🥇 COLUMNA VERTEBRAL 5/5 - (Articulaciones y Ligamentos). Fácil y Sencillo

Introduction to the Spine's Articulations

Overview of the Video

• Juan José Sánchez introduces the fifth installment of a series on the spine, focusing on its articulations. This is the final part of a detailed exploration into spinal anatomy.

• The video will cover six groups of joints in the vertebral column, specifically highlighting four main types: joints between vertebral bodies and those between vertebral arches. Special attention will be given to unique joints involving C1 (atlas) and C2 (axis).

Types of Joints Discussed

• The discussion includes two additional joint types not covered in this video: those between thoracic vertebrae and ribs, as well as those between sacral bones and coxal bones. These will be addressed in future classes.

• The focus remains on four primary types of articulation relevant to understanding spinal structure and function.

Joints Between Vertebral Bodies

Structure and Classification

• The first type discussed is symphysis-type joints formed by fibrocartilaginous discs that connect adjacent vertebral bodies, classified under fibrous cartilage joints. Understanding these classifications is crucial for grasping subsequent content in the video.

• Notably, the first intervertebral disc exists between C2 and C3; there are no discs between C1 and C2 due to C1 lacking a body. This highlights an important anatomical distinction within cervical vertebrae.

Intervertebral Discs Composition

• Intervertebral discs consist of two parts:

• Nucleus Pulposus: A gelatinous center providing support and nutrition.

• Annulus Fibrosus: An outer ring that connects vertebral bodies while also serving a joint union function. This structure plays a critical role in cushioning impacts during movement.

Significance of Intervertebral Discs

Role in Spinal Length

• Intervertebral discs account for approximately 25% of total spinal length; for example, if an individual measures 1 meter tall, about 10 centimeters would be attributed to these discs alone. This emphasizes their importance in overall spinal structure.

Aging Effects on Discs

• As individuals age, intervertebral discs lose water content leading to decreased height over time—a common phenomenon observed particularly among older adults due to dehydration within these structures.

Pathologies Related to Intervertebral Discs

Herniated Discs Explained

• Herniated discs occur when damage affects the annulus fibrosus allowing nucleus pulposus material to protrude outwards, potentially compressing nearby nerves exiting through intervertebral foramina—this can lead to significant pain commonly experienced by older populations.

Anatomical Relationships

Anatomy of Spinal Joints and Ligaments

Structure of Intervertebral Discs

• The intervertebral discs are likened to a hamburger, where the bodies represent the loaves and the disc is the meat. Between each disc and body lies a cartilaginous sheet, creating a structure of body, cartilaginous sheet, disc, cartilaginous sheet, and body again.

Understanding Joint Types

• Contrary to previous beliefs that certain spaces between cervical vertebrae were synovial joints (uncovertebral joints or Luschka joints), they are now understood as fibrocartilaginous symphysis type joints with fissures in the annulus fibrosus. These clefts are not true synovial joints.

Ligaments Connecting Vertebral Bodies

• The anterior longitudinal ligament (also known as common anterior vertebral ligament) connects vertebral bodies from C1 down to the sacrum and fuses partially with intervertebral discs. It also extends upwards to connect with the anterior occipitoatloid membrane at C1.

• The posterior common longitudinal ligament is thinner than its anterior counterpart and resides within the vertebral canal, connecting bodies from behind while also attaching to intervertebral discs at their level. This ligament continues down into the sacral region covering sacral vertebrae inside the canal.

Tectorial Membrane Connection

• The posterior common longitudinal ligament reaches up to C2's body before continuing as the tectorial membrane towards the edges of the occipital bone at foramen magnum, indicating its role in maintaining structural integrity within the spinal canal.

Zygapophyseal Joints Overview

Anatomy of the Cervical Vertebrae and Associated Ligaments

Overview of Zygapophyseal Joints

• The zygapophyseal joints, also known as arthrodia or flat joints, are formed by the articular processes of cervical vertebrae.

Supraspinous Ligament

• The supraspinous ligament connects the tips of transverse processes to the middle sacral crest, reinforcing the vertebral arches. It is named for its position atop the spinous processes.

