Superficial structure of neck
1. skin
The neck skin is thin, with a large amount of activity and obvious horizontal stripes. A transverse incision should be made during the operation to facilitate healing.
2. Superficial fascia
The superficial cervical fascia is generally thin and contains a small amount of fat, and there is platysma in the anterior superficial cervical fascia. There are also superficial veins, superficial lymph nodes and cutaneous nerves in the superficial fascia, all of which are located in the deep layer of platysma.
(1) platysma (fig. 6-2) platysma is a wide and thin muscle slice, which emanates from the fascia on the upper part of pectoralis major and the surface of deltoid muscle, and the anterior muscle fibers are attached to the lower edge of mandible. The fibers in the posterolateral part extend across the lower edge of the mandible to the face and interweave with the muscle fibers in the corners of the mouth. The anterior fibers interweave with the opposite lateral platysma fibers under the chin, and the intermuscular distance is lower. The platysma muscle has great variation and can be unilaterally or bilaterally missing. When contracting, oblique wrinkles appear on the neck skin. The front fiber can help the lower jaw, and the rear fiber can pull down the lower lip and corners of the mouth. The platysma muscle is innervated by the cervical branch of facial nerve and the cutaneous branch of cervical plexus.
Figure 6-2 Surface structure of platysma and neck
(2) superficial jugular vein
(1) The external jugular vein (Figure 6-3 and Figure 4) is the largest vein in the neck, which consists of the anterior branch and the posterior branch. The anterior branch is the posterior branch of the posterior facial vein; The posterior branch consists of occipital vein and posterior auricular vein. The two branches meet at the mandibular angle, go outward and downward along the superficial surface of sternocleidomastoid muscle, pass through deep fascia, and pour into subclavian vein 2.5 cm above the midpoint of clavicle. The deep fascia and vein wall healed at the penetration point. When the vein is injured, the lumen cannot be closed, and air embolism is easy to occur. At the end of the external jugular vein, there are usually only a pair of valves, which can not completely prevent the blood from flowing back. Therefore, when the reflux of superior vena cava is blocked and the venous pressure rises, the external jugular vein can be inflated.
Figure 6-3 Superficial jugular vein
(2) The anterior jugular vein of the anterior jugular vein (Figure 6-2, 3 and 4) starts from submental, descends along both sides of the midline, enters the suprasternal space, turns at right angles to the outside, passes through the deep surface of sternocleidomastoid muscle, and injects into the external jugular vein, occasionally injecting into subclavian vein or innominate vein. In the suprasternal space, there are often transverse anastomosis branches between the two anterior jugular veins, which are called jugular vein arch. The anterior jugular vein has no valve and is close to the heart, which is greatly influenced by the negative pressure in the chest. Therefore, attention should be paid to prevent air from inhaling into veins during neck surgery (such as thyroid surgery and tracheotomy). Sometimes there is only one anterior jugular vein, which is located in the midline.
(3) The superficial cervical lymph nodes (Figure 6-5) are arranged along the external jugular vein, receiving the superficial lymphatic vessels of the external ear, the lower parotid gland and the mandibular angle, and their outlet pipes are injected into the deep cervical lymph nodes.
(4) Cervical cutaneous nerve includes cutaneous branch from cervical plexus and cervical branch of facial nerve.
(1) The cutaneous branches of the cervical plexus pass through the superficial layer of the deep cervical fascia at the midpoint of the posterior margin of the sternocleidomastoid muscle, and are distributed subcutaneously (Figures 6-2 and 4).
Suboccipital nerve goes up along the posterior edge of sternocleidomastoid muscle and distributes in occipital skin.
The greater auricular nerve runs forward and upward around the superficial surface of sternocleidomastoid muscle, and is distributed in auricle and its surrounding skin. The nerve is thick and can be touched through the skin when it is attacked by leprosy.
The transverse cervical cutaneous nerve passes through the superficial surface of sternocleidomastoid muscle and is a fan-shaped branch, which is distributed in the skin at the front of the neck.
Fig. 6-4 cutaneous branches of cervical plexus
The supraclavicular nerve runs downward and outward, and is divided into three branches: anterior, middle and posterior, which are distributed in the anterolateral part of the neck, above the second rib of the chest wall and the skin of the shoulder.
(2) The cervical branch of facial nerve passes through the lower part of parotid gland, forwards and downwards, and distributes in platysma, which is the motor nerve of this muscle. In parotidectomy, the cervical branch of facial nerve can be used as one of the signs to find the facial nerve trunk.
Superficial cervical muscle
1. sternocleidomastoid muscle The sternocleidomastoid muscle (Figure 6-6) starts from the sternal stalk and the sternal end of the clavicle at both ends, forming a muscular abdomen, obliquely upward, and ends at the lateral part of the mastoid and occipital neck line. When one side contracts, the head tends to turn from the same side to the opposite side; Both sides contract at the same time, which can make the head lean back and the neck bend. It is innervated by the accessory nerve and the branches of the anterior branches of the second and third cervical nerves.
2. The suprahyoid muscle group and the infrahyoid muscle group (Figure 6-6) The suprahyoid muscle group is located between the hyoid mandible, the styloid process of the temporal bone and the mastoid process, and is mainly the muscle that closes the floor of the mouth, and consists of the superficial digastric muscle and the styloid hyoid muscle; Deep jaw hyoid muscle and geniohyoid muscle. Subhyoid muscle group is flat muscle located on both sides of the midline, and the superficial layer is parallel sternohyoid muscle and scapulohyoid muscle. The deep layer consists of upper and lower sternum thyroid and thyrohyoid muscle. See table 6- 1 for the specific starting and ending time:
Figure 6-5 superficial cervical lymph nodes
Figure 6-6 Neck muscles
Table 6- 1 Names, starting and ending points, functions and innervation of upper and lower hyoid muscles.
