GMS 6605 - Neck - Part 2 PDF

Neck – Part 2 Course: GMS 6605 Instructor: Panida Webb, Ph.D. 1. Neck - deep - Prevertebral muscles - Root of neck 2. Viscera of neck - Endocrine layer - Respiratory layer - Alimentary layer The Deep structures of the neck The preverte...

Neck – Part 2 Course: GMS 6605 Instructor: Panida Webb, Ph.D. 1. Neck - deep - Prevertebral muscles - Root of neck 2. Viscera of neck - Endocrine layer - Respiratory layer - Alimentary layer The Deep structures of the neck The prevertebral muscles - a group of deep neck muscles situated anterior to the cervical vertebrae The root of the neck - the anatomical region where the neck transitions into the thorax, containing major blood vessels like the subclavian artery and brachiocephalic trunk, all enveloped by deep cervical fascia layers. Many muscles are located in the deep structures of the neck Prevertebral muscles run in front of the cervical vertebrae, and they contract generally to flex the neck and bow the head The anterior prevertebral muscles: Longus capitis: superior to colli attaches to occipital bone innervated by c1-3, flexes head Longus colli: runs anterior to the vertebrae from c5 to c1 innervated by c2-6 , flexes and rotates neck Rectus capitis anterior: Run from atlas to occipital bone innervated by c1-2, flex head Anterior scalene: from transverse process c3-6 to first rib innervated by c4-6, flex neck and head The lateral prevertebral muscles: run more along the sides of the neck Work to laterally flex the neck (tilt your head to one side): Splenius capitis: Originates on the spinous C7-T3. It inserts onto the mastoid process of the temporal bone Rectus capitis lateralis: Run from atlas to occipital bone innervated by c1-2, flex head Middle scalene: c5-7 post tubercles and inserts onto the 1st rib, flex neck and head; raise ribs Posterior scalene: originates adjacent to middle scalene and attaches to second rib, flex neck and head; raise ribs The Root of the neck (the thoracic inlet) The junctional area between the thorax and neck Boundaries: Laterally – 1st pair of ribs and their costal cartilages Anteriorly - manubrium of the sternum Posteriorly - body of the T1 Contents: the brachiocephalic trunk, common carotid arteries, and the subclavian arteries the external and anterior jugular veins and the subclavian vein the vagus nerve, phrenic nerves and the sympathetic trunks  The phrenic nerve runs across the anterior scalene after exiting between the anterior and middle. Also exiting between these scalenes are the roots of the brachial plexus, c5-t1 The brachiocephalic and subclavian veins run anterior to the ant. Scalene The subclavian arteries run between the anterior and middle scalene Arteries in root of neck: Brachiocephalic artery Common carotid arteries Subclavian arteries (first & second parts) Branches of the first part: Vertebral Thyrocervical trunk (& its branches) Internal thoracic Branch of the second part: Costocervical trunk (& its branches) Veins in the root of neck : The external jugular vein  drains blood from the scalp and face The anterior jugular vein  drains blood from the anterior aspect of the neck The anterior jugular vein descends into the root of the neck where it drains into the external jugular vein or the subclavian vein The subclavian vein is a continuation of the axillary vein passes over the first rib anterior to the scalene only one tributary = the external jugular vein, and ends when it joins with the internal jugular vein to form the brachiocephalic vein Nerves: Vagus (longest cranial nerve) descends in the carotid sheath with the common carotid and the internal jugular vein and give rise to the recurrent laryngeal n. The right recurrent loops inferior to the right subclavian while the left loops inferior to the aortic arch. The right passes under the artery at the T1-2 level while the left is lower at T4-5 ( remember the embryological reason for this?) Phrenic - originates from the C3, C4, and C5 nerve roots in the cervical plexus. It descends vertically in the neck, crossing the anterior scalene muscle from lateral to medial. Sympathetic trunk consist of the superior (level C1-2), middle (level C6) and inferior cervical ganglia (level C8). 