Triangles of the Neck

The neck is considered to be quadrangular. This shape is the basis to study various components of the neck and their relations. The boundaries of the quadrangular shape include the mandible, upper border of the clavicle, midline of the neck, and anterior margin of the trapezius. The quadrangular shape is divided into an anterior and posterior triangle by the sternocleidomastoid muscle (SCM). The anterior and posterior triangles are the 2 primary subdivisions and are delineated by easily recognized anatomic structures. Each triangle houses muscles, nerves, vasculature, lymphatics, and adipose tissue Adipose tissue Adipose tissue is a specialized type of connective tissue that has both structural and highly complex metabolic functions, including energy storage, glucose homeostasis, and a multitude of endocrine capabilities. There are three types of adipose tissue, white adipose tissue, brown adipose tissue, and beige or "brite" adipose tissue, which is a transitional form. Adipose Tissue.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Table of Contents

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Overview

  • Boundaries of the neck:
    • Superior: mandible 
    • Inferior: superior border of the clavicle
    • Anterior: anatomical midline
    • Posterior: anterior margin of the trapezius
  • Triangles of the neck: 
    • Topographic areas bounded by the neck muscles
    • Contain glands, nerves, vessels, and lymph nodes
  • Sternocleidomastoid muscle (SCM) divides the neck into the 2 major neck triangles:
    1. Anterior triangle: subdivided into smaller triangles
      • Muscular triangle
      • Carotid triangle
      • Submandibular triangle
      • Submental triangle
    2. Posterior triangle: subdivided by the omohyoid muscle
      • Occipital triangle
      • Supraclavicular triangle
  • The muscles of the neck Muscles of the Neck The muscles of the neck can be divided into 3 groups: anterior, lateral, and posterior neck muscles. Each of the groups is subdivided according to function and the precise location of the muscles. Muscles of the Neck can be primarily divided into 3 groups:
    1. Anterior neck muscles
    2. Lateral neck muscles
    3. Posterior neck muscles
Lateral view of the neck

Lateral view of the neck:
featuring the anterior (blue) and posterior (green) triangles of the neck, separated by the sternocleidomastoid muscle

Image by Lecturio.

Anterior Triangle

Overview

  • Boundaries
    • Superior: mandible
    • Anterior: anatomical midline
    • Posterior: SCM
  • Subdivisions:
    • Muscular triangle
    • Carotid triangle
    • Submandibular triangle
    • Submental triangle

Muscular triangle

Boundaries:

  • Superior: hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones
  • Lateral: superior belly of omohyoid and anterior border of sternocleidomastoid
  • Medial: midline of the neck
  • Roof: integument, superficial fascia, platysma, deep fascia

Contents:

  • Muscles: infrahyoid “strap” muscles (thyrohyoid, sternothyroid, and sternohyoid)
  • Vessels: superior and inferior thyroid arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries, anterior jugular veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins
  • Viscera: thyroid gland Thyroid gland The thyroid gland is one of the largest endocrine glands in the human body. The thyroid gland is a highly vascular, brownish-red gland located in the visceral compartment of the anterior region of the neck. Thyroid Gland, parathyroid glands Parathyroid glands The parathyroid glands are 2 pairs of small endocrine glands found in close proximity to the thyroid gland. The superior parathyroid glands are lodged within the parenchyma of the upper poles of the right and left thyroid lobes; the inferior parathyroid glands are close to the inferior tips or poles of the lobes. Parathyroid Glands, larynx Larynx The larynx, also commonly called the voice box, is a cylindrical space located in the neck at the level of the C3-C6 vertebrae. The major structures forming the framework of the larynx are the thyroid cartilage, cricoid cartilage, and epiglottis. The larynx serves to produce sound (phonation), conducts air to the trachea, and prevents large molecules from reaching the lungs. Larynx, trachea Trachea The trachea is a tubular structure that forms part of the lower respiratory tract. The trachea is continuous superiorly with the larynx and inferiorly becomes the bronchial tree within the lungs. The trachea consists of a support frame of semicircular, or C-shaped, rings made out of hyaline cartilage and reinforced by collagenous connective tissue. Trachea, esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus
Muscular triangle of the neck

Muscular triangle of the neck

Image by Lecturio.

Carotid triangle

Boundaries:

  • Anterior: superior belly of the omohyoid muscle
  • Superior: stylohyoid and posterior belly of the digastric muscles
  • Posterior: anterior border of the SCM
  • Roof: integument, superficial fascia, platysma, deep fascia
  • Floor: thyrohyoid membrane, hyoglossus, middle and inferior pharyngeal constrictor muscles

Contents:

  • Arteries: common carotid, external carotid (and branches except maxillary, superficial temporal, and posterior auricular), internal carotid
  • Veins: internal jugular, common facial, lingual, superior thyroid, middle thyroid 
  • Nerves: vagus and hypoglossal, part of the sympathetic trunk
  • Viscera: upper portion of the larynx Larynx The larynx, also commonly called the voice box, is a cylindrical space located in the neck at the level of the C3-C6 vertebrae. The major structures forming the framework of the larynx are the thyroid cartilage, cricoid cartilage, and epiglottis. The larynx serves to produce sound (phonation), conducts air to the trachea, and prevents large molecules from reaching the lungs. Larynx and lower portion of the pharynx Pharynx The pharynx is a component of the digestive system that lies posterior to the nasal cavity, oral cavity, and larynx. The pharynx can be divided into the oropharynx, nasopharynx, and laryngopharynx. Pharyngeal muscles play an integral role in vital processes such as breathing, swallowing, and speaking. Pharynx
Carotid triangle

Carotid triangle

Image by Lecturio.

