5 Anterior triangle.pdf

Neck compartments    Visceral Vertebral Tow vascular The anterior triangle Boundaries: - Superiorly: body of the mandible - Posteriorly: sternocleidomastoid muscle - Anteriorly: midline  Subdivisions: - Carotid triangle - Digastric triangle - Submental triangle - Muscular triangle  Submand...

Neck compartments    Visceral Vertebral Tow vascular The anterior triangle Boundaries: - Superiorly: body of the mandible - Posteriorly: sternocleidomastoid muscle - Anteriorly: midline  Subdivisions: - Carotid triangle - Digastric triangle - Submental triangle - Muscular triangle  Submandibular (Digastric) triangle    Boundaries: - Superiorly: inferior border of the mandible - Inferiorly: anterior and posterior bellies of the digastric muscle Contents: Submandibular gland; submandibular lymph nodes; hypoglossal nerve [XII]; mylohyoid nerve; facial artery and vein Floor: formed by the mylohyoid and hyoglossus muscles and the middle pharyngeal constrictor Submental triangle       Boundaries: Inferiorly: the hyoid bone Laterally: the anterior belly of the digastric muscle The midline Contents: Submental lymph nodes; tributaries forming the anterior jugular vein Floor: formed by the two mylohyoid muscles Muscular triangle       Boundaries: Superiorly: the hyoid bone, Laterally: the superior belly of the omohyoid muscle, and the anterior border of the sternocleidomastoid muscle The midline Contents: Sternohyoid, omohyoid, sternothyroid, and thyrohyoid muscles; thyroid and parathyroid glands; pharynx  Floor: formed by the sternohyoid, sternothyroid, muscles Carotid triangle       Boundaries: Anteroinferiorly: the superior belly of the omohyoid muscle Superiorly: the stylohyoid muscle and posterior belly of the digastric, Posteriorly: anterior border of the sternocleidomastoid muscle. Floor: thyrohyoid, hyoglossus, middle and inferior constrictors of pharynx Contents: Tributaries to common facial vein; cervical branch of facial nerve [VII]; common carotid artery; external and internal carotid arteries; superior thyroid; ascending pharyngeal; lingual, facial, and occipital arteries; internal jugular vein; vagus [X], accessory [XI], and hypoglossal [XII] nerves; superior and inferior roots of ansa cervicalis; transverse cervical nerve Muscles in the anterior triangle Digastric:  Origin  (Posterior belly): Mastoid process  (Anterior belly): Digastric fossa on lower inside of mandible  Insertion: Intermediate tendon is held to hyoid by fascial sling  NS:  Anterior : Nerve to mylohyoid  Posterior: Facial nerve  Action: Depresses mandible or elevates hyoid bone Muscles in the anterior triangle Stylohyoid:  Origin: Styloid process  Insertion: Lateral area of body of hyoid bone  NS: Facial nerve  Action: Elevates hyoid bone Muscles in the anterior triangle Mylohyoid:  Origin: Mylohyoid line of body of mandible  Insertion: Body of hyoid bone  NS: Inferior alveolar nerve  Action: Elevates floor of mouth and hyoid bone or depresses mandible Muscles in the anterior triangle Geniohyoid  Origin: Inferior mental spine of mandible  Insertion: Body of hyoid bone  NS: 1st cervical nerve  Action: Elevates hyoid bone or depresses mandible Muscles in the anterior triangle Sternohyoid  Origin: Manubrium sterni and clavicle  Insertion: Body of hyoid bone  NS: Ansa cervicalis; C1, 2, and 3  Action: Depresses hyoid bone Muscles in the anterior triangle Sternothyroid  Origin: Manubrium sterni  Insertion: Oblique line on lamina of thyroid cartilage  NS: Ansa cervicalis; C1, 2, and 3  Action: Depresses larynx Muscles in the anterior triangle Thyrohyoid  Origin: Oblique line on lamina of thyroid cartilage  Insertion: Lower border of body of hyoid bone  NS: 1st cervical nerve  Action: Depresses hyoid bone or elevates larynx common carotid artery       The right common carotid artery arises from the brachiocephalic artery The left artery arises from the arch of the aorta Runs under cover of the anterior border of the sternocleidomastoid muscle Begins: sternoclavicular joint Ends: upper border of the thyroid cartilage. Divisions: external and internal carotid arteries common carotid artery      The carotid sinus: localized dilatation in the terminal part of the common carotid artery Contains numerous nerve endings derived from the glossopharyngeal nerve. serves as a reflex pressoreceptor mechanism The carotid body: is a small structure that lies posterior to the point of bifurcation of the common carotid artery Innervated by the glossopharyngeal nerve. The carotid body is a chemoreceptor, being sensitive to excess carbon dioxide and reduced oxygen tension in the blood. Relations of common carotid artery   Anterolaterally: skin, fascia, sternocleidomast oid, sternohyoid, sternothyroid, and the superior belly of the omohyoid Posteriorly: The transverse processes of the lower four cervical vertebrae, the prevertebral muscles, and the sympathetic trunk (In the lower part of the neck are the vertebral vessels. Deep cervical fascia      Organized into several distinct layers: Investing layer: which surrounds all structures in the neck Prevertebral layer: surrounds the vertebral column and the deep muscles associated with the back Pretracheal layer: encloses the viscera of the neck Carotid sheath: vascular Relations of common carotid artery   Medially: The larynx and pharynx and, below these, the trachea and esophagus The lobe of the thyroid gland Laterally: The internal jugular vein and, posterolaterally,the vagus nerve The external carotid artery     Begins: at the level of the upper border of the thyroid cartilage Terminates: in the substance of the parotid gland behind the neck of the mandible by dividing into the superficial temporal and maxillary arteries. Medial to the internal carotid artery, then passes backward and lateral to it. Crossed by the posterior belly of the digastric and the stylohyoid Relations of the External Carotid Artery  Anterolaterally: - Beginning: anterior border of the sternocleidomastoi d - Crossed by: the hypoglossal nerve the posterior belly of the digastric muscle, and the stylohyoid muscles. Within the parotid gland, facial nerve - The internal jugular vein first  lies lateral to the artery and then posterior to it. Medially: The wall of the pharynx and the internal carotid artery. The stylopharyngeus muscle, the glossopharyngeal nerve, and the pharyngeal branch of the vagus pass between the external and internal carotid arteries Branches of the External Carotid Artery    Superior Thyroid Artery: curves downward to the upper pole of the thyroid gland, It is accompanied by external laryngeal nerve, which supplies the cricothyroid muscle. Ascending Pharyngeal Artery: ascends along and supplies the pharyngeal wall. Lingual Artery: loops upward and forward and supplies the tongue Branches of the External Carotid Artery      Facial Artery Occipital Artery Posterior Auricular Artery Superficial Temporal Artery Maxillary Artery Internal Carotid Artery     Begins: bifurcation of the common carotid artery at the level of the upper border of the thyroid cartilage Ascends in the neck embedded in the carotid sheath Passes deep to the parotid gland Leaves the neck by passing through the carotid canal Relations of the Internal Carotid Artery in the Neck     Anterolaterally: Below the digastric. skin, the fascia, the anterior border of the sternocleidomastoid, and the hypoglossal nerve. Above the digastric lie the stylohyoid muscle, the stylopharyngeus muscle, the glossopharyngeal nerve, the pharyngeal branch of the vagus, the parotid gland, and the external carotid artery Posteriorly: The sympathetic trunk, the longus capitis muscle, and the transverse processes of the upper three cervical vertebrae Medially: The pharyngeal wall and the superior laryngeal nerve Laterally: The internal jugular vein and the vagus nerve The internal jugular vein      Receives blood from the brain, face, and neck Starts: continuation of the sigmoid sinus and leaves the skull through the jugular foramen. Descends through the neck in the carotid sheath lateral to the vagus nerve and the internal and common carotid arteries. Ends: by joining the subclavian vein behind the medial end of the clavicle to form the brachiocephalic vein Closely related to the deep cervical lymph nodes. Relations of the Internal Jugular Vein  Anterolaterally: The skin, the fascia, the sternocleidomastoi d, and the parotid salivary gland. Infrahyoid muscles. crossed by the stylohyoid, the posterior belly of the digastric, and the spinal part of the accessory nerve. Relations of the Internal Jugular Vein   Posteriorly: The transverse processes of the cervical vertebrae, muscles that attach to the vertebrae , the phrenic nerve, the thyrocervical trunk, the vertebral vein, and the first part of the subclavian artery Medially: Above lie the internal carotid artery and the 9th, 10th, 11th, and 12th cranial nerves. Below lie the common carotid artery and the vagus nerve. The vagus nerve      Motor and sensory fibers, emerges from medulla oblongata Passes laterally through the posterior cranial fossa and leaves the skull through the jugular foramen. The vagus nerve has both superior and inferior sensory ganglia. Below the inferior ganglion, the cranial root of the accessory nerve joins the vagus nerve Descends through the neck alongside the carotid arteries and internal jugular vein within the carotid sheath It passes through the mediastinum of the thorax Vagus nerve branches     Pharyngeal branch: contains nerve fibers from the cranial part of the accessory nerve. joins the pharyngeal plexus and supplies all the muscles of the pharynx (except the stylopharyngeus) and of the soft palate (except the tensor veli palatini). Superior laryngeal nerve, divides into: Internal laryngeal nerve: sensory to the mucous membrane of the larynx down as far as the vocal cords. External laryngeal nerve: motor, located close to the superior thyroid artery; supplies the cricothyroid muscle. Vagus nerve branches       Recurrent laryngeal nerve: Right: hooks around the first part of the subclavian artery and then ascends in the groove between the trachea and the esophagus. Left: hooks around the arch of the aorta and then ascends