• This ligament extends from C7 upwards but does not connect with other cervical vertebrae's spinous processes, only reaching C7 before transitioning into a triangular membrane.

Triangular (Nuchal) Ligament

• The triangular ligament, also referred to as the nuchal ligament or posterior cervical ligament, continues from C7 to C1 and attaches to the occipital bone at the external occipital crest and protuberance.

• It has three edges: an upper edge (occipital), an anterior edge (cervical), and a free posterior edge that is a continuation of the supraspinous ligament.

Interspinous and Yellow Ligaments

• Interspinous ligaments connect adjacent spinous processes while yellow ligaments (ligamenta flava) join laminae together; they are notable for their yellow color due to elastin content. These ligaments form the posterior limit of the vertebral canal.

• The yellow ligaments extend from C2's lamina to C1's posterior arch but do not exist between C1 and occipital bone due to lack of lamina in that region; instead, this space is filled by a membrane called the posterior occipitoatlantal membrane.

Intertransverse Ligament

• Intertransverse ligaments connect transverse processes across different vertebrae; although poorly developed in humans, they play a role in spinal stability.

Occipitoatlantal Joint

Understanding the Occipitoatlantal Joint and Its Ligaments

Overview of the Occipitoatlantal Joint

• The occipitoatlantal joint is formed by the articulation of the occipital bone and the atlas (C1), with anterior and posterior parts identified.

• This joint is classified as a condylar synovial joint, allowing movement in two axes: flexion/extension on the lateral axis and abduction/adduction on the anteroposterior axis.

Joint Capsule and Ligament Reinforcement

• The occipitoatlantal joints are reinforced by a joint capsule, typical for all synovial joints, which provides stability.

• Key ligaments include:

• Anterior occipitoatloid membrane connecting the anterior arch of the atlas to the occipital foramen.

• Posterior occipitoatloid membrane linking the posterior arch of the atlas to posterior edges of bones at the occipital foramen.

Special Articulation Between Atlas and Axis

• The articulation between C1 (atlas) and C2 (axis) involves three synovial joints, including two lateral atlaidoaxial joints that are flat or arthroid joints.

• The middle atlaidoaxial joint occurs between the anterior arch of atlas and odontoid process (C2), functioning as a trochoid or pivot type joint enabling head rotation.

Movement Mechanics

• The trochoid joint allows internal/external rotation movements; while C1 rotates around C2, it enables head rotation due to its attachment to C1.

Ligament Support for Atlaidoaxial Joints

• The articular capsule connects lower part of lateral mass of atlas to inferior articular facet with superior articular process of axis.

• Additional ligaments include:

Understanding the Cruciform Ligament and Occipito-Odontoid Joint

Cutting the Tectorial Membrane

• The tectorial membrane is cut to reveal structures near the odontoid process, which is anterior in the spine. This highlights its proximity to the atlantoaxial joint.

Structure of the Cruciform Ligament

• The cruciform ligament consists of two main fascicles: a transverse ligament connecting lateral masses of the atlas and superior/inferior longitudinal ligaments extending to occipital bone and C2 body respectively. This structure resembles a cross, hence its name.

Components of the Cruciform Ligament

• The three components of the cruciform ligament are:

• Transverse ligament: Connects lateral masses of atlas.

• Superior longitudinal ligament: Reaches anterior edge of occipital bone.

• Inferior longitudinal ligament: Extends to back of C2 body.

Deep Portion of Tectorial Membrane

• The deep portion of the tectorial membrane connects from lateral mass of atlas to body of C2; it may not always be present, indicating variability in anatomy.

Anterior Ligaments and Their Function

• After cutting through various ligaments, including the cruciform, we observe that these ligaments primarily connect C2 (the axis) with occipital bone rather than being part of atlantoaxial joint structures. This forms an occipito-odontoid joint subtype.

Reinforcement by Additional Ligaments

• The occipito-odontoid joint is reinforced by:

• Middle occipito-odontoid ligament (apical): Connects odontoid process to anterior edge of occipital foramen.

• Lateral occipito-odontoid ligaments: Extend from odontoid process to lateral edges of occipital foramen, resembling wings (also known as alar ligaments).

Functional Anatomy Insights