Trachea (Cervical Part)

• The trachea is a noncollapsible, wide tube forming the beginning of the lower respiratory passages. 
• It is kept patent because of the presence of C-shaped cartilaginous ‘rings' in its wall. 
• The cartilages are deficient posteriorly, this part of the wall being made up of muscle (trachealis) and fibrous tissue. 
• The soft posterior wall allows expansion of the oesophagus during passage of food.

DIMENSIONS

• The trachea is about 10 to 15 cm long. 
• Its upper half lies in the neck and its lower half in the superior mediastinum. 
• The external diameter measures 2 cm in the male and 1.5 cm in the female.
• The lumen is smaller in the living than in cadavers. 
• It is about 3 mm at l year of age, and corresponds to the age in years during childhood, with a maximum of 12 mm at puberty.

CERVICAL PART OF TRACHEA

1. The trachea begins at the lower border of the cricoid cartilage opposite the lower border of vertebra C6.

It runs downwards and slightly backwards in front of the oesophagus, follows the curvature of the spine,

and enters the thorax in the median plane.

2. In the neck, the trachea is comparatively superficial and has the following relations.

Anterior

1. Isthmus of the thyroid gland covering the second and third tracheal rings.

2. Inferior thyroid veins below the isthmus.

3. Pretracheal fascia enclosing the thyroid and the inferior thyroid veins.

4. Sternohyoid and sternothyroid muscles.

5. Investing layer of the deep cervical fascia and the suprasternal space.

6. The skin and superficial fascia.

7. In children, the left brachiocephalic vein extends into the neck and, then, lies in front of the trachea.

Posterior

1. Oesophagus

2. Longus colli

3. Recurrent laryrngeal nerve in the tracheo-oesophageal groove.

On Each Side

1 The corresponding lobe of the thyroid glands.

2 The common carotid artery within the carotid sheath

• The trachea is supplied by branches from the inferior thyroid arteries. 
• Its veins drain into the left brachiocephalic vein. 
• Lymphatics drain into the pretracheal and paratracheal nodes.
• Parasympathetic nerves (from the vagus through the recurrent laryngeal nerve) are sensory and secretomotor to the mucous membrane, and motor to the trachealis muscle. 
• Sympathetic nerves (from the cervical ganglion) are vasomotor.

Clinical Anatomy

• The trachea may be compressed by pathological enlargements of the thyroid, the thymus, lymph nodes and the aortic arch. This causes dyspnoea, irritative cough, and often a husky voice.
• Tracheostomy is an emergency operation done in cases of laryngeal obstruction (foreign body, diphtheria, carcinoma, etc.). 
• It is commonly done in the retrothyroid region after retracting the isthmus of the thyroid gland.

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Trachea | Extent | Dimensions | Structure | Relations | Clinical Anatomy