Regional Anatomy II Week 3 SU22 PDF

Week 3 Larynx and viscera Skeleton of the Larynx 3 large, unpaired cartilages 1. 2. 3. Thyroid Cricoid Epiglottis Thyroid Cartilage Composed of 2 quadrilateral laminae fused together in the anterior midline to form laryngeal prominence. Superior thyroid notch is a V-shaped notch located above...

Week 3 Larynx and viscera Skeleton of the Larynx 3 large, unpaired cartilages 1. 2. 3. Thyroid Cricoid Epiglottis Thyroid Cartilage Composed of 2 quadrilateral laminae fused together in the anterior midline to form laryngeal prominence. Superior thyroid notch is a V-shaped notch located above the laryngeal prominence. Thyroid Cartilage ● ● ● Posterior border of each lamina projects superior and inferior as superior and inferior horns Inferior horns articulate with cricoid cartilage Oblique line - ridge on lateral aspect of each lamina that gives attachment to sternothyroid, thyrohyoid, and inferior pharyngeal constrictor muscles Cricoid Cartilage ● ● ● Located inferior to thyroid cartilage Shaped like a signet ring; more narrow anterior (arch), wider posterior (lamina) There is a small articular facet on each side for the inferior horn of thyroid cartilage Cricoid Cartilage ● ● Superior border of lamina has a small articular facet on each side for the base of arytenoid cartilage Inferior border marks boundary between larynx and trachea Epiglottis ● ● Leaf-shaped plate of elastic cartilage that stands almost vertically posterior to root of tongue and hyoid bone Superior end is broad and free Epiglottis ● ● Inferior end is narrow (stalk) attached to angle formed by 2 laminae of thyroid cartilage by thyroepiglottic ligament Anterior surface is attached to body of hyoid by hyoepiglottic ligament Larynx Skeleton Paired cartilages 1. Arytenoid 2. Corniculate 3. Cuneiform Arytenoid Cartilage ● ● ● ● Shaped like a pyramid Located on superior border of cricoid lamina (one on each side) Base is directed inferior & articulates with lamina of cricoid Apex is directed superior & articulates with the corniculate cartilage Arytenoid Cartilage Two processes originate from base: ● ● Vocal process directed anterior and gives attachment to vocal ligament Muscular process directed laterally gives attachment to posterior and lateral cricoarytenoid muscles Corniculate Cartilage ● ● Small nodule of elastic cartilage that lies on apex of arytenoid cartilage Located in posteroinferior part of aryepiglottic fold, where forms a small elevation (corniculate tubercle) Joints of the Larynx Cricothyroid joint is a synovial joint between articular facets on lateral aspect of cricoid cartilage and on inferior horn of thyroid cartilage. The right and left cricothyroid joints working together allow thyroid cartilage to tilt forward and backward on cricoid cartilage (visor-like movement) Joints of the Larynx Cricoarytenoid joint is a synovial joint between articular facets on superior border of cricoid lamina and on base of arytenoid cartilage. It allows rotation of arytenoid around vertical axis and gliding of arytenoid Laryngeal Joints 1. Cricoarytenoid 2. Cricothyroid Membranes and Ligaments of the Larynx Thyrohyoid membrane suspends larynx from hyoid bone & connects body and greater horns of hyoid to upper border and superior horns of thyroid cartilage. It is pierced by internal laryngeal nerve and superior laryngeal vessels. Ligaments of the Larynx Hyoepiglottic and thyroepiglottic ligaments connect the epiglottis to hyoid bone and thyroid cartilage. Ligaments Vocal ligament extends from vocal process of arytenoid to internal aspect of angle between laminae of thyroid cartilage. Ligaments Conus elasticus (cricovocal membrane) is an elastic membrane that extends from the vocal ligaments (superiorly) to arch of cricoid cartilage (inferiorly) Larynx Key Points Responsible for: ● ● ● Sound production Breathing Protection of trachea from aspiration Located C3 - C6 in an adult Begins at the epiglottis and ends at the cricoid cartilage Has a skeleton made up of 3 paired and unpaired cartilages Controlled by intrinsic and extrinsic muscles Muscles and general sensation to the laryngeal inlet are innervated by branches of the vagus except for the cricothyroid muscle and general sensation to the laryngeal inlet Larynx: Internal Features Three parts/regions: 1. 