Anatomy: Back

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Questions and Answers

What is the function of the vertebral arch?

To provide attachment points for muscles

To protect the spinal cord (correct)

To form the sides of the vertebral foramen

To increase the weight of the vertebral column

What is the term for the space enclosed by the vertebral arch and body?

Vertebral canal

Vertebral foramen (correct)

Central cavity

Spinal canal

How many articular processes are found in a typical vertebra?

Two

Eight

Six

Four (correct)

What is the direction of the spinous process in a typical vertebra?

Posteriorly Signup and view all the answers

What is the term for the cylindrical structures that form the sides of the vertebral arch?

Peclicles Signup and view all the answers

What is the total number of processes that arise from the vertebral arch?

Seven Signup and view all the answers

What is the shape of the sacrum?

Concave anteriorly Signup and view all the answers

What is the primary reason for the formation of the cervical curve in infants?

Child's ability to raise his or her head and keep it poised on the vertebral column Signup and view all the answers

At which level does the sacral hiatus occur?

Posterior inferior end of the sacral canal Signup and view all the answers

What is the usual number of vertebrae fused together to form the coccyx?

Four Signup and view all the answers

What is the characteristic of the thoracic and sacrococcygeal curves?

They are primary curvatures Signup and view all the answers

What is the result of the sacrum's wedge-shaped structure?

It allows the head to balance on top of the vertebral column Signup and view all the answers

What is the term for the fusion of the fifth lumbar vertebra with the sacrum?

Sacralization of the L5 vertebra Signup and view all the answers

What is the result of the development of the secondary curves?

A modification in the shape of the vertebral bodies and the intervertebral discs Signup and view all the answers

How many foramina are present on each of the anterior and posterior surfaces of the sacrum?

Four Signup and view all the answers

What is the characteristic of the lumbar curve in adult females?

It is more pronounced than in adult males Signup and view all the answers

What is the condition when the first coccygeal vertebra is not fused or is incompletely fused with the second vertebra?

The first coccygeal vertebra is separate Signup and view all the answers

What is the characteristic of the fetal vertebral column during initial development?

It has a single continuous anterior concavity Signup and view all the answers

What is the term for the incorporation of the first sacral vertebra into the lumbar spine?

Lumbarization of the S1 vertebra Signup and view all the answers

When does the lumbar curve form in infants?

Toward the end of the 1st year Signup and view all the answers

What can be absent from the posterior wall of the sacral canal?

Laminae and spines Signup and view all the answers

Where do the laminae of the fifth sacral vertebra and sometimes those of the fourth sacral vertebra meet?

In the midline Signup and view all the answers

What does the dermatomyotome differentiate into?

Dermatome and myotome Signup and view all the answers

Where do the posterior and lateral outgrowths of the mesenchymal vertebral body grow?

Around the neural tube between the segmental nerves Signup and view all the answers

What forms from the fusion of the caudal half of each sclerotome with the cephalic half of the immediately succeeding sclerotome?

Mesenchymal vertebral arch Signup and view all the answers

What is the primary reason for the increase in lumbar concavity during later months of pregnancy?

To preserve the center of gravity Signup and view all the answers

What is the characteristic of the vertebral column in old age?

It returns to a continuous anterior concavity Signup and view all the answers

What forms from the lateral outgrowths of the mesenchymal vertebral body?

Mesenchymal rib primordium Signup and view all the answers

During which week of development do the mesenchymal cells of the sclerotome rapidly divide and migrate medially?

4th week Signup and view all the answers

What is the typical cause of minor lateral vertebral curves in the thoracic region during late childhood?

Predominant use of one of the upper limbs Signup and view all the answers

What is the characteristic of the cervical and lumbar curves in the adult vertebral column?

They have posterior concavities Signup and view all the answers

What surrounds the notochord during the 4th week of development?

Mesenchymal cells of the sclerotome Signup and view all the answers

What is the term for the part of the sclerotome that gives rise to the posterior and lateral outgrowths?

Ventromedial part Signup and view all the answers

What is the purpose of the compensatory curves in the vertebral column?

To compensate for minor lateral vertebral curves Signup and view all the answers

What is the term for the part of the dermatomyotome that gives rise to the myotome and dermatome?

Dermatomyotome Signup and view all the answers

What is the direction of the curvature of the thoracic and sacrococcygeal curves in the adult vertebral column?

