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The anterior triangle is one of the two large triangles of the neck (the other being posterior).
It is situated in front of the sternocleidomastoid (SCM).
Important because it contains major vessels, nerves, glands, and viscera of the neck.
Hyoid bone: palpable at the level of C3 vertebra.
Thyroid cartilage: Adam’s apple; lies opposite C4–C5 vertebrae.
Cricoid cartilage: corresponds to C6 level.
Jugular notch: between sternal ends of clavicles and upper sternum.
Sternocleidomastoid muscle: divides neck into anterior and posterior triangles.
Lies between the two anterior borders of SCM.
Extends from chin (mentum) to sternal notch.
Contains:
Subcutaneous tissue and platysma
Investing layer of deep cervical fascia
Infrahyoid (strap) muscles:
Sternohyoid
Sternothyroid
Thyrohyoid
Omohyoid (superior belly)
Viscera of the neck:
Thyroid gland
Parathyroid glands
Trachea
Oesophagus
Larynx and pharynx
Vessels and nerves: Ansa cervicalis, superior and inferior thyroid arteries.
Make a midline incision from the chin to the sternum.
Reflect skin laterally to expose platysma.
Identify:
Anterior jugular veins in the superficial fascia.
Deep cervical fascia layers: investing, pretracheal, and carotid sheath.
Separate and identify infrahyoid muscles and thyroid gland.
Note the relations of trachea and larynx, and location of carotid sheath.
Goitre: Enlargement of thyroid gland — may compress trachea, oesophagus, or recurrent laryngeal nerves.
Tracheostomy: Performed in the lower part of anterior triangle, below isthmus of thyroid gland.
Cricoid cartilage (C6): Surgical landmark for tracheostomy and start of oesophagus.
Laryngeal prominence: More prominent in males due to acute angle between laminae of thyroid cartilage.
Cricothyrotomy: Emergency airway through cricothyroid membrane between thyroid and cricoid cartilages.
Injury to anterior jugular vein: May cause bleeding or air embolism.
Medially: Anterior median line of the neck
Laterally: Anterior border of sternocleidomastoid (SCM)
Superiorly (base): Lower border of mandible and a line joining its angle to mastoid process
Apex: Suprasternal notch
Roof: Skin, superficial fascia (with platysma, cutaneous nerves, veins), and investing layer of deep cervical fascia
Floor: Pretracheal fascia covering pharynx, larynx, and thyroid gland
Divided by digastric muscle and superior belly of omohyoid into:
Submental triangle
Digastric (submandibular) triangle
Carotid triangle
Muscular triangle
Type: Median triangle
Boundaries:
On each side: Anterior belly of digastric
Base: Body of hyoid bone
Apex: Chin
Floor: Right and left mylohyoid muscles with median raphe
Contents:
2–4 submental lymph nodes (drain chin, central lower lip, gums, anterior floor of mouth, tip of tongue)
Submental veins → form anterior jugular vein
Clinical relevance:
Enlarged submental lymph nodes → infection of lower lip or tip of tongue.
Sublingual dermoid cysts may cause swelling both below chin and inside mouth.
Boundaries:
Anteroinferior: Anterior belly of digastric
Posteroinferior: Posterior belly of digastric + stylohyoid
Superior (base): Mandible and a line joining angle of mandible to mastoid process
Roof:
Skin, superficial fascia (platysma, cervical branch of facial nerve), and deep fascia (splitting around submandibular gland)
Floor:
Mylohyoid (anteriorly), hyoglossus (posteriorly), and part of middle constrictor of pharynx
Contents (superficial to deep):
Submandibular gland (superficial part)
Facial vein and submandibular lymph nodes (superficial)
Facial artery (deep to gland)
Submental artery
Mylohyoid nerve and vessels
Hypoglossal nerve (XII)
Clinical importance:
Common site for submandibular sialadenitis.
Facial artery can be palpated at the lower border of mandible (anteroinferior angle).
Remove deep fascia from anterior bellies of digastric to expose both mylohyoids.
Identify submental lymph nodes between them.
Reflect deep fascia from mandible downward → expose submandibular gland.
