How does a healthy rat breathe? - briefly
A healthy rat draws air through its nostrils into the lungs, where oxygen passes across alveolar walls into the blood and carbon dioxide is expelled on exhalation. Resting respiration usually occurs at 70–120 breaths per minute.
How does a healthy rat breathe? - in detail
A healthy rat inhales and exhales through a highly efficient respiratory system that supports its high metabolic rate. Air enters the nasal cavity, where it is warmed, humidified, and filtered by nasal turbinates and mucous membranes. The olfactory epithelium occupies a substantial portion of the nasal passage, allowing simultaneous scent detection and airflow.
From the nasopharynx, air passes through the larynx into the trachea, a rigid tube supported by cartilaginous rings that prevent collapse during rapid ventilation. The trachea bifurcates into primary bronchi, each entering a lung lobe. Rats possess five lung lobes on the right and two on the left, providing extensive surface area for gas exchange.
Within the bronchi, successive branching creates bronchioles that terminate in alveolar sacs. Alveoli are lined by a thin epithelial layer and a dense capillary network. The alveolar–capillary membrane, approximately 0.5 µm thick, enables diffusion of oxygen into the blood and removal of carbon dioxide.
Ventilation is driven by the diaphragm and external intercostal muscles. During inspiration, the diaphragm contracts and descends, expanding the thoracic cavity; the external intercostals lift the ribs, increasing lung volume and reducing intrapulmonary pressure. Air flows in until alveolar pressure equals atmospheric pressure. Expiration is primarily passive: diaphragm relaxation and elastic recoil of lung tissue raise intrapulmonary pressure, forcing air out. In periods of heightened activity, internal intercostal muscles and abdominal musculature contract to accelerate exhalation.
Key physiological parameters:
- Resting respiratory rate: 80–150 breaths min⁻¹, varying with age and ambient temperature.
- Tidal volume: ≈0.2 mL g⁻¹ body weight, sufficient to maintain arterial oxygen tension above 90 mm Hg.
- Minute ventilation: product of respiratory rate and tidal volume, typically 15–30 mL min⁻¹ g⁻¹.
- Oxygen consumption (VO₂): 0.5–0.8 mL min⁻¹ g⁻¹, reflecting high basal metabolic demand.
- Carbon dioxide elimination (VCO₂): proportional to VO₂, maintaining arterial CO₂ partial pressure near 40 mm Hg.
Ventilatory control resides in the brainstem respiratory centers. Chemoreceptors in the carotid bodies detect arterial PO₂ and PCO₂ changes, adjusting neuronal output to modulate diaphragm and intercostal activity. The vagus nerve conveys pulmonary stretch receptor signals that inhibit overinflation, ensuring stable tidal volumes.
Overall, the rat’s respiratory architecture combines rapid airflow, extensive alveolar surface, and precise neural regulation to sustain oxygen delivery and carbon dioxide removal under both resting and active conditions.