ANATOMY OF LARYNX

DEVELOPMENT OF LARYNXLarynx develops from the tracheobroncheal groove which is ventral midline respiratory diverticulum of the foregut.

Epiglottis and the Thyroid cartilage develop from the fourth branchial arch.

SITUATION OF LARYNX

Situated in midline of neck from the level of C-3 to C-6 vertebrae lying in front of laryngopharynx.

CONSTITUTION OF LARYNX

Formed by a cartilaginous skeleton held together by ligaments.

At puberty male larynx increases in size rapidly, and the thyroid cartilage projects to form the Adams apple.

CARTILAGES OF LARYNX

CARTILAGES OF LARYNX-EPIGLOTTISEpiglottis-leaf shaped fibro elastic cartilage and projects behind the base of the tongue.The narrow lower border is attached by the thyro-epiglottic ligament to the posterior surface of thyroid alae below thyroid notch.

CARTILAGES OF LARYNX-THYROID CARTILAGELargest cartilage of larynx with two wings or alae joined anteriorly in midline.

Two alae form a right angle between them in male while in female the angle is obtuse. the alae project backwards and have superior and inferior cornu.

CARTILAGES OF LARYNX- CRICOIDIt is signet ring shaped with a broad lamina posteriorly and narrow arch in front. cricoid, thyroid and epiglottis are unpaired cartilages of larynx where as arytenoid,corniculate and cuneiform cartilages are paired.

CARTILAGES OF LARYNX-ARYTENOIDShaped like a pyramidBase participates in crico-arytenoid joint.Anterior vocal process gives attachment to vocal cord.The lateral mescular process provides attachment to the posterior and lateral cricoarytenoid muscles

CARTILAGES OF LARYNX-CORNICULATE & CUNEIFORMCorniculate are situated at the apex of the arytenoids cartilages.

Cuneiform lie in the aryepiglottic folds, lateral to the Corniculate cartilages.

JOINTS AND LIGAMENTSTwo synovial joints on either side1) Cricothyroid joint2) crico-arytenoid jointIntrinsic ligaments1) Quadrangular membrane2) Conus elasticus3) thyro-epiglottic ligament

Extrinsic ligaments1)Thyrohyoid membrane2)Medial and lateral thyrohyoid ligament3)Cricothyroid membrane4)Cricotracheal membrane

MUSCLES OF LARYNX-INTRINSIC

INTRINSIC MUSCLES OF LARYNX AND THEIR ACTIONPosterior crico-arytenoid- AbductorLateral crico-arytenoid, inter arytenoid, thyro arytenoid, cricothyroid- AdductorsCricothyroid, vocalis and thyro-arytenoid- tensors and adductorsThyro-epiglottic-Opener of laryngeal inletInterarytenoid, aryepiglottic- Closers of laryngeal inlet

EXTRINSIC MUSCLESStrap muscles

Pharyngeal muscles including inferior constrictor muscle

CAVITY OF LARYNXEXTENT- from laryngeal inlet above to lower border of cricoid cartilage.

Inlet of larynx communicates with laryngopharynx.

CAVITY OF LARYNX

Divided into three parts by 2 folds of mucus membrane: False cords and True vocal cordsParts are Vestibule, ventricle and subglottic spaceLength of glottis is about 2.5cm in adult male and about 7-9mm in a child

HISTOLOGY OF LARYNX

Mucous membrane lines the entire larynx.Stratified squamous epithelium lines true vocal cords and upper parts of vestibule.Columnar ciliated epithelium lines rest of the cavity.Mucous glands preset in all parts except on free edges of vocal cords

BLOOD SUPPLY OF LARYNXSuperior thyroid artery

Inferior thyroid artery

Cricothyroid artery

NERVE SUPPLY OF LARYNXSuperior laryngeal nerve-internal branch is sensory supplies larynx above the level of vocal cords and external branch supplies cricothyroid muscle.Recurrent laryngeal nerve-motor branch supplies all muscles of larynx except the cricothyroid and sensory branch supplies subglottis.

LYMPHATIC DRAINAGE

SUPRAGLOTTIS-pre-epiglottic and upper deep cervical nodes.

GLOTTIS-Lymphatics are practically absent

SUBGLOTTIS-prelaryngeal and pretracheal nodes also lower deep cervical nodes

LARYNGEAL SPACES

PRE-EPIGLOTTIC SPACE

PARAGLOTTIC SPACE

REINKES SPACE