Neck Anatomy Overview PDF

Neck Saad Datti Department of Anatomy, BUK  Introduction  Neck is the transitional area between the cranium superiorly and the clavicles inferiorly.  Is relatively slender and allow some degree of flexibility necessary to position t...

Neck Saad Datti Department of Anatomy, BUK  Introduction  Neck is the transitional area between the cranium superiorly and the clavicles inferiorly.  Is relatively slender and allow some degree of flexibility necessary to position the head to maximize the efficiency of its sensory organs.  Is a well-known region of vulnerability. Vital structures (trachea, esophagus and thyroid gland) lack the bony protection afforded other parts of the systems to which these structures belong.  It serves as a major conduit for structures (Nerves, Oesophagus and trachea). 11/10/2024  Intro…  Brachial plexuses of nerves originate in the neck and pass inferolaterally to enter the axillae and continue into and supply the upper limbs.  Arterial blood flow to the head and neck (carotid arteries) and the principal venous drainage (the jugular veins) lie anterolaterally in the neck.  Lymph from structures in the head and neck drain into cervical lymph nodes.  Lymph from all of the body except the superior right quadrant enters the venous system through the thoracic duct in the root of the neck. 11/10/2024  Bones of the Neck  The skeleton of the neck is formed by; I. Cervical vertebrae II. Hyoid bone III. Manubrium of the sternum IV. Clavicles 11/10/2024  Cervical vertebrae  Seven cervical vertebrae form the cervical region of the vertebral column, which encloses the spinal cord and meninges.  The stacked, centrally placed vertebral bodies support the head, and the intervertebral (IV) articulation especially the craniovertebral joints at its superior end that provide the flexibility necessary to allow positioning of the head. 11/10/2024  Typical Cervical Vertebrae(3-6) I. The vertebral body is small and longer from side to side than anteroposteriorly; the superior surface is concave, and the inferior surface is convex. II. Vertebral foramen is large and triangular. III. Transverse processes of all typical CV are smaller. IV. Superior facets of the articular processes are directed superoposteriorly, and the inferior facets are directed inferoposteriorly. V. Spinous processes are short and bifid. 11/10/2024  Atypical Cervical vertebrae (1,2 and 7) I. The C1 vertebrae or atlas: a ring- like, kidney-shaped bone lacking a spinous process or body and consisting of two lateral masses connected by anterior and posterior arches. Its concave superior articular facets receive the occipital condyles. II. The C2 vertebrae or axis: a peg- like dens (odontoid process) projects superiorly from its body. III. Spinous process of C7 vertebra is prominent and not bifid. IV. Transverse processes are large, but its transverse foramina are small. 11/10/2024  Hyoid bone  It lies in the anterior part of the neck at the level of the C3 vertebra in the angle between the mandible and the thyroid cartilage.  Its suspended by muscles that connect it to the mandible, styloid processes, thyroid cartilage, manubrium and scapulae.  The hyoid consists of a body, greater and lesser horns.  It is unique among bones for its isolation from the remainder of the skeleton. 11/10/2024  Structure of Hyoid  The body of the hyoid, its middle part, faces anteriorly and is approximately 2.5 cm wide and 1 cm thick.  Its anterior convex surface projects anterosuperiorly; its posterior concave surface projects posteroinferiorly.  Each end of its body is united to a greater horn that projects posterosuperiorly and laterally from the body.  In younger people, the greater horns are united to the body by fibrocartilage usually united by bone in older people. 11/10/2024  Structure of Hyoid…  Each lesser horn is a small bony projection from the superior part of the body of the hyoid near its union with the greater horn.  It is connected to the body of the hyoid by fibrous tissue and sometimes to the greater horn by a synovial joint.  The lesser horn projects superoposteriorly toward the styloid process; it may be partly or completely cartilaginous in some adults. 11/10/2024  Fascia of the Neck  Structures in the neck are surrounded by a layer of subcutaneous tissue (superficial fascia) and are compartmentalized by layers of deep cervical fascia.  The subcutaneous tissue of the neck (superficial cervical fascia) is a layer of fatty connective tissue that lies between the dermis of the skin and the investing layer of deep cervical fascia.  It is usually thinner than in other regions, especially anteriorly. It contains cutaneous nerves, blood and lymphatic vessels, superficial lymph nodes, and variable amounts of fat and anterolaterally it contains the platysma 11/10/2024  Platysma  Is a broad, thin sheet of muscle in the subcutaneous tissue of the neck.  It develops from a continuous sheet of musculature derived from mesenchyme in the 2nd pharyngeal arch and supplied by branches of the facial nerve, CN VII (Cervical branch).  The external jugular vein (EJV), descending from the angle of the mandible to the middle of the clavicle and the main cutaneous nerves of the neck are deep to the platysma.  The platysma covers the anterolateral aspect of the neck. Its fibers arise in the deep fascia covering the superior parts of the deltoid and pectoralis major muscles and sweep superomedially over the clavicle to the inferior border of the mandible. 11/10/2024  Deep cervical fascia  It consists of three fascial layers (sheaths): investing, pretracheal, and prevertebral.  These layers support the viscera (e.g., the thyroid gland), muscles, vessels, and deep lymph nodes.  The deep cervical fascia also condenses around the common carotid arteries, internal jugular veins (IJVs), and vagus nerves to form the carotid sheath.  These fascial layers form natural cleavage planes through which tissues may be separated during surgery, and they limit the spread of abscesses (collections of pus) resulting from infections.  