Photo 2. How to skin (leaving subcutaneous tissue) with tools

Photo 3. Platysma mm.

Note: The platysma m. is a delicate, subcutaneous muscle separating the skin from the deeper anterior muscles of the neck. Variable in extent, the platysma typically spans the space between the superior margins of pectoralis major m. and deltoid m. (inferior to clavicle) to the inferior margins of the facial muscles. The platysma m. is part of the Superficial Musculo-Aponeurotic System (SMAS), a superficial layer of muscles, aponeuroses, and fascia that are contiguous over the anterolateral neck and face.  

Note: The platysma m. is a weak depressor of the mandible and lower lip, and when maximally contracted will give the skin of the anterior neck a tense, flat, triangular appearance with oblique ridges. The platysma is innervated by the cervical br. of the facial n. (CN VII).

2.) Reflect the platysma mm. from their inferior margins superiorly toward to the mandible. Take care to not damage and identify structures deep to the platysma, in particular the:

• external and anterior jugular veins,

• cutaneous nerve branches from the cervical plexus emanating from the ‘nerve point of the neck’ (Erb’s point), and

• cervical branch of the facial n. (CN VII).

Note: The superficial veins of the neck, named for their relative position to the deep fascia of the neck, are extremely inconstant in size, appearance, and connection. There are two major superficial veins of the neck: the external jugular v. and the anterior jugular v.

Note: The external jugular v. (EJV) is typically the most obvious superficial vein of the neck. The EJV is formed by the junction of the posterior division of the retromandibular v. and the posterior auricular v. The EJV runs superficial to the sternocleidomastoid m. (SCM), and drains into the subclavian v. lateral and deep to the SCM.

Note: The anterior jugular v. is formed from the coalescence of superficial submandibular vv. The anterior jugular v. descends anterior to the superficial infrahyoid mm., often nestling under the SCM before draining into the EJV or the subclavian v. directly. The anterior jugular v. is valveless.

Photo 4. Superficial veins

3.) Starting at the nerve point of the neck, locate and trace the lesser occipital n., great auricular n., transverse cervical n., and supraclavicular nn.

Note: The nerve point of the neck (often called Erb’s point) is a common pathway for cutaneous nerves of the neck arising from the cervical plexus. Typically found just superior to the midpoint of the posterior margin of the SCM, four cutaneous nerve trunks radiate from the nerve point of the neck:

• lesser occipital n. (C2,3)

• great auricular n. (C2,3)

• transverse cervical n. (C2,3)

• supraclavicular nn. (C3,4)

Note: The cervical branch of the facial n. (CN VII) is the inferior-most branch of the cervicofacial division of the facial n. This branch arises deep to the inferior-most part of the parotid gland and can be located deep to the platysma m.

Photo 5. Nerve point of the neck with cutaneous brs. of cervical plexus

Locate the neck muscles and ‘cervical triangles’

Find these structures:

• Sternocleidomastoid m.

• Anterior cervical triangle

• Accessory n. (CN XI)

4.) Locate and carefully clean the sternocleidomastoid (SCM) mm. Palpate the base of the mandible. Using these muscles and skeletal landmark, identify the anterior cervical triangles.

Note: The anterior cervical triangle is bounded medially by the midline, laterally by the anterior border of the SCM, and superiorly by the base of the mandible.

Photo 6. Anterior cervical triangle

5.) Reflect the sternocleidomastoid m. from its attachments to the sternum and clavicles. Reflect the SCM superiorly and laterally to see deeper structures, specifically the accessory n. (CN XI).

Photo 7. SCM reflected, omohyoid intact and cleaned

Note: Trapezius and SCM mm. are both efferently (motor) innervated by the accessory n. (CN XI). The accessory n. is strictly efferent; therefore, afferent supply to these muscles comes from ventral primary rami of cervical nerves (C2-C4). Typically, C2-C3 (sometimes C4) afferently serve the SCM, whereas C3-C4 afferently serve the trapezius. It is likely that C2-C4 also carry some motor fibers.

Photo 8. Accessory n. (CN XI)

Find these structures:

• Infrahyoid (strap) mm.

  • Sternohyoid m.

  • Omohyoid m.

    • Superior belly

    • Inferior belly

  • Sternothyroid m.

  • Thyrohyoid m.

• Digastric m.

  • Anterior belly

6.) Palpate the hyoid bone. Locate and carefully clean the superficial infrahyoid (strap) mm. Be careful to preserve branches of the ansa cervicalis, which innervate these muscles.