2. 3. Laryngeal inlet or supraglottal Glottus Infraglottal Laryngeal Inlet ● ● ● Communication between laryngopharynx and larynx Obliquely placed plane of inlet passes posteriorly and inferiorly from epiglottis to arytenoid cartilages Boundaries: ○ ○ ○ Anterior and superior - superior border of epiglottis Lateral - aryepiglottic folds (contain corniculate and cuneiform cartilages in their lower part) Posterior and inferior - interarytenoid notch (fold) Interior Larynx Laryngeal inlet: ● ● Communicates with the laryngopharynx Obliquely the inlet passes from epiglottis to arytenoid cartilages Covered by respiratory epithelium and innervated by superior laryngeal nerve. Interior of Larynx Glottis ● ● ● 2 mucosal folds on each side project into laryngeal lumen: vestibular fold (superior) and vocal fold (inferior) Vestibular fold is also known as false vocal cord and contains no muscle; assists with resonance with the voice Vocal fold is also known as the true vocal cord and is covered by stratified squamous epithelium and is innervated by the vagus nerve Interior of Larynx Vocal fold is a prominent, wedge-shaped mucosal fold that contains vocal ligament close to its free margin Interior of Larynx Glottis is a part of larynx most directly concerned with production of sounds and consists of two vocal folds and space between them (rima glottidis) Vocal fold movement Vocal fold paralysis Interior of Larynx Infraglottic part of extends from vocal folds (superiorly) to inferior border of cricoid cartilage (inferiorly) Clinical Considerations Vocal cord polyp Laryngitis 1. 2. 3. 4. 5. Infections Gastroesophageal reflux Allergies Smoking or other inhaled irritants Voice overuse or abuse Foreign body trauma Extrinsic Laryngeal Muscles Support the position of the larynx 1. Suprahyoid - elevates the larynx 2. Infrahyoid - depresses the larynx 3. Pharyngeal constrictors Intrinsic Laryngeal Muscles 1. 2. 3. 4. 5. 6. Cricothyroid Posterior cricoarytenoid Lateral cricoarytenoid Transverse arytenoid Thyroarytenoid Vocalis Muscles of the larynx allow movement of the vocal ligaments for phonation and respiration. Posterior cricoarytenoid originates from cricoid lamina and inserts into the muscular process of the arytenoid, becoming an abductor and external rotator of the vocal folds. Muscles of Larynx Transverse arytenoid is an unpaired muscle that attaches to the posterior surface of both arytenoid cartilages and acts to pull the arytenoid cartilages medially, becoming an adductor of the vocal folds. Muscles of Larynx Thyroarytenoid originates from inner aspect of thyroid lamina (close to anterior midline) & inserts into arytenoid & draws arytenoid cartilage forward relaxing the vocal fold (decreases its tension) thereby lowering the pitch of the voice. The internal portion (vocalis muscle) is responsible for vibration of the cords or phonation. Muscles of Larynx Vocalis muscle is formed by most medial fibers of thyroarytenoid. It is responsible for controlling pitch by making minute adjustments of the vocal ligament, selectively tensing and relaxing different parts of it. Innervation of Larynx Motor nerve supply: ● ● External laryngeal nerve (branch of superior laryngeal nerve) supplies cricothyroid All other muscles are supplied by the recurrent laryngeal nerve Innervation of Larynx Sensory nerve supply: ● ● Internal laryngeal nerve (branch of superior laryngeal nerve) pierces thyrohyoid membrane to supply laryngeal mucosa from inlet to vocal folds Recurrent laryngeal nerve supplies laryngeal mucosa below vocal folds Vasculature of Larynx Superior laryngeal artery ● Branch of superior thyroid artery that accompanies internal laryngeal nerve Inferior laryngeal artery ● Branch of inferior thyroid artery that