The vertebral column part 3 Flashcards
How many sacral vertebrae are there
5 (FUSED)
How many coccygeal vertebrae are there?
1-4 (FUSED)
How many vertebrae are there in total
30-33 depending on how many coccygeal vertebrae there are
Where do the spinal nerves emerge relative to their verebra
C1-C7 - above vertebrae
C8-coccygeal - below vertebrae
Where does the spinal cord extend from
The spinal cord extends from the foramen magnum to approximately the level of the disc between vertebrae LI and LII in adults, although it can end as high as vertebra TXII or as low as the disc between vertebrae LII and LIII (Fig. 2.47). In neonates, the spinal cord extends approximately to vertebra LIII but can reach as low as vertebra LIV.
Describe the distal end of the spinal cord
The distal end of the cord (the conus medullaris) is cone shaped. A fine filament of connective tissue (the pial part of the filum terminale) continues inferiorly from the apex of the conus medullaris.
Is the spinal cord uniform in diameter?
The spinal cord is not uniform in diameter along its length. It has two major swellings or enlargements in regions associated with the origin of spinal nerves that innervate the upper and lower limbs. A cervical enlargement occurs in the region associated with the origins of spinal nerves C5 to T1, which innervate the upper limbs. A lumbosacral enlargement occurs in the region associated with the origins of spinal nerves L1 to S3, which innervate the lower limbs.
Describe the external features of the spinal cord
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The anterior median fissure extends the length of the anterior surface.
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The posterior median sulcus extends along the posterior surface.
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The posterolateral sulcus on each side of the posterior surface marks where the posterior rootlets of spinal nerves enter the cord.
Describe the internal features of the spinal cord
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The gray matter is rich in nerve cell bodies, which form longitudinal columns along the cord, and in cross section these columns form a characteristic H-shaped appearance in the central regions of the cord.
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The white matter surrounds the gray matter and is rich in nerve cell processes, which form large bundles or tracts that ascend and descend in the cord to other spinal cord levels or carry information to and from the brain.
Ultimately, what does the blood supply to the spinal cord consist of
The arterial supply to the spinal cord comes from two sources (Fig. 2.49). It consists of:
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longitudinally oriented vessels, arising superior to the cervical portion of the cord, which descend on the surface of the cord; and
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feeder arteries that enter the vertebral canal through the intervertebral foramina at every level; these feeder vessels, or segmental spinal arteries, arise predominantly from the vertebral and deep cervical arteries in the neck, the posterior intercostal arteries in the thorax, and the lumbar arteries in the abdomen.
What do the longituidnal vessels consist of
a single anterior spinal artery, which originates within the cranial cavity as the union of two vessels that arise from the vertebral arteries—the resulting single anterior spinal artery passes inferiorly, approximately parallel to the anterior median fissure, along the surface of the spinal cord; and
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two posterior spinal arteries, which also originate in the cranial cavity, usually arising directly from a terminal branch of each vertebral artery (the posterior inferior cerebellar artery)—the right and left posterior spinal arteries descend along the spinal cord, each as two branches that bracket the posterolateral sulcus and the connection of posterior roots with the spinal cord.
Describe the segmental spinal arteries
After entering an intervertebral foramen, the segmental spinal arteries give rise to anterior and posterior radicular arteries. This occurs at every vertebral level. The radicular arteries follow, and supply, the anterior and posterior roots. At various vertebral levels, the segmental spinal arteries also give off segmental medullary arteries. These vessels pass directly to the longitudinally oriented vessels, reinforcing these.
Describe how the longituidnal arteries can be reinforced by the medullary arteries
The anterior and posterior spinal arteries are reinforced along their length by eight to ten segmental medullary arteries. The largest of these is the arteria radicularis magna or the artery of Adamkiewicz. This vessel arises in the lower thoracic or upper lumbar region, usually on the left side, and reinforces the arterial supply to the lower portion of the spinal cord, including the lumbar enlargement.
Summarise the venous drainage of the spinal cord
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Two pairs of veins on each side bracket the connections of the posterior and anterior roots to the cord.
