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Triangles of the Neck: Anatomy

The neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess is considered to be quadrangular. This shape is the basis to study various components of the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess and their relations. The boundaries of the quadrangular shape include the mandible Mandible The largest and strongest bone of the face constituting the lower jaw. It supports the lower teeth. Jaw and Temporomandibular Joint: Anatomy, upper border of the clavicle Clavicle A bone on the ventral side of the shoulder girdle, which in humans is commonly called the collar bone. Clavicle Fracture, midline of the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess, and anterior margin of the trapezius. The quadrangular shape is divided into an anterior and posterior triangle by the sternocleidomastoid Sternocleidomastoid Muscles of the Neck: Anatomy 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: Histology.

Last updated: 31 Mar, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Overview

Lateral view of the neck

Lateral view of the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess:
featuring the anterior (blue) and posterior (green) triangles of the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess, separated by the sternocleidomastoid muscle

Image by Lecturio.

Anterior Triangle

Overview

  • Boundaries
  • 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. Bones: Structure and Types
  • Lateral: superior belly of omohyoid and anterior border of sternocleidomastoid
  • Medial: midline of the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess
  • Roof: integument, superficial fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis, platysma Platysma Muscles of the Neck: Anatomy, deep fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis

Contents:

  • Muscles: infrahyoid “strap” muscles (thyrohyoid, sternothyroid, and sternohyoid)
  • Vessels: superior and inferior thyroid Thyroid 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: Anatomy 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: Histology, 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: Histology
  • 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: Anatomy, parathyroid glands Parathyroid glands 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. Parathyroid Glands: Anatomy, 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: Anatomy, 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: Anatomy, 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: Anatomy
Muscular triangle of the neck

Muscular triangle of the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess

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 Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis, platysma Platysma Muscles of the Neck: Anatomy, deep fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis
  • 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 Thyroid 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: Anatomy, middle thyroid Thyroid 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: Anatomy 
  • 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: Anatomy 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: Anatomy
Carotid triangle

Carotid triangle

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Submandibular triangle

Boundaries:

  • Superior: inferior border of mandible Mandible The largest and strongest bone of the face constituting the lower jaw. It supports the lower teeth. Jaw and Temporomandibular Joint: Anatomy
  • 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. Skin: Structure and Functions, fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis, platysma Platysma Muscles of the Neck: Anatomy

Contents:

  • Vessels: facial artery and vein, submental artery and vein, lingual artery Lingual artery Lips and Tongue: Anatomy and vein
  • Nerves: mylohyoid and hypoglossal
  • Viscera: submandibular gland Submandibular gland One of two salivary glands in the neck, located in the space bound by the two bellies of the digastric muscle and the angle of the mandible. It discharges through the submandibular duct. The secretory units are predominantly serous although a few mucous alveoli, some with serous demilunes, occur. Salivary Glands: Anatomy and lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy, caudal part of the parotid gland Parotid gland The largest of the three pairs of salivary glands. They lie on the sides of the face immediately below and in front of the ear. Salivary Glands: Anatomy
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. Bones: Structure and Types
  • Lateral: anterior belly of digastric muscle
  • Medial: midline of the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess
  • 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. Skin: Structure and Functions, fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis, platysma Platysma Muscles of the Neck: Anatomy

Contents:

Submental triangle

Submental triangle

Image by Lecturio.

Related videos

Posterior Triangle

Overview

  • Boundaries
    • Inferior: superior border of clavicle Clavicle A bone on the ventral side of the shoulder girdle, which in humans is commonly called the collar bone. Clavicle Fracture
    • Anterior: SCM
    • Posterior: anterior margin of trapezius muscle
  • Subdivisions:
    • Occipital Occipital Part of the back and base of the cranium that encloses the foramen magnum. Skull: Anatomy triangle
    • Supraclavicular triangle

Occipital Occipital Part of the back and base of the cranium that encloses the foramen magnum. Skull: Anatomy 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. Skin: Structure and Functions, superficial and deep fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis

Contents:

  • Vessels: transverse cervical vessels
  • Nerves: accessory nerve, supraclavicular nerve, branches of the cervical plexus Cervical Plexus A network of nerve fibers originating in the upper four cervical spinal cord segments. The cervical plexus distributes cutaneous nerves to parts of the neck, shoulders, and back of the head. It also distributes motor fibers to muscles of the cervical spinal column, infrahyoid muscles, and the diaphragm. Peripheral Nerve Injuries in the Cervicothoracic Region, uppermost part of brachial plexus Brachial Plexus The large network of nerve fibers which distributes the innervation of the upper extremity. The brachial plexus extends from the neck into the axilla. In humans, the nerves of the plexus usually originate from the lower cervical and the first thoracic spinal cord segments (c5-c8 and T1), but variations are not uncommon. Peripheral Nerve Injuries in the Cervicothoracic Region
  • Viscera: lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy (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: Anatomy 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: Anatomy/ clavicle Clavicle A bone on the ventral side of the shoulder girdle, which in humans is commonly called the collar bone. Clavicle Fracture 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. Skin: Structure and Functions, fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis, platysma Platysma Muscles of the Neck: Anatomy

Contents:

  • Vessels: 3rd portion of subclavian artery, external jugular vein, subclavian vein, transverse cervical vessels
  • Nerves: brachial plexus Brachial Plexus The large network of nerve fibers which distributes the innervation of the upper extremity. The brachial plexus extends from the neck into the axilla. In humans, the nerves of the plexus usually originate from the lower cervical and the first thoracic spinal cord segments (c5-c8 and T1), but variations are not uncommon. Peripheral Nerve Injuries in the Cervicothoracic Region trunks, nerve to subclavius Subclavius Muscles of the Neck: Anatomy muscle
  • Muscles: subclavian muscle
  • Viscera: lymph nodes Lymph Nodes They are oval or bean shaped bodies (1 – 30 mm in diameter) located along the lymphatic system. Lymphatic Drainage System: Anatomy
Schematic of the supraclavicular triangle

Schematic of the supraclavicular triangle

Image by Lecturio.

Clinical Relevance

  • Jugular venous distension Jugular Venous Distension Cardiovascular Examination ( JVD JVD Cardiovascular Examination): the clinical measurement of the pressure of blood in the venous system. Jugular venous distension Jugular Venous Distension Cardiovascular Examination 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 Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR) ( 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 Cricothyroidotomy Basic Procedures: an emergency procedure used to establish a patent airway Airway ABCDE Assessment when other procedures, such as intubation Intubation Peritonsillar Abscess, are contraindicated or insufficient. The procedure involves an incision of the cricothyroid Cricothyroid Larynx: Anatomy membrane, located directly inferior to the thyroid Thyroid 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: Anatomy 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: Histology 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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