MOB part 2-cranio-vertbral junction

The suboccipital muscles are a group of four muscles situated underneath the occipital bone. All the muscles in this group are innervated by the ==suboccipital nerve==. They are located within the suboccipital compartment of the neck; deep to the sternocleidomastoid, trapezius, splenius and semispinalis muscles. They collectively ==act to extend== and ==rotate the head.==

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^^Rectus Capitis Posterior Major^^

-The rectus capitis posterior major is the ==larger of the rectus capitis muscles.==

-The Rectus capitis posterior major is ==located laterally== to the rectus capitis posterior minor.

• The Rectus capitis posterior major originates from ==the spinous process of the C2 vertebrae (axis)==, and inserts into the ==lateral part of the inferior nuchal line of the occipital bone==.

^^Rectus Capitis Posterior Minor^^

The rectus capitis posterior minor is the ==most medial of== the suboccipital muscles.

The rectus capitis posterior minor rns from the ==posterior tubercle of the C1 vertebra== to the ==medial part of the inferior nuchal line of the== ==occipital bone.==

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^^Obliquus Capitis Inferior(OCI)^^

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-Obliquus capitis inferior is the ==most inferiorly== positioned of the suboccipital muscles. It is the only capitis muscle that ==has no attachment to the cranium.==

•Obliquus Capitis Inferior(OCI) Originates ==from the spinous process of the C2== vertebra, and attaches into the ==transverse process of C1.==

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^^Obliquus Capitis Superior^^

The obliquus capitis superior is located ==laterally== in the suboccipital compartment.

• Obliquus Capitis Superior(OCS) originates from ==the transverse process of C1== and attaches into ==the occipital bone== (between the superior and inferior nuchal line)

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^^Suboccipital Triangle^^

The suboccipital triangle is an area bordered by three of the suboccipital muscles:

1. ==Superomedial==: Rectus capitus posterior major
2. ==Superolateral==: Obliquus capitus superior
3. ==Inferior==: Obliquus capitus inferior

• ==Floor==: Posterior atlanto-occiptal membrane and posterior arch of the C1 vertebrae (atlas)

• ==Roof==: Semispinalis capitus

The contents that the suboccipital triangle have is ==the vertebral artery==, ==suboccipital venous plexus== and ==suboccipital nerve==

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^^CERVICAL BONES^^

The cervical spine is the ==most superior portion== of the vertebral column, lying between the cranium and the thoracic vertebrae.

It consists of ==seven distinct vertebrae==, two of which are given unique names:

• The first cervical vertebrae (C1) is known as the ==atlas==.

• The second cervical vertebrae (C2) is known as the ==axis==.

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^^Characteristics of cervical vertebra^^

The cervical vertebrae have three features :

1. Triangular vertebral foramen.
2. Bifid spinous process – this is where the spinous process splits into two distally.
3. Transverse foramina – holes in the transverse processes. They give passage to the ==vertebral artery==, ==vein== and ==sympathetic nerves==.

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C1 & C2 vertebra

^^Atlas^^

-The atlas (C1) differs from the other cervical vertebrae in that it has ==no vertebral body== and ==no spinous process==.

-The atlas has ==an articular facet anteriorly==, which articulates with the ==dens of the axis==.

-The atlas also has lateral masses on either side of the vertebral arch, which provide an ==attachment for the transverse ligament of the atlas==.

The posterior arch has a groove for the ==vertebral artery== and ==C1 spinal nerve.==

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^^Axis^^

-The axis (C2) is easily identifiable due to ==its dens== (odontoid process) which extends superiorly from the anterior portion of the vertebra.

-The dens articulates with the ==articular facet of the atlas==, in doing so creating the ==medial atlanto-axial joint==. This allows for ==rotation of the head== independently.

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^^WHAT IS Present throughout Vertebral Column?^^

There are two different joints present throughout the vertebral column:

• Between vertebral bodies – adjacent vertebral bodies are joined by intervertebral discs, made of ==fibrocartilage==. This is a type of cartilaginous joint, ==known as a symphysis.==

• Between vertebral arches – formed by the articulation of superior and inferior articular processes from adjacent vertebrae. ==It is a synovial type joint==.

^^Whats Unique to Cervical Spine?^^

The ==atlanto-axial== and ==atlanto-occipital joints== are unique to the cervical spine.

The atlanto-axial joints are formed by the articulation between the ==atlas and the axis==:

• There are ==two lateral atlanto-axial joints== which are formed by the articulation between the ==inferior facets of the lateral masses of C1== and ==the superior facets of C2==. These are ==plane type== synovial joints.

• The ==medial atlanto-axial joint== is formed by the articulation of ==the dens of C2== with the ==articular facet of C1==. This is a ==pivot type== synovial joint.

The ==atlanto-occipital joints== consist of an articulation between ==the spine== and the ==cranium==. They occur ==between the superior facets of the lateral masses of the atlas== and ==the occipital condyles at the base of the cranium==. These are ==condyloid type== synovial joints, and permit ==flexion at the head i.e. nodding.==

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^^ATLANTO-OCCIPITAL AND ATLANTO-AXIAL JOINTS^^

• Synovial joints, ==no IV discs==

• Atlanto-occipital joints- ==permit flexion and extension==-nodding movement (YES), ==synovial condyloid.==

• Atlanto-axial joint- ==3== articulations, ==2== lateral atlanto-axial joints ==(plane)==, ==1== median atlanto axial joint==(pivot)==, pivot movement turning from side to side(NO).

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^^LIGAMENTS^^

• Joints are supported by numerous ligaments;

^^1.Anterior Longitudinal ligament(ALL)^^

Attached ==superiorly to the base of the skull== and runs the length of vertebral column to ==insert inferiorly to the anterior surface of the sacrum==.

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^^2.Posterior Longitudinal Ligament (PLL)^^

==Posterior surface the vertebral body==. Like the (ALL) attached along the length of the vertebral column to IV discs and vertebral bodies.

==Upper part of the PLL that connects C2== to the base of the skull is called the ==tectorial membrane.==

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^^SUPRASPINOUS LIGAMENT AND LIGAMENTUM NUCHAE^^

• Supraspinous ligament: connects and passes along the tips of spinous processes of ==C7-sacrum==.

• From vertebra C7 to skull the ligament becomes distinct- ==Ligamentum nuchae==

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^^Anatomical Relationships^^

The transverse foramina of the cervical vertebrae provide a passageway through which the ==vertebral artery, vein and a plexus of sympathetic nerves can pass.==

There are two vertebrae where this is not the case:

• ==C7 – the vertebral artery runs around the vertebra==, instead of passing through through the transverse foramen. ==The vertebral vein and associated nerves are still present in the foramen.==

• Atlas – the ==vertebral artery runs along the groove== for the vertebral artery ==instead of through the transverse foramen.==

The spinal nerves extend from above their respective cervical vertebrae, through the intervertebral foramen created by ==the joints at the articular processes.==

The C7 vertebra has a set of ==spinal nerves extending from above (C7) and below (C8) the vertebra.== Therefore there are ==eight spinal nerves== associated with seven cervical vertebra(I know right,confusion!)