Trachea

TRACHEA

Basic Information

Commonly known as the windpipe, the trachea is a narrow, 4 inch tube that connects the lungs to the heart. The trachea (windpipe) extends from the larynx (voice box) to the breastbone (sternum). There is one bronchus for each lung once the trachea has been divided into two smaller tubes.

There are approximately 20 rings of strong cartilage that make up the trachea. The trachea rings are approximately 2 to 2.5 cm in diameter and 0.4 to 0.5 cm wide. The rings are mucous membrane lining that provides continuity and flexibility. Muscle and connective tissue make up the rear portion of each ring. The trachea's inside is lined with a moist, smooth tissue known as mucosa. The trachea opens and closes with each breath, gradually reverting to its resting size when the exhalation occurs.

It is important to note that the trachea is not too rigid like a bone and not too flexible like a muscle. Its rigidity is permitted by the cartilage while its flexibility or freedom of movement is permitted by the muscle, particularly the trachealis muscle (the muscle in the trachea).

The tracheal carina is a ridge that runs along the base of the trachea (windpipe) and divides the primary bronchial apertures on each side of it (the large air passages that lead from the trachea to the lungs).

Structure

The esophagus expands anteriorly when we swallow a large piece of food, while the open parts of the rings abut the esophagus and keep it patent, or open, despite pressure changes that occur during breathing. The trachea is fairly rigid because its walls are reinforced with C-shaped rings of hyaline cartilage.

Length

Tracheal or windpipe air goes from the larynx to the fifth thoracic vertebra at roughly midchest, a distance of 10 to 12 cm (4 inches).

Cilia

Mucus filled with dust particles and other debris is pushed out of the lungs by beating ciliated mucosa that line the trachea and move it to the throat, where it can be eaten or spat out.

Bronchial Tree

The bronchial tree refers to the increasingly smaller tubes in the tracheal region. As one progresses into the depths of the lungs, the size of the tubes decreases. There are 14 generations in the left lung and 28 generations in the right lung. The total surface area of the generation is greater than the level before it.

Lobar Division

Anatomically, the human trachea (windpipe) is divided into two major bronchi (also known as mainstem bronchi) at the carina. The right main bronchus is shorter and broader than the left main bronchus. The right and left major bronchi split into three and two lobar bronchi, respectively.

These lobar bronchi are then further divided into segmentalinic bronchi or tertiary bronchi, which are all connected by the lobar bronchi. "The segmental bronchi divide into many primary bronchioles that divide into terminal bronchioles, each of which then gives rise to several respiratory bronchioles, which go on to divide into and terminate in tiny air sacs called alveoli" (Respiratory Zone | Boundless Anatomy and Physiology, 2019).

Initially, the primary bronchi has a mucous membrane that is lined by a ciliated cuboidal epithelium. However, this gradually becomes a simple cuboidal epithelium then simple squamous epithelium. The bronchi contribute to anatomical dead space since they are located in the conducting zone.

When the smooth muscles of the bronchi constrict due to various reasons, it becomes more difficult to breathe. This condition is known as bronchoconstriction.

REFERENCES:

Respiratory System Anatomy and Physiology. (2017, May 1). Nurseslabs. https://nurseslabs.com/respiratory-system/#trachea

Respiratory Zone | Boundless Anatomy and Physiology. (2019). Lumenlearning.com. https://courses.lumenlearning.com/boundless-ap/chapter/respiratory-zone/

IMAGE SOURCES:

https://www.lecturio.com/concepts/bronchial-tree/

http://www.pharmacy180.com/article/trachea-3657/

https://www.medicalnewstoday.com/articles/trachea

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