University:
Kentucky State University
Course:
BIO 301 | Human Anatomy
Academic year:

2024
Views:

251

Pages:

75
Author:

Hundebuchesn

The Neck The neck is the region of the body that lies between the lower margin of the mandible above and the suprasternal notch and the upper border of the clavicle below. Posteriorly, from superior nuchal line to intervertebral disc between C7 and T1 Muscles of the neck 1- Sternocleidomastoid muscle 2- Scalene muscles 3- Infrahyoid muscles 4- Suprahyoid muscles 5- Platysma Superficial Sternocleidomastoid Origin: Manubrium sterni and medial third of clavicle (two heads) Insertion: Mastoid process and superior nuchal line Nerve supply: Spinal part of accessory nerve and C2 and 3 Action: Two muscles acting together extend head and flex neck; one muscle rotates head to opposite side When Sternocleidomastoid contracts, it appears as an oblique band crossing the side of the neck from the sternoclavicular joint to the mastoid process of the skull You can feel and touch the left one when you turn your face to the right and vice versa Ipsilateral flexion When you try to touch your shoulder with your ear Looking up into the sky ➢The carotid pulse can be easily felt just anterior to the middle third of sternocleidomastoid ➢Sensory cutaneous branches of cervical plexus emerge at the posterior border of sternocleidomastoid For anaesthesia of the neck area, a cervical plexus block can be used. Local anaesthetic is injected along the posterior border of sternocleidomastoid where the cutaneous branches of the cervical plexus emerge, known as the nerve point of the neck (Erb’s point/ punctum nervosum) Congenital torticollis Facts about sternocleidomastoid The accessory nerve • Leaves the skull through the jugular foramen - Two roots : • The cranial root: joins the vagus nerve • The spinal root: runs downward and laterally and enters the deep surface of sternocleidomastoid, and crosses the posterior triangle of the neck to supply trapezius Supplies both sternocleidomastoid and trapezius ▪ Scalene muscles In latin : the ladder So you can memorize them by picturing them as a ladder between your ribs and cervical vertebrae Scalenus anterior Origin: Transverse processes of C3-C6 Insertion: First rib Nerve supply: Anterior rami of cervical nerves Action: Elevates first rib; laterally flexes the cervical spine Unilateral contraction Lateral flexion: Bending of cervical spine to the side Bilateral contraction: Ventral flexion: Bending of cervical spine to the front Scalenus medius Origin: Transverse processes of C2-C7 Insertion: First rib (dorsal to scalene anterior) Nerve supply: Anterior rami of cervical nerves Action: Elevates first rib; laterally flexes the cervical spine Scalenus posterior Origin: Transverse processes of C4-C6 Insertion: Second rib Nerve supply: Anterior rami of cervical nerves Action: Elevates second rib; laterally flexes the cervical spine Scalenus anterior The scalenus anterior muscle is a key muscle in understanding the root of the neck. It is deeply placed and it descends almost vertically from the vertebral column to the first rib Scalenus medius Scalenus posterior Remember ➢ Brachial plexus lies between scalene anterior and scalene medius ➢Scalene anterior divides the subclavian artery into three parts Bones of the Neck Cervical Vertebrae Hyoid Bone Larynx At C3 level ✓ The hyoid bone is a mobile single bone found in the midline of the neck below the mandible and abides the larynx ✓ It does not articulate with any other bones ✓The hyoid bone is U shaped and consists of: 1- Body 2- Two greater horns 3- Two lesser horns ✓ It is attached to the skull by the stylohyoid ligament ✓ It is attached to the thyroid cartilage by the thyrohyoid membrane ✓The hyoid bone forms a base for the tongue Lesser horn Greater horn Body Stylohyoid ligament Hyoid bone Thyroid cartilage Trachea Thyrohyoid membrane Muscles superior to hyoid are classified as suprahyoid muscles 1. 2. 3. 4. Stylohyoid Digastric Mylohyoid Geniohyoid Raise the hyoid (during swallowing) Positioning of hyoid bone Muscles inferior to hyoid are classified as infrahyoid muscles (strap muscles) 1. 2. 3. 