GAS Back

What are the main skeletal components of the back

Mainly the vertebral column (vertebrae + intervertebral discs); the skull, scapulae, pelvic bones, and ribs also contribute.

What are the four major functions of the spine

Support the trunk; protect the spinal cord; provide muscle attachment; hematopoiesis (blood cell production).

What are the four movements of the spine listed in the lecture

Flexion/extension, lateral flexion, rotation, and circumduction.

How many vertebrae are in each region

Cervical 7; thoracic 12; lumbar 5; sacral 5 fused; coccygeal 4 fused.

What are the primary spinal curvatures

Thoracic and sacral kyphotic curves; dorsally convex and present at birth.

What are the secondary spinal curvatures

Cervical and lumbar lordotic curves; dorsally concave and develop after birth.

When does cervical lordosis begin to develop

Around 3 months, as the baby begins lifting the head.

When does lumbar lordosis begin to develop

Around 1 year, as the baby begins walking.

What distinguishes scoliosis from kyphosis or lordosis

Scoliosis involves lateral curvature plus rotation of the vertebrae.

What Cobb angle defines excessive kyphosis in this lecture

Greater than 30°.

What is the most common type of scoliosis listed

Adolescent idiopathic scoliosis.

What is ankylosing spondylitis

A chronic autoimmune inflammatory disease in which ligaments may calcify and vertebrae may fuse, causing chronic pain and immobility.

What are the three main parts of a typical vertebra

Body (centrum), neural/vertebral arch, and vertebral foramen.

What makes up the neural/vertebral arch

Lamina posteriorly and pedicles attaching the arch to the vertebral body.

How many processes does a typical vertebra have

Seven: two superior articular, two inferior articular, two transverse, and one spinous.

What is the difference between a process and a facet/fovea

A process is a bony outgrowth; a facet/fovea is an articular joint surface.

What is the function of the intervertebral foramen

Passageway for a spinal nerve to exit.

What are the two components of an intervertebral disc

Annulus fibrosus and nucleus pulposus.

How are cervical spinal nerves named

C1–C8 are named for the vertebra below them; C8 exits below C7.

How are thoracic, lumbar, sacral, and coccygeal spinal nerves named

They are named for the vertebra above them.

Why are there 8 cervical spinal nerves but only 7 cervical vertebrae

An extra C8 nerve exits below C7.

What passes through cervical transverse foramina

Vertebral arteries, except the artery does not pass through the C7 transverse foramen.

Which cervical vertebrae have bifid spinous processes

C1–C6.

What are the three atypical cervical vertebrae

C1, C2, and C7.

What is unique about C1 (atlas)

It has no body and articulates with the occipital condyles.

What movement occurs primarily at the atlanto-occipital joint

Anteroposterior 'yes' nodding.

What is unique about C2 (axis)

It has the odontoid process (dens).

What is the developmental relationship between the dens and C1

The dens represents the developmentally 'missing' body of C1.

What movement is enabled by the dens

Lateral head rotation—the 'no' motion.

What stabilizes the dens

The anterior arch of C1 and transverse atlantal ligament.

What is unique about C7

It has a large, easily palpable spinous process (vertebra prominens).

What are uncinate processes

U-shaped processes on C3–C7 bodies that limit lateral flexion.

What feature is characteristic of thoracic vertebrae

Costal facets/foveae for articulation with ribs.

What is atypical about T1

Rib 1 does not articulate with C7.

How do ribs 10–12 differ in vertebral articulation

Their heads articulate only with their own vertebral body, not the one above.

Where does the rib head articulate on typical thoracic vertebrae

With the superior/inferior demi-facets of adjacent thoracic vertebrae.

Where does the rib tubercle articulate

With the transverse costal facet.

What distinguishes lumbar vertebrae

No transverse foramina or costal facets; they have the largest bodies.

What attaches to the lumbar mamillary process

Multifidus muscle.

What is atypical about L5

It is the largest vertebra overall.

How many vertebrae form the sacrum

Five fused vertebrae.

What is the sacral promontory

The most anterior margin of S1; it is obstetrically relevant.

Why is the sacral promontory clinically relevant in obstetrics

It is less pronounced in females, providing more room in the birth canal.

What does the auricular surface of the sacrum articulate with

The ilium.

What passes through the anterior and posterior sacral foramina

Sacral spinal nerves S1–S4 and vessels.

What forms the median sacral crest

Fused spinous processes.

What forms the intermediate sacral crest

Fused articular processes.

What forms the lateral sacral crest

Fused transverse processes.

