ANTERIOR TRIANGLE It is in front of the

ANTERIOR TRIANGLE It is in front of • the Sternomastoid muscle.

BOUNDARIES Anteriorly : midline of • the neck. Posteriorly: anterior • border of sternomastoid. Superiorly: lower • margin of the body of the mandible.

BOUNDARIES Roof: • skin, superficial • fascia (containing platysma) and the Investing layer of deep cervical fascia.

SUBDIVISIONS The anterior • triangle is subdivided by : The Anterior and • Posterior bellies of the Digastric and The Superior belly • of Omohyoid into (4) smaller triangles.

SUBDIVISIONS SUBMENTAL SUB CAROTIDMUSCULAR MANDIBULAR

SUBMENTAL TRIANGLE It lies below the chin. • Boundaries : • Anteriorly: midline of the • neck. Laterally: Anterior belly • of Digastric.

BOUNDARIES Inferiorly : body • of the hyoid. Floor: Mylohyoid • muscle.

CONTENTS Submental • lymph nodes. They receive • lymph from the tip of the tongue.

MYLOHYOID MUSCLE It is a flat triangular • sheet that supports the floor of the mouth and tongue (forms the main part of the floor of the mouth). Origin : • Mylohyoid line of the • mandible.

MYLOHYOID Insertion: • The anterior fibers: • Into a Fibrous Raphe. The posterior fibers: • Into the body of hyoid bone.

MYLOHYOID Nerve supply : • Nerve to • mylohyoid.

MYLOHYOID Action : • If the mandible is fixed: • Elevates the floor of the mouth as in deglutition. If the hyoid bone is fixed: • Depresses the mandible and opens the mouth.

DIGASTRIC TRIANGLE It lies below the body of • the mandible. Boundaries: • Anteriorly: • Anterior belly of • Digastric. Posteriorly: • Posterior belly of • digastric & Stylohyoid.

DIGASTRIC TRIANGLE Superiorly: • Lower border of • the body of the mandible. Floor: • Mylohyoid. • Hyoglossus.

CONTENTS A. Anterior part : • (1) Submandibular • salivary gland. (2) Facial artery (deep to • gland). (3) Facial vein • (4) Submandibular lymph • nodes. The vein and lymph • nodes are superficial to the gland.

CONTENTS (5) Hypoglossal • nerve. (6) Nerve and • vessels to mylohyoid.

CONTENTS B. posterior part: • 1. Carotid • sheath and its contents. 2. parotid gland • (Lower part)

DIGASTRIC MUSCLE It has two bellies: • Anterior and Posterior. • Posterior belly : • Arises from the mastoid • process. Inserted into the • intermediate tendon. Anterior belly attached to • the lower border of body of mandible.

DIGASTRIC MUSCLE Insertion : to the • Intermediate Tendon. • It pierces the • insertion of stylohyoid. It binds to the hyoid • bone by a loop of deep fascia.

NERVE SUPPLY Posterior belly: • Facial Nerve Anterior belly: • The nerve to • Mylohyoid.

ACTION Depression of the mandible. OR Elevation of the • hyoid bone.

STYLOHYOID MUSCLE Origin: • The styloid process. • It runs along the upper • border of the posterior belly of digastric. Insertion: • Hyoid bone (between • body and greater horn).

STYLOHYOID MUSCLE Nerve supply : • Facial nerve. • Action : • Elevation of • hyoid bone.

CAROTID TRIANGLE It is behind the hyoid • bone. Boundaries : • Superiorly: • Posterior belly of • Digastric. Inferiorly: • Superior belly of • Omohyoid.

BOUNDARIES Posteriorly: • Anterior border of • sternomastoid. Floor: • Thyrohyoid. • Hyoglossus. Middle & Inferior • constrictors of the pharynx.

CONTENTS (1) Carotid sheath • (2) Hypoglossal nerve • and its descending branch. (3) Acessory nerve. •

CONTENTS (4) Internal and • External laryngeal nerves. (5) Deep cervical • lymph nodes.

CAROTID SHEATH It is a • condensation of deep cervical fascia. It is attached to • the base of the skull superiorly and fuses with the pericardium inferiorly.

CONTENTS 1. Common and • internal carotid arteries. 2. Internal jugular • vein. 3. Vagus nerve. • 4. Deep cervical • lymph nodes. They form a chain along the internal jugular vein.

CAROTID SHEATH It is crossed by • Glossopharynge • al. Hypoglossal. • Spinal part of • acessory.

MUSCULAR TRIANGLE It lies below the hyoid • bone. Boundaries: • Anteriorly : • Midline of the neck. • Superiorly: • Superior belly of • Omohyoid.

MUSCULAR TRIANGLE Inferiorly: • Anterior border of • Sternomastoid Floor: • Sternohyoid. • Sternothyroid.

FLOOR Beneath the floor • lie: Thyroid gland. • Larynx. • Trachea. • Esophagus. •

INFRAHYOID MUSCLES STERNO HYOID STERNOTHYRO OMOHYOID THYROID HOID

ORIGIN Sternohyoid & • Sternothyroid : Posterior surface of • the manubrium. Thyrohyoid: • Oblique line of thyroid • cartilage.

ORIGIN Omohyoid : • Inferior belly : • Suprascapular ligament • and Suprascapular notch. Superior belly: • Intermediate tendon. •

INSERTION Sternohyoid & • Sternothyroid : Hyoid bone (lower • border). Oblique line of • thyroid cartilage. Thyrohyoid: • Hyoid bone (lower • border).

INSERTION Omohyoid • Hyoid bone • (lower border).

NERVE SUPPLY Ansa Cervicalis • (C 1, 2&3) EXCEPT • Thyrohyoid: • (C 1) through the • hypoglossal nerve.

ACTION (1) stabilization of • the hyoid bone to make a base for the movements of the tongue. (2) Assistance in • the movements of the larynx in swallowing.