Vertebral Column: Anatomy

Overview

Definition

The vertebral column is the primary axis of the skeleton:

• Supports the trunk
• Provides an attachment for ligaments and muscles that move the body
• Protects the spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy and nerve roots

The vertebral column consists of 33 vertebrae placed in series and connected by intervertebral discs and ligaments.

Regions of the vertebral column

Five different groups of vertebrae:

• Cervical
• Thoracic
• Lumbar
• Sacral
• Coccygeal

Number of vertebrae per segment:

• Cervical: 7
• Thoracic: 12
• Lumbar: 5
• Sacral: 5
• Coccygeal: 4 (ranges from 3–5, below sacrum)

Curvatures of the vertebral column

• Primary (develop before birth):
  • Thoracic and sacral
  • Kyphosis Kyphosis Deformities of the spine characterized by an exaggerated convexity of the vertebral column. The forward bending of the thoracic region usually is more than 40 degrees. This deformity sometimes is called round back or hunchback. Osteoporosis: forward rounding of thoracic spine
• Secondary (develop after birth):
  • Cervical and lumbar
  • Lordosis: inward curvature of lumbar spine

Spinal canal Spinal Canal The cavity within the spinal column through which the spinal cord passes. Spinal Cord Injuries

• The vertebrae form the spinal canal Spinal Canal The cavity within the spinal column through which the spinal cord passes. Spinal Cord Injuries, which houses the spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy and spinal nerves Spinal nerves The 31 paired peripheral nerves formed by the union of the dorsal and ventral spinal roots from each spinal cord segment. The spinal nerve plexuses and the spinal roots are also included. Spinal Cord: Anatomy.
• Intervertebral foramen Intervertebral Foramen Spinal Stenosis (or neural foramen): foramen for the spinal nerves Spinal nerves The 31 paired peripheral nerves formed by the union of the dorsal and ventral spinal roots from each spinal cord segment. The spinal nerve plexuses and the spinal roots are also included. Spinal Cord: Anatomy exiting between 2 spinal vertebrae

Vertebrae

Vertebrae protect the spinal column.

Two adjacent vertebrae are often referred to as a motion segment or functional unit of the spine (e.g., C6 and C7).

Components of the vertebrae

• Body:
  • Anterior portion of vertebra
  • Weight-bearing function
  • Lined with hyaline cartilage Hyaline cartilage A type of cartilage characterized by a homogeneous amorphous matrix containing predominantly type II collagen and ground substance. Hyaline cartilage is found in articular cartilage; costal cartilage; laryngeal cartilages; and the nasal septum. Cartilage: Histology superiorly and inferiorly
• Vertebral arch:
  • Lateral and posterior portion of vertebra
  • Encloses the vertebral canal
  • Vertebral arch consists of the following components:
    • Pedicles 
    • Laminae 
    • Processes: transverse (lateral), articular, and spinous (posterior)

Vertebral foramen

• Large central opening in vertebrae that collectively form the spinal canal Spinal Canal The cavity within the spinal column through which the spinal cord passes. Spinal Cord Injuries 
• Contains the spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy, nerve roots, and blood vessels

Intervertebral foramen Intervertebral Foramen Spinal Stenosis (neural foramen)

• Boundaries include the superior and inferior notches of the vertebrae.
• Spinal nerves Spinal nerves The 31 paired peripheral nerves formed by the union of the dorsal and ventral spinal roots from each spinal cord segment. The spinal nerve plexuses and the spinal roots are also included. Spinal Cord: Anatomy exit here.
• Contents: spinal nerve root, dorsal root ganglion, segmental arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology/ veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology, fat
• Cervical spine:
  • C1–C7 nerve roots exit superiorly to the pedicles of C1–C7.
  • C8 nerve root exits inferiorly to the pedicles of C7.
• Thoracic and sacral nerve roots exit inferiorly to their corresponding vertebrae.
• May become stenotic with injury or degenerative changes Degenerative Changes Spinal Stenosis

Atlas and axis

• C1 and C2 are specially named because of their unique functions.
• Atlas (C1):
  • Supports the entire skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull: Anatomy
  • Does not possess a vertebral body
  • Primary function is to allow head to nod up and down.
• Axis (C2):
  • Possesses a bony projection called the dens (also known as odontoid process):
    • Serves as a pivot point to allow head to rotate side to side
    • Commonly fractured during high-impact injuries
  • Has a bifid spinous process