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One midline channel parallels the anterior median fissure. (anterior spinal vein)
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One midline channel passes along the posterior median sulcus. (posterior spinal vein)
Where do the veins of the spinal cord drain into
These longitudinal channels drain into an extensive internal vertebral plexus in the extradural (epidural) space of the vertebral canal, which then drains into segmentally arranged vessels that connect with major systemic veins, such as the azygos system in the thorax. The internal vertebral plexus also communicates with intracranial veins.
Describe the spinal dura mater
The spinal dura mater is the outermost meningeal membrane and is separated from the bones forming the vertebral canal by an extradural space. Superiorly, it is continuous with the inner meningeal layer of cranial dura mater at the foramen magnum of the skull. Inferiorly, the dural sac dramatically narrows at the level of the lower border of vertebra SII and forms an investing sheath for the pial part of the filum terminale of the spinal cord.
This terminal cord-like extension of dura mater (the dural part of the filum terminale) attaches to the posterior surface of the vertebral bodies of the coccyx.
How do the spinal nerves emerge through the meninges
As spinal nerves and their roots pass laterally, they are surrounded by tubular sleeves of dura mater, which merge with and become part of the outer covering (epineurium) of the nerves.
Describe the arachnoid mater of the spinal cord
The arachnoid mater is a thin delicate membrane against, but not adherent to, the deep surface of the dura mater (Fig. 2.51). It is separated from the pia mater by the subarachnoid space. The arachnoid mater ends at the level of vertebra SII. Hence the sub-arachnoid space ends at S2.
Describe the sub arachnoid space of the spinal cord
The subarachnoid space between the arachnoid and pia mater contains CSF (Fig. 2.51). The subarachnoid space around the spinal cord is continuous at the foramen magnum with the subarachnoid space surrounding the brain. Inferiorly, the subarachnoid space terminates at approximately the level of the lower border of vertebra SII
Describe the arachnoid trabeculae
Delicate strands of tissue (arachnoid trabeculae) are continuous with the arachnoid mater on one side and the pia mater on the other; they span the subarachnoid space and interconnect the two adjacent membranes. Large blood vessels are suspended in the subarachnoid space by similar strands of material, which expand over the vessels to form a continuous external coat.
What is the clinical benefit of the subarachnoid space ending inferiorly to the spinal cord
The subarachnoid space extends further inferiorly than the spinal cord. The spinal cord ends at approximately the disc between vertebrae LI and LII, whereas the subarachnoid space extends to approximately the lower border of vertebra SII. The subarachnoid space is largest in the region inferior to the terminal end of the spinal cord, where it surrounds the cauda equina. As a consequence, CSF can be withdrawn from the subarachnoid space in the lower lumbar region without endangering the spinal cord.
Describe the spinal pia mater
The spinal pia mater is a vascular membrane that firmly adheres to the surface of the spinal cord. It extends into the anterior median fissure and reflects as sleeve-like coatings onto posterior and anterior rootlets and roots as they cross the subarachnoid space. As the roots exit the space, the sleeve-like coatings reflect onto the arachnoid mater
Describe the denticulate ligaments
On each side of the spinal cord, a longitudinally oriented sheet of pia mater (the denticulate ligament) extends laterally from the cord toward the arachnoid and dura mater (Fig. 2.51).
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Medially, each denticulate ligament is attached to the spinal cord in a plane that lies between the origins of the posterior and anterior rootlets.
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Laterally, each denticulate ligament forms a series of triangular extensions along its free border, with the apex of each extension being anchored through the arachnoid mater to the dura mater.
What is the function of these denticulate ligaments
The lateral attachments of the denticulate ligaments generally occur between the exit points of adjacent posterior and anterior rootlets. The ligaments function to position the spinal cord in the center of the subarachnoid space
What is the vertebral canal bordered by
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anteriorly by the bodies of the vertebrae, intervertebral discs, and posterior longitudinal ligament.
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laterally, on each side by the pedicles and intervertebral foramina; and
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posteriorly by the laminae and ligamenta flava, and in the median plane the roots of the interspinous ligaments and vertebral spinous processes.
What space is present in the vertebral column that you don’t find in the skull?
Epidural/Extradural space
Summarise the epidural space and state the structures found in this space
Between the walls of the vertebral canal and the dural sac is an extradural space containing a vertebral plexus of veins embedded in fatty connective tissue.