Anterior concavity Signup and view all the answers

What is the relationship between the development of minor lateral vertebral curves and handedness?

Right-handed individuals tend to develop right-sided curves Signup and view all the answers

What is the significance of the vertebral column curvatures in the adult?

They align the center of gravity Signup and view all the answers

Which muscles produce abduction (lateral flexion) in the neck region?

Sternocleidomastoid and scalene muscles Signup and view all the answers

What determines the range of movements possible in each region of the spinal column?

Both A and B Signup and view all the answers

Which joints permit extensive flexion and extension of the head?

Atlanto-occipital joints Signup and view all the answers

Which muscles produce rotation in the thoracic region?

Unilateral semispinalis and rotatores muscles Signup and view all the answers

What restricts the range of movement in the thoracic region?

Ribs and costal cartilages Signup and view all the answers

Which muscles produce flexion in the lumbar region?

Rectus abdominis and psoas muscles Signup and view all the answers

What is the primary function of the atlanto-axial joints?

To allow rotation of the head Signup and view all the answers

Which muscles produce abduction (lateral flexion) in the lumbar region?

Quadratus lumborum and oblique muscles Signup and view all the answers

What percentage of the cervical range of motion occurs at the atlanto-occipital joints?

50% Signup and view all the answers

In which region of the vertebral column does great mobility mainly result from circumduction and pelvic tilting?

Lumbar region Signup and view all the answers

What is the primary reason why dislocations without fracture occur only in the cervical region?

Obliquely oriented articular processes Signup and view all the answers

What type of injury typically causes anterior compression fractures of the vertebral bodies?

Excessive compression Signup and view all the answers

At which sites do anterior compression fractures of the vertebral bodies typically occur?

Junction of the mobile and fixed regions Signup and view all the answers

What is the characteristic of intervertebral movement in the cervical region?

Extensive flexion and extensive rotation Signup and view all the answers

What is the relationship between the atlanto-occipital joints and the cervical range of motion?

The atlanto-occipital joints contribute to 50% of the cervical range of motion Signup and view all the answers

What is the characteristic of intervertebral movement in the lumbar region?

Extensive flexion and limited rotation Signup and view all the answers

What is the primary function of the nucleus pulposus in the intervertebral disc?

To allow for flexibility and movement in the vertebral column Signup and view all the answers

What is the composition of the intervertebral disc?

Primarily water with a small amount of collagen and cartilage Signup and view all the answers

What happens to the nucleus pulposus when there is a sudden increase in compression load on the vertebral column?

It flattens and the surrounding anulus fibrosus accommodates the outward bulging Signup and view all the answers

What is the arrangement of the concentric layers of fibrocartilage in the intervertebral disc?

Perpendicular to each other Signup and view all the answers

What is the result of the outward thrust of the nucleus pulposus being too great for the anulus fibrosus?

The anulus fibrosus ruptures and the nucleus pulposus herniates Signup and view all the answers

What is the characteristic of the fibers in the anulus fibrosus?

They are more numerous and thicker anteriorly and laterally Signup and view all the answers

What is the location of the intervertebral disc in relation to the posterior margin of the vertebral body?

Slightly closer to the posterior margin Signup and view all the answers

What is the purpose of the anulus fibrosus in the intervertebral disc?

To accommodate the outward bulging of the nucleus pulposus Signup and view all the answers

What is the main consequence of the water content of the nucleus pulposus diminishing with age?

The discs become thinner, less elastic, and stiffer Signup and view all the answers

What is the role of the anterior and posterior longitudinal ligaments in the vertebral column?

They act as a continuous band down the vertebral column, providing stability Signup and view all the answers

What is the significance of the meningeal branches of the spinal nerves in the vertebral joints?

They innervate the joints between the vertebral bodies Signup and view all the answers

What is the effect of the degeneration of the collagen fibers of the anulus on the vertebral discs?

The anulus cannot contain the nucleus pulposus under stress Signup and view all the answers

What is the result of the shortening of the vertebral column with age?

Decreased body height Signup and view all the answers

What is the characteristic of the vertebral discs in old age?

They are thinner, less elastic, and stiffer Signup and view all the answers

What is the function of the anterior longitudinal ligament in the vertebral column?

