The document describes the anatomy of the anterior and posterior triangles of the neck. It details the bones, muscles, blood vessels, nerves and other structures found in each triangle. Key structures mentioned include the cervical vertebrae, carotid artery, thyroid gland, larynx, and various nerves such as the hypoglossal and recurrent laryngeal nerves. The triangles described are the submandibular, submental and carotid triangles located in the anterior neck region.

1. The Anterior and Posterior Triangles of the Neck

3. Anterior Triangle of the Neck

4. BONY SKELETON OF THE NECK Like other regions of the body, the neck has a central bony skeletal core upon which other structures attach or are related. The bones of the neck consist of the base of the skull and the 7 cervical vertebrae. If we take a look at the base of the skull, the major parts that are related to the upper neck are the: Foramen magnum Occipital condyle (articulates with the superior process of the atlas. External occipital protuberance Mastoid process

5. Below the base of the skull, you will find the vertebral column. The top vertebrae (7 cervical) provide support for the neck structures. You will also note that these vertebrae allow passage of an important arterial supply to the brain and brain stem, the vertebral artery.

6. The first cervical vertebra is the atlas and is considered an atypical cervical vertebra because it has no body or spinous process. It articulates with the occipital condyles of the skull above it and with the superior articular processes of the axis below it. It also articulates with the dens of the axis below. If viewed from above, you can identify the following parts of the atlas: Anterior arch Anterior tubercle Superior articular process (articulate with the occipital condyle of the skull) Foramen transversarium Transverse process Posterior arch Posterior tubercle Vertebral canal (continuous with the foramen magnum at the base of the skull). The brain stem continues inferiorly as the spinal cord at the margin of the foramen magnum.

7. The axis is the second cervical vertebra. This vertebral is also called an atypical vertebra because it has an upward projection called the dens that articulates with the inner aspect of the anterior arch of the atlas just posterior to the anterior tubercle. Some of the identifiable parts are the: dens body superior articular process transverse process with its vertebral foramen pedicle lamina bifid spine

8. The 3rd, 4th, 5th, and 6th cervical vertebrae are known as the typical cervical vertebrae because they all have the same characteristics and except for the foramen for the vertebral artery similar to other typical vertebrae of the spinal cord. These characteristics are: body pedicle foramen for vertebral artery superior articular process lamina spinous process (bifid in case of cervical vertebrae) vertebral canal transverse process (consists of a groove that carries a cervical spinal nerve and, of course the foramen for the vertebral artery)

9. The 7th cervical vertebra starts to pick up characteristics of the upper thoracic vertebrae. Differences from other cervical vertebrae no foramen for the vertebral artery After the vertebral artery arises from the subclavian artery, it enters the transverse foramen of the 6th cervical vertebra bypassing the 7th may not have a bifid spinous process the spinous process of the 7 cervical vertebra is longer than the other cervical vertebrae it is not buried under the ligamentum nuchae of the neck so it is easy to see and to palpate and is called the vertebra prominens can serve as a surface landmark demarcating the neck (cervical) from the thoracic regions of the body.

10. Anterior Neck Common carotid artery (cc) Internal carotid artery (ic) External carotid artery (ec) Carotid sinus Major Landmarks

11. Superficial structures from the lateral view of the neck. sternomastoid trapezius occipital lymph nodes (on) retroauricular lymph nodes (ran) superficial cervical lymph nodes (scn) submental lymph nodes (smn) buccal lymph nodes (bn) parotid lymph nodes (pn) submandibular lymph nodes (not labeled but uner angle of mandible)

12. Abnormalities of the superficial neck Swollen lymph nodes – sign of an infection in an area that is drained by the nodes The superficial group of nodes in the neck drain the skin of the face and nose, scalp and external ear. The submental nodes also drain the tip of the tongue. Deeper regions of the head and neck drain into a deep group of lymph nodes and are less palpable. Other important landmarks the cartilages of the larynx and trachea the thyroid gland is closely associated with the cricoid cartilage the tracheal rings the carotid artery carotid artery pulse can be felt by pushing lateral to the upper border of the thyroid cartilage just under the anterior edge of the sternomastoid muscle.

13. Anterior Triangle of the Neck In Detail Anterior Triangle submental (smen) submandibular (sm) muscular-visceral (mus) carotid (car) Posterior Triangle occipital supraclavicular (omoclavicular) The neck is arbitrarily subdivided into two triangles by the sternocleidomastoid muscle: Starting above the hyoid bone in the anterior triangle, we have two small triangles: submental and submandibular (or digastric). We will start this study by looking at the submandibular triangle first then the submental.

14. Triangles within the Anterior Triangle of the Neck

15. The Submandibular Triangle Boundaries mastoid & mandible above anterior belly of digastric anteriorly (abd) posterior belly of digastric (pbd) stylohyoid posteriorly (sh)

16. The superficial (roof) structures of the submandibular region are: platysma facial vein (fv) cervical branch of facial nerve (cbf)

17. Removal of the superficial structures displays the submandibular salivary gland itself.

18. contents of the submandibular triangle are structures passing through: facial artery (fa) lingual nerve and submandibular ganglion (ln) submandibular duct (smd) lingual artery (la) hypoglossal nerve (XII) the lingual nerve and submandibular duct pass through a gap between the hypoglossal (hg) and mylohyoid (mh) muscles the lingual artery passes deep to the hyoglossus muscle.

19. The Submental Triangle located between the two anterior digastric muscles (abd). Structures submental lymph node(s) (ln) - drain the floor of the mouth. mylohyoid muscle (mh) arise from the body of the hyoid bone and insert into the mylohyoid line of the inside of the mandible. aids in swallowing and in depressing the mandible.

