the neck

This lecture covers the anterior aspect of the neck, the thoracic area, the diaphragm, and briefly touches on the abdominal wall.
Focus is on bony structures, musculature involved in breathing, and key structures passing through the diaphragm.

Recall normal cervical spine curvature.
Understand muscular triangles formed in the anterior neck and their contents.
Learn origins and insertions of sternocleidomastoid (SCM) muscle.
Understand the relevance of scalene muscles.
Consider connectivity between thoracic and neck regions.
Identify key bony points (sternum, ribs, hyoid bone, costal cartilages).
Understand the role of the diaphragm and intercostal muscles in breathing.
Identify structures passing through the diaphragm and its nerve supply.
The mix of our neck and then our thoracic and respiratory areas that we're thinking about.
The neck is often called cervical cervical or coli, it means column, and it is exactly that.

The neck acts as a column supporting the skull, enabling head movement, and serving as a conduit for essential structures.
Functions:
- Movement and stabilization of the head.
- Conduit for blood supply to and from the brain.
- Passage for nerve supply via the spinal cord and cranial nerves.
- Protection of vital structures.
- Accommodation of visceral structures for breathing and eating (pharynx, trachea).
- Housing thyroid gland tissue.
Key Considerations:
- Vertebral column movements and curves.
- Protection of the spinal cord.
- Musculature contributing to anterior neck movement.

Description: U-shaped bone located under the mandible (top jaw).
Mobility: Mobile, connected by ligaments and muscles, not bone-to-bone joints.
Connections: Suspends and connects to various structures via ligaments and membranes, including the thyroid cartilage.
Position: Sits in front of the third cervical vertebra (C3).
Structure:
- Body (middle part).
- Greater horns (projecting backward).
- Lesser horns (projecting upwards, like vampire teeth).
Attachments: Lesser horns connect to the styloid and mastoid processes. Muscles attach to the mandible.
Function:
- Maintains an open airway.
- Essential for swallowing, aided by suprahyoid and infrahyoid muscles.
Clinical Relevance: Critical for swallowing and maintaining an open airway.

Movements: Flexion, extension, lateral bending, rotation.
Flexion:
- Assisted by gravity.
- Controlled eccentrically by posterior spinal muscles anchoring to the cranium.
- Tightness in the back of the neck occurs due to constant eccentric work of muscles like splenius.
Anterior Flexion:
- Accomplished by small, deep muscles hugging the vertebral bodies.
- These muscles work to flex the head and vertebral column, such as lifting the head off a pillow.
Sternocleidomastoid (SCM):
- A major muscle for neck movement.
- Origin: Sternum (sterno), clavicle (cleido).
- Insertion: Mastoid process (behind the ear).
- Actions: Flexion, rotation, and extension of the head.
Scalene Muscles:
- Assist SCM.
- Location: Radiate from cervical vertebrae to the top two ribs.
- Primary Role: Lift ribs 1 and 2 during breathing.

Deep Group:
- Small, long muscles overlapping vertebral bodies (Longus Coli).
- Linear, flat, and extend along vertebral bodies to the occipital bone.
- Function: Assist in flexing the head.
Prevertebral Muscles: Anterior prevertebral muscles for these muscles.
Suprahyoid and Infrahyoid Muscles:
- Attach to the hyoid bone from above and below.
- Involved in swallowing.
  Note: These muscles are not covered in detail in this course.

Location: Deep, originating from cervical vertebrae to ribs 1 and 2.
Association: Closely associated with the brachial plexus.
Groups: Anterior, middle, and posterior.
Action:
- Lift ribs 1 and 2 during forced inhalation (accessory breathing muscles).
- Side bending of the neck (lateral flexion).
Brachial Plexus:
- Passes through the muscle bellies of the scalenes.
- Damage to scalenes can risk the brachial plexus.

Action: Visible ridge when turning the head.
Origin:
- Sternal head: Manubrium (top of sternum).
- Clavicular head: Clavicle.
Insertion: Mastoid process (temporal bone behind the ear).
Action:
- Unilateral contraction: Turns head to the opposite side and side bends.
- Bilateral contraction: Extension and flexion.
Nerve Supply: Cranial nerve XI (accessory nerve), same as trapezius.

SCM serves as a key landmark dividing the neck into anterior and posterior triangles.

Borders:
- Anterior: Sternocleidomastoid.
- Posterior: Trapezius.
- Inferior (Base): Clavicle.
Contents:
- Brachial plexus
- Subclavian artery
Significance: Conduit for structures related to the upper limb.

Borders:
- Superior: Mandible
- Lateral: Sternocleidomastoid
- Medial: Midline of the neck
Contents & Significance:
- Function: Conduit for structures essential for life: digestion, breathing, and blood supply to the brain.
- Major Arteries: Carotid arteries (blood to the brain).
- Major Veins: Internal jugular veins (blood from the brain).
- Cranial Nerve: Vagus nerve (CN X) - speaking, cardiac function
- Glandular Tissue

Arrangement: On each side of the neck:
- Vagus nerve (yellow).
- Common carotid artery (red).
- Internal jugular vein (blue).
Vagus Nerve:
- Runs alongside the carotid artery and internal jugular vein.
- Supplies larynx (speech), heart, and abdomen.
Carotid Artery: Branches to supply the brain and facial regions.
Internal Jugular Vein: Returns blood from the brain and face to the heart.
Carotid Sheath: These three structures (vagus nerve, carotid artery, internal jugular vein) are bundled together within a connective tissue sheath.

Key Structures:
- Brachial plexus.
- Subclavian artery.
Vulnerability: This area is prone to injury from clavicular fractures or trauma, potentially affecting the upper limb.