into the neck between the trachea and the esophagus. Related to the inferior thyroid artery Supplies: all the muscles of the larynx, except the cricothyroid muscle, the mucous membrane of the larynx below the vocal cords, and the mucous membrane of the upper part of the trachea. Cardiac branches: arise in the neck, descend into the thorax, and end in the cardiac plexus The glossopharyngeal nerve     Motor and sensory nerve, emerges from the medulla oblongata passes laterally in the posterior cranial fossa and leaves the skull by passing through the jugular foramen The superior and inferior sensory ganglia are located on the nerve as it passes through the foramen. Descends through the upper part of the neck to the back of the tongue The glossopharyngeal nerve branches    Nerve to the stylopharyngeus muscle Pharyngeal branches: run to the pharyngeal plexus and also receive branches from the vagus nerve Lingual branch: passes to the mucous membrane of the posterior third of the tongue (including the vallate papillae). The hypoglossal nerve      Motor nerve. emerges on the medulla oblongata Crosses the posterior cranial fossa, and leaves the skull through the hypoglossal canal. Passes downward and forward in the neck and crosses the internal and external carotid arteries to reach the tongue hooking around the occipital artery In the upper part of its course, it is joined by C1 fibers from the cervical plexus. Branches of the Hypoglossal Nerve    Descending branch (C1 fibers) passes downward and joins the descending cervical nerve (C2 and 3) to form the ansa cervicalis. supply the omohyoid, the sternohyoid, and the sternothyroid muscles. Nerve to the thyrohyoid muscle (C1) Muscular branches: to all the muscles of the tongue except the palatoglossus (pharyngeal plexus)   Nerve to the geniohyoid muscle (C1). Does not give off any branches as it passes through the anterior triangle of the neck The accessory nerve Leave the skull through the jugular foramen. - Two roots :  The cranial root: joins the vagus nerves  The spinal root: runs downward and laterally and enters the deep surface of the sternocleidomastoid muscle, and crosses the posterior triangle of the neck to supply the trapezius muscle   Gives off no branches as it passes through the anterior triangle The thyroid gland Two lobes connected by a narrow isthmus  Attached to the larynx and the trachea by a sheath derived from the pretracheal layer of deep fascia  Each lobe is pear shaped - Apex: directed upward as far as the oblique line on the lamina of the thyroid cartilage - Base: at the level of the fourth or fifth tracheal ring.  Clinical notes   Any pathologic neck swelling that is part of the thyroid gland will move upward when the patient is asked to swallow. Pathologic enlargement of the thyroid commonly results in pressure on the trachea Relations of the Lobes    Anterolaterally: The sternothyroid, the superior belly of the omohyoid, the sternohyoid, and the anterior border of the sternocleidomastoid Posterolaterally: common carotid artery, the internal jugular vein, and the vagus nerve Medially: The larynx, the trachea, the pharynx, and the esophagus. the cricothyroid muscle and its nerve supply, recurrent laryngeal nerve The isthmus     Extends across the midline in front of the second, third, and fourth tracheal rings pyramidal lobe: is often present, and it projects upward from the isthmus, usually to the left of the midline. Usually connected to the hyoid bone by a fibrous or muscular band levator glandulae thyroideae: (if it is muscular) - Relations:  Anteriorly: The sternothyroids, sternohyoids, anterior jugular veins, fascia, and skin  Posteriorly: The second, third, and fourth rings of the trachea Blood supply   The superior thyroid artery: a branch of the external carotid artery, descends to the upper pole of each lobe, accompanied by the external laryngeal nerve Thyroid ima artery? arises from the brachiocephalic trunk or the arch of the aorta and ascends on the anterior surface of the trachea to supply the thyroid gland Blood supply  The inferior thyroid artery: a branch of the thyrocervical trunk (branch of first part of subclavian artery, ascends behind the gland to the level of the cricoid cartilage. It then turns medially and downward to reach the posterior border of the gland Venous drainage    Superior thyroid vein: drains into the internal jugular vein Middle thyroid: drains into the internal jugular vein Inferior thyroid veins: anastomose with one another as they descend in front of the trachea. They drain into the left brachiocephalic vein Lymphatic drainage   Deep cervical paratracheal nodes Parathyroid Glands Ovoid bodies measuring about 6 mm long in their greatest diameter.  Four in number on the posterior border of the thyroid gland, within its fascial capsule - Two superior parathyroid glands: at the level of the middle of the posterior border of the thyroid gland. - Two inferior parathyroid glands: usually lie close to the inferior poles of the thyroid gland, but may be found: * Embedded in the thyroid substance * Superior mediastinum 