Anterior Triangle Anatomy (PDF)

Triangles of the neck II Lecture ID # 9032 By Dr. Sampath Madhyastha Monday, 16th December 2024; 1 to 1.50 pm Objectives 1. Describe t...

Triangles of the neck II Lecture ID # 9032 By Dr. Sampath Madhyastha Monday, 16th December 2024; 1 to 1.50 pm Objectives 1. Describe the boundaries of the anterior triangle (anterior cervical region) and its subdivisions 2. List the contents of anterior triangle specific to its subdivisions 3. Describe the arteries, their branches and anastomosis located at the anterior triangle 4. Describe the internal jugular veins and their tributaries 5. Describe the nerves and lymphatic systems of the anterior triangle 6. Describe the clinical importance of anterior triangle and its contents Anterior triangle Boundaries Posteriorly: Anterior border of the sternocleidomastoid muscle Anteriorly: Anterior midline of the neck extending from symphysis menti to the suprasternal notch. Base: Lower border of the body (base) of the mandible and a line joining angle of the mandible to mastoid process. Apex: It is directed downwards towards the suprasternal notch. Subdivision of the Anterior triangle The superior belly of the omohyoid and posterior belly of the digastric muscles divide the anterior triangles into 1. Digastric (Submandibular) 2. Carotid 3. Muscular 4. Submental triangles. The submental triangle is a midline triangle shares both right and left anterior triangles. Posterior belly of digastric Anterior belly of Sternomastoid digastric Omohyoid superior belly Carotid triangle In front and above (Anterosuperior): Posterior belly of the digastric and stylohyoid muscles In front and below (Anteroinferior): Superior belly of the omohyoid Behind (Posterior): Anterior border of the sternomastoid muscle Roof: Skin, superficial fascia with platysma, investing layer of deep cervical fascia Floor: Four muscles – Hyoglossus, Thyrohyoid, Middle and Inferior constrictor muscles of pharynx Contents of the Carotid triangle 1. Common carotid artery and its bifurcation 2. External carotid artery and its branches 3. Carotid sheath with its contents 4. Ansa cervicalis – a nerve loop in front of the carotid sheath 5. Spinal accessory nerve 6. Hypoglossal nerve 7. Deep cervical lymph nodes  1. Common carotid artery bifurcates at the level of upper border of the lamina of the thyroid cartilage (dis between C3 & C4 vertebra) Carotid tubercle is the anterior tubercle of the transverse process of the C6 vertebra, separating the carotid artery from the vertebral artery and against which the carotid artery may be compressed by the finger. Carotid pulse: is felt deep to the anterior border of the sternocleidomastoid muscle at the level of upper border of thyroid cartilage. Carotid sinus: baro-receptor & carotid sinus syndrome Carotid body: chemo-receptor Carotid Artery Palpation: The carotid tubercle serves as a reference point for locating the common carotid artery. When palpating the carotid pulse, the carotid tubercle helps orient the clinician to the correct spot for the artery, which lies just beneath the tubercle and is accessible for checking circulation in the neck. Compression of the Carotid Artery: The carotid tubercle is important in carotid artery compression. It can be gently pressed to reduce blood flow in the carotid artery in cases of severe bleeding, as this point provides leverage to compress the artery against the vertebra. This is sometimes used in emergency situations to control hemorrhage from the head or neck. Surgical Significance: Surgeons may use the carotid tubercle as a landmark during neck surgeries to avoid injury to the carotid artery or to guide the dissection of surrounding structures. Vertebral Artery Considerations: The carotid tubercle also marks the location near the vertebral artery entrance into the transverse foramen of the cervical vertebrae. It can be a helpful landmark in understanding the positioning of vascular structures in the neck during procedures. 2. External carotid artery & its branches Occipital artery 1. Ascending pharyngeal artery Superficial temporal artery 2. Superior thyroid artery 3. Lingual artery Maxillary artery 4. Facial artery Facial artery 5. Occipital artery 6. Posterior auricular artery 7. Maxillary artery Lingual artery 8. Superficial temporal artery Superior thyroid artery Facial artery gives following branches in Posterior auricular artery the neck 1. Ascending palatine Ascending 2. Tonsillar arteries pharyngeal artery 3. Glandular branches 4. Submental artery Lingual artery gives deep lingual, dorsal lingual, sub lingual & suprahyoid branches 3. Carotid sheath & its content 3a. Common carotid artery and internal carotid artery 3b. Internal jugular vein 3c. Vagus nerve 3c. Vagus nerve in the neck Branches: 1. Superior laryngeal nerve a) Internal laryngeal nerve –Sensory to the upper part of the cavity of the larynx a) External laryngeal nerve – Motor to cricothyroid muscle 2. Recurrent laryngeal nerve (on right side) – Motor to all the muscles of the larynx + sensory to lower part of the cavity of the larynx 3. Cardiac branches – parasympathetic fibers to the heart 4. Branches to carotid body & sinus 5. Auricular branch (Alderman’s nerve) 6. Pharyngeal branch 3b.Internal jugular vein (IJV) & its tributaries Internal jugular vein brings venous blood from brain and the cranial cavity. It is the continuation of the sigmoid sinus. It has following tributaries 1. Inferior petrosal sinus 2. Pharyngeal veins 3. Common facial vein 4. Lingual vein 5. Middle & inferior thyroid veins Termination: IJV joins with subclavian vein to form brachiocephalic vein 4. Ansa Cervicalis 1. Superior root (Descendens hypoglossi) 2. Inferior root (Descendens cervicalis) Hypoglossal nerve Ventral