Identify anterior and posterior bellies of digastric and stylohyoid.
Locate intermediate tendon of digastric, facial artery and vein, and hypoglossal nerve.
Boundaries:
Anterosuperiorly: Posterior belly of digastric and stylohyoid
Anteroinferiorly: Superior belly of omohyoid
Posteriorly: Anterior border of sternocleidomastoid
Floor:
Middle and inferior constrictors of pharynx, thyrohyoid membrane
Roof:
Skin, platysma, and investing layer of deep fascia
Contents:
Arteries: Common carotid (bifurcation), internal and external carotid with branches
Veins: Internal jugular vein and tributaries
Nerves:
Hypoglossal (XII)
Vagus (X)
Accessory (XI)
Glossopharyngeal (IX)
Superior root of ansa cervicalis
Other structures: Deep cervical lymph nodes, carotid sinus, and carotid body
Clean region between posterior belly of digastric and superior belly of omohyoid.
Expose common, internal, and external carotid arteries with internal jugular vein.
Identify cranial nerves IX–XII and ansa cervicalis.
Note floor muscles: middle and inferior constrictors and thyrohyoid membrane.
Anteromedial: Midline of neck from hyoid to sternum.
Superolateral: Superior belly of omohyoid.
Inferolateral: Anterior border of sternocleidomastoid.
Roof: Skin, superficial fascia (with platysma and anterior jugular vein), and investing layer of deep cervical fascia.
Floor: Pretracheal fascia covering strap muscles (sternohyoid and sternothyroid) and underlying viscera of neck (thyroid gland, larynx, trachea, and oesophagus).
Infrahyoid strap muscles: Sternohyoid and sternothyroid (mainly), occasionally superior belly of omohyoid along upper part.
Viscera of neck: Thyroid and parathyroid glands, larynx, trachea, and oesophagus (upper portion).
Vessels: Superior thyroid artery and vein, anterior jugular vein.
Nerves: Ansa cervicalis branches to strap muscles, and nerve to thyrohyoid (from C1 via hypoglossal).
Incise the deep fascia between the midline and sternocleidomastoid.
Reflect platysma and identify superior belly of omohyoid.
Clean and trace sternohyoid and sternothyroid muscles to their attachments.
Reflect sternohyoid to expose sternothyroid and thyroid gland deep to it.
Identify anterior jugular vein and superior thyroid vessels.
Definition: A nerve loop lying superficially on carotid sheath, supplying infrahyoid strap muscles.
Roots:
Superior root: Fibres from C1 through hypoglossal nerve.
Inferior root: Fibres from C2 and C3 of cervical plexus.
Formation: Superior and inferior roots join to form a loop (anterior to internal jugular vein and carotid artery).
Branches to: Sternohyoid, sternothyroid, and both bellies of omohyoid.
Clinical note: Injury to ansa → weakness of infrahyoid muscles and impaired swallowing movements.
Origin:
Right: From brachiocephalic trunk behind sternoclavicular joint.
Left: From arch of aorta in thorax.
Course: Ascends within carotid sheath with internal jugular vein (lateral) and vagus nerve (posterior).
Level of bifurcation: Upper border of thyroid cartilage (C3–C4) → internal and external carotid arteries.
Relations (Anterior): Skin, platysma, fasciae, and sternocleidomastoid.
Posterior relations: Prevertebral muscles, sympathetic trunk.
Medial relations: Viscera of neck (pharynx, larynx, trachea, oesophagus).
Lateral relations: Internal jugular vein.
Carotid Sheath contents: Common carotid artery, internal jugular vein, vagus nerve.
Surface marking: A line from sternoclavicular joint to mid-point of thyroid cartilage upper border.
Clinical importance:
Site for carotid pulse palpation.
Carotid endarterectomy to remove atheromatous plaque.
Carotid sinus reflex may cause bradycardia or syncope on pressure.
Goitre: Diffuse or nodular enlargement of thyroid produces neck swelling within muscular triangle.
Thyroidectomy: Caution to preserve recurrent laryngeal nerve and parathyroids.
Carotid sinus hypersensitivity: Leads to fainting or cardiac inhibition.