accompanies recurrent laryngeal nerve Veins of Larynx Veins include superior and inferior laryngeal veins. They join the superior and inferior thyroid veins. ● ● Superior thyroid vein drains into IJV Inferior thyroid veins drains into brachiocephalic vein Viscera of the Neck Thyroid gland ● ● Endocrine gland that secretes thyroxine (T4) and triiodothyronine (T3), which stimulate metabolic rate . It also secretes calcitonin, which lowers blood calcium levels 2 types of cells: ○ ○ ● Follicular cells C cells Surrounded by a connective tissue sheath, derived from pretracheal layer of deep cervical fascia, which attaches the gland to the trachea and larynx. The gland will move up and down with swallowing Viscera of the Neck ● ● ● ● Two lobes, an isthmus, and a pyramidal lobe (not always present) Lobes are roughly the pear-shaped, with the apex directed upward and reaching the oblique line of the thyroid cartilage, and the base directed downward and reaching the 4th or 5th cartilages Isthmus extends across midline, anterior to 2nd and 3rd tracheal cartilages Pyramidal lobe projects upward from isthmus and represents the distal part of the thyroglossal duct Thyroid Gland Anatomical relations of the lobes: ● ● ● ● Anterolateral - sternothyroid (covers gland directly), sternohyoid, anterior border of SCM Posterolateral - carotid sheath and its contents Medial - larynx, trachea, pharynx, esophagus, external laryngeal nerve, recurrent laryngeal nerve Posterior - parathyroid glands Thyroid Gland ● ● Originates from endoderm of floor of pharynx (in the region where the tongue develops). It migrates inferiorly to assume its final position in the neck. Its point of origin is indicated on the dorsal surface of the tongue by foramen cecum During its migration, the thyroid gland remains connected to the tongue by a narrow canal. This thyroglossal duct later disappears Thyroid Gland Blood supply ● ● ● Superior thyroid artery - from the external carotid artery Inferior thyroid artery - from the thyrocervical trunk Thyroid ima (lowest) artery ○ Present in ~10% of people Thyroid Gland ● ● Superior and middle thyroid veins drain into the internal jugular vein Inferior thyroid veins descend anterior to the trachea and posterior to the manubrium to drain into the corresponding brachiocephalic vein. Sometimes the right and left inferior thyroid veins join to form a single trunk, which drains into the left brachiocephalic vein Parathyroid Glands ● ● ● ● ● ● ● 2 superior and 2 inferior Flattened, oval bodies located on the posterior aspect of the lobes of the thyroid gland, under the fascial sheath Superior glands lie approximately at the level of lower border of cricoid cartilage Inferior glands lie near inferior pole of lobes of the thyroid gland, making their position less constant. They can sometimes be found below the level of the thyroid gland, into the superior mediastinum and near the thymus. Secrete parathormone (parathyroid hormone), which increases blood calcium levels Arterial supply - superior and inferior thyroid arteries Veins - parathyroid veins drain into thyroid venous plexus Clinical Considerations Thyroid cancer: ● ● Most common in women over 30 Thyroid cells are unique and are the only cells that have the ability to absorb iodine ○ ● Why is iodine important in the thyroid? 5 main types: ○ ○ ○ ○ Papillary Follicular ■ Hurthle cell cancer Medullary Anaplastic Clinical Considerations Thyroid cancer: ● ● Papillary - develops from follicular cells, grows slowly. Most common type, usually found in one lobe. Differentiated. Can often spread to lymph nodes. Follicular - develops from follicular cells, grows slowly. Differentiated. Less common that papillary and rarely spreads to lymph nodes. ○ ● ● Hurthle cell carcinoma - more likely to spread to lymph nodes than other follicular thyroid cancers Medullary - develops in C cells and is sometimes the result of multiple endocrine neoplasia type 2 (MEN2). Anapalstic - develops from follicular cells. Rare, fast growing, poorly differentiated.