ramus of C1 Geniohyoid & Thyrohyoid Ventral ramus of C2 Ventral ramus of C3 Superior root/descendens Inferior hypoglossi root/descendens cervicalis Infrahyoid muscle 5. Spinal part of the accessory nerve It supplies sternocleidomastoid and trapezius muscles 6. Hypoglossal nerve It winds forward superficial to three arteries namely internal carotid, external carotid and loop of the first part of the lingual artery. Hypoglossal nerve supplies muscles of the tongue 9th 11th 7. Deep cervical Lymph nodes: A chain of deep cervical lymph nodes lies in intimate relations to the IJV. The jugulo-digastric nodes lie above 12th the posterior belly of the digastric & jugulo-omohyoid below it. Digastric triangle (Submandibular triangle) Boundaries Above: Base of the mandible, line extending from angle of mandible to mastoid process Below & behind: Posterior belly of digastric & Stylohyoid Below & in front: Anterior belly of digastric Floor: Mylohyoid, Hyoglossus & Middle constrictor Digastric triangle Posterior belly of digastric Anterior belly of digastric Contents in the anterior part Submandibular gland Facial vein & submandibular lymph node Facial artery Mylohyoid vessels & nerve Hypoglossal nerve Contents in the posterior part Parotid gland External carotid artery Carotid sheath with its contents Facial vein Glossopharyngeal nerve 3 muscles attached to styloid process Mylohyoid nerve and vessel Submandibular gland Facial vein Facial artery Muscular triangle Anteriorly: Anterior midline of the neck extending from body of the hyoid bone to suprasternal notch. Behind and above (posterosuperiorly): Superior belly of the omohyoid muscle Behind and below (posteroinferiorly): Anterior border of the lower part of the sternocleidomastoid muscle. Infrahyoid muscles 1. Sternohyoid 2. Sternothyroid 3. Thyrohyoid 4. Omohyoid These muscles are supplied by the Ansa cervicalis  Symphysis menti Submental triangle Anterior belly of Boundaries the digastric Apex: Symphysis menti Mylohyoid Base: Hyoid bone Sides: Anterior belly of digastric Body of the hyoid bone Floor: Mylohyoid Contents Submental lymph nodes: drain central part of lower lip, floor of mouth & tip of tongue. Anterior jugular vein Anterior jugular vein Take Home Message Sternocleidomastoid muscle → Takes origin from the sternum and medial end of the clavicle, inserted into the mastoid process. It is supplied by spinal accessory nerve and ventral rami of C2 and C3. Acting unilaterally, it turns the face to the opposite side and acting bilaterally draws the head forwards. Boundaries of the Carotid triangle → In front and above by posterior belly of the digastric muscle, in front and below by superior belly of omohyoid, posteriorly by sternocleidomastoid muscle. Floor of the Carotid triangle → Hyoglossus, thyrohyoid, middle and inferior constrictor muscles of pharynx Contents of the Carotid triangle → Common carotid artery with its terminal branches external and internal carotid arteries, Branches of external carotid artery, Internal jugular vein, vagus, ansa cervicalis, spinal accessory and hypoglossal nerves and deep cervical lymph nodes. Common carotid artery → Branch of arch of aorta on left side and branch of brachiocephalic trunk on the right side. It terminates at the level of the upper border of the thyroid cartilage (between C3 and C4 vertebra) into external and internal carotid arteries. The pulsation of the artery can be felt anterior to the sternocleidomastoid muscle, against the anterior tubercle of the C6 vertebra (carotid tubercle). External carotid artery → It is one of the terminal branches of the common carotid artery, ascends in carotid and digastric triangles and parotid gland. At the level of the neck of the mandible it is terminated by superficial temporal and maxillary arteries. It gives following branches-Superior thyroid, ascending pharyngeal, facial, lingual, posterior auricular and occipital arteries. Internal jugular vein → It is the continuation of the sigmoid sinus of the cranial cavity at the jugular foramen. It descends in the neck along with internal and common carotid arteries and vagus nerve within the carotid sheath. It ends by joining subclavian vein to form brachiocephalic vein. It has following tributaries – common facial, lingual, pharyngeal, superior thyroid, middle thyroid veins and inferior petrosal sinus. Ansa cervicalis → A nerve loop present anterior to the carotid sheath. It has two roots-superior root is (descendens hypoglossi) formed by ventral ramus of C1 joining hypoglossal nerve emerging as superior root. Inferior root (descendens cervicalis) formed by ventral rami of C2 and C3 nerves. The two roots join to form a loop. Ansa cervicalis supplies – infrahyoid muscles (omohyoid, sternohyoid and sternothyroid muscles). Branches of vagus nerve in the neck → Cardiac branches to cardiac plexus, Right recurrent laryngeal nerve, Superior laryngeal nerve which divides into external and internal laryngeal nerves. Hypoglossal nerve in the neck → It crosses superficial to 3 arteries (internal carotid, external carotid and first part of the lingual artery), passes superficial to hyoglossus muscle to supply muscles of the tongue. Boundaries of the Digastric triangle → Above by lower border of mandible and imaginary line extending from angle of the mandible to mastoid process. Below and behind by the posterior belly of the digastric muscle. Below and in front by the anterior belly of the digastric muscle. Major contents of the Digastric triangle → Superficial part of the submandibular gland, facial artery, facial vein, hypoglossal nerve. Carotid sheath → An extension of the deep fascia covers common and internal carotid arteries medially, internal jugular vein laterally and vagus nerve in between.