1. Neck - deep - Prevertebral muscles - Root of neck 2. Viscera of neck - Endocrine layer - Respiratory layer - Alimentary layer Cervical viscera are organized in three layers (superficial to deep): Endocrine layer Thyroid Parathyroids Respiratory layer Larynx Trachea Alimentary (digestive) layer Pharynx Esophagus Endocrine layer Thyroid Thyroid hormone  controls rate of metabolism Calcitonin  controls calcium metabolism Parathyroids Parathyroid hormone (PTH)  controls the metabolism of phosphorus and calcium in the blood Thyroid gland Located in the anterior neck (C5-T1) Consists of two lobes (left and right)  connected by a central isthmus anteriorly – this produces a butterfly-shape appearance In the visceral compartment of the neck (along with the trachea, oesophagus and pharynx). This compartment is bound by the pretracheal fascia Arterial Supply: Superior thyroid artery Arises as the first branch of the external carotid artery Inferior thyroid artery Arises from the thyrocervical trunk (a branch of the subclavian artery) In a small proportion of people (around 10%) – the thyroid ima artery  arises from the brachiocephalic trunk and supplies the anterior surface and isthmus of the thyroid gland Venous Drainage: The superior and middle veins drain into the internal jugular vein The inferior empties into the brachiocephalic vein Innervation: The thyroid gland is innervated by branches derived from the sympathetic trunk Parasympathetic – from vagus nerve These nerves do not control the secretory function of the gland – the release of thyroid hormones is regulated by the pituitary gland The most anterior structure is the thyroid gland which lies anterior and lateral to the trachea. Posterior to the thyroid and imbedded in the gland are the Parathyroid gland The parathyroids are variable in their location  may be anywhere from superior to the hyoid bone all the way to the aortic arch. Typically, the are located posterior to the thyroid as indicted in this drawing The vascular supply is similar to that of the thyroid gland Most individuals have four parathyroid glands, although variation in number (from two to six) is common: Superior parathyroid glands (x2) Inferior parathyroid glands (x2)  Respiratory layer Larynx Trachea The main functions of the respiratory viscera are: Routing air and food into the respiratory tract and esophagus, respectively Providing a patent airway and an active valve for it, enabling it to be sealed off temporarily Producing tone for the mouth (tongue, teeth, and lips) to modify into voice The larynx Located in the anterior compartment of the neck, suspended from the hyoid bone, and spanning between C3 and C6 Continuous inferiorly with the trachea, and opens superiorly into the laryngeal part of the pharynx Covered anteriorly by the infrahyoid muscles, and laterally by the lobes of the thyroid gland Posterior to the larynx is the esophagus. This is of clinical relevance during emergency intubation – as pressure can be applied to the cricoid cartilage of the larynx to occlude the esophagus, and thus prevent regurgitation of gastric contents (known as cricoid pressure or Sellick’s maneuver) Functions: protect the lower respiratory tract from aspirating food into the trachea while breathing. It also contains the vocal cords and functions as a voice box for producing sounds, i.e., phonation The larynx consists of: A cartilaginous skeleton Membranes and ligaments Intrinsic and extrinsic muscles Mucosal lining The laryngeal skeleton consists of nine cartilages joined by ligaments and membranes Three cartilages are single - thyroid, cricoid, and epiglottic Three are paired - arytenoid, corniculate, and cuneiform The vocal folds are attached anteriorly to the laryngeal cartilage and posterior to the arytenoids Larynx Ligaments: Support the cartilaginous skeleton of the larynx, while the folds are involved in airway protection and phonation 1. Extrinsic ligaments - attach the larynx to other structures such as the hyoid or the trachea The thyrohyoid membrane, hyoepiglottic and cricotracheal ligaments 2. Intrinsic ligaments - connect the larynx cartilages Extrinsic ligaments Laryngeal Folds: There are two important soft tissue folds located within the larynx – the vestibular