The deep cervical fascial layers also afford the slipperiness that allows structures in the neck to move and pass over one another without difficulty, such as when swallowing and turning the head and neck. 11/10/2024 11/10/2024  Investing Layer  The investing layer of deep cervical fascia, the most superficial deep fascial layer, surrounds the entire neck deep to the skin and subcutaneous tissue.  It splits into superficial and deep layers to enclose (invest) the trapezius and sternocleidomastoid (SCM) muscles.  Superiorly, the investing layer of deep cervical fascia attaches to the: i. Superior nuchal line of the occipital bone. ii. Mastoid processes of the temporal bones. iii. Zygomatic arches. iv. Inferior border of the mandible. v. Hyoid bone. vi. Spinous processes of the cervical vertebrae. 11/10/2024  Pretracheal Layer  Its limited to the anterior part of the neck.  It extends inferiorly from the hyoid into the thorax, where it blends with the fibrous pericardium covering the heart.  It includes a thin muscular part, which encloses the infrahyoid muscles, and a visceral part, which encloses the thyroid gland, trachea, and esophagus and is continuous posteriorly and superiorly with the buccopharyngeal fascia of the pharynx.  It blends laterally with the carotid sheaths. In the region of the hyoid, a thickening of the pretracheal fascia forms a pulley or trochlea through which the intermediate tendon of the digastric muscle passes, suspending the hyoid. 11/10/2024  Prevertebral Layer  It forms a tubular sheath for the vertebral column and the muscles associated with it, such as the longus colli and longus capitis anteriorly, the scalenes laterally, and the deep cervical muscles posteriorly.  The prevertebral layer of fascia is fixed to the cranial base superiorly. Inferiorly, it blends with the endothoracic fascia peripherally and fuses with the anterior longitudinal ligament centrally at approximately the T3 vertebra  The prevertebral fascia extends laterally as the axillary sheath, which surrounds the axillary vessels and brachial plexus.  The cervical parts of the sympathetic trunks are embedded in the prevertebral layer of deep cervical fascia. 11/10/2024  Carotid Sheath  Is a tubular fascial investment that extends from the cranial base to the root of the neck.  It blends anteriorly with the investing and pretracheal and posteriorly with the prevertebral layer of fascia.  Carotid sheath and pretracheal fascia communicate freely with the mediastinum and the cranial cavity.  The carotid sheath contains; i. The common and internal carotid arteries ii. The internal jugular vein iii. The vagus nerve (CN X) iv. Some deep cervical lymph nodes v. The carotid sinus nerve vi. Sympathetic nerve fibers (carotid periarterial plexuses). 11/10/2024  Retropharyngeal space  Is the largest and most important interfascial space in the neck.  It is a potential space that consists of loose connective tissue between the visceral part of the prevertebral layer of deep cervical fascia and the buccopharyngeal fascia surrounding the pharynx superficially.  It extends laterally and terminates in the carotid sheath.  It permits movement of the pharynx, esophagus, larynx, and trachea relative to vertebral column during swallowing.  Its closed superiorly by the cranial base and on each side by the carotid sheath 11/10/2024  Regions of the neck 11/10/2024  Clinical anatomy 11/10/2024  Cervical pain (neck pain)  It has several causes, including inflamed lymph nodes, muscle strain or protruding intervertebral (IV) discs.  Enlarged cervical lymph nodes may indicate a malignant tumor in the head; however, the primary cancer may be in the thorax or abdomen  Neck connects the head to the trunk (e.g., lung cancer may metastasize through the neck to the cranium). 11/10/2024  Fractured hyoid bone  It occurs in people who are manually strangled by compression of the throat.  This results in depression of the body of the bone onto the thyroid cartilage.  Inability to elevate the hyoid and move it anteriorly beneath the tongue which makes swallowing and maintenance of the separation of the alimentary and respiratory tracts difficult  May result in aspiration pneumonia 11/10/2024  Paralysis of the Platysma  Its due to injury to the cervical branch of the facial nerve.  Causes the skin to fall away from the neck in slack folds.  Consequently, during surgical dissections of the neck, extra care is necessary to preserve the cervical branch of the facial nerve.  When suturing wounds of the neck, surgeons carefully suture the skin and edges of the platysma.  If this is not done, the skin wound will be distracted (pulled in different directions) by the contracting platysma muscle fibers, and a broad ugly scar may develop. 11/10/2024  Deep cervical fascia Infections  The investing layer of deep cervical fascia helps prevent the spread of abscesses caused by tissue destruction.  If an infection occurs between the investing layer of deep cervical fascia and the muscular part of the pretracheal fascia surrounding the infrahyoid muscles, the infection will usually not spread beyond the superior edge of the manubrium.  If, however, the infection occurs between the investing fascia and the visceral part of pretracheal fascia, it can spread into the thoracic cavity anterior to the pericardium.  Pus from an abscess posterior to the prevertebral layer of deep cervical fascia may extend laterally in the neck and form a swelling posterior to the SCM.  The pus may perforate the prevertebral layer of deep cervical fascia and enter the retropharyngeal space, producing a bulge in the pharynx (retropharyngeal abscess).  This abscess may cause difficulty in swallowing (dysphagia) and speaking (dysarthria).  Infections in the head may also spread inferiorly posterior to the esophagus and enter the posterior mediastinum, or anterior to the trachea and enter the anterior mediastinum.  Infections in the retropharyngeal space may also extend inferiorly into the superior mediastinum 11/10/2024  END 11/10/2024