Deep cervical fascia and fascial space
The deep fascia of the neck is located on the deep surface of the superficial fascia and platysma, surrounding the muscles, blood vessels, nerves and organs of the neck, forming three layers: shallow, middle and deep. The neck organs are separated by dense fascia, and there is a gap between the fascia, which is full of loose connective tissue, called fascial space. (Figure 6-7, 8).
1. Thin layer
The superficial layer of the deep cervical fascia, also known as the sheath, surrounds the neck. The posterior part is attached to the nuchal ligament and spinous process of the cervical spine, then turns to the lateral side and forwards, and then bypasses trapezius muscle and sternocleidomastoid muscle in turn, covering the surface of hyoid muscle group until the midline and the contralateral side heal, forming a white line of the neck.
Above the superficial fascia, it adheres to the cervical line and mastoid of occipital bone, and wraps the parotid gland forward to form a parotid sheath; Then it is divided into two layers under the mandible, which surround the submandibular gland and attach to the mandible to form the submandibular gland sheath. The lower part of superficial fascia is attached to acromion, clavicle and sternal stalk. Above the jugular vein notch, there are two layers, shallow and deep, which are attached to the front and back edges of the notch respectively. The space between them is called suprasternal space, which contains jugular arch and lymph nodes.
2. Visceral fascia is the middle layer of deep cervical fascia.
Also known as the anterior tracheal fascia, it can be divided into visceral layer and parietal layer. Visceral layer is thin and loose around neck organs, such as larynx, trachea, thyroid gland, pharynx and esophagus, and the part around thyroid gland constitutes thyroid pseudocapsule. The wall is dense, located in front of the cervical organ and attached to the hyoid muscle group, forming a carotid sheath to both sides, surrounding the common carotid artery, internal jugular vein and vagus nerve. Pretracheal space is formed between the visceral layer and the parietal layer, which contains loose connective tissue. Thyroid azygos vein plexus composed of left and right inferior thyroid veins is located in the gap. There is an upper thymus in the lower segment of pretracheal space in children, which goes down to the front of the upper mediastinum. Therefore, when there is infection or bleeding in the cervical pretracheal space, it can reach the anterior mediastinum along this gap. If there is emphysema in the anterior mediastinum, it can also extend to the neck along this gap.
3. Anterior fascia
That is, the deep fascia of the neck is covered by the anterior vertebral muscle, anterior scalene muscle, levator scapulae, brachial plexus and subclavian vessels, forming the bottom of the lateral cervical triangle, extending outward and downward, and surrounding subclavian artery and vein, brachial plexus and axillary sheath. Upward attached to the skull base and downward fused with the anterior longitudinal ligament of the spine. The retropharyngeal space is located between the anterior fascia of vertebra and the posterior pharyngeal wall. The abscess in this space may bulge into the pharyngeal cavity, and the patient may have difficulty swallowing and pronouncing. Infection can extend down to the posterior mediastinum. There is a prespinal space between the prespinal fascia and the cervical spine. Abscess and pus of cervical tuberculosis mostly accumulate in this space, and can also spread downward to the posterior mediastinum, or to both sides of the neck, or penetrate the anterior fascia of the vertebra to the retropharyngeal space.
Figure 6-7 Cervical Fascia and Cervical Fascia Space (median sagittal section)
Figure 6-8 Cervical Fascia and Cervical Fascia Space (Cross Section)
4. carotid sheath
Carotid sheath is formed by the thickening of visceral fascia around the great vessels of the neck, which surrounds the common carotid artery, internal carotid artery, internal carotid vein and vagus nerve. The sheath reaches the skull base, down to the mediastinum, and is continuous with the superficial layer of the deep fascia of the neck and the anterior fascia of the vertebra, with loose connective tissue.
Neck dissection
Figure 6-9 Neck Segmentation
The neck is divided into three regions by the sternocleidomastoid muscle, namely, the anterior cervical region, the sternocleidomastoid muscle region and the lateral cervical region. The border of the anterior cervical region is the anterior border of sternocleidomastoid muscle, the anterior midline and the lower edge of mandible, which is a triangle with downward tip and upward bottom, so it is also called the anterior cervical triangle. The anterior cervical region can be divided into the following four small (triangular) regions, namely, the mandibular triangle surrounded by the anterior and posterior abdomen of the digastric muscle and the lower edge of the mandible, which contains submandibular glands; The submental triangle surrounded by the anterior abdomen of the left and right digastric muscles and the hyoid body; The scapulohyoid muscle and trachea triangle (muscle triangle) surrounded by the anterior border of sternocleidomastoid muscle, the anterior cervical midline and the epigastrium of scapulohyoid muscle contains thyroid and trachea. The carotid triangle surrounded by the anterior edge of sternocleidomastoid muscle, the upper abdomen of scapulohyoid muscle and the posterior abdomen of digastric muscle contains common carotid artery, internal carotid artery, external carotid artery and their branches. The boundary of lateral cervical region is the posterior edge of sternocleidomastoid muscle, the anterior edge of trapezius muscle and clavicle, which is a triangle on the bottom tip, also called lateral cervical triangle. The lateral cervical region can be divided into two small (triangular) regions, that is, the oblique lower abdomen of the scapulohyoid muscle is the supraoccipital triangle of the scapulohyoid muscle and the subclavian triangle (clavicular fossa). There are accessory nerves in the occipital triangle that obliquely penetrate from the middle point to the lower side. The subclavian artery passes through the deep part of the clavicular triangle of the scapulohyoid muscle, and the lung apex and pleural apex protrude from the chest cavity (Figure 6-9).