Ansa cervicalis block: Used in surgical procedures to relax infrahyoid muscles.
One of the two terminal branches of the common carotid artery.
Lies anterior to the internal carotid artery in the neck.
Principal artery supplying structures of the face, scalp, and neck.
Begins in the carotid triangle at the level of the upper border of the thyroid cartilage (C3–C4).
Runs upward and slightly backward and laterally.
Ends behind the neck of the mandible within the parotid gland, dividing into:
Superficial temporal artery
Maxillary artery
In the carotid triangle:
Superficial relations: Sternocleidomastoid, platysma, hypoglossal nerve, facial veins.
Deep relations: Pharyngeal wall and superior laryngeal nerve.
In the parotid gland: Lies deep to facial nerve and retromandibular vein.
Crossed superficially by hypoglossal nerve, facial vein, and lingual vein.
There are eight branches, grouped as anterior, posterior, medial, and terminal.
Superior thyroid artery:
Supplies thyroid gland, infrahyoid muscles, and larynx.
Lingual artery:
Supplies tongue, floor of mouth, and sublingual gland.
Facial artery:
Supplies face and submandibular region; tortuous to allow free movement.
Occipital artery:
Runs backward to supply posterior scalp.
Posterior auricular artery:
Small; supplies scalp behind ear and auricle.
Ascending pharyngeal artery:
Smallest branch; supplies pharyngeal wall and prevertebral muscles.
Maxillary artery:
Larger terminal branch; passes into infratemporal fossa to supply deep facial structures.
Superficial temporal artery:
Smaller terminal branch; supplies scalp and temple; palpable above zygoma.
“Some Anatomists Like Freaking Out Poor Medical Students”
S – Superior thyroid
A – Ascending pharyngeal
L – Lingual
F – Facial
O – Occipital
P – Posterior auricular
M – Maxillary
S – Superficial temporal
bd-chaurasias-human-anatomy-vol…
Lies below the inferior border of mandible.
Corresponds to submental triangle.
Communicates with submandibular spaces on both sides.
Clinical Note:
Infections here cause midline swelling below chin (e.g., cellulitis of lower incisors).
Between anterior and posterior bellies of digastric and the inferior border of mandible.
Communicates with sublingual and submental spaces.
Clinical Note:
Infection → Ludwig’s angina (bilateral submandibular cellulitis).
Around parotid gland, behind the ramus of mandible.
Communicates with retropharyngeal space and may extend to mediastinum.
Clinical Note:
Parotid abscess can track down into parapharyngeal or retropharyngeal spaces.
In suprahyoid region, lateral to pharynx.
Continuous with retropharyngeal space.
Clinical Note:
Infection may spread from tonsillar or dental origin.
Between buccopharyngeal fascia (anteriorly) and prevertebral fascia (posteriorly).
Communicates with peritonsillar, submental, and mediastinal spaces.
Clinical Note:
Infection can spread into the posterior mediastinum → life-threatening mediastinitis.
Between capsule of palatine tonsil and superior constrictor muscle.
Communicates with sublingual space.
Clinical Note:
Site of peritonsillar abscess (quinsy) following tonsillitis.
Mnemonic: “Some Anatomists Like Freaking Out Poor Medical Students”
S → Superior thyroid artery
A → Ascending pharyngeal artery
L → Lingual artery
F → Facial artery
O → Occipital artery
P → Posterior auricular artery
M → Maxillary artery
S → Superficial temporal artery
Tip for memory:
The first six branches arise in the neck (within or near carotid triangle), and the last two are terminal within the parotid gland.
Apex of triangles:
Apex of the anterior triangle lies near the sternum.
Apex of the posterior triangle lies near the mastoid process.
Submental triangle:
Lies half on each side of the midline.
Contains submental lymph nodes draining the tip of the tongue and lower lip.
Vascular richness:
Carotid triangle contains the maximum number of major vessels in the neck.
Superficial temporal artery:
Pulsation can be felt in front of the ear, just above the zygomatic arch (preauricular point).
Carotid sinus reflex:
Compression of the carotid sinus can slow the heart rate (vagal effect).
