Head and Neck Anatomy II Overview

Surface and sectional anatomy of the neck covers anatomical relationships and entities.
Understanding layers of deep cervical fascia and fascial spaces is crucial for clinical relevance.
Knowledge of cutaneous supply and cervical plexus can assist in performing cervical plexus blocks.

The neck extends from the base of the skull to the inferior border of the mandible and superior thoracic aperture.
It is a tubular structure connecting the head to the trunk, serving as a conduit for various structures.

Divided into four regions: anterior, right lateral, left lateral, and posterior (nucha).
Anterior Region:
- Contains strap muscles and visceral structures (pharynx, esophagus, larynx, trachea).
- Includes key vessels, thyroid, parathyroid glands, and four cranial nerves.
- Palpable structures: hyoid bone, thyroid cartilage, cricoid cartilage, tracheal rings, and common carotid artery.
Right and Left Lateral Regions:
- Composed of superficial muscles and cervical lymph nodes.
- Palpable structures: mastoid process, clavicle, sternocleidomastoid muscle, trapezius, external jugular vein, atlas vertebra's transverse process.
Posterior Region:
- Comprises cervical vertebral column (C1 to C7) and spinal cord.
- Palpable structures: external occipital protuberance, superior nuchal line, and spine of the 7th cervical vertebra.

Also known as tension or cleavage lines; indicate the orientation of collagen fibers in the dermis.
Incisions aligned with these lines tend to heal better and result in less scarring.

Comprises two primary layers: superficial fascia and deep fascia.
Superficial Fascia:
- A thin layer of subcutaneous connective tissue, housing platysma muscle and cutaneous structures.
- Contains nerves, blood, lymph vessels, and varying amounts of fat.
Platysma:
- A broad sheet of muscle that assists in venous return and mandibular depression.
- Extends from pectoralis major and deltoid muscle to facial skin and mandible.
Deep Fascia:
- Encloses muscles, viscera, and neurovascular structures.
- Investing layer surrounds sternocleidomastoid and trapezius muscles, forming a musculofascial collar, facilitating head rotation and neck flexion.

Superiorly attached to the superior nuchal line, lower border of the mandible, and mastoid process.
Posteriorly connected to the ligamentum nuchae and C7 cervical spine.### External Occipital Protuberance
Anteriorly located near the symphysis menti.
Inferior relations include the hyoid bone, manubrium, fascia of the opposite side, clavicle, acromion process, and spine of scapula.

Pretracheal fascia: Encloses visceral organs, lies deep to infrahyoid strap muscles, attaches to hyoid bone and thyroid cartilage, splits to surround the thyroid gland, and blends with surrounding structures.
Prevertebral fascia: Encloses intrinsic neck muscles, forms the vertebral compartment, extends from the skull base to T3, allows gliding of adjacent structures during neck movements.
Carotid sheath: Contains neurovascular structures, formed by connective tissue, encompasses the internal jugular vein, common or internal carotid arteries, and vagus nerve, while the sympathetic trunk sits posteriorly.

Musculofascial collar: Includes muscles and investing fascia for head rotation.
Muscular compartment: Regulates hyoid during swallowing and speaking.
Visceral compartment: Contains essential structures like pharynx, larynx, esophagus, trachea, thyroid, and parathyroid glands.
Neurovascular compartment: Houses major arteries, veins, lymphatic vessels, and nerves.
Vertebral compartment: Contains vertebrae and intrinsic neck muscles, contributes to neck movement.

Fascial spaces prevent adhesion of structures, facilitating movement of organs.
They play a significant role in the spread of infection, notably odontogenic infections reaching the mediastinum.

Located postero-laterally to the pharynx, extends into sublingual region.
Serves as an interface between interfascial spaces and the mandible, closely linked to lymph nodes draining the nose, throat, and jaw.
Infections can access the pharyngeal space from various sources, such as teeth or glands.

Positioned between the vertebral column and visceral neck compartment, extending from the skull base to the diaphragm.
Allows expansion of the pharynx during swallowing, significant for the spread of infections from the mouth.

Characterized by bilateral swelling affecting submental, sublingual, and submandibular spaces, often due to dental abscesses.
Patients present with difficulty in swallowing (dysphagia) and elevated tongue, with risk of infection spreading to the mediastinum.

Derived from C2, C3, and C4 spinal segments, with C1 lacking cutaneous branches.
Nerve point (Erb’s point) located at the sternocleidomastoid muscle's midpoint, supplying various skin areas.

Formed by anterior rami of C1-C4, provides sensory and motor innervation to neck and trunk.
Superficial branches supply skin, while deep branches innervate neck muscles.

Used for surgical procedures involving neck and shoulders, involves administering anesthetic at Erb’s point.
Can affect both superficial skin areas and deeper neck muscles, including the diaphragm.

Located behind carotid sheaths, consists of superior, middle, and inferior cervical ganglia, which form plexuses around nearby arteries.

Results from sympathetic trunk interruption, presenting with constricted pupil (miosis), drooping eyelid (ptosis), lack of sweating (anhidrosis), and sinking eyeball (enophthalmos).
Can arise from various causes, including spinal cord lesions and Pancoast tumors.