It acts as a continuous band down the anterior surface of the vertebral column Signup and view all the answers

What is the effect of the replacement of the water content of the nucleus pulposus with fibrocartilage on the vertebral discs?

The discs become less elastic and stiffer Signup and view all the answers

What is the primary function of the ligamentum flavum?

To connect the laminae of adjacent vertebrae Signup and view all the answers

What is the direction of the longitudinal axis of movement of the vertebral column?

Through the centers of the vertebral bodies Signup and view all the answers

What is the result of the movement of flexion in the vertebral column?

Anterior bending of the vertebral column Signup and view all the answers

What is the significance of the ligamentum nuchae in the cervical region?

It is greatly thickened to form a strong ligament Signup and view all the answers

What movement is possible in the vertebral column due to the intertransevere ligaments?

Large degrees of movement along the length of the vertebral column Signup and view all the answers

What is the term for the movement of circumduction in the vertebral column?

Circumduction Signup and view all the answers

What is the level at which the spinal nerve runs through the intervertebral foramen?

CS Signup and view all the answers

What is the source of the arterial supply to the spinal cord?

Spinal arteries and segmental arteries Signup and view all the answers

What is the relationship between the spinal nerves and the vertebrae in the thoracic, lumbar, and sacral regions?

The spinal nerves emerge through the IVF below the same-numbered vertebra Signup and view all the answers

What is the course of the posterior spinal arteries?

They run inferiorly down the spinal cord, close to the attachments of the posterior spinal nerve rootlets Signup and view all the answers

What is the exception to the rule that the spinal nerves emerge through the IVF below the same-numbered vertebra?

Coccygeal nerve Signup and view all the answers

What is the relationship between the spinal nerve and the affected IVF in the cervical region?

The spinal nerve is one number higher than the affected IVF Signup and view all the answers

What is the effect of slackening of the anterior and posterior longitudinal ligaments?

Increased mobility of the vertebral bodies Signup and view all the answers

Which region has the most susceptible discs to herniation?

Lumbar region Signup and view all the answers

What is the location of the anterior spinal artery?

It runs within the anterior median fissure Signup and view all the answers

What is the number of spinal arteries that run longitudinally?

Three Signup and view all the answers

What is the result of the escape of the nucleus pulposus?

Narrowing of the space between the vertebral bodies Signup and view all the answers

What is the relationship between the spinal nerve and the affected IVF in the thoracic or lumbar region?

The spinal nerve is the same number as the affected IVF Signup and view all the answers

What is the consequence of abnormal mobility of the vertebral bodies?

Local pain and possible subsequent development of osteoarthritis Signup and view all the answers

What is the location of the most susceptible discs to herniation in the cervical region?

Between the C5 and 6 or C6 and 7 vertebrae Signup and view all the answers

What is the purpose of maximizing the flexion of the lumbar spine during lumbar puncture?

To open the interlamina spaces to a maximum Signup and view all the answers

What is the usual direction of the needle during lumbar puncture?

Medially towards the midline Signup and view all the answers

What is the cause of post-lumbar puncture headache?

Leakage of cerebrospinal fluid through the dural puncture Signup and view all the answers

What is the significance of the imaginary line joining the highest points on the iliac crests?

It passes over the fourth lumbar spine Signup and view all the answers

What is the purpose of using a small-gauge styletted needle during lumbar puncture?

To reduce the risk of post-lumbar puncture headache Signup and view all the answers

What is the significance of the supraspinous ligament during lumbar puncture?

It is a structure that the needle passes through Signup and view all the answers

What is the usual depth of the needle insertion during lumbar puncture in an obese adult?

Around 4 inches (10 cm) Signup and view all the answers

What is the primary function of the cerebrospinal fluid?

To remove waste products associated with neuronal activity and provide a fluid medium that surrounds the spinal cord Signup and view all the answers

What is the primary precaution to take during lumbar puncture in cases of raised intracranial pressure?

Avoiding the procedure altogether Signup and view all the answers

What is the approximate distance between the sacral hiatus and the lower end of the subarachnoid space at the S2 vertebra in adults?

2 in. Signup and view all the answers

What is the term for the segment of the filum terminale from the conus medullaris to the end of the dura-arachnoid sac?

Filum terminale internum Signup and view all the answers

What is the purpose of caudal anesthesia in obstetrics?