4. Omohyoid Sternohyoid Thyrohyoid Sternothyroid Depress the hyoid Except sternothyroid Infrahyoid muscles All infrahyoid muscles are supplied by ansa cervicalis (C1,C2,C3) except thyrohyoid, supplied by C1 Sternohyoid Origin: Manubrium sterni (dorsal surface) and sternoclavicular joint Insertion: Body of hyoid bone Nerve supply: Ansa cervicalis (C1, 2, and 3) Action: Depresses hyoid bone Sternohyoid is the most superficial of infrahyoid muscles Manubrium sterni Superior belly Omohyoid Origin: Body of hyoid bone Insertion: Intermediate tendon is held to clavicle and first rib by fascial sling Nerve supply: Ansa cervicalis (C1, 2, and 3) Action: Depresses hyoid bone Intermediate tendon Inferior belly of Omohyoid Origin: Upper margin of scapula Scapula omo-= shoulder The intermediate tendon is attached to the carotid sheet which contains IJV, CCA, vagus nerve and lymph nodes), by pulling this sheet, it prevents the big thin IJV from collapsing and maintains a low pressure in the IJV This increases the blood return from the head to Superior vena cava Sternothyroid Origin: Manubrium sterni (dorsal surface) Insertion: Thyroid cartilage Nerve supply: Ansa cervicalis (C1, 2, and 3) Action: Depresses larynx Thyrohyoid Origin: Thyroid cartilage Insertion: Body of hyoid bone Nerve supply: First cervical nerve Action: Depresses hyoid bone or elevates larynx Thyroid cartilage Infrahyoid muscles Thyrohyoid Omohyoid Sternohyoid Sternothyroid Suprahyoid muscles Involved in swallowing and movement of the larynx Stylohyoid Origin: Styloid process Insertion: Body of hyoid bone Nerve supply: Facial nerve Action: Elevates hyoid bone Stylohyoid Anterior belly of digastric Origin: Digastric fossa of the mandible Nerve supply: Nerve to mylohyoid (mandibular nerve) Insertion: Intermediate tendon is held to hyoid by fascial sling Action: Depresses mandible or elevates hyoid bone Posterior belly of digastric Origin: Mastoid notch Nerve supply: Facial nerve The mylohyoid raphe is where both muscles meet. It inserts into body of hyoid Mylohyoid Origin: Mylohyoid line of mandible Insertion: Body of hyoid bone and fibrous raphe Nerve supply: Nerve to mylohyoid (from inf. alveolar n/ mandibular n) Action: Elevates floor of mouth and hyoid bone or depresses mandible Geniohyoid Origin: Inferior mental spine of mandible Insertion: Body of hyoid bone Nerve supply: First cervical nerve (cervical plexus) Action: Elevates hyoid bone or depresses mandible Mentum Genio Chin Superficial Fascia It is a thin layer of fascia that contains: 1- Platysma muscle 2- Superficial veins 3- Cutaneous nerves 4- Superficial lymph nodes Superficial Veins 1- External Jugular Vein 2- Anterior Jugular Vein 1- External Jugular Vein ✓ Begins just behind the angle of mandible by union of posterior auricular vein with posterior division of retromandibular vein ✓ Descends vertically across sternocleidomastoid ✓ Just above the clavicle in the posterior triangle, it pierces the deep fascia (investing layer) and drains into subclavian vein Its course extends from the angle of the mandible to the middle of the clavicle Posterior division of retromandibular vein Superficial temporal vein Posterior auricular vein Retromandibular vein Facial vein Anterior division of retromandibular vein External jugular vein Internal jugular vein Common facial vein ✓The retromandibular vein is formed when superficial temporal and maxillary veins join in the substance of parotid gland ✓On leaving the parotid gland, it divides into anterior and posterior divisions The external jugular vein begins by the union of the posterior auricular vein with the posterior division of the retromandibular vein Facial Vein is joined by the anterior division of the retromandibular vein, and drains into the internal jugular vein. Superficial Veins 2- Anterior JugularVein ✓Begins just below the chin ✓Runs down the neck close to the midline ✓Just above the suprasternal notch, the veins of the two sides are united by a transverse trunk called the jugular arch ✓At the lower part of the neck, it passes beneath sternocleidomastoid and drains into external jugular vein Jugular arch Anterior JugularVein drains the anterior aspect of the neck Cutaneous Nerves of the neck Back: is supplied segmentally by posterior rami of cervical nerves 2 to 5 Remember Greater occipital nerve (C2) supplies the back of the scalp Front and sides: is supplied by anterior rami of cervical nerves 2 to 4 through branches of cervical plexus The first cervical nerve has no cutaneous branch Cervical plexus C1 C2 The cervical plexus is formed by the anterior rami of C1-C4 C3 C4 Branches: 1- Cutanous nerves emerge from the posterior border of sternocleidomastoid and visible on posterior triangle 2- Superior and inferior