Xvi: Tracheostomy Anatomy
Origin
- Superior: inferior end of larynx (cricoid cartilage and level of C6 vertebra)
- Inferior: tracheal bifurcation at plane of Ludwig (level of sternal angle and T4 vertebrae)
- Terminates by division into right & left mainstem bronchi
Course
- Runs at 15° parallel to surface of neck, such that distal trachea is deeper than proximal trachea (slants from anterior position beneath larynx to posterior position at carina)
- Tracheal length 10-13cm
- Tracheal width 1.5-2cm (wider in men than women)
- D-shaped cross section
- Anterior wall formed by 18-22 incomplete cartilaginous rings which maintain tracheal patency
- C shaped cartilages (first cartilage is bigger than others in cervical trachea)
- Joined vertically by fibro-elastic tissue
- Posterior wall of trachea spanned by longitudinal smooth muscle known as trachealis
- Anterior wall formed by 18-22 incomplete cartilaginous rings which maintain tracheal patency
- Divided into 2 parts
- Cervical: begins at inferior border of larynx (cricoid cartilage) located at level of C6 → level of jugular notch of sternum (upper border of superior mediastinum)
- Thoracic: begins from superior thoracic aperture → ends at tracheal bifurcation (level of sternal angle and T4/5)
Relationships (Cervical part)
Anterior
- Visceral cervical fascia
- Isthmus of thyroid: crosses trachea between 2nd – 4th tracheal cartilages
- Superior to isthmus: inferior thyroid arteries
- Inferior to isthmus: pretracheal fascia, inferior thyroid veins, thymus
- Pretracheal lymph nodes
Posterior
- Oesophagus
- Vertebral column (C6-T1)
Lateral
- Vessels: anterior jugular veins, common carotid artery and branches, inferior thyroid arteries and branches, inferior laryngeal arteries
- Thyroid: lobes of thyroid gland which extend inferiorly until the 6th tracheal cartilage
- Nerves: recurrent laryngeal nerve located slightly posteriorly compared to the rest
- Paratracheal cervical lymph nodes
- Muscles: sternohyoid, sternothyroid muscles
Relationships (Thoracic part)
Anterior
From superior → inferior
- Inferior thyroid veins, manubrium of sternum and attachments of sternohyoid and sternothyroid muscles
- Brachiocephalic trunk and left common carotid artery
- Aortic arch, left brachiocephalic vein, cardiac plexus and paratracheal thoracic lymph nodes
Posterior
- Oesophagus
- Vertebral column (T1-T4/5)
Lateral on right side
- Right vagus nerve
- Right brachiocephalic vein
- Superior vena cava
- Azygos vein
Lateral on left side
- Aortic arch
- Left recurrent laryngeal nerve
- Left common carotid artery
- Left subclavian artery
Blood Supply
- Arterial
- Proximal half: tracheal branches of inferior thyroid artery
- Distal half & carina: superior and middle bronchial arteries
- Venous: inferior thyroid venous plexus
Lymphatic Drainage
- Pretracheal nodes
- Paratracheal cervical and thoracic lymph nodes
Innervation
- Pulmonary plexus
- Recurrent laryngeal nerves
Histological Layers
- Mucosa: ciliated pseudostratified columnar epithelium
- Submucosa: consists of connective tissue that contains mucus glands, smooth muscle, vessels, nerves and lymphatics
- Musculo-cartilaginous layer: cartilaginous rings and intervening smooth muscle
- Fibroelastic adventitia
Surface Anatomy
Midline neck structure
- Laryngeal structures: hyoid (C3), thyroid cartilage, cricothyroid membrane, cricoid cartilage (C6)
- Sternal notch
- Thyroid lobes: lie lateral to trachea
Layers of Dissection
- Skin
- Subcutaneous fat
- Superficial & deep pretracheal fascia
- Tracheal wall: ideally between 1st & 2nd rings
Anatomical Variation
- Variant thyroid pyramidal lobe may extend over cricothyroid membrane
- High-riding innominate artery
- Median anterior jugular vein
Author: Novia Tan