To relieve pain during the first and second stages of labor Signup and view all the answers

What is the location of the spinal part of the subarachnoid space?

Inferiorly to the level of the second sacral vertebra Signup and view all the answers

What is contained within the dural sac in the sacral canal?

The cauda equina and spinal nerves Signup and view all the answers

What is the origin of the cerebrospinal fluid?

Choroid plexuses in the ventricles of the brain Signup and view all the answers

What is the term for the portion of the filum terminale from the sac to the coccyx?

Filum terminale coccygeum Signup and view all the answers

What is the significance of the posterior wall in the sacral canal?

It is formed by the fusion of the laminae Signup and view all the answers

What is the function of the pia mater in the spinal cord?

To extend along the spinal nerve roots and end by merging with the filum terminale Signup and view all the answers

What is the relationship between the dural sac and the coccyx?

The dural sac is tethered to the coccyx by the filum terminale Signup and view all the answers

What is the direction of the circulation of cerebrospinal fluid?

Both upward over the surface of the cerebral hemispheres and downward through the spinal cord Signup and view all the answers

What is the result of the fusion of the filum terminale with the dura-arachnoid sac?

The formation of the spinal part of the subarachnoid space Signup and view all the answers

What is the name of the process in the sacral vertebra shown in the diagram?

Third sacral spinous process Signup and view all the answers

What is the term for the opening in the sacrum where the diagram shows the third posterior sacral foramen?

Posterior sacral foramen Signup and view all the answers

What is the structure formed by the fusion of the fourth and fifth sacral vertebrae?

Sacrum Signup and view all the answers

What is the function of the lamina of the fourth sacral vertebra?

To form the posterior wall of the sacral canal Signup and view all the answers

How many sacral foramina are present on each of the anterior and posterior surfaces of the sacrum?

Four Signup and view all the answers

Study Notes

Vertebral Column Structure

A typical vertebra consists of a rounded body anteriorly and a vertebral arch posteriorly, which enclose a space called the vertebral foramen.
The vertebral arch gives rise to seven processes: one spinous, two transverse, and four articular.
The laminae of the fifth sacral vertebra sometimes fail to meet in the midline, forming the sacral hiatus.

Sacrum

The sacrum consists of five rudimentary vertebrae fused together to form a wedge-shaped bone, concave anteriorly.
The upper border, or base, has four foramina for the passage of the anterior and posterior rami of the upper four sacral nerves.
The sacrum plays a crucial role in maintaining the center of gravity of the body through the pelvis, allowing upright posture.

Coccyx

The coccyx usually consists of four vertebrae fused together to form a single, small triangular bone that articulates at its base with the lower end of the sacrum.
The first coccygeal vertebra may not be fused or is incompletely fused with the second vertebra.

Vertebral Column Curvatures

The adult vertebral column has four regional curvatures in the sagittal plane: thoracic, sacrococcygeal, cervical, and lumbar.
The thoracic and sacrococcygeal curves have anterior concavities, while the cervical and lumbar curves have posterior concavities.
The curves serve to align the center of gravity of the body, allowing upright posture.

Development of Vertebral Column

In the embryo, the vertebral column has only one continuous anterior concavity.
As development proceeds, the lumbo-sacral angle appears, forming two anteriorly concave curves.
The cervical curve forms in association with the child raising its head and keeping it poised on the vertebral column.
The lumbar curve forms in association with the child sitting up and standing upright.

Development of Vertebral Body

The mesenchymal vertebral body gives rise to posterior and lateral outgrowths on each side.
The posterior outgrowths grow around the neural tube between the segmental nerves to form the mesenchymal vertebral arch.
The lateral outgrowths pass between the myotomes to form the mesenchymal costal process or primordia of the ribs.

Vertebral Column Movements

The vertebral column permits several types of movements, including flexion, extension, abduction (lateral flexion), rotation, and circumduction.
The range of movements possible in each region of the vertebral column depends on the thickness of the intervertebral discs and the shape and direction of the articular processes.

Regional Intervertebral Movements

In the cervical region, flexion and extension are extensive, with -50% of the cervical range of motion occurring at the atlanto-occipital joints.
Abduction (lateral flexion) is also extensive in the cervical region.
Rotation is extensive in the cervical region, with -50% of the cervical range of rotation occurring at the atlantoaxial joints.
Circumduction is also extensive in the cervical region.

