Neck Anatomy PDF - King's College London

Anatomy of the head and neck – The neck Anatomy of the Head & Neck The neck [email protected] ANATOMY 0 Lecture outcomes Ø Describe the layers of cervical fascia and state their role in the spread of infection in the neck Ø Define the anterior and posterior triangles of the neck in terms of...

Anatomy of the head and neck – The neck Anatomy of the Head & Neck The neck [email protected] ANATOMY 0 Lecture outcomes Ø Describe the layers of cervical fascia and state their role in the spread of infection in the neck Ø Define the anterior and posterior triangles of the neck in terms of their borders and contents Ø Describe the course of the cranial nerve which pass through the neck and the course and distribution of those which supply structures in the neck Ø Identify the origin, course and distribution of both the motor and sensory fibres of the cervical plexus Ø Examine the position, blood supply and venous drainage of the viscera of the neck ANATOMY 1 The neck Ø The neck can be described as the region of the body bounded: above by the base of the skull (posteriorly) or the mandible (anteriorly) below by the clavicles and the top of the sternum Ø It serves the role of communication between the structures of the head and the rest of the body, but also the cervical vertebrae supporting the weight of the head ANATOMY 2 Boundaries of the neck © Grays Anatomy for Students 3rd Ed ANATOMY Bony landmarks of the neck 3 Compartments of the neck Ø In axial view the neck displays 4 main compartments Ø These are: - visceral - 2 vascular - vertebral ANATOMY © Grays Anatomy for Students 3rd Ed 4 Compartment contents Ø Vertebral: 7 cervical vertebrae; support the head while also allowing considerable flexibility; muscles such as the sternocleidomastoid and trapezius muscles that surround the posterior and lateral parts of the neck, as well as other, postural muscles within the intermediate and deep layers that assist in position or movement of head Ø Visceral: comprise the passageways of the larynx and pharynx, e.g. trachea, for air and food, and visceral like the thyroid gland Ø Vascular, aka the carotid sheath: these comprise the tubes of fascia containing the common carotid artery, in the lower part of the neck, the interval jugular vein and the vagus nerve ANATOMY 5 The supporting role by the neck Ø The vertebrae of the neck need to provide essential support to a ‘heavy’ head, as well as protect the spinal cord and vertebral arteries… Ø … Yet needs to provide proper flexibility Ø This is achieved through two unusually shaped vertebrae – axis and atlas – that have no intervertebral discs Ø The weight of the skull is supported by the synovial joints only and these are reinforced by numerous ligaments to enhance stability ANATOMY Synovial joint 6 The cervical vertebrae Ø The vertebrae of the neck differ from all the others in that these contain the transverse foramen, the passageway for the vertebral artery Transverse foramen ANATOMY 7 Superficial structures of the neck C7 Transverse section of the neck at the C7 level ANATOMY The coloured area shows the superficial fascia along with the platysma muscle 8 Superficial structures of the neck - platysma Ø The superficial layers of the neck also contain cutaneous nerves, blood and lymphatic vessels as well as fat Ø At this level, lies the platysma, a flat, thin muscle that covers the entire anterior half of the neck, from the mandible to the clavicles ANATOMY 9 © Moore Clin Orient Anat 7th Ed The platysma Ø Some posterior fibres of the platysma, attach to the deltoid muscle Ø The area that this muscle covers varies greatly between individuals as well as with age Ø Its main role is to simply tense the skin (often seen in men when shaving), helping to depress the mandible or in generating some facial expressions Ø One of the more telling signs of paralysis of the platysma muscle, from damage to the facial nerve, is a visible droop of skin ANATOMY 10 Deep structures of the neck Ø The deep fascia of the neck, shown in green in the figure below, comprises of structures enveloped in tough membranes. Examples are the carotid sheath enclosing the large vessels Ø Muscles, also invested, include the sternocleidomastoid (1) and the trapezius (2) 1 2 ANATOMY 11 Major muscles acting on the neck Sternocleidomastoid ANATOMY Trapezius 12 Large muscles of the neck Ø The sternocleidomastoid muscle, as the name suggests, courses from the sternum and clavicles to the mastoid process of the temporal bone Ø Contraction of only one of these muscle – unilateral – causes the skull to rotate to the opposite side and lateral flexion to the same side (e.g. shortening the right sternocleidomastoid causes the head to rotate to the left and tilt to the right). Bilateral recruitment though, act to either hold the head straight, so has a stabilizing role, or to flex the head Ø The trapezius muscle originates from the back of the head – occipital protuberance – as well as the spinous processes of the cervical vertebrae and inserts onto the lateral third of the clavicle and spine of scapula Ø Contracting this muscle moves the scapula when the spine is fixed or viceversa ANATOMY 13 Muscles used to keep neck straight/upright