What does the sacral canal contain

Sacral epidural space, spinal meninges, lumbar/sacral spinal nerves, filum terminale, venous plexus, and fat.

Where does the sacral canal terminate

At the sacral hiatus.

What is the sacral hiatus

A natural gap caused by incomplete fusion of the S5 laminae.

What does the sacral hiatus contain

S5 nerve, coccygeal nerve, and filum terminale.

What type of joints are zygapophyseal (facet) joints

Synovial, plane, diarthrotic joints.

What is the main function of facet joints

They permit gliding, limit spinal rotation, and stabilize the joint.

What does the anterior longitudinal ligament do

Stabilizes vertebral bodies/annulus fibrosus and limits extension.

What does the posterior longitudinal ligament do

Stabilizes vertebral bodies/annulus fibrosus and limits flexion.

What does the ligamenta flava do

Stabilizes laminae and limits flexion.

What does the interspinous ligament do

Stabilizes spinous processes and limits flexion.

What does the supraspinous ligament do

Limits flexion and continues as the ligamentum nuchae above C7.

What is the ligamentum nuchae

The cervical extension of the supraspinous ligament.

Which ligament limits spinal extension

Anterior longitudinal ligament.

Which structures limit spinal flexion

Posterior longitudinal ligament, ligamenta flava, interspinous ligaments, and supraspinous ligament.

What limits spinal rotation

Zygapophyseal (facet) joints.

What type of joint is formed by intervertebral discs

Symphyseal joint.

Approximately what percentage of vertebral column length is made up by discs

About 25%.

Approximately how much water does the nucleus pulposus contain

About 80%, decreasing with age.

What is the origin of the nucleus pulposus

Remnant of the notochord.

What happens in whiplash according to the lecture

Hyperextension can tear the anterior longitudinal ligament and may cause vertebral avulsion fracture.

What is the usual direction of disc herniation

Dorsolateral.

Why does the nucleus pulposus usually herniate dorsolaterally

The dorsolateral annulus is the thinnest region.

According to the lecture, which nerve is compressed by an L4–L5 disc herniation

The L4 nerve exiting above the level.

What symptoms can result from disc herniation

Burning or sharp radiating limb pain; many herniations are asymptomatic.

How are most disc herniations treated

Usually no treatment or conservative treatment.

What rare structures can severe disc herniation irritate

The spinal cord or cauda equina.

What are the three layers of back muscles

Superficial, intermediate, and deep.

What innervates the superficial back muscles

Branches of the brachial plexus.

What is the primary function of the superficial back muscles

Act on the upper extremity.

What innervates the intermediate back muscles

Anterior rami of intercostal nerves.

What is the primary function of intermediate back muscles

Act on the ribs during respiration.

What innervates the deep/true back muscles

Dorsal rami of spinal nerves.

What is the primary function of deep/true back muscles

Act on the axial skeleton.

What are the main actions of trapezius

Superior fibers elevate scapula and extend head/neck; middle retract scapula; inferior depress scapula; superior + inferior produce superior scapular rotation.

What is the motor innervation of trapezius

CN XI (accessory nerve).

What provides proprioception to trapezius

Anterior rami C3–C4.

What is the innervation of latissimus dorsi

Thoracodorsal nerve.

What are the main actions of latissimus dorsi

Extends, adducts, and medially rotates the humerus.

What is the innervation of levator scapulae

Dorsal scapular nerve.

What is the main action of levator scapulae

Elevates the scapula.

What is the innervation of rhomboid major and minor

Dorsal scapular nerve.

What are the main actions of rhomboids

Adduct, elevate, and inferiorly rotate the scapula.

What does serratus posterior superior do

Elevates ribs 2–5 during inhalation.

What does serratus posterior inferior do

Depresses ribs 9–12 during exhalation; may also have some role in inhalation.

How are serratus posterior muscles innervated

By anterior rami of intercostal nerves.

What are the three groups of deep/true back muscles from superficial to deep

Spinotransversalis → erector spinae → transversospinalis.

What muscles comprise the spinotransversalis group listed

Splenius capitis and splenius cervicis.

What does splenius capitis do

Unilaterally turns the face to the same side; bilaterally draws the head back/extends the neck.

What does splenius cervicis do

Unilaterally turns the face to the same side; bilaterally extends the neck.

What three muscles make up erector spinae

Spinalis, longissimus, and iliocostalis.

What are the bilateral actions of erector spinae

Straighten the back/return the spine to upright and extend the head.

What is the unilateral action of erector spinae

Lateral bending to the same side.