Anatomy and Functions of the Spine

Anatomy of the Spine

• The spine is the central axis of the body, composed of vertebrae.
• It provides structural support and balance for upright posture.
• Its function includes protection of the spinal cord and nerve roots, as well as internal organs.
• The spine possesses flexibility in six degrees of freedom, including flexion, extension, side bending, and rotation.

Anatomical Planes

• The coronal plane (also called the frontal plane) is a vertical cut dividing the body into front and back sections.
• A-P X-rays of scoliotic spines in the coronal plane are used to evaluate scoliosis.
• The coronal plane view assists in evaluating spinal disorders such as scoliosis.

Functions of the Spine -Protection

• The spine protects the spinal cord and nerve roots.
• It protects vital internal organs.

Functions of the Spine - Flexibility

• The spine exhibits flexibility in multiple degrees of freedom, crucial for movement and posture.
• These degrees of freedom include flexion and extension, side bending, and rotation.

Functions of the Spine - Structural Support

• The spine acts as the central support structure for the upper body.
• This effectively distributes the weight of the head, shoulders, and thorax to the lower extremities (through the sacrum and pelvis.)
• This load distribution minimizes the amount of work required of spinal muscles, promoting a healthier posture.

Functions of the Spine

• To effectively fulfill these crucial roles, the spine must exhibit resistance to axial loading forces, with specific anatomical features contributing to this ability, such as the interplay of kyphotic and lordotic spinal curves.
• The spine must contain increased vertebral mass along its length.
• Elasticity is also vital in the spine, accomplished by alternating lordotic and kyphotic curves and multiple segmental motions.

The Motion Segment

• The functional unit of the spine are its motion segments.
• These composed of two adjacent vertebrae, an intervertebral disc, ligaments connecting the vertebrae, and facet joints with their surrounding capsules.

Regions of the Spine

• Cervical spine (C1-C7): Divided into upper and lower cervical sections. The lower cervical section (C3-C7) vertebral structures are similar throughout this segment of the spine. C7 (Vertebra Prominens) is distinct from the other cervical vertebrae due to its larger, non-bifurcated spinous process.
• Thoracic spine (T1-T12): Characterized by a progressive increase in the mass of vertebrae from the top to the bottom portion. Key characteristics include the vertebral body being heart-shaped when viewed from above, small diameter pedicles, vertical, roof-tile arrangements of laminae, long, and overlapping spinous processes directed downwards, larger intervertebral foramina, and less incidence of nerve compression.
• Lumbar spine (L1-L5): The lumbar vertebrae are also distinguished by their shape and function.
• Sacrococcygeal (Sacrum and Coccyx): Nine fused vertebrae form the sacrum and coccyx.

Basic Vertebral Structures

• Illustrates the distinct shapes and structures of cervical, thoracic, and lumbar vertebrae.

Vertebral Structures (Specific Parts)

• The vertebral body, pedicle, transverse process, lamina, spinous process, vertebral foramen, superior articular process, inferior articular process, pars, and intervertebral foramen are explicitly labeled and defined.

Vertebral Structures (Pedicle Notches and Intervertebral Foramina)

• Pedicle notches and intervertebral foramina are crucial spaces allowing spinal nerve roots to exit the spinal cord.

The Atlas (C1)

• The atlas (C1) is a unique structure of the cervical spine with specific distinguishing features, including anterior and posterior tubercles, an articular facet for dens, lateral masses, transverse foramina, and lamina.

The Axis (C2)

• The axis (C2) includes an odontoid process, termed dens, distinguishable superior articular facets, lateral masses, a body, and a spinous process and transverse process.

Lower Cervical Vertebrae (C3-C7)

• The vertebrae in this segment exhibit similar structures. Features include uncinate processes, uncovertebral joints (also known as Joints of Luschka), and sulcus for spinal nerves.

Vertebra Prominens (C7)

• The vertebra prominens (C7) is distinguished by its longer, non-bifurcated spinous process, hence its name.

Thoracic Vertebrae (T1-T12)

• Describes detailed characteristics of thoracic vertebrae.
• Includes aspects like body (heart-shape), pedicles (small diameter), laminae (vertical arrangement), spinous processes (long and angled downwards), vertebral foramina (round), and articular processes.