Note: The hyoid bone is U-shaped and suspended from the styloid processes of the temporal bones via stylohyoid ligaments. It superiorly supports the larynx via the thyrohyoid ligament, and serves as an attachment for muscles of the extrinsic tongue (geniohyoid m., hyoglossus m.), pharynx (middle pharyngeal constrictor m., stylohyoid m.), suprahyoid region (mylohyoid m.), and infrahyoid region (sternohyoid m., thyrohyoid m., omohyoid m.).

Note: Infrahyoid (strap) muscles largely occupy the area inferior to the hyoid, superior to the sternum, and medial to the carotid sheaths (excepting the inferior belly of the omohyoid). The infrahyoids may be classified into two groups: superficial (sternohyoid mm. & omohyoid mm.) and deep (sternothyroid mm. & thyrohyoid mm.). To help in locating individual infrahyoid mm., understand they are named for their attachments.

Note: All infrahyoid mm. (excepting the sternothyroid mm.) attach to the hyoid bone, and therefore are important in both depression and stabilization of the hyoid. Any infrahyoid muscle attaching to the thyroid cartilage (sternothyroid mm. & thyrohyoid mm.) will act upon the larynx .

Note: The sternohyoid m. connects the posterior aspects of the manubrium, medial clavicle, and posterior sternoclavicular ligament to the inferior body of the hyoid. The sternohyoid m. stabilizes the hyoid, or it may depress an elevated hyoid. The sternohyoid m. is innervated by branches of ansa cervicalis.

Photo 9. Superficial infrahyoid (strap) mm.

7.) Relieve the fascial sling connecting the intermediate tendon of the omohyoid m. to the clavicle (on one side only).

Note: The omohyoid m. consists of two bellies (superior and inferior) that are connected by an intermediate tendon. The superior belly connects the intermediate tendon to the inferior margin of the body of the hyoid (lateral to the attachment of the sternohyoid m.). The inferior belly connects the intermediate tendon to the upper border of the scapula, medial to the scapular notch. The intermediate tendon is anchored to the medial clavicle via a fascial sling. The omohyoid m. stabilizes the hyoid, or it may depress an elevated hyoid. The omohyoid m. is innervated by branches of ansa cervicalis.

8.) Bluntly separate the right and left sternohyoid mm. On the ipsilateral side of the free omohyoid, superiorly reflect the sternohyoid m. to reveal deeper structures.

Note: The sternothyroid m. connects the manubrium of the sternum to the oblique line of the thyroid cartilage. The sternothyroid m. inferiorly pulls an elevated larynx. The sternothyroid m. is innervated by branches of ansa cervicalis.

Note: The thyrohyoid m. connects the oblique line of the thyroid cartilage to the inferior border of the hyoid bone. The thyrohyoid m. may either inferiorly depress the hyoid bone, or elevate the larynx.

Photo 10. Deep infrahyoid mm.

9.) In the suprahyoid area (inferior to the mandible and superior to the hyoid bone), locate and clean the anterior bellies of the digastric mm. DO NOT follow the posterior bellies of the digastric mm. to their attachments on the temporal bones.

Note: The digastric m. consists of two bellies (anterior and posterior) connected by an intermediate tendon. The anterior belly attaches to the digastric fossa of the mandible, the posterior belly attaches to the mastoid notch of the temporal bone, and the intermediate tendon connects to the hyoid bone via a fibrous loop. Formed from the mesenchyme of the 1st (anterior) and 2nd (posterior) pharyngeal arches, each belly is separately innervated. The anterior belly is innervated by the nerve to mylohyoid (a branch of V3), whereas the posterior belly is innervated by the facial n. (CN VII). The digastric mm. may either weakly depress the mandible, or elevate the hyoid bone.

Photo 11. Digastric mm.

Find these structures:

• Anterior triangle

  • Muscular triangle

  • Carotid triangle

  • Submandibular triangle

  • Submental triangle

10.) Return all previously reflected muscles to their anatomical positions. Identify the four sub-triangles within the anterior triangle of the neck.

Note: The anterior triangle of the neck may be subdivided into four triangles. They are the:

submandibular (digastric) triangle: the most superior triangle; bordered inferiorly by the anterior and posterior bellies of the digastric m., and superiorly by the mandible; typically contains the submandibular gland and the facial a. & v.

submental triangle: bordered medially by the midline, laterally by the anterior belly of the digastric m., and inferiorly by the hyoid bone.

carotid triangle: bordered superiorly by the posterior belly of the digastric m., laterally by the sternocleidomastoid m., and medially by the superior belly of the omohyoid m.; typically contains the carotid sheath (and contents).

muscular triangle: the most inferior (and irregular) triangle; bordered medially by the midline, inferolaterally by the sternocleidomastoid m., and superolaterally by the superior belly of the omohyoid m.; typically contains the infrahyoid mm., thyroid gland, and the larynx.  