Sacrum and coccyx

• Sacrum
  • Consists of 5 fused vertebrae below the lumbar vertebrae
  • Represents the terminal portion of the vertebral canal
  • Articulates with the ilium ( hip bone Hip bone Bones that constitute each half of the pelvic girdle in vertebrates, formed by fusion of the ilium; ischium; and pubic bone. Pelvis: Anatomy) to form the pelvic girdle
• Coccyx
  • Consists of 3–5 fused vertebrae
  • Articulates with the inferior sacrum

Intervertebral Discs, Ligaments, and Joints of the Spine

Intervertebral discs

Intervertebral discs form the primary connection between vertebrae.

• 23 discs (6 cervical, 12 thoracic, 5 lumbar) account for 25%–30% of the length of the spine.
• Provide shock-absorbing protection within the spine
• 3 major components:
  • Annulus fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans:
    • Ring-shaped fibrous Fibrous Fibrocystic Change connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue: Histology around the nucleus pulposus Nucleus Pulposus Fibrocartilage inner core of the intervertebral disc. Prolapsed or bulged nucleus pulposus leads to intervertebral disc displacement while proliferation of cells in the nucleus pulposus is associated with intervertebral disc degeneration. Spinal Disk Herniation
    • Multilayered alignment of predominantly collagen Collagen A polypeptide substance comprising about one third of the total protein in mammalian organisms. It is the main constituent of skin; connective tissue; and the organic substance of bones (bone and bones) and teeth (tooth). Connective Tissue: Histology fibers → remarkable strength.
    • Adhere dorsally to the posterior longitudinal ligament
  • Nucleus pulposus Nucleus Pulposus Fibrocartilage inner core of the intervertebral disc. Prolapsed or bulged nucleus pulposus leads to intervertebral disc displacement while proliferation of cells in the nucleus pulposus is associated with intervertebral disc degeneration. Spinal Disk Herniation:
    • Center of the intervertebral disc
    • Mucoid or gel-like structure
    • Responsible for much of the strength and flexibility of the spine
    • 70%–80% water when young, the remainder composed of collagen Collagen A polypeptide substance comprising about one third of the total protein in mammalian organisms. It is the main constituent of skin; connective tissue; and the organic substance of bones (bone and bones) and teeth (tooth). Connective Tissue: Histology fibers and proteoglycans Proteoglycans Glycoproteins which have a very high polysaccharide content. Basics of Carbohydrates; % of water decreases with aging
    • Receives nutrition through diffusion Diffusion The tendency of a gas or solute to pass from a point of higher pressure or concentration to a point of lower pressure or concentration and to distribute itself throughout the available space. Diffusion, especially facilitated diffusion, is a major mechanism of biological transport. Peritoneal Dialysis and Hemodialysis
  • Cartilaginous end plates anchor the discs to the adjacent vertebrae.

Ligaments of the vertebral column

The ligaments of the vertebral column are essential for stability of the spine:

• Ligaments are composed of sheets of fibrous Fibrous Fibrocystic Change connective tissue Connective tissue Connective tissues originate from embryonic mesenchyme and are present throughout the body except inside the brain and spinal cord. The main function of connective tissues is to provide structural support to organs. Connective tissues consist of cells and an extracellular matrix. Connective Tissue: Histology.
• Prevent excessive motion (e.g., hyperextension of the spine)

Joints of the spine

Joints of the spine consist of intervertebral discs and facet joints:

• The vertebral bodies articulate with each other via the intervertebral discs.
• The facet joints (zygapophyseal joints) consist of cartilage-covered surfaces with a joint capsule Capsule An envelope of loose gel surrounding a bacterial cell which is associated with the virulence of pathogenic bacteria. Some capsules have a well-defined border, whereas others form a slime layer that trails off into the medium. Most capsules consist of relatively simple polysaccharides but there are some bacteria whose capsules are made of polypeptides. Bacteroides. Each vertebra has 2 sets of facet joints (facing superiorly and inferiorly).

