The cartilage rings in trachea are incomplete at dorsal surface.
The trachea (windpipe) is a cylinder that reaches out from the lower edge of the larynx to the upper piece of the chest (over the heart).
The motivation behind the trachea is to lead air between the larynx and the lungs.
It has a structure of ligaments to keep it open.
These ligaments are formed like a minor horseshoe or the letter C and are found along the whole length of the trachea...

**Tracheal Cartilaginous Rings in Mammals**

The trachea, also known as the windpipe, is a tube-like structure that connects the larynx (voice box) to the bronchi of the lungs. It serves as a pathway for air to enter and exit the respiratory system. In mammals, the trachea is composed of a series of cartilaginous rings that provide structural support and help maintain the airway's shape.

**Incomplete Dorsally**

The tracheal cartilaginous rings in mammals are incomplete dorsally. This means that the cartilaginous rings do not form a complete circle around the trachea's circumference on the dorsal (back) side. Instead, there is a gap or opening in the cartilage along the dorsal aspect of the trachea.

This incomplete dorsal arrangement allows the trachea to be flexible and adaptable to changes in the size and shape of the surrounding structures. It allows the trachea to move and expand when necessary, such as during swallowing or when the animal is in different body positions.

**Function of Incomplete Dorsal Rings**

The incomplete dorsal rings of the trachea provide several advantages:

1. Flexibility: The trachea needs to be flexible to accommodate movements of the neck and surrounding structures. The incomplete dorsal rings allow for bending and stretching without compromising the trachea's integrity.

2. Compression: The incomplete dorsal rings allow for compression of the trachea during swallowing. When an animal swallows, the trachea needs to be compressed to prevent food or liquid from entering the airway. The incomplete dorsal rings facilitate this compression.

3. Expansion: The incomplete dorsal rings allow the trachea to expand and contract during changes in the size and shape of the respiratory system. For example, during deep inhalation, the trachea needs to expand to accommodate the increased airflow.

4. Protection: The incomplete dorsal rings provide a protective barrier for the trachea against external pressure or compression. They help maintain the trachea's shape and prevent collapse or obstruction.

In conclusion, the tracheal cartilaginous rings in mammals are incomplete dorsally. This arrangement allows for flexibility, compression, expansion, and protection of the trachea, ensuring its proper functioning in the respiratory system.