Photo 12. Anterior cervical triangle subdivisions

Locate the carotid sheath, and examine its contents

Find these structures:

• Ansa cervicalis

  • Superior root (limb)

  • Inferior root (limb)

• Common carotid artery

  • Carotid bifurcation

    • External carotid a.

    • Internal carotid a.

• Internal jugular v.

• Anterior cervical lymph nodes

  • Lateral cervical nodes

    • Superior deep nodes

    • Inferior deep nodes

• Vagus n. (CN X)

11.) Locate the carotid sheath deep to the sternocleidomastoid m. and lateral to the infrahyoid mm. Locate the ansa cervicalis superficial to (or within) the carotid sheath.

Note: The ansa cervicalis is a delicate loop of nerve consisting of two limbs: a superior limb (C1, sometimes C2), and an inferior limb (C2,3). The superior limb is proximally associated with the hypoglossal n. (CN XII), as fibers of the ventral primary ramus of C1 ‘hitchhike’ along the hypoglossal n., before rejoining the superior limb. Keep in mind that nerves are collections of axons in the peripheral nervous system, and that these axons may move among different nerves on their way to or from target tissues. The ansa cervicalis innervates nearly all infrahyoid mm. (excepting the thyrohyoid m.). The thyrohyoid m. is innervated by fibers from C1 that also hitchhike along the hypoglossal n. and exit distal to the superior limb of ansa.

Note: The limbs of the ansa cervicalis lie upon (and sometimes within) the carotid sheath. The ansa may be located by following its branches from the infrahyoid mm. back to the ansa loop, and then carefully (bluntly) dissecting the limbs from the carotid sheath.

Photo 13. Ansa cervicalis

12.) Open the carotid sheath to reveal its contents.

Note: The carotid sheath is a collection of deep cervical fascia surrounding the:

• proximal portion of the internal carotid a.

• common carotid a.,

• internal jugular v.,

• vagus n. (CN X),

• and sometimes the ansa cervicalis.

Areolar connective tissue binds the carotid sheath to adjacent structures and their fasciae, and often may adhere the ansa loop to the sheath. The cervical sympathetic chain may be found immediately posteromedial to the carotid sheath.

Note: Within and around the carotid sheath, you may notice deep lateral cervical lymph nodes. These nodes are divided into a superior and an inferior group (named relative to their position to the omohyoid m). The deep lateral cervical nodes are closely associated with the internal jugular v. Lymph is conducted from the superior deep cervical nodes to the inferior deep cervical nodes before entering the jugular trunk.

Photo 14. Superior and deep lymph nodes

Photo 15. Carotid sheath contents

13.) Follow the common carotid a. superiorly to the carotid bifurcation, where the common carotid becomes the internal and external carotid arteries.

Note: The common carotid artery is an important pulse palpation location.

Note: The internal carotid has no branches in the neck. It travels to the cranium, where it is transmitted through the carotid canal, and supplies blood to the brain, orbit, and forehead.

Note: The external carotid a. is the primary source of blood to the face and superficial head. The external carotid has eight branches:

• superior thyroid a.

• ascending pharyngeal a.

• occipital a.

• lingual a.

• facial a.

• posterior auricular a.

• maxillary a.

• superficial temporal a.

Photo 16. Carotid bifurcation

Locate the thyroid gland and associated neurovasculature

Find these structures:

• Thyroid gland

  • Lobes

  • Isthmus

  • Pyramidal lobe

• Trachea

  • Tracheal cartilages

• Thyroid cartilage

• Parathyroid glands

• Brachiocephalic v.

  • Internal jugular v.

    • Superior thyroid v.

    • Middle thyroid v.

  • Inferior thyroid v.

• External carotid artery

  • Superior thyroid a.

    • Superior laryngeal a.

• Thyrocervical trunk

  • Inferior laryngeal a.

• Superior laryngeal n.

14.) On the ipsilateral side as the previously dissected sternohyoid m., reflect the sternothyroid m. superiorly, above the oblique line of the thyroid cartilage.

Photo 17. Procedural: reflecting the sternothyroid m.