Connective tissue
Fat
Internal vertebral venous plexus
What can be palpated in the lumbar and thoracic regions of the vertebral column
The vertebral spinous processes can be palpated through the skin in the midline in thoracic and lumbar regions of the back. Between the skin and spinous processes is a layer of superficial fascia. In lumbar regions, the adjacent spinous processes and the associated laminae on either side of the midline do not overlap, resulting in gaps between adjacent vertebral arches.
What structures are penetrated when carrying out lumbar puncture
When carrying out a lumbar puncture (spinal tap), the needle passes between adjacent vertebral spinous processes, through the supraspinous and interspinous ligaments, and enters the extradural space. The needle continues through the dura and arachnoid mater and enters the subarachnoid space, which contains CSF.
Why do we see an epidural space in the vertebral column
Periosteal layer of dura mater reflects back onto the meningeal layer at the foramen magnum.
What happens at L2
Spinal cord ends- just a bundle of nerves (cauda esquina- looking to leave the vertebral column)
Summarise the movements of the spine
Flexion
Extension
Lateral Flexion
Rotation
Each region has differing degrees of these movements - reflecting presence of ribs and nature of articular facets
What are the muscles of the back organised into
Muscles of the back are organized into superficial, intermediate, and deep groups.
Describe the superficial and intermediate groups
Muscles in the superficial and intermediate groups are extrinsic muscles because they originate embryologically from locations other than the back. They are innervated by anterior rami of spinal nerves:
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The superficial group consists of muscles related to and involved in movements of the upper limb.
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The intermediate group consists of muscles attached to the ribs and may serve a respiratory function.
Describe the deep group
Muscles of the deep group are intrinsic muscles because they develop in the back. They are innervated by posterior rami of spinal nerves and are directly related to movements of the vertebral column and head.
State the superficial muscles
· Trapezius
· Latissimus dorsi
· Levator scapulae
· Rhomboid minor
· Rhomboid major
State the intermediate muscles
· Serratus posterior superior
· Serratus posterior inferior
State the deep muscles
· Spinotransversales
· Erector spinae
· Transversospinales
· Interspinales
· Intertransversarii
Describe the origin, insertion and function of the trapezius
Origin – external occipital protuberance, cervical and thoracic spine
Insertion – clavicle, scapula and acromion
Function – elevate and rotate the scapula when the humerus is abducted
Describe the origin, insertion and function of the latissimus dorsi
Origin – T7 to sacrum + thoracolumbar fasica + posterior 1/3 of iliac crest
Insertion – intertubercular sulcus of the humerus
Function – extends, adducts and medially rotates the humerus
Describe the origin, insertion and function of the levator scapulae
Origin – transverse processes of C1-C4
Insertion – upper medial scapula
Function – elevates the scapula
Describe the OIF of the rhomboid major
Origin – spinous processes of T2-T5
Insertion – medial border of scapula
Function – adduct and elevate scapula
Describe the OIF of the rhomboid minor
Origin – spinous processes of C7-T1
Insertion – medial border of scapula
Function – adduct and elevate scapula
Describe the OIF of the serratus posterior superior
Origin – C7-T3
Insertion – upper border of ribs 2-5
Function – elevates ribs 2-5
Describe the OIF of the serratus posterior inferior
Origin – T11-L3
Insertion – lateral inferior margins of ribs 9-12
Function – depresses ribs 9-12 and prevents lower limbs from elevating when the diaphragm contracts
Describe the OIF of the spinotransversales
Extensors and rotators of the head and neck
The two spinotransversales muscles run from the spinous processes up to T6 and ligamentum nuchae, running superiorly and laterally
Describe the OIF of the erector spinae and transversospinales
Extensors and rotators of the vertebral column
Erector spinae lie posterolaterally to the vertebral column between the spinous processes medially and the angles of the ribs laterally
Transversospinales run obliquely upward and medially from the transverse process to the spinous process
Describe the OIF of the Interspinales and Intertransversarii
These are short segmental muscles that are the stabilisers of the vertebral column
Interspinales – pass between adjacent spinous processes
Intertransversarii – pass between adjacent transverse processe
Why may the range of motion be diminished
Joint pain
Inflammation
What are the consequences of injury at spinal level T10
outflow caudal to T10 will be diminished
What happens as you get further down the spinal cord
Spinal cord level becomes further away from the vertebral level- nerves leave more obliquely at the bottom.
