The rat trachea, or windpipe, is a tube-like passage in the rat’s respiratory system. Positioned in the lower neck and upper chest, it extends from the voice box (larynx) towards the lungs. It provides the primary pathway for air to travel to and from the lungs.
Structure and Role
The rat trachea is a fibrocartilaginous tube, 30 to 35 millimeters long, with an inner diameter of 1.6 to 1.7 millimeters. It is supported by 16 to 20 incomplete, C-shaped rings of hyaline cartilage. These rings are connected vertically by ligaments, providing support and flexibility to prevent collapse during breathing.
The posterior wall contains the trachealis muscle. This muscle allows slight changes in diameter, aiding in expelling foreign particles during a cough. Its inner lining is a mucous membrane of pseudostratified ciliated columnar epithelium, including goblet cells. Goblet cells produce mucus that traps inhaled dust and debris. Cilia, tiny hair-like projections, rhythmically move the mucus and trapped particles upwards, away from the lungs, for swallowing or expulsion.
The trachea transports air to and from the lungs. Inhaled air passes through the larynx and enters the trachea. From there, it branches into two main bronchi, leading to the lungs. This open pathway ensures oxygen reaches respiratory surfaces and carbon dioxide is expelled.
Unique Characteristics
The rat trachea differs from that of other mammals, such as humans. While the general structure is conserved, the rat trachea has adaptations related to its smaller size and higher metabolic rate. The rat trachea is shorter and narrower than a human trachea, which is 90-150 mm long and 20-25 mm in diameter.
Despite its smaller absolute size, rats have a proportionally wider trachea compared to humans when adjusted for body weight. This wider airway, combined with a higher respiratory rate, compensates for increased ventilatory dead space and ensures efficient airflow. Mucociliary clearance velocity in the rat trachea is 1.9–5.5 mm/min. While slower than in humans (3.6–21.5 mm/min), this results in quicker overall particle clearance due to the shorter length of rat airways.
The branching pattern of the tracheobronchial tree is another difference. Humans exhibit a dichotomous, symmetric branching pattern where airways divide into two roughly equal branches. In contrast, the rat lung displays a monopodial branching pattern, with airways branching off like side stems, resulting in different lengths from the trachea to the alveoli. This arrangement can lead to heterogeneous deposition of inhaled substances within rat alveoli compared to humans.