Trachea

To understand what is trachea, let us go through the following information. The human trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, enabling air to move through. It is found in almost all air-breathing species. From the larynx, the trachea divides into two main bronchi. 

The cricoid cartilage binds the trachea to the larynx at the tip. The trachea is made up of a series of horseshoe-shaped rings that are bound vertically by overlying ligaments as well as at their edges by the trachealis muscle. While swallowing, the epiglottis seals the gap to the larynx.

In the 2nd cycle of embryo growth, the trachea starts to form, getting bigger and therefore more defined in its place over time. Column-shaped cells containing hair-like projections called cilia line the epithelium, which is surrounded by goblet cells that contain protective mucins.

Inflammation or infection of the trachea may happen as a consequence of a viral illness impacting other areas of the respiratory tract, including the larynx and bronchi, known as croup, which can cause a barking cough. A bacterial infection affects mainly the trachea, causing narrowing or obstruction.

Since the human trachea is such a vital part of the respiratory system, it may become blocked and restrict oxygen from accessing the lungs, necessitating a tracheostomy. In contrast, if mechanical ventilation is needed while a patient is medicated, a tube called intubation is introduced into the respiratory system trachea.

Trachea Structure

When you learn about the structure of the trachea, it becomes easier to understand what is trachea. The trachea structure or trachea anatomy shows that an adult is 1.5 to 2 centimeters (0.59 to 0.79 in) in diameter and 10 to 11 centimeters (3.9 to 4.3 in) in length, with males having a broader trachea than females. It starts at the base of the larynx and finishes at the carina, in which the trachea divides further into left and right key bronchi.

The trachea in human body is enclosed by 16 to 20 hyaline cartilage rings that are 4mm long, unfinished, and C-shaped in adults. Ligaments link the circles together. The trachealis muscle passes across the back wall of the trachea, linking the ends of the incomplete loops. The trachea anatomy displays that the trachea starts at the bottom of the laryngeal cricoid cartilage and finishes at the carina, in which the trachea splits across the left and right major bronchi. The respiratory system trachea starts only at the sixth cervical vertebra (C6) and ends at the fourth thoracic vertebra (T4), however, its location might change during breathing.

Cilia in Trachea: 

A sticky mucous membrane layer lining the trachea is made up of cells with thin hairlike projections called cilia (Cilia in the trachea). To capture particles, the cilia expand into the trachea's channel (lumen). Mucus particles and molecules of water are secreted by cells and tubes in the mucous membrane.

Microanatomy

A surface of interspersed layers of column-shaped cells with cilia lines the trachea. Goblet cells, which seem to be column-shaped, glandular cells that are composed of mucins, the key part of mucus, are located in the epithelium. Mucus keeps the airways moist and secure.

Mucus surrounds the ciliated cells of the trachea, trapping inhaled foreign particles, which the cilia eventually waft upwards through the larynx, therefore the pharynx, where it could be swallowed or released as phlegm. Mucociliary clearance is the name given to this self-clearing process.

16-20 rings of hyaline cartilage cover the trachea; such 'rings' are unfinished and C-shaped. Two or maybe more cartilages frequently bind together, partially or entirely, and are occasionally differentiated at their extremities. The rings are usually very elastic, but as they age, they can calcify.

Clinical Significance

Inflammation and Infection: 

• Tracheitis is the swelling of the trachea, which is typically caused by an infection. Viruses are the most common cause, with bacterial infections appearing nearly exclusively in infants.

• Infections of the trachea are more often characterized by inflammation of several other parts of the respiratory tract, including the larynx and bronchi, which is recognized as croup. Nevertheless, bacterial infections can impact the trachea on their own, but they are more commonly affected by the latest viral infection.

• Croup is caused by parainfluenza viruses 1-3, with influenza viruses A and B often inducing croup but typically resulting in more severe infections. Bacteria such as Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, and Moraxella catarrhalis can also induce croup. Additional bacteria which can develop tracheitis in hospitalized patients include Klebsiella pneumoniae, Escherichia coli, and Pseudomonas aeruginosa.

Intubation:

• The introduction of a tube down the trachea is known as tracheal intubation. This technique is widely used throughout surgery to guarantee that a patient gets sufficient oxygen while sedated. The catheter is mounted to a system that controls oxygenation, airflow, and a number of other parameters. This is frequently one of an anesthetist’s duties during surgery.

• A tracheostomy is done to introduce a tube for breathing during an emergency and whenever tracheal intubation is considered impossible, typically when complex forms of surgery must be conducted and the airway must be held open. A tracheostomy is the provision of an opening by a tracheotomy.

Narrowing:

• A narrowed or squeezed trachea might happen as a consequence of enlarged nearby trachea, lymph nodes, or nearby structure tumours, large thyroid goiters, or, less frequently, certain mechanisms including excessively swollen blood vessels.

• A contraction of the trachea might be caused by bruising from intubation, or tracheobronchial injury, or inflammation involved with granulomatosis with polyangiitis (tracheal stenosis). 

• Stridor is a loud breathing sound that is invariably caused by obstruction. Bronchoscopy is a technique that involves inserting a camera through the mouth into another trachea that investigates the source of obstruction.

• The treatment of obstructions is determined by the cause. Surgery, chemotherapy, or radiotherapy can be used to treat obstructions caused by cancer. Over the barrier, a stent might be inserted. Benign lesions, including scarring-induced narrowing, are more prone to have been surgically removed.