Hypersensitivity leads to carotid sinus syndrome (syncope on head turning).
Safety of tight clothing:
Tight neckties or collars may compress the carotid arteries, reducing blood flow to the brain.
Clinical palpation:
The common carotid artery pulse is felt at the anterior border of the SCM.
The facial artery pulse is felt at the lower border of mandible, anterior to the masseter.
Fascial layers:
Deep cervical fascia prevents spread of infection, but defines potential spaces that allow deep infections to descend into mediastinum.
Ansa cervicalis:
Located superficial to the carotid sheath; supplies strap muscles (except thyrohyoid, which gets C1 via hypoglossal).
Level landmarks:
Hyoid bone → C3
Thyroid cartilage → C4–C5
Cricoid cartilage → C6 (level where larynx joins trachea and pharynx joins oesophagus).
Explanation:
Midline swelling that moves with swallowing and tongue protrusion = Thyroglossal cyst.
It develops from persistence of a part of the thyroglossal duct connecting the thyroid gland to the foramen cecum of the tongue.
Located usually below the hyoid bone, but can occur anywhere along the thyroglossal tract.
Movement:
Upward on swallowing → attached to larynx via pretracheal fascia.
Upward on tongue protrusion → connected to foramen cecum.
Treatment:
Sistrunk’s operation — excision of cyst along with central part of hyoid bone and tract up to foramen cecum.
Explanation:
The common carotid artery and its bifurcation lie within the carotid triangle.
A pulsatile swelling here may be a carotid artery aneurysm.
Differentiation:
Swelling expands with systole and does not move with deglutition (unlike thyroid).
Complications: May compress nearby cranial nerves (IX, X, XI, XII) → dysphagia, hoarseness, or tongue deviation.
Explanation:
Spinal accessory nerve (cranial XI) passes through the posterior part of the carotid triangle before entering the posterior triangle.
Injury → paralysis of trapezius → shoulder droop and difficulty raising arm above horizontal.
Explanation:
Pressure near the angle of mandible stimulates the carotid sinus (baroreceptor zone) at the bifurcation of the common carotid artery.
Afferents via glossopharyngeal nerve (IX) → medulla → vagal efferents → reflex bradycardia and hypotension.
Seen in carotid sinus hypersensitivity.
Explanation:
Swelling could be due to goitre (thyroid enlargement).
Recurrent laryngeal nerves, which run in the tracheoesophageal groove, may be compressed, leading to paralysis of intrinsic laryngeal muscles → hoarseness.
Dyspnoea may occur due to tracheal compression.
Explanation:
Infection may involve submandibular and submental spaces, which communicate freely around the mylohyoid muscle.
The result is Ludwig’s angina — a rapidly spreading cellulitis involving both submandibular spaces and floor of mouth.
May cause airway obstruction if untreated.
Explanation:
The anterior jugular veins run just deep to platysma in the midline of neck, interconnected by a jugular venous arch.
Injury to this arch leads to severe bleeding; careful dissection and ligation required.
Explanation:
The glossopharyngeal nerve (IX) supplies both the palatine tonsil and middle ear (via tympanic branch).
Postoperative irritation → referred otalgia (pain in ear).
Explanation:
Pressure on carotid sinus during surgery stimulates baroreceptors → reflex via glossopharyngeal (afferent) and vagus (efferent) → cardiac slowing or arrest.
Controlled by local infiltration anesthesia to carotid sinus before dissection.
Explanation:
Due to absence of fascial barriers between submental, submandibular, and parapharyngeal spaces.
Infection spreads across midline and downward to mediastinum, producing airway compromise.
Submental triangle
Digastric (Submandibular) triangle
Carotid triangle
Muscular triangle
Anteriorly: Median line of the neck
Posteriorly: Anterior border of sternocleidomastoid
Superiorly: Base of mandible and a line from the angle of mandible to mastoid process
Apex: Suprasternal notch
Roof: Skin, superficial fascia, and platysma
Floor: Pretracheal fascia and muscles (e.g., mylohyoid, hyoglossus, thyrohyoid)
Arteries: Common carotid artery and its bifurcation into internal and external carotid arteries
Veins: Internal jugular vein and its tributaries
Nerves: Vagus, hypoglossal, spinal accessory, and branches of cervical sympathetic chain
Lymph nodes: Deep cervical nodes
Sternohyoid, Sternothyroid, Thyrohyoid, Omohyoid (superior belly)
Supplied by ansa cervicalis (C1–C3), except thyrohyoid, which receives C1 fibers via hypoglossal nerve.