Pre vertebral muscles Post vertebral muscles ANATOMY 14 Did you know… Ø Unlike the thorax, the vertebrae of the neck do not attach to ribs, thus the vertebra offer little protection to the viscera and vasculature, which which makes the neck very vulnerable to serious injury Ø In addition, the large vessels that supply the brain and head are, at the base of the neck, very superficial thus an easy pulse point or to insert a central line, for emergency cricothyrotomy, or to access the thyroid gland when surgery to this organ is warranted ANATOMY Source: https://icuunwrapped.co.uk/2018/07/24/central-lines/ 15 Triangles of the neck Ø Doing a central line is possible by first determining what is termed the anterior triangle Ø The outer surface of the neck is divided into 4 triangles, 2 anterior and 2 posterior. Ø Each is defined by resorting to specific anatomical structures that form its edges ANATOMY 16 Triangles of the neck – cont. ANATOMY © Grays Anatomy for Students 3rd Ed 17 Triangle boundaries Ø Anterior triangle: median vertical line of the neck inferior margin of the mandible anterior margin of the sternocleidomastoid muscle Ø Posterior triangle: middle one-third of the clavicle anterior margin of the trapezius posterior margin of the sternocleidomastoid. ANATOMY Ø Thus, the sternocleidomastoid muscle forms the boundary between the anterior and posterior triangles 18 Posterior triangle Ø One of the more important structure of the posterior triangle are: - the accessory nerve which crosses the triangle almost vertically from the posterior border of the sternocleidomastoid to the anterior border of the trapezius - the 4 superficial branches of the cervical plexus which emerge around the posterior border of the sternocleidomastoid ANATOMY Sternocleidomastoid Accessory nerve Trapezius - the external jugular vein, which passes obliquely down over the sternocleidomastoid muscle to enter the posterior triangle 19 © Visible Body Anterior triangle Ø The main structures of interest within the anterior triangle are: - the muscles that attach to the hyoid bone - the carotid arteries - the internal jugular vein - the vagus nerve - the elements of the respiratory and gastrointestinal system - the thyroid and parathyroid glands ANATOMY 20 Anterior triangle – cont. ANATOMY © Grays Anatomy for Students 3rd Ed 21 Vasculature within the anterior triangle Ø All of the arteries of the anterior triangle derive from the common carotid artery Ø The common carotid artery arises from the brachiocephalic artery on the right side of the body and directly from the arch of the aorta on the left side Ø The artery enters the neck within the carotid sheath and gives no branches Ø The internal jugular vein is the main vein of the anterior triangle, draining the anterior region of the neck Ø It emerges from the base of the skull and travels in the carotid sheath Ø It receives tributaries from most of the head and neck regions ANATOMY More detail will be given in the next lecture 22 Innervation of the neck Ø Several structures of the neck, as well as face, receive innervation from the cranial nerves VII-XII Ø There are also 8 cervical spinal nerves which, typical of these nerves, divide into anterior and posterior branches Ø The posterior branches supply the extensor muscles of the vertebral column and, except for C1, supply the skin of the posterior parts of the scalp and neck Ø The anterior rami form the cervical and brachial plexuses Ø The cervical plexus (C1-C4) supply the muscles and cutaneous region of the neck. Also form the phrenic nerve ANATOMY Ø The cervical plexus may be divided into superficial and deep groups. The superficial supply the skin of the anterior and lateral parts of the neck and the side of the head while the deep group supplies muscles23 Cervical plexus ANATOMY 24 Cervical plexus – cutaneous branches Lesser occipital great auricular (Accessory) Transverse nerve of the neck ANATOMY supraclavicular 25 © Visible Body Ansa cervicalis and the hypoglossal nerve Ansa cervicalis innervates the omohyoid muscle, as well as sternothyroid and sternohyoid muscles ANATOMY 26 The brachial plexus Ø The anterior rami of the lower four cervical nerves and first thoracic nerve (C5, C6, C7, C8, and T1) form the brachial plexus Ø This network of nerves projects towards the armpit to supply the entirety of the upper limb ANATOMY © Grays Anatomy for Students 3rd Ed 1. Oesophagus 2. Trachea 3. Internal Jugular Vein 4. Subclavian Vein 5. Thoracic Duct 27 The carotid sheath ANATOMY 28 Contents of the carotid sheath ANATOMY 1. Internal jugular vein 2. Common carotid artery 3. Vagus nerve 29 Contents of the carotid sheath – cont. Anterior view ANATOMY 1. External carotid artery 2. Internal jugular vein 3. Vagus nerve Posterior view 1. 2. 3. 4. Vagus nerve Common carotid artery Right recurrent laryngeal nerve Left recurrent laryngeal nerve 30 Lymphatic drainage Ø All of the lymph vessels in the head and neck drain into the deep cervical lymph nodes Ø The efferent vessels of the deep cervical nodes drain into the jugular trunk that ultimately lead into the venous system at the junction of the internal jugular and subclavian veins. ANATOMY 31 Questions? Email: [email protected] ANATOMY 32