folds and vocal folds. They play a crucial role in protection of the airway, breathing, and phonation Vocal Folds The vocal folds (true vocal cords)  Under the control of the muscles of phonation, they are abducted, adducted, relaxed and tensed to control the pitch of the sound created Each fold contains: Vocal ligament Vocalis muscle Because vocalis inserts on the vocal ligament, it can relax very specific segments of the vocal ligament to adjust the pitch The vocal folds are relatively avascular, and appear white in color. The space between the vocal folds is known as the rima glottidis Vestibular Folds The vestibular folds (false vocal cords) lie superiorly to the true vocal cords. They consist of the vestibular ligament covered by a mucous membrane, and are pink in color. They are fixed folds, which act to provide protection to the larynx The glottis (vocal apparatus of the larynx) makes up the vocal folds and processes, together with the rima glottidis The shape of the rima (L. slit) varies according to the position of the vocal folds Note: The folds vibrate when they are closed to obstruct the airflow through the glottis: they are forced open by increased air pressure in the lungs, and closed again as the air rushes past the folds, lowering the pressure (Bernoulli's principle) Variation in the tension and length of the vocal folds, in the width of the rima glottidis, and in the intensity of the expiratory effort produces changes in the pitch of the voice  The lower range of pitch of the voice of post pubertal males results from the increased laryngeal prominence resulting in greater (aka. Recurrent laryngeal nerve) MUSCLES OF LARYNX: The laryngeal muscles are divided into: The extrinsic laryngeal muscles move the entire larynx. The infrahyoid muscles are depressors of the hyoid bone and larynx, whereas the suprahyoid and stylopharyngeus (muscle of the pharynx) muscles are elevators of the hyoid and larynx The intrinsic laryngeal muscles move the laryngeal parts, making alterations in the length and tension of the vocal folds and the size and shape of the rima glottidis Cricothyroid, thyroarytenoid, posterior cricoarytenoid, lateral cricoarytenoid, transverse and oblique arytenoids All, except the cricothyroid - innervated by the inferior laryngeal nerve – the terminal branch of the recurrent laryngeal nerve  a branch of the vagus nerve The cricothyroid is innervated by the external branch of the superior laryngeal nerve  derived from the vagus nerve Muscles that affect the arytenoids and cricoid cartilages alter the length and tension on the vocal folds. These muscles include: Lateral cricoarytenoids (adductors) and transverse oblique arytenoids (approximators)  bring the vocal folds together for phonation ? The muscle most responsible for the abduction of the vocal folds is the : A. Arytenoid B. Cricothyroid C. Lateral cricoarytenoid D. Posterior cricoarytenoid E. Thyroarytenoid  Widen s openin g Narrows opening Shorten and Helps close opening Narrow Vasculature: Arterial supply - the superior and inferior laryngeal arteries: Superior laryngeal artery – a branch of the superior thyroid artery (derived from the external carotid). It follows the internal branch of the superior laryngeal nerve into the larynx Inferior laryngeal artery – a branch of the inferior thyroid artery (derived from the thyrocervical trunk). It follows the recurrent laryngeal nerve into the larynx Venous drainage - the superior and inferior laryngeal veins The superior laryngeal vein drains to the internal jugular vein via the superior thyroid The inferior laryngeal vein drains to the left brachiocephalic vein via the inferior thyroid vein Innervation: The larynx receives both motor and sensory innervation via branches of the vagus nerve: Recurrent (inferior) laryngeal nerve – provides sensory innervation to the infraglottis, and motor innervation to all the internal muscles of larynx (except the cricothyroid) Superior laryngeal nerve – the internal branch provides sensory innervation to the supraglottis, and the external branch provides motor innervation to the cricothyroid muscle The Trachea Extending from the inferior end of the larynx into the thorax Terminates at the sternal angle  divides into