Thoracic Region

In the thoracic region, the range of movement is limited due to the ribs, costal cartilages, and sternum.
Unilateral semispinalis and rotatores muscles, assisted by the oblique muscles of the anterolateral abdominal wall, produce rotation.

Lumbar Region

In the lumbar region, the rectus abdominis and psoas muscles produce flexion, whereas the postvertebral muscles produce extension.
The postvertebral muscles, quadratus lumborum, and the oblique muscles of the anterolateral abdominal wall produce abduction (lateral flexion).

Intervertebral Discs

Intervertebral discs are composed of a mucopolysaccharide gel with high water content (-80+%) and a small amount of collagen and cartilage.
The discs have a fibrocartilaginous annulus and a gel-like nucleus pulposus.
The nucleus pulposus allows for changes in shape and permits one vertebra to rock on another.

Vertebral Column Dislocation

Dislocations without fracture occur only in the cervical region due to the obliquely oriented articular processes.
Anterior compression fractures of the vertebral bodies are usually caused by an excessive flexion compression type of injury.

Vertebral Joint Nerve Supply

The joints receive nerve fibers from two adjacent spinal nerves.
Small meningeal branches of each spinal nerve innervate the joints between the vertebral bodies.

Ligaments

The anterior and posterior longitudinal ligaments run as continuous bands down the anterior and posterior surfaces of the vertebral column.
The ligamentum flavum connects the laminae of adjacent vertebrae.
In the cervical region, the supraspinous and interspinous ligaments are greatly thickened to form the strong ligamentum nuchae.

Lumbar Puncture

Lumbar puncture is performed with the patient lying on their side with the vertebral column well flexed, opening the lumbar interlaminal spaces to a maximum.
The needle passes through the following anatomic structures before entering the subarachnoid space: skin, superficial fascia, supraspinous ligament, interspinous ligament, ligamentum flavum, areolar tissue, dura mater, and arachnoid mater.

Anatomy of Complications

Postlumbar puncture headache starts after the procedure and lasts 24 to 48 hours, caused by a leak of CSF through the dural puncture, especially after using a wide-bore needle.
The leak reduces the volume of CSF, which, in turn, causes a downward displacement of the brain and stretches the nerve-sensitive meninges.
Assuming the recumbent position relieves the headache.
Using small-gauge styletted needles and avoiding multiple dural holes reduces the incidence of headache.

Brain Herniation

Lumbar puncture is contraindicated in cases where intracranial pressure is significantly raised.

Spinal Cord Blood Supply

The spinal cord receives its arterial supply from two primary sources: (1) the spinal arteries, which originate from the vertebral arteries within the cranial cavity, and (2) the radicular (radiculomedullary) arteries, which branch from segmental arteries alongside the vertebral column.
Three small spinal arteries run longitudinally: two posterior spinal arteries and one anterior spinal artery.
The posterior spinal arteries run inferiorly down the spinal cord, close to the attachments of the posterior spinal nerve rootlets.
The anterior spinal artery runs down within the anterior median fissure.

Spinal Cord and Spinal Nerve Development

The spinal cord runs the entire length of the trunk of the body.
The numerical relationships of the spinal nerves to the vertebrae are important to consider when evaluating the effects of a herniated intervertebral disc.
Stenosis of a cervical IVF would affect the spinal nerve one number higher than the IVF itself.
Narrowing of a thoracic or lumbar IVF would affect the spinal nerve of the same number as the affected IVF.

Cerebrospinal Fluid

The cerebrospinal fluid (CSF) is a clear, colorless fluid formed mainly by the choroid plexuses, within the ventricles of the brain.
CSF circulates through the ventricular system and enters the subarachnoid space through three foramina in the roof of the fourth ventricle.
CSF provides a fluid medium that surrounds the spinal cord and effectively protects it from trauma.

Embryology Notes

The spinal cord develops from the neural tube and runs the entire length of the trunk of the body.
The spinal nerves develop from the posterior section of the neural tube.

Sacral Vertebrae

The fourth sacral spinous process is a notable feature
The third sacral spinous process is a key landmark
The lamina of the fourth sacral vertebra is an important anatomical structure
The third posterior sacral foramen is a distinct opening in the sacrum

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Description

Learn about the vertebral arch, its components, and the processes it gives rise to. Understand the common features of all vertebrae.