20. The Carotid Triangle The boundaries of the carotid triangle are: posterior belly of digastric muscle (pbd) superior belly of the omohyoid muscle (so) anterior border of sternomastoid muscle (st) Starting from the most superficial aspects of the carotid triangle, we will point out the items that are related to it.

21. Roof of the Carotid Triangle The first layer, under the skin and superficial fascia includes the platysma, which forms the roof of the carotid triangle. Note the location of the carotid triangle in purple.

22. Veins of the Carotid Triangle With the roof removed, here are the boundaries of the carotid triangle and the superficial veins related to it: common facial vein (cf) ( within carotid triangle) Other structures near by: retromandibular vein ( rm ) posterior auricular vein ( pav ) facial vein ( fv ) external jugular vein ( ej ) anterior jugular vein ( aj )

23. Nerves within the Carotid Triangle The nerves that enter the carotid triangle and that lie superficial to the internal jugular vein, internal and external carotid arteries are: hypoglossal (XII) C1 root of ansa cervicalis (C1) C1 fibers running with hypoglossal nerve (nerve to thyrohyoid muscle (nth) C2-C3 root of ansa cervicalis ansa cervicalis (ac)

24. Nerves within the Carotid Triangle

25. Reflection of sternomastoid and removal of common facial vein cca -common carotid artery eca -external carotid artery sta -supterior thyroid artery oa -occipital artery la -lingual artery fa -facial artery ica -internal carotid artery

26. Arteries in the Carotid Triangle

27. Floor of the carotid triangle The floor is the the deepest aspect of the carotid triangle. The muscles, at this level, are the middle and lower pharyngeal constrictors (mpc and ipc). The structures seen passing through this level are: superior laryngeal nerve, a branch of the vagus its 2 terminal branches internal laryngeal (ilb--sensory to upper part of the larynx) external laryngeal (elb--motor to the cricoid muscle)

28. Muscular or Visceral Triangle The muscular triangle has the following boundaries: mid line of neck (1) superior belly of omohyoid (2) sternomastoid (3) The muscles forming and within the triangle are seen in image labeled (these muscles are often called the strap muscles, for obvious reasons: superficial layer sternohyoid (sh) superior belly of omohyoid (oh) deep layer thyroid (th) sternothyroid (st)

29. Thyroid gland and its arterial supply When the strap muscles are reflected, you can see the thyroid gland (tg) with its arteries (superior thyroid artery from the external carotid (sta) and the inferior thyroid artery from the thyrohyoid trunk from the subclavian (ita).

30. If the thyroid gland is reflected laterally, the structures making up the larynx and trachea are seen: thyrohyoid membrane (thm) thyroid cartilage (Adam's apple)(tc) cricothyroid membrane and ligament (ctm) cricoid cartilage (cc) tracheal rings (tr) Cartilages and membranes

31. Anterior View of Thyroid Gland The thyroid gland is hidden under the sternohyoid and sternothyroid muscles and consists of two lobes and an isthmus. An occasional pyramidal lobe extends upward near the mid line. The inferior thyroid artery is closely associated with the recurrent laryngeal nerve (rln).

32. Deep Surface of Thyroid Gland Four small reddish-brown pea-sized glands may be seen on the deep surface of the thyroid gland. These are the superior and inferior parathyroid glands (ptg). Also note the close relationship of the recurrent laryngeal nerves to the thyroid gland and inferior thyroid artery (rln, ita).

33. Clinical Considerations The cricothyroid ligament and membrane are frequently pierced in emergency situations to open the airway. It has been known that an empty ball-point pen or a hollow stem has been used in the field to save lives, where an air passage has been closed above this region.

34. Structures Found At the Root of the Neck After the sternoclavicular joint is disarticulated the structures located at the root of the neck can be identified. The root of the neck is bounded by the manubrium of the sternum anteriorly, the first rib laterally and the first thoracic vertebra posteriorly. All structures passing from the head through the neck to lower regions pass through this area as well as structures arising in the thoracic cavity and passing out through this region.

35. Most anterior structures: brachiocephalic vein vertebral vein internal jugular vein subclavian vein thoracic duct thymus gland

36. The next layer can be considered the artery-nerve layer: lung vagus nerve common carotid artery subclavian artery ansa subclavius thyrocervical trunk vertebral artery internal thoracic artery trachea esophagus

37. The upper lobe of the lung (1) extends into the neck region. This is clinically important for anyone entering this region surgically since the lung can be punctured if the surgeon isn't careful.

38. The posterior part of the root of the neck is made up of the anterior surface of the body of the 1st thoracic vertebra with its anterior longitudinal ligament (in gray). When observing this area, you can see the nerves: ventral ramus of C8 ventral ramus of T1 lower trunk of brachial plexus stellate ganglion (inferior cervical + 1st thoracic ganglia)

39. Table of Muscles Muscle Origin Insertion Action Nerve Supply Sternohyoid sternum hyoid ansa Omohyoid Suprascapular notch hyoid ansa Sternothyroid Below sternohyoid on manubrium Thyroid cartilage oblique line ansa Thyrohyoid Thyroid cartilage oblique line hyoid C1-C2 (ansa) Anterior Belly Digastric -----intermediate tendon------ Inner surface of mandile Trigeminal nerve Posterior Belly Digastric Medial aspect of the mastoid process -intermediate tendon- Facial nerve Mylohyoid Mylohyoid line of mandible Hyoid bone Trigeminal nerve Hyoglossus Hyoid bone Lateral side of tongue hypoglossal Stylohyoid Styloid process hyoid Facial nerve