15.) Clean the pre-tracheal fascia from the thyroid gland, and observe the venous drainage of the gland.

Note: The thyroid gland has two lobes connected by a central isthmus, and sits between the C5-T1 vertebra. Nearly 50% of people have an accessory (pyramidal) lobe, which varies in size and typically connects the isthmus of the thyroid gland to the hyoid bone (Moore et al., 7th edition).

Photo 18. Thyroid gland

Note: The richly vascularized thyroid gland is typically drained via three sets of veins:

• superior thyroid vv., typically drain into the internal jugular vv.,

• middle thyroid vv., typically drain into the internal jugular vv., and

• inferior thyroid vv., typically drain into the left brachiocephalic v.

Photo 19. Thyroid vv.

16.) Locate the superior thyroid a. and follow it to the thyroid gland, noting its branch, superior laryngeal a. The superior laryngeal n., a branch of the vagus n., will be located in this area as well.

Note: The superior thyroid a. is the first branch of the external carotid a. It has several other branches, one of which is the superior laryngeal a. The superior laryngeal a. accompanies the internal br. of superior laryngeal n. as they pierce the thyrohyoid membrane to serve the superior larynx.

Photo 20. Superior thyroid & superior laryngeal aa. and nn.

17.) Make a midsagittal cut through the isthmus of the thyroid gland. Carefully reflect either lobe of the thyroid gland to locate parathyroid glands and the inferior thyroid artery. Follow the inferior thyroid a. to the thyrocervical trunk. Locate the thyroid cartilage, trachea, and tracheal cartilages.

Note: Parathyroid glands may be found in a variety of locations, but are typically on the posterior aspect of the thyroid gland. There are typically four parathyroid glands (a superior pair and an inferior pair), but there may be more or fewer. The superior parathyroids are the most constant in size and position. Parathyroid glands may be supplied by either set of thyroid arteries (as determined by location), but typically the inferior thyroid aa. supply the parathyroids.

Note: The inferior thyroid a. is a branch of the thyrocervical trunk (a branch of the first part of the subclavian a.). The inferior thyroid aa. typically cross the recurrent laryngeal nn. deep to the thyroid gland in the vicinity of the larynx.

Photo 21. Parathyroid glands & inferior thyroid a.

Reflect the manubrium and clavicles anteroinferiorly to identify brachiocephalic vv. and superior vena cava

Find (or conceptualize) these structures:

• Superior vena cava

  • Brachiocephalic v.

18.) Detach the infrahyoid (strap) mm. from the posterior portion of the manubrium. If the thymus gland extends into this area, use blunt dissection to reflect this superiorly.

19.) Palpate the entire length of the clavicles. Remove any soft tissue on the anterior portions of the clavicles. Depress any contents deep to the clavicles to protect from damage. Make sure all soft tissue is removed from the clavicles before cutting. This will allow for a cleaner and more exact cut.

20.) Cut through each clavicle with a small saw, just medial to the clavicular attachment of the trapezius muscle. Depending on your specimen, this may already be complete.

Photo 22. Clavicular cut

21.) Free any clavicular attachments (subclavius mm. and costoclavicular ligaments) to the 1st ribs. This can be completed by blunt dissection and scissor cuts, if necessary. Important neurovasculature is found just deep to the clavicle.

Photo 23. Subclavius m. and costoclavicular ligament

Photo 24. Protection of neurovasculature and muscle attachments

22.) Disarticulate the manubrium and the 1st ribs. This will involve chiseling or cutting (using a chisel or bone shears) through the synchondroses (cartilaginous joints) of the 1st ribs.

Photo 25. Disarticulation of the sychondroses of the 1st rib

23.) Lift the clavicles and manubrium anteriorly, and locate the internal thoracic aa. and vv. as they pass deep to the 1st ribs. Cut this vasculature at this level.

24.) Using scissors, cut the intercostal mm. in the intercostal space inferior to the 1st ribs, along the midaxillary line. Cut any remaining ribs along the midaxillary line. Anteriorly, pull to remove the cut portions of the anterior thorax to uncover deep structures.

When pulling, this needs to be done forcibly to break ribs or tissues not completely cut in previous step. Care should be taken to not allow the sharp ends of cut bone to contact your skin.

Photo 26. Procedural: soft tissue and bone cuts

25.) Locate and clean the brachiocephalic vv. and follow to the formation of the superior vena cava. Locate the inferior thyroid vv. draining into either the R or L brachiocephalic vv.

Photo 27. Venous angles, brachiocephalic v., & superior vena cava