Clinical Relevance

• Herniated disk or herniated nucleus pulposus Nucleus Pulposus Fibrocartilage inner core of the intervertebral disc. Prolapsed or bulged nucleus pulposus leads to intervertebral disc displacement while proliferation of cells in the nucleus pulposus is associated with intervertebral disc degeneration. Spinal Disk Herniation: Herniated nucleus pulposus Nucleus Pulposus Fibrocartilage inner core of the intervertebral disc. Prolapsed or bulged nucleus pulposus leads to intervertebral disc displacement while proliferation of cells in the nucleus pulposus is associated with intervertebral disc degeneration. Spinal Disk Herniation occurs when the nucleus pulposus Nucleus Pulposus Fibrocartilage inner core of the intervertebral disc. Prolapsed or bulged nucleus pulposus leads to intervertebral disc displacement while proliferation of cells in the nucleus pulposus is associated with intervertebral disc degeneration. Spinal Disk Herniation prolapses or herniates through a tear in the surrounding annulus fibrosus Annulus Fibrosus Spinal Disk Herniation. This herniation Herniation Omphalocele results in pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways from irritation and injury to adjacent nerve roots and surrounding tissue. Herniated discs occur most commonly in the cervical or lumbar spine. Physical therapy Physical Therapy Becker Muscular Dystrophy is the 1st-line treatment for a disk herniation Herniation Omphalocele.
• Degenerative disk disease Disk Disease Examination of the Lower Limbs: Intervertebral discs undergo age- and trauma-related changes. The proteoglycan and water concentrations decrease in the disc, which decreases the height of the disk and leads to anatomical and biomechanical changes. These changes typically lead to low back pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, which is primarily managed through the use of nonsteroidal antiinflammatory drugs Nonsteroidal Antiinflammatory Drugs Nonsteroidal antiinflammatory drugs (NSAIDs) are a class of medications consisting of aspirin, reversible NSAIDs, and selective NSAIDs. NSAIDs are used as antiplatelet, analgesic, antipyretic, and antiinflammatory agents. Nonsteroidal Antiinflammatory Drugs (NSAIDs).
• Spinal stenosis Stenosis Hypoplastic Left Heart Syndrome (HLHS): occurs from narrowing of the spinal canal Spinal Canal The cavity within the spinal column through which the spinal cord passes. Spinal Cord Injuries. Spinal stenosis Stenosis Hypoplastic Left Heart Syndrome (HLHS) is described as central and/or lateral stenosis Stenosis Hypoplastic Left Heart Syndrome (HLHS), based on the location. Depending on the position and severity, the spinal nerves Spinal nerves The 31 paired peripheral nerves formed by the union of the dorsal and ventral spinal roots from each spinal cord segment. The spinal nerve plexuses and the spinal roots are also included. Spinal Cord: Anatomy, spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy, or blood vessels may be affected by the compression Compression Blunt Chest Trauma. Classically, pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways from spinal stenosis Stenosis Hypoplastic Left Heart Syndrome (HLHS) improves when leaning forward.
• Cervical spondylosis Cervical Spondylosis Neck Pain: Stenosis Stenosis Hypoplastic Left Heart Syndrome (HLHS) of the cervical canal Cervical canal Uterus, Cervix, and Fallopian Tubes: Anatomy secondary to degenerative changes Degenerative Changes Spinal Stenosis to the cervical spine leads to cervical spondylosis Cervical Spondylosis Neck Pain, which may lead to cervical myelopathy when there is encroachment on the cervical spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy.
• Abnormal curvature of the spine:
  • Scoliosis Scoliosis Scoliosis is a structural alteration of the vertebral column characterized by a lateral spinal curvature of greater than 10 degrees in the coronal plane. Scoliosis can be classified as idiopathic (in most cases) or secondary to underlying conditions. Scoliosis: lateral curvature of the spine; usually an idiopathic Idiopathic Dermatomyositis process
  • Kyphosis Kyphosis Deformities of the spine characterized by an exaggerated convexity of the vertebral column. The forward bending of the thoracic region usually is more than 40 degrees. This deformity sometimes is called round back or hunchback. Osteoporosis: excessive thoracic curvature; can occur congenitally or be due to a traumatic event Traumatic event An emotionally painful, shocking, stressful, and sometimes life-threatening experience. It can result from witnessing distressing events such as natural disasters, physical or sexual abuse, and terrorism or other acts of violence. Posttraumatic Stress Disorder (PTSD). Kyphosis Kyphosis Deformities of the spine characterized by an exaggerated convexity of the vertebral column. The forward bending of the thoracic region usually is more than 40 degrees. This deformity sometimes is called round back or hunchback. Osteoporosis is also referred to as a “hunchback” deformity Deformity Examination of the Upper Limbs.
  • Lordosis: excessive curvature of the lumbar spine