roots of ansa cervicalis (C1-C3): innervates the infrahyoid muscles 3- Phrenic nerve (C3-C5) Cutanous branches of Cervical plexus The lesser occipital nerve (C2): supplies the skin over the lateral part of the occipital region and the medial surface of the auricle (upper half) The great auricular nerve (C2 and 3): supplies the skin over the angle of the mandible and on both surfaces of the auricle (lower half) The transverse cervical nerve (C2 and 3): supplies the skin on the anterior and lateral surfaces of the neck, from the body of the mandible to the sternum The supraclavicular nerves (C3 and 4) descend across the side of the neck down to the level of the second rib. The medial supraclavicular nerve crosses the medial end of the clavicle and supplies the skin as far as the median plane. The intermediate supraclavicular nerve crosses the middle of the clavicle and supplies the skin of the chest wall. The lateral supraclavicular nerve crosses the lateral end of the clavicle and supplies the skin over the shoulder and the upper half of the deltoid muscle and the posterior aspect of the shoulder as far down as the spine of the scapula Sensory cutaneous branches of cervical plexus emerge at the posterior border of sternocleidomastoid muscle (Erb’s point) Supraclavicular nerves are important clinically, because pain may be referred along them from the phrenic nerve (C3C4C5) (gallbladder disease ) Cutanous branches of Cervical plexus C1 Lesser occipital nerve (C2) C2 Great auricular nerve (C2 and 3) Transverse cervical nerve (C2 and 3) C3 Supraclavicular nerve (C3 and 4) C4 C5 Great auricular nerve (C2 and 3) Lesser occipital nerve (C2) Transverse cervical nerve (C2 and 3) Ansa cervicalis Ansa cervicalis innervates the infrahyoid muscles except thyrohyoid (C1) ✓A branch from C1 joins the hypoglossal nerve Some of these C1 fibers later leave the hypoglossal as the descending hypoglossi which unites with the descending cervicalis nerve (C2 and3 ) to form the ansa cervicalis ✓The first, second, and third cervical nerve fibers within the ansa cervicalis supply: 1- Omohyoid 2- Sternohyoid 3- Sternothyroid ✓Other C1 fibers within the hypoglossal nerve leave it as the nerve to the thyrohyoid and geniohyoid Superior root Inferior root Ansa cervicalis Ansa cervicalis innervates the infrahyoid muscles except thyrohyoid (C1) Superior root Inferior root Cervical plexus Phrenic nerve (C3C4C5) supplies the diaphragm Muscular branches of Cervical plexus Geniohyoid Thyrohyoid C1 C2 C3 C4 C5 Phrenic nerve Visceral (anterior) Deep fascia Vascular (Lateral) Neck compartments Visceral compartment: contains parts of digestive and repiratory systems and several endocrine glands Vertebral compartment: contains cervical vertebrae, spinal cord, cervical nerves and vertebral muscles Two vascular compartments: contain major blood vessels and vagus nerve Vertebral compartment (posterior) Deep fascia Deep cervical fascia is organized into several layers. These layers act like a shirt collar, supporting the structures and vessels of the neck. 1- Investing layer: surrounds all structures in the neck 2- Prevertebral layer: surrounds the vertebral column and the muscles around it 3- Pretracheal layer: encloses the viscera of the neck and infrahyoid muscles 4- Carotid sheaths: receive contribution from the other three layers Surround neurovascular bundles on the side of the neck In the neck, deep fascia not only act to support internal structures, but also help to compartmentalize structures of the neck Trapezius Sternocleidomastoid Investing layer of deep fascia Anterior Sternocleidomastoid Trapezius Investing layer splits to enclose sternocleidomastoid and trapezius muscles Posterior Pretracheal fascia Thyroid gland Trachea Esophagus Anatomically, it can be divided into two parts: Muscular part: encloses the infrahyoid muscles. Visceral part: encloses the thyroid gland, trachea and esophagus. Thyroid cartilage Thyroid gland Trachea Infrahyoid muscles Pretracheal fasciaMuscular part Pretracheal fasciaVisceral part Anterior Pretracheal layer posterior to the pharynx is called Buccopharyngeal fascia (invests the pharyngeal muscles and is continued forward onto the buccinator) Esophagus Posterior Note: more precisely, the superior portion posterior to the pharynx is termed the retropharyngeal space, while the inferior continuation is the retroesophageal space. Anterior Prevertebral fascia Cervical vertebra Vertebral muscles