Explain how the ciliated epithelial cells lining the trachea are columnar in their appearance.

The ciliated epithelial cells in the trachea are columnar in shape and are arranged in a wheel-like pattern throughout the respiratory tract. There are approximately ten cilia per square centimetre.

Expert Answers

An illustration of the letter 'A' in a speech bubbles

The ciliated epithelial cells that line the trachea are columnar in shape. There are approximately ten cilia per square centimetre in the normal human respiratory tract. The cilia are arranged in wheel-like patterns throughout the respiratory tract. Each individual cilium is very small, measuring six micrometers long and 250 nanometers...

See
This Answer Now

Start your 48-hour free trial to unlock this answer and thousands more. Enjoy eNotes ad-free and cancel anytime.

Get 48 Hours Free Access

The ciliated epithelial cells that line the trachea are columnar in shape. There are approximately ten cilia per square centimetre in the normal human respiratory tract. The cilia are arranged in wheel-like patterns throughout the respiratory tract. Each individual cilium is very small, measuring six micrometers long and 250 nanometers wide. The cilia move in a wavelike motion to expel mucus that has trapped harmful pathogens, viruses, germs, and bacteria toward the pharynx, where it can be removed from the human body through coughing, spitting, or swallowing.

The direction that each individual cilium moves depends upon which way the small claw-like structure located on the tip of each cilium points. The tips of the cilia only touch the mucus when they are fully extended during a certain phase of each wavelike movement. Cilia receive signals to move through neural, chemical, and cell-to-cell communication, which allows for a constant wavelike movement.

Cilia located outside of the "wheel" tend to move more vigorously than cilia located inside of the "wheel." The consistency of the mucus should be watery and can be achieved through adequate hydration. Dehydration can result in a lack of mucus or thickened mucus, which will cause the mucus to be less effective in trapping harmful pathogens.

Approved by eNotes Editorial Team
An illustration of the letter 'A' in a speech bubbles

As the name implies, the columnar cells of the epithelium in the trachea have a regular, column-like appearance. This distinguishes them from other epithelial types, such as simple squamous and simple cuboidal epithelia, which are respectively flat and circular and low and square-like. Important to this question, however, is how a columnar morphology facilitates the function of tracheal epithelial cells.

Near the surface of the tracheal mucosa there are many goblet cells, which release mucus into the air pathway. This mucus captures free dust and food particles and prevents it from moving further down the trachea into the lungs. Undulation of the columnar cells moves tiny laminal extensions, called cilia, upward toward the oral cavity. This movement forces food and dust particles up and out of the respiratory tract where they cannot harm the underlying lung tissue. Thus, tracheal epithelial cells are columnar because this shape best facilitates undulation and the movement of food upward out of the trachea itself.

In histological slides, you will also notice that the epithelium is supported by a submucosa, which is well supplied with blood vessels. These blood vessels bring water to the goblet cells, allowing them to create mucus with which to coat the outside of the trachea. Together, these two layers of the trachea work together to keep the lungs free of invasive matter.

Approved by eNotes Editorial Team