Medial: Common or internal carotid artery
Lateral: Internal jugular vein
Posterior: Vagus nerve
Ansa cervicalis lies on its anterior wall, embedded in fascia.
From the sternoclavicular joint to a point midway between mastoid process and angle of mandible.
At the level of the upper border of thyroid cartilage (C3–C4).
Carotid sinus: Baroreceptor regulating blood pressure.
Carotid body: Chemoreceptor sensitive to blood O₂, CO₂, and pH.
Both are supplied by glossopharyngeal (IX) and vagus (X) nerves.
Hyoid bone (C3) → Level of tongue base.
Thyroid cartilage (C4–C5) → Laryngeal prominence.
Cricoid cartilage (C6) → Junction of larynx and trachea.
Boundaries:
Anterior → Midline of neck
Posterior → Superior belly of omohyoid and anterior border of SCM
Superior → Hyoid bone
Contents:
Infrahyoid muscles
Thyroid and parathyroid glands
Trachea, oesophagus, and larynx
It allows movement of pharynx during swallowing, but also acts as a pathway for infection from throat or teeth to spread into the posterior mediastinum.
It is a rapidly spreading cellulitis involving submental, submandibular, and sublingual spaces.
May cause airway obstruction if untreated due to elevation of the tongue and edema of the floor of the mouth.
A. Anterior border of sternocleidomastoid
B. Midline of the neck
C. Superior border of the clavicle
D. Base of the mandible
Answer: C
Explanation: The superior border of the clavicle forms the base of the posterior triangle, not the anterior.
A. Carotid triangle
B. Submental triangle
C. Occipital triangle
D. Muscular triangle
Answer: C
Explanation: The occipital triangle lies in the posterior part of the neck.
A. Submandibular gland
B. Submental lymph nodes
C. Internal jugular vein
D. Hypoglossal nerve
Answer: B
Explanation: The submental lymph nodes lie between the anterior bellies of digastric and drain the tip of tongue and chin.
A. External carotid artery and its branches
B. Subclavian artery
C. Thoracic duct
D. Vertebral artery
Answer: A
Explanation: The carotid triangle contains the carotid bifurcation, internal jugular vein, and vagus nerve.
A. Infrahyoid muscles
B. Thyroid gland
C. Trachea
D. Submandibular gland
Answer: D
Explanation: The submandibular gland lies in the digastric (submandibular) triangle.
A. Sternohyoid
B. Sternothyroid
C. Thyrohyoid
D. Omohyoid
Answer: C
Explanation: Thyrohyoid is supplied by C1 fibers via the hypoglossal nerve, not by ansa cervicalis.
A. Chemoreceptor
B. Baroreceptor
C. Mechanoreceptor
D. Proprioceptor
Answer: B
Explanation: The carotid sinus monitors arterial blood pressure and sends signals via the glossopharyngeal nerve (IX).
A. Baroreceptor
B. Thermoreceptor
C. Chemoreceptor
D. Mechanoreceptor
Answer: C
Explanation: The carotid body detects changes in blood oxygen, CO₂, and pH levels.
A. Internal carotid artery
B. Internal jugular vein
C. Vagus nerve
D. All of the above
Answer: D
Explanation: The carotid sheath encloses all three — internal carotid artery (medial), internal jugular vein (lateral), and vagus nerve (posterior).
A. Midline of the neck
B. Angle of mandible
C. Lower border of mandible anterior to masseter
D. Mastoid process
Answer: C
Explanation: The facial artery crosses the lower border of mandible just anterior to the masseter, where its pulse can be felt.
A. Hyoid bone
B. Cricoid cartilage
C. Upper border of thyroid cartilage
D. C6 vertebra
Answer: C
Explanation: The common carotid artery divides into internal and external carotids at the upper border of thyroid cartilage (C3–C4).
