Spine, pelvis, and tempromandicular joint anatomy | Musculoskeletal system

Spine and pelvis region

24 moveable bones
9 fused bones
- Divided into 5 areas- cervical, thoracic, lumbar, sacral, and coccygeal

Provides a strong and flexible framework that supports the body’s weight, allowing for standing, walking, and moving freely.
Encases and protects the spinal cord
Connecting discs allow for a wide range of motion, including flexion, extension, rotation, and lateral flexion.
Thoracic spine protects vital internal organs such as the heart and lungs.
Carries nerve signals between the brain and the body, enabling us to feel, move, and control bodily functions.
Maintain proper balance and posture by distributing the body’s weight evenly.
Plays a role in breathing, digestion, and other involuntary movements.

Definitions

Vertebral body: The cylindrical anterior part of the C3 to L5 vertebrae and consists of a thin layer of compact bone
Pedicles: Either of two short cylindrical bony processes lying on either side of a vertebra that project posteriorly from the vertebral body and fuse with the laminae to form a neural arch
Lamina/facets: Flat, arched bone that forms the posterior (back) part of each vertebra
Transverse processes: Bony projections on the sides of the vertebrae that help support the spine and attach muscles.
Spinous process: A bony projection located at the back of each vertebra in the spinal column

Cervical
- C1 and C2 allow for rotation without compression of spinal cord
Costotransverse and costovertebral
- Articulation between ribs and transverse processes of spine
Thoracic
- Prominent (easily palpable) spinous process
Lumbar
- Largest and most prominent (easily palpable) spinous process
Sacrum
- Composed of 5 fused bones
Ilium
- Made of 3 fused bones- ischium, ilium, and pubis

Atlanto-occipital joint- articulation between occipital bone and C1 which allows head nodding to occur
- Atlanto-axial joint- articulation between C1 and C1 which allows for head rotation
Facet joints
- Aid in movement of spine as a whole
Intervertebral joints
- Allow for movement at single vertebral body and assist with transferring load from one vertebral body to another
Sacroiliac joints
- Aid in movements of lower axial skeleton and lower extremities

Alar
- Connects dens to occipital condyle
- Functions to limit flexion, contralateral lateral flexion, and contralateral rotation
Anterior longitudinal ligament
- Connects anterior and lateral surfaces of vertebral bodies from C2- sacrum
- Function to reinforce the anterolateral portion of the intervertebral discs
Posterior longitudinal ligament
- Located on the posterior surface of vertebral bodies from C2- sacrum
- Function to prevent hyperflexion of the vertebral column and to protect the spinal cord from foreign objects and displaced disc material.
Ligamentum flavum
- Connects vertebra to the lamina above it; runs from C2-sacrim
- Function to limit flexion (greatest in lumbar spine)
Interspinous ligament
- Runs between spinous processes
- Function to limit flexion
Iliolumbar ligament
- Connects L5 vertebrae to ilium
- Functions to limit motion between L5 and S1

Facet joints
- Role is to provide reinforcement to ligaments by limiting motion and stabilizing spine
Sacroiliac joints
- Role is stabilizing the sacroiliac joint, limiting its movement, and protecting the joint by distributing biomechanical loads.

Spinal nerves are mixed nerves that connect the spinal cord to the rest of the body. They carry both sensory (dorsal rami) and motor (ventral rami) information between the central nervous system (brain and spinal cord) and the peripheral nervous system (body and muscles).
Location of spinal nerves
- Cervical: exit at the level above the associated vertebrae
- Thoracic/lumbar: exit below the level of associated vertebrae

Flexion (bending forward):
- When you bend forward, the facet joints on the back of the spine open up, allowing for more space between the vertebrae.
Extension (bending backward):
- Conversely, when you bend backward, the facet joints close together, creating a more stable and compressed position.
Sidebending:
- During sidebending, the facet joints on the side you are bending towards close, while the facet joints on the opposite side open.
Rotation:
- During rotation, the facet joints on the ipsilateral side compress together, while the facet joints on the opposite side tend to open.

Facets will move to allow for movements to occur

Secondary movements that consistently accompany a primary motion; examples are flexion and extension or lateral flexion and rotation

Cervical spine
- C1: lateral bending and rotation occur in different directions (occurs if spine in neutral, flexion, and extension)
- C2-C7: lateral bending and rotation occurring in the same direction (occurs if spine in neutral, flexion, and extension)
Lumbar/thoracic spine
- If spine in flexion: side bending and rotation will occurring in same direction
- If spine in extension/neutral: side bending and rotation will occur in opposite directions
Lumbopelvic joint
- When in flexion: lumbar spine flexes followed by pelvis rotation anteriorly, ending with hip flexion
- When in extension (when coming from flexed position): hips extend followed by pelvis rotating posteriorly, and spine extending
Sacroiliac joint
- Nutation: flexion of sacrum causes posterior tilt of ilium (in frontal plane)
- Counternutation: extension of sacrum causes anterior tilt of ilium (in frontal plane)
- Anterior innominate: anterior superior iliac spine (ASIS) moves downward (in sagittal plane)
- Posterior innominate: anterior superior iliac spine (ASIS) moves upward (in sagittal plane)