Why does a rat breathe through its sides? - briefly
Rats ventilate mainly by expanding the rib cage laterally, because their diaphragm provides only a modest contribution to tidal volume. This side‑to‑side chest movement, driven by intercostal muscles, enables efficient airflow within their compact anatomy.
Why does a rat breathe through its sides? - in detail
Rats obtain most of their ventilation by expanding the lateral portions of the thorax rather than the anterior‑posterior dimension typical of larger mammals. The rib cage is composed of short, highly mobile ribs that rotate outward, allowing the side walls to increase in volume with each inspiratory effort. This motion is driven primarily by the external intercostal muscles, which contract to lift the ribs and widen the thoracic cavity laterally.
The diaphragm contributes by flattening, which lowers intra‑abdominal pressure and pulls the central tendon downward. Simultaneously, the internal intercostal muscles relax, preventing counter‑movement that would restrict lateral expansion. The combined action produces a rapid change in lung volume, generating airflow through the trachea and bronchi.
Key anatomical and physiological factors that enable side‑focused breathing include:
- Short, overlapping ribs that pivot around the vertebral column.
- Prominent external intercostal muscle mass positioned to lift ribs outward.
- A diaphragm that spans the entire ventral surface, providing a powerful suction force.
- Highly compliant lung tissue allowing substantial volume change with modest pressure differences.
- Neural control centers in the medulla that favor rapid, shallow breaths, suited to the animal’s high metabolic rate.
Behaviorally, the lateral expansion minimizes disturbance of the surrounding environment, which is advantageous when the animal is concealed in narrow burrows or dense vegetation. The pattern also reduces the need for large chest excursions that could compromise the animal’s agility or expose it to predators.