Cervical spinal nerve Posterior Carotid sheath is a column of fascia (from base of skull to thoracic cavity) that surrounds 1- Common carotid artery 2- Internal carotid artery 3- Internal jugular vein 4- Vagus nerve Carotid sheath Carotid sheath Investing fascia Anterior Prevertebral fascia Pretracheal fascia Carotid sheath Posterior Anterior 1 5 3 4 6 1: Investing layer 2: Trapezius 3: Sternomastoid 4: Prevertebral layer 5: Pretracheal layer 6: Carotid sheath 2 Posterior The investing layer of deep cervical fascia encloses the whole neck The investing fascia can be thought of as a tube; with superior, inferior, anterior and posterior attachments: Superiorly (from backwards to forwards): External occipital protuberance and Superior nuchal line Mastoid process External acoustic meatus Lower border of body of mandible from the angle of mandible to the symphysis menti Inferiorly (from backwards to forwards): Spinous process of C7 Spine and acromion of scapula Clavicle Suprasternal notch Posteriorly: attaches along the nuchal ligament of the vertebral column Anteriorly: attaches to the hyoid bone The pretracheal layer spans between the hyoid bone superiorly and the superior mediastinum inferiorly (where it fuses with the pericardium). The prevertebral layer is fixed above to the base of the skull, and below to the body of the fourth thoracic vertebra (it extends behind the esophagus into the posterior mediastinum) “An important function of the cervical fascia is to limit the spread of infection (for example, a superficial skin abscess may be prevented from spreading deeper into the neck by the investing fascia). However, a potential pathway for spread of infection exists...” Between the fascial layers in the neck are spaces that may provide a conduit for the spread of infections from the neck to the mediastinum 1- Pretracheal space 2- Retropharyngeal space (located between the buccopharyngeal fascia (posterior aspect of the visceral pretracheal fascia) and the prevertebral fascia) 3- Space within prevertebral layer Note that the pretracheal and prevertebral layers continue inferiorly into the thoracic cavity The infection tends to spread within compartments or within the spaces between the fascial layers If infection arises in the pretracheal space, it may spread inferiorly into the superior mediastinum and lie anterior to the pericardium The fascial spaces: -They are potential spaces that consist largely of fatty areolar tissue and lymph nodes -These spaces can provide a conduit for the spread of infections from the neck to the mediastinum Pretracheal space Retropharyngeal space Space within prevertebral layer Common Carotid Artery ➢ Right common carotid artery arises from brachiocephalic artery behind the right sternoclavicular joint ➢Left common carotid artery arises from arch of aorta in superior mediastinum ➢The common carotid artery runs upward through the neck under cover of sternocleidomastoid At the upper border of the thyroid cartilage it divides into external and internal carotid arteries External Carotid Artery ➢ Is one of the terminal branches of the common carotid artery ➢ Supplies structures in the neck, Face, scalp, tongue and the maxilla ➢ It lies outside the carotid sheath ➢ 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 Branches of External Carotid Artery 1. 2. 3. 4. 5. 6. 7. 8. Superior thyroid artery Ascending pharyngeal artery Lingual artery Facial artery Occipital artery Posterior auricular artery Maxillary artery Superficial temporal artery Some American Ladies Find Our Petra So Magnificent 8 Posterior belly of digastric 7 3- Facial artery 6- Posterior auricular artery 2- Lingual artery 1- Superior thyroid artery 5- Occipital artery 4- Ascending pharyngeal artery Superior belly of omohyoid Branches of External Carotid Artery Internal jugular vein Left internal jugular vein Left Subclavian vein Left Brachiocephalic vein Right Brachiocephalic vein Right Subclavian vein ➢ Starts as a continuation of sigmoid sinus ➢ Leaves the skull through jugular foramen ➢ Descends through the neck in carotid sheath ➢ Ends by joining the subclavian vein behind the medial end of clavicle to form brachiocephalic vein ➢Has a dilatation at its upper end called the superior bulb and another near its termination called the inferior bulb Superior vena cava The internal jugular vein is closely related to the deep cervical lymph nodes

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