The neck has a well-defined hierarchy from superficial to deep (from anterior to posterior): skin, superficial fascia, deep cervical fascia, and muscle. The deep fascia is subdivided into three layers: superficial, middle and deep. The sheath formed between the superficial, middle and deep layers accommodates the trachea, esophagus and blood vessels passing through the neck. The layers are interspersed with loose connective tissue and form the cervical space. I. Skin The skin is thin and mobile with transverse skin lines. The superficial fascia is loose and contains skin muscles, skin veins, skin nerves and lymph nodes. 1.Dermatome: The dermatome is the broad cervical muscle, thin and extensive. It reaches up to the face and down to the second rib plane, crossing the entire length of the two earliest ossified bones in the human body, namely the clavicle and the superficial surface of the mandible, and the midline of the neck and the lower part of the anterior cervical triangle are not covered by this muscle. The dermal nerve and dermal vein in the superficial fascia are located on the deep side of the muscle, and the muscle becomes an important symbol of this level of superficial fascia. 2.Dermal veins and lymph nodes: There are superficial anterior jugular veins and superficial external jugular veins, which are surrounded by accompanying lymph nodes. In the root of the neck, both veins enter the two interstices formed by the deep cervical fascia, namely the suprasternal and supraclavicular interstices, and have transverse anastomotic branches. 3.Dermal nerves: The dermal nerves are the cervical plexus dermal branches, including the lesser occipital nerve, the greater auricular nerve, the transverse cervical nerve, and the supraclavicular nerve. These dermal nerves all travel from the midpoint of the posterior border of the sternocleidomastoid muscle to radiate around, where the small occipital nerve hooks around the paramedian nerve and rises along the posterior border of the sternocleidomastoid muscle, lifting the small occipital nerve can hook out the paramedian nerve, which is a sign to find the paramedian nerve, and the posterior border of the sternocleidomastoid muscle is a sign to find the small occipital nerve. The greater auricular nerve travels vertically toward the earlobe. The transverse cervical nerve crosses the middle of the sternocleidomastoid muscle vertically. The supraclavicular nerve is subparallel to the paracranial nerve but lies below it. C. Deep cervical fascia The deep cervical fascia is the muscle coat of the neck muscles and its continuation, from front to back are the superficial cervical deep fascia, the middle cervical deep fascia and the deep cervical deep fascia. 1.Superficial cervical fascia: Superficial cervical fascia is also called envelope fascia. It forms a closed sheath-like structure around the whole neck, which forms the basic environment for the activities of the organs in the neck and becomes the first line of defense for the protection of the organs in the neck. The fascia also wraps around the sternocleidomastoid and trapezius muscles to form two muscle sheaths, wraps around the parotid and submandibular glands to form two glandular fascial sheaths, and divides into two layers on the sternum and clavicle to form two gaps. 2, deep cervical fascia middle layer (cervical visceral fascia): cervical visceral fascia is divided into two parts, one part wraps around the large blood vessels and nerves in the neck, forming the carotid sheath. the other part wraps around the trachea, esophagus and thyroid gland, forming a total visceral sheath, the second envelope, building the second line of defense to protect the organs. It also extends into the trachea, esophagus and thyroid gland, forming the tracheal, esophageal and thyroid sheaths respectively. 3. Deep cervical fascia: deep cervical fascia is also called prevertebral fascia, which is the muscle coat of the prevertebral muscles in the neck, and the fascia reaches the third thoracic vertebra from the base of the skull. The cervical fascial gaps are suprasternal gap, supraclavicular gap, pre-tracheal gap, posterior esophageal gap, and prevertebral gap. 1. Suprascapular space: located at the upper edge of the sternal stalk, formed by the envelope fascia divided into two layers, containing the anterior cervical venous arch. 2.Supraclavicular space: located at the upper edge of the clavicle, formed by the envelope fascia divided into two layers, containing the anterior superficial jugular vein and the external jugular vein. 3.Pre-tracheal space: located between the pre-tracheal fascia and the superficial layer of deep cervical fascia, it contains the inferiormost thyroid artery, cephalic trunk, left cephalic brachial vein, inferior thyroid vein, thyroid odd vein plexus, and pediatric thymus, which is the most dangerous local area of the neck. 4.Posterior pharyngeal space: located between the buccopharyngeal fascia and the anterior vertebral fascia, infection in this space can spread to the posterior mediastinum. 5. Prevertebral space: located between the prevertebral fascia and the cervical and thoracic vertebrae, up to the base of the skull and down to the third thoracic vertebrae, the infection in this space can spread to the lateral cervical area on both sides in addition to being confined to this area. V. Cervical white line Formed by the superficial layer of the deep cervical fascia in the median line, this local level is simple and is the best access route into the neck.