A. Facial vein
B. Retromandibular vein
C. Pterygoid venous plexus
D. Both A and C
Answer: D
Explanation: Facial vein communicates with cavernous sinus via angular vein and pterygoid plexus, providing a dangerous route for infection.
A. Submandibular and submental
B. Carotid
C. Retropharyngeal
D. Parapharyngeal
Answer: A
Explanation: Ludwig’s angina is a rapidly spreading cellulitis involving submandibular and submental spaces, causing airway obstruction.
A. Mastoid process
B. Suprasternal notch
C. Hyoid bone
D. Clavicle
Answer: B
Explanation: The apex of the anterior triangle lies inferiorly at the suprasternal notch.
A. Pretracheal fascia
B. Prevertebral fascia
C. Investing layer of deep cervical fascia
D. Buccopharyngeal fascia
Answer: B
Explanation: The prevertebral fascia forms the posterior boundary of the carotid sheath.
Anterior: Median line of neck.
Posterior: Anterior border of sternocleidomastoid.
Superior: Base of mandible and a line joining angle of mandible to mastoid process.
Apex: Suprasternal notch.
Roof: Skin, superficial fascia (with platysma), and investing fascia.
Floor: Pretracheal fascia covering pharynx, larynx, and thyroid gland.
Submental triangle
Digastric (submandibular) triangle
Carotid triangle
Muscular triangle
Boundaries:
Lateral → Anterior bellies of digastric.
Base → Hyoid bone.
Apex → Chin.
Floor → Mylohyoid muscles.
Contents:
Submental lymph nodes.
Submental veins forming the anterior jugular vein.
Superior: Base of mandible.
Anteroinferior: Anterior belly of digastric.
Posteroinferior: Posterior belly of digastric and stylohyoid.
Submandibular gland.
Facial artery and vein.
Hypoglossal nerve (XII).
Submandibular lymph nodes.
Mylohyoid nerve and vessels.
Boundaries:
Anterosuperior → Posterior belly of digastric and stylohyoid.
Anteroinferior → Superior belly of omohyoid.
Posterior → Anterior border of SCM.
Contents:
Common carotid artery (and its bifurcation).
Internal jugular vein.
Vagus, accessory, hypoglossal nerves.
Ansa cervicalis.
Deep cervical lymph nodes.
Boundaries:
Anterior → Median line of neck.
Posterior → Superior belly of omohyoid and anterior border of SCM.
Superior → Hyoid bone.
Contents:
Infrahyoid muscles.
Thyroid gland and parathyroids.
Trachea and oesophagus.
Medial: Common/internal carotid artery.
Lateral: Internal jugular vein.
Posterior: Vagus nerve.
Anterior wall: Ansa cervicalis.
At the upper border of the thyroid cartilage — opposite C3–C4 vertebrae.
Mnemonic: Some Anatomists Like Freaking Out Poor Medical Students
→ Superior thyroid, Ascending pharyngeal, Lingual, Facial, Occipital, Posterior auricular, Maxillary, and Superficial temporal arteries.
Carotid sinus: Baroreceptor (blood pressure regulation).
Carotid body: Chemoreceptor (detects O₂, CO₂, and pH).
Supplied by ansa cervicalis (C1–C3) except thyrohyoid, which gets C1 via hypoglossal nerve.
Site for carotid pulse palpation.
Carotid endarterectomy for removing plaques.
Location of carotid sinus and carotid body for reflex studies.
It is a bilateral infection of submandibular and submental spaces.
Rapidly spreads, causing tongue elevation and airway obstruction.
Cricoid cartilage (C6 level).
Pretracheal fascia, part of deep cervical fascia.
Because it remains connected to the foramen cecum of the tongue through a fibrous tract derived from the thyroglossal duct.
Hypoglossal nerve (XII).
Appears deep to posterior belly of digastric.
Crosses both carotid arteries.
Passes deep to mylohyoid to supply the tongue muscles.
Thyroid gland and trachea lie within it.
Surgical procedures like tracheostomy and thyroidectomy are performed here.
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