Submandibular triangle

Boundaries:

  • Superior: inferior border of mandible
  • Lateral: posterior belly of digastric muscle
  • Medial: anterior belly of digastric muscle
  • Floor: mylohyoid and hyoglossus 
  • Roof: skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin, fascia, platysma

Contents:

  • Vessels: facial artery and vein, submental artery and vein, lingual artery and vein
  • Nerves: mylohyoid and hypoglossal
  • Viscera: submandibular gland and lymph nodes, caudal part of the parotid gland
Submandibular triangle

Submandibular triangle

Image by Lecturio.

Submental triangle

Boundaries:

  • Inferior: hyoid bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones
  • Lateral: anterior belly of digastric muscle
  • Medial: midline of the neck
  • Floor: mylohyoid muscles
  • Roof: skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin, fascia, platysma

Contents:

  • Vein: anterior jugular
  • Viscera: submental lymph nodes
Submental triangle

Submental triangle

Image by Lecturio.

Related videos

Posterior Triangle

Overview

  • Boundaries
    • Inferior: superior border of clavicle
    • Anterior: SCM
    • Posterior: anterior margin of trapezius muscle
  • Subdivisions:
    • Occipital triangle
    • Supraclavicular triangle

Occipital triangle

Boundaries:

  • Anterior: posterior margin of SCM
  • Posterior: anterior margin of trapezius
  • Inferior: inferior belly of omohyoid 
  • Floor: semispinalis capitis, splenius capitis, levator scapulae, medial and posterior scalene muscles
  • Roof: skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin, superficial and deep fascia

Contents:

  • Vessels: transverse cervical vessels
  • Nerves: accessory nerve, supraclavicular nerve, branches of the cervical plexus, uppermost part of brachial plexus
  • Viscera: lymph nodes (along the posterior border of the SCM)
Schematic of the occipital triangle

Schematic of the occipital triangle

Image by Lecturio.

Supraclavicular triangle

The supraclavicular triangle is also called the omoclavicular or subclavian triangle, and it is smaller with the arm Arm The arm, or "upper arm" in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm raised and bigger with the arm Arm The arm, or "upper arm" in common usage, is the region of the upper limb that extends from the shoulder to the elbow joint and connects inferiorly to the forearm through the cubital fossa. It is divided into 2 fascial compartments (anterior and posterior). Arm/clavicle depressed.

Boundaries:

  • Superior: inferior belly of omohyoid 
  • Anterior: posterior edge of sternocleidomastoid 
  • Posterior: anterior edge of trapezius
  • Floor: medial scalene, 1st digitation of serratus anterior, 1st rib 
  • Roof: skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin, fascia, platysma

Contents:

  • Vessels: 3rd portion of subclavian artery, external jugular vein, subclavian vein, transverse cervical vessels
  • Nerves: brachial plexus trunks, nerve to subclavius muscle
  • Muscles: subclavian muscle
  • Viscera: lymph nodes
Schematic of the supraclavicular triangle

Schematic of the supraclavicular triangle

Image by Lecturio.

Clinical Relevance

  • Jugular venous distension (JVD): the clinical measurement of the pressure of blood in the venous system. Jugular venous distension can be useful in the differentiation of different forms of heart and lung disease. The condition is measured by assessing the degree of distension of the external jugular vein as it crosses the SCM. Jugular venous distention is classically elevated in the setting of congestive heart failure Congestive heart failure Congestive heart failure refers to the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Echocardiography can confirm the diagnosis and give information about the ejection fraction. Congestive Heart Failure ( CHF CHF Congestive heart failure refers to the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Echocardiography can confirm the diagnosis and give information about the ejection fraction. Congestive Heart Failure).
  • Cricothyroidotomy: an emergency procedure used to establish a patent airway when other procedures, such as intubation, are contraindicated or insufficient. The procedure involves an incision of the cricothyroid membrane, located directly inferior to the thyroid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage and superior to the upper border of the cricoid. The incision is made within the muscular triangle.

References

  1. Drake, RL, et al. (Eds.) (2020). Neck. In Drake, RL, et al. (Eds.), Gray’s Anatomy for Students. (4th Ed, pp. 995–1006). Churchill Livingstone/Elsevier.
  2. Moore, KL, et al. (Eds.) (2014). In Moore, KL, et al. (Eds.), Clinically Oriented Anatomy. (7th Ed., pp. 989–1007). Lippincott Williams & Wilkins, a Wolters Kluwer business.
  3. Shah, A. (2021). Anatomy, head, and neck, anterior cervical region. StatPearls. https://www.statpearls.com/ArticleLibrary/viewarticle/32264#
  4. Casale, J, & Varacallo, M. (2021). Anatomy, head, and heck, submandibular triangle. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK534833/

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