Triangles of the Neck: Anatomy

Overview

• Boundaries of the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess:
  • Superior: mandible Mandible The largest and strongest bone of the face constituting the lower jaw. It supports the lower teeth. Jaw and Temporomandibular Joint: Anatomy 
  • Inferior: superior 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
  • Anterior: anatomical midline
  • Posterior: anterior margin of the trapezius
• Triangles of the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess:
  • Topographic areas bounded by the neck muscles Neck muscles 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: Anatomy
  • Contain glands, nerves, vessels, 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
• 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 Occipital Part of the back and base of the cranium that encloses the foramen magnum. Skull: Anatomy triangle
     • Supraclavicular triangle
• The muscles of the neck can be primarily divided into 3 groups:
  1. Anterior neck muscles Anterior neck muscles Muscles of the Neck: Anatomy
  2. Lateral neck muscles Lateral neck muscles Muscles of the Neck: Anatomy
  3. Posterior neck muscles Posterior neck muscles Muscles of the Neck: Anatomy

Anterior Triangle

Overview

• Boundaries
  • Superior: mandible Mandible The largest and strongest bone of the face constituting the lower jaw. It supports the lower teeth. Jaw and Temporomandibular Joint: Anatomy
  • 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. Bones: Structure and Types
• Lateral: superior belly of omohyoid and anterior border of sternocleidomastoid Sternocleidomastoid Muscles of the Neck: Anatomy
• 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 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 gland, parathyroid Parathyroid 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: Anatomy 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: 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

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 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: common carotid, external carotid (and branches except maxillary, superficial temporal, and posterior auricular), internal carotid
• 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: 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

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

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:

• Vein: anterior jugular
• Viscera: submental 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

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)

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 Sternocleidomastoid Muscles of the Neck: Anatomy 
• 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 muscle Subclavius muscle Chest Wall: Anatomy
• 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

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 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) (HF).
• 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.