Anatomy for Tracheostomy
*** This page is under construction
To perfrom a tracheostomy, knowledge of the following is required:
- surface anatomy
- course of the trachea
- structure of the tracheal rings
- layers of dissection
- components of the larynx
- related structures (e.g. nerves, vessels and organs)
- hyoid bone (C3)
- thyroid cartilage
- cricothyroid membrane (ligament)
- cricoid cartilage (C6)
- thyroid gland
- sternohyoid muscle just lateral to the midline structures, overlies sternothyroid and thyrohyoid)
- Pathway of the trachea from anterior at the cricoid cartilage (C6)
- to more posterior as it enters the chest behind the sternal notch
- trachea is 10 cm long, stretches to 15cm on inspiration (fibroelastic structure)
- C shaped cartilages (first cartilage is bigger than the others in the cervical trachea)
- joined vertically by fibroelastic tissue
- connected posteriorly by the trachealis muscle
LAYERS OF DISSECTION FOR TRACHEOSTOMY
- subcutaneous tissue
- pretracheal fascia (superficial and deep)
- valve separating the trachea from the upper aerodigestive tract
- allows vocalisation
- necessary for an effective cough or valsalva manoeuvre
- prevents aspiration during swallowing
- Hyoid bone – attachment to epiglottis and strap muscles
- Thyroid cartilage – anterior attachment of vocal folds; posterior articulation with cricoid cartilage
- Cricoid cartilage – complete signet-shaped ring; articulates with thyroid and arytenoid cartilages
- Arytenoids – two cartilages which glide along the posterior cricoid and attach to posterior ends of vocal folds.
Larynx — Cartilages (videos from Anatomy Zone)
Larynx and vocal cords — mucosa
Larynx – muscles (see more here)
- Supraglottis – usually covered with respiratory epithelium containing mucous glands
- Epiglottis – leaf-shaped mucosal-covered cartilage, which projects over larynx
- Aryepiglottic folds – extend from the lateral epiglottis to the arytenoids
- False vocal cords – mucosal folds superior to the true glottis. Separated from true vocal folds by the ventricle
- Ventricle – mucosal-lined sac, variable in size, which separates the supraglottis from the glottis
- Glottis – the true vocal folds attach to the thyroid cartilage at the anterior commissure. The posterior commissure is mobile, as the vocal folds attach to the arytenoids. Motion of the arytenoids affects abduction or adduction of the larynx. The bulk of the vocal fold is made up of muscle covered by mucosa. The free edge is characterised by stratified squamous epithelium. The vocal folds abduct for inspiration and adduct for phonation, cough and valsalva.
- Subglottis – below the vocal folds, extending to the inferior border of the cricoid cartilage.
Branches of the vagus nerve.
- Superior laryngeal nerve — sensation of the glottis and supraglottis — Motor fibres to the cricothyroid muscle, which tenses the vocal folds — This nerve leaves the vagus high in the neck
- Recurrent laryngeal nerve — sensation of the subglottis — motor fibres to intrinsic muscles of the larynx — This nerve branches from the vagus in the mediastinum, then turns back up into the neck — On the right, it travels inferior to the subclavian artery, and on the left, the aorta
- anterior jugular veins run vertically close to midline
- inferior thyroid vessels and variant thryoidea ima artery run over lower trachea
- other vessels more lateral: internal jugular, carotid, external jugular
- lobes extend to 6th tracheal ring
- isthmus overlies rings 2,3,4
- variant pyramidal lobe may extend over cricothyroid membrane
References and Links
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.
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