Trachea or Wind Pipe
Trachea is cartilaginous tube passage way of air. It also known as windpipe. Trachea is hollow long tube that connects larynx (voice box) to bronchi of lungs.
Size and Location of Trachea
Trachea size - 5 inches in length
Diameter of Trachea - 2 cm
Trachea width wider in male than in female.
Extending from lower part of Larynx at level of 6th cervical vertebra, where it divided into -
1. Right primary bronchi
2. Left secondary bronchi
Trachea providing air flow to and from the lungs for respiration.
Structure of Trachea
Trachea and extrapulmonary (right and left) bronchi composed of -
1. Hyaline cartilage
2. Fibrous tissue
3. Muscular fibers
4. Mucus membrane and
5. Glands
Inner surface of trachea is lined by mucus membrane, which is itself covered with cillia.
Layer of Trachea
From deep to superficial, layer of trachea as following-
1. Mucosa (inner)
2. Submucosa
3. Hyaline cartilage
4. Adventitia (outer)
1. Mucous Layer
Mucous membrane is continuous above with larynx and below with bronchi.
Consist of pseudostratified ciliated columnar epithelium.
Underlying layer of lamina propria contains elastic and reticular fibers.
2. Submucosa Layer
Submucosa layer is composed of loose meshwork of areolar connective tissue.
This layer containing large blood vessels, nerves and mucus gland.
3. Hyaline Cartilage
Hyaline cartilage consist of cartilages and bands of smooth muscle that wind around the trachea in helical arrangement.
First cartilage is broader than the rest, it is the connected by cricotracheal ligament with the lower border of the cricoid cartlage.
Last cartilage thick and broad in the middle.
Ridge(top)of cartilage in the trachea that occurs between the division of two main bronchi, is Carina (last tracheal cartilage, curve downward and backward between two bronchi).
It separates the openings of the right and left main bronchi -
1. Right primary bronchi
2. Left primary bronchi
Trachealis Muscles
Thick band of smooth muscles fibers, that bridge the end of each cartilages ring that help to stabilized the entire length of windpipe.
The gap in each ring is bridged by a conbination of elastic connective tissue and smooth muscle, terms trachealis muscles.
Primary function of trachealis muscle is to constrict the trachea, allowing air to be expelled with more force. Example, during coughing
4. Adventitia (outer most layer)
Adventitia layer composed of areolar connective tissue.
This layer joins the trachea to the surrounding tissues and also encloses the cartilage.
Function of Trachea
1. Passage way for air, provide a clear air ways for air to enter and exit the lungs
2. Warming, humidifying and filtering
3. Support and prevent kinking, twist
4. Connects larynx to bronchi of the lungs.
5. Submucosa help in Cough reflex, mucus membrane of Carina is one of the most sensitive area of the entire larynx and trachea. Triggering a cough reflex.
6. Protection, Mucociliary escalator, cilia of mucus membrane
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