some complications of a spinal tap?
Headaches (typically 24-48 hours later, thought to be due to continued leakage of CSF out of the meninges; autologous injection of blood @ site sometimes performed to help alleviate problem) *Brain herniation, as the loss of CSF out of the lumbar leak forces the brain down the spinal canal; this can be life threatening*
Inferior articular processes face __________ and ________, while superior articular processes face _______ and _______.
Inferior and lateral Superior and medial
Where in the spinal cord is the preganglionic nerve cell body located?
Intermediolateral column
A horizontal line across the superior iliac crests generally falls between _____ and _____ or on the _____ spinous process.
L3 and L4 L4
CSF is most commonly taken from the lumbar cisterna by inserting a spinal tap needle between ____/____ or ____/_____.
L3/L4 L4/L5
Where does spondylolysis typically occur? Most rarely?
L5 (85-95%) *L4 (5-15%)* Very rarely higher lumbar areas
Describe the special features of lumbar vertebrae.
Large kidney shaped vertebral bodies with no facets for ribs *Articular processes project superior and inferior thus limiting rotation while permiting flexion and extension* Contain an additional process for muscle attachment - the mammillary process (also present on 4 inferior thoracic vertebrae) *Looks like a moose's head because spinous process is very thick and rounded*
What is the function of the articular facets?
Limit rotation and flexion of adjacent vertebral bodies; adds stability to the vertebral column.
Which regions of the spine are involved most frequently in scoliosis?
Lumbar and thoracic
Where do typical spinal taps collect CSF from?
Lumbar cisterna: Largest subarachnoid space, caudal to conus medullaris and prior to termination of the dura mater at about S2.
What is the function of the cerebrospinal fluid?
Mechanical and protective support for the brain *Ion sink, important for brain excitability*
Describe the location, orientation, and function of the posterior longitudinal ligament.
Narrower in lower lumbar region, weaker than anterior longitudinal ligament *Runs within the vertebral canal, just anterior to the spinal cord (posterior to the vertebral bodies)* Helps stabilize the vertebral bodies
How are the radicular and medullary arteries related?
Often one cannot determine where the artery terminates, so the term radiculmedullary artery is then used.
Describe C7's foramen transversarium (what goes through it?).
Only contains accessory vertebral vein (in most of the population).
What is the sacral hiatus?
Opening on the posterior surface at the end of the sacral canal. *Marked on either side by inferior sacral cornu and covered by the posterior sacrococcygeal ligament.* Due to failure of the posterior arch of S5 (and occassionally S4) to form and fuse in the midline. *Easy access for an epidural*
What portion of the vertebra is often defective in spondylolisthesis?
Pars interarticularis (portion between superior and inferior articular facet on each vertebra)
In which direction does the posterior ligament grow larger (cranial/caudal)? Anterior?
Posterior grows larger as you move cranially *Anterior grows larger as you move caudally*
Describe the location of the spinal somatic sensory nerve cell body, its axon, and what it innervates.
Resides in the dorsal root ganglia (typically sits within interveterbral foramen) receiving information via an axon from the periphery and synapsing on nerves in the dorsal horn of the spinal cord. *Pseudo-unipolar sensory neuron*
What is the denticulate ligament?
Ribbon-like structure, formed of pia mater, extending laterally from the midline from each of the spinal cord to attach to the inner surface of the dura in 21 tooth-like projections. *Denticulate ligament stabilizes the spinal cord within the dura matter*
Describe the location, orientation, and function of the ligamentum flavum.
Rich in elastic (yellow) fibers *Extend from lamina to lamina* Forms the posterior boundary of intervertebral foramen and the posterior wall of spinal canal along with the lamina of the vertebrae
What is a rhizotomy?
Sectioning of the dorsal (sensory) or ventral (motor) roots of a spinal nerve in order to relieve intractable pain (dorsal rhizotomy) or spastic paralysis (ventral rhizotomy)
Describe the arachnoid mater.
Separates the pia from the dura by a fluid filled space (subarachnoid space) *Applied both directly to the inner surface of the dura (parietal layer) and sends arachnoid trabeculae through the subarachnoid space to the pia (visceral layer)* Arachnoid mater on the inner dural surface is normally impermeable to most fluid flow and thus is responsible for containing the cerebral spinal fluid.
Where do short preganglionic sympathetic fibers synapse? Where else can longer fibers synapse?
Short = paravertebral (sympathetic chain) ganglia *Longer = prevertebral ganglia (such as celiac and mesenteric)*
Describe the appearance, specific gravity, and pressure of normal CSF.
Should be clear fluid w/ specific gravity of 1.007 *Normal pressure of 70-180 mm*
The spinal cord connects what two things?
The central nervous system and peripheral nervous system.
What is special about the cervical vertebrae?
They have a transverse foramen (hole in the transverse process) for the vertebral artery in C1-C6
Which regions of the spine retain their primary curvature?
Thoracic and sacral
What is spondylolysis?
Typically is a defect in the pars interarticularis (part between the superior and inferior facets)
