Trachea
Definition
A continuation of larynx down.
Extent
From larynx upto the level of T5 where it divides into two major bronchi right and left
The junction called Carina
10 cm
Situation
In the thoracic cavity
In front of the oesophagus
Median plane
Structures associated with trachea
Superiorly : larynx
Inferiorly : right and left major bronchi (Carina)
Anteriorly : isthmus of the thyroid gland
arch of aorta
sternum
Posteriorly : oesophagus separating the trachea from the thoracic vertebrae
Laterally : lobes of the thyroid
lungs
Structure
16 - 20 incomplete rings of hyaline cartilages ( C shaped)
Cartilages one above the other
Incomplete posteriorly
Connective tissue and involuntary muscles join the ends of the C
Three layers of tissues :
1. Outer : fibrous and elastic tissue
2. middle : cartilages and bands of smooth muscle and areolar tissue with blood vessels, lymph vessels and autonomic nerves
3. inner : ciliated columnar epithelium containing mucus secreting goblet cells
Blood and nerve supply, lymph drainage
Arterial Blood Supply : inferior thyroid arteries
bronchial arteries
venous return : by the inferior thyroid veins to the brachiocephalic vein
Nerve supply : recurrent laryngeal nerves
vagus nerves
sympathetic ganglia
Functions
Support and patency
Hose pipe like arrangement of cartilages prevents kinking when the neck is flexed
Posteriorly incomplete ring : allows for dilatation of the air passage
allows the oesophagus to expand when the food passes
Mucociliary escalator
Ciliary movement sends the mucus and adherent particles upwards to be coughed out or swallowed
Cough reflex
Nerve endings in the larynx, trachea, and bronchi sensitive to irritation; cause cough reflex and protect from collection of mucus and foreign bodies
Humidification
Warms up, humidifies and filters the air