the right and left main bronchi 2.5 cm in diameter in adults, diameter of a pencil in infants A fibrocartilaginous tube, supported by incomplete cartilaginous tracheal rings  The rings keep the trachea patent Lateral to the trachea are the common carotid arteries and lobes of thyroid gland Alimentary (digestive) layer Pharynx Esophagus Although the pharynx conducts air to the larynx, trachea, and lungs, its constrictor muscles direct (and the epiglottis deflects) food to the esophagus The esophagus - involved in food propulsion  the beginning of the alimentary canal (digestive tract) The pharynx - a muscular tube that connects the oral and nasal cavity to the larynx and esophagus Begins at the base of the skull Ends at the inferior border of the cricoid cartilage (C6) Note: It starts at the nose and continuous as the esophagus Comprised of three parts (superior to inferior): Nasopharynx – posterior to the nose, superior to the soft palate Oropharynx – posterior to the mouth Laryngopharynx – posterior to the larynx Nasopharynx: Located between the base of the skull and the soft palate It is continuous with the nasal cavity, and performs a respiratory function by conditioning inspired air and propagating it into the larynx Lined with respiratory epithelium The posterosuperior nasopharynx contains the pharyngeal tonsils (adenoid tonsils)  enlarge between 3-8 years of age and then regress Oropharynx: The middle part of the pharynx, between the soft palate and the superior border of the epiglottis Has a digestive function Involved in the voluntary and involuntary phases of swallowing Contains: Posterior 1/3 of the tongue Lingual tonsils – lymphoid tissue at the base of the tongue Palatine tonsils – lymphoid tissue located in the tonsillar fossa (between the palatoglossal and palatopharyngeal arches of the oral cavity) Superior constrictor muscle Laryngopharynx (hypopharynx): The most distal part of the pharynx Located between the superior border of the epiglottis and inferior border of the cricoid cartilage (C6) It is continuous inferiorly with the esophagus Found posterior to the larynx and communicates with it via the laryngeal inlet, lateral to which one can find the piriform fossae (Branches of the internal laryngeal and recurrent laryngeal nerves lie deep to the mucous membrane of the piriform fossa) Contains the middle and inferior pharyngeal constrictors Pharyngeal muscles Innervated by the vagus nerve –except the stylopharyngeus (glossopharyngeal nerve) 1. External layer – 3 pharyngeal constrictor muscles: Contract sequentially from superior to inferior to constrict the lumen and propel food into esophagus Superior pharyngeal constrictor – the uppermost pharyngeal constrictor  located in the oropharynx Middle pharyngeal constrictor – located in the laryngopharynx Inferior pharyngeal constrictor – located in the laryngopharynx. All pharyngeal constrictors are innervated by the vagus nerve (CN Posterior view of pharyngeal constrictors superior, middle and inferior X) Pharyngeal Constrictors 2. Internal layer The stylopharyngeus, palatopharyngeus and salpingopharyngeus Act to shorten and widen the pharynx, and elevate the larynx during swallowing Stylopharyngeus – arises from the styloid process of the temporal bone, inserts into the pharynx Innervated by the glossopharyngeal nerve (CN IX) Palatopharyngeus – arises from hard palate of the oral cavity, inserts into the pharynx Salpingopharyngeus – arises from the Eustachian tube, inserts into the pharynx In addition to contributing to swallowing, it also opens the Eustachian tube to equalize the pressure in the middle ear Styloglossus and Stylopharyngeus Pharynx vasculature: Arterial supply - branches of the external carotid artery: Venous drainage - the pharyngeal venous plexus  drains into the internal jugular vein ESOPHAGUS A muscular tube  extends from the laryngopharynx to the stomach Consists of striated (voluntary) muscle in its upper third, smooth (involuntary) muscle in its lower third, and a mixture of striated and smooth muscle in between The thoracic duct adheres to the left side of the esophagus and lies between the pleura and the esophagus Esophagus can be divided into 3 segments: cervical, thoracic, and abdominal