Canine Respiratory System: Anatomy and Physiology

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-11

Key Takeaways

• The canine nasal cavity, characterized by complex conchae, significantly conditions inspired air through warming, humidification, and particulate trapping, with stenotic nares in brachycephalic breeds increasing inspiratory resistance and contributing to obstructive airway syndrome.
• Laryngeal function as a protective sphincter and airflow regulator is critically dependent on the recurrent laryngeal nerves; dysfunction leads to laryngeal paralysis, manifesting as inspiratory stridor due to failed arytenoid cartilage abduction.
• The incomplete dorsal tracheal rings and dorsal membrane facilitate tracheal collapse during coughing but predispose to airway narrowing in tracheal collapse conditions; the right principal bronchus's steeper angle makes it a more common site for aspirated foreign bodies.
• Limited collateral ventilation in canine lungs, due to incomplete interlobular septa, predisposes to rapid atelectasis distal to bronchial obstruction, highlighting the importance of early airway clearance in managing pneumonia.
• Pulmonary surfactant, produced by type II pneumocytes, is vital for reducing alveolar surface tension and preventing collapse; oxidant injury to surfactant proteins, particularly SP-B, impairs biophysical function and gas exchange, relevant in smoke inhalation and oxygen toxicity.
• Lymphatic drainage into the venous system is phasic with respiration, regulated by the ostial valve at the thoracic duct terminus, a mechanism critical for understanding chylothorax pathogenesis and management.

This article provides a structured reference on the canine respiratory tract from the external nares to the alveoli, written for veterinary students and practitioners seeking a functional approach to anatomy. The content integrates structural detail with physiological principles and clinical correlations, preparing the reader for physical examination, diagnostic imaging, and therapeutic decision-making in canine patients. Emphasis is placed on how anatomical features predict physiological behavior and clinical failure modes.

At a Glance

Nasal Cavity and Pharynx

The canine nasal cavity is a complex, high-resistance conduit that conditions inspired air before it reaches the lower airways. The nasal planum and nares form the external aperture, and the alar folds contribute a dynamic valvular function. In brachycephalic breeds, stenotic nares and elongated soft palates increase upper airway resistance, producing the characteriztic inspiratory stertor and exercise intolerance of brachycephalic obstructive airway syndrome.

Within the nasal cavity, the dorsal, ventral, and ethmoidal conchae project from the lateral walls as delicate scrolls of bone covered by highly vascularised mucosa. These turbinates greatly increase the surface area available for heat exchange and humidification. The ventral meatus provides the most direct passage for a nasogastric tube, while the common meatus, adjacent to the nasal septum, is the primary route of inspired airflow. The ethmoidal labyrinth, located caudodorsally, houses the olfactory epithelium and communicates with the frontal sinuses through the fronto-ethmoidal opening.

The nasopharynx lies dorsal to the soft palate and receives the choanae rostrally and the auditory tube openings laterally. The laryngopharynx continues caudally to the larynx. The pharyngeal region is a common site for foreign body impaction, particularly linear foreign bodies that anchor under the tongue and cause progressive oropharyngeal trauma.

Larynx and Trachea

The larynx serves three integrated functions: airway protection, phonation, and regulation of airflow. The paired arytenoid cartilages and the epiglottis form the rima glottidis, the narrowest portion of the entire airway. The recurrent laryngeal nerves innervate the cricoarytenoideus dorsalis muscle, the sole abductor of the arytenoid cartilages. When this nerve is damaged, as in idiopathic laryngeal paralysis or iatrogenic injury during cervical surgery, the arytenoids fail to abduct during inspiration, producing inspiratory stridor and exercise intolerance.

The trachea extends from the cricoid cartilage to the carina, where it divides into principal bronchi. Its C-shaped hyaline cartilage rings are incomplete dorsally, where the tracheal membrane, composed of smooth muscle and elastic connective tissue, bridges the gap. This design permits the trachea to collapse slightly during coughing, increasing expiratory airflow velocity and aiding mucus clearance. In tracheal collapse, the dorsal membrane becomes lax and the cartilage rings flatten, allowing the trachea to narrow during inspiration, expiration, or both, depending on the segment affected.

The tracheal bifurcation at the carina is a common site for foreign body lodgement, particularly in small breeds. The right principal bronchus arises at a less acute angle than the left, making it the more frequent site of aspirated material.

Bronchial Tree and Pulmonary Architecture

The canine lung is divided into lobules by incomplete interlobular septa, a feature that limits collateral ventilation between adjacent lobules. This anatomical arrangement means that when a bronchus becomes obstructed by mucus, exudate, or a foreign body, the distal lung collapses rapidly because air cannot pass through adjacent alveolar pores to maintain aeration. This explains the high frequency of atelectasis in canine pneumonia and the value of early airway clearance in managing lower respiratory disease.

The bronchial tree undergoes approximately 20 to 25 generations of branching from the trachea to the terminal bronchioles. Cartilage is present in the walls of bronchi but is absent from bronchioles, which rely on elastic recoil and smooth muscle tone to maintain patency. The transition from conducting airways to respiratory bronchioles marks the beginning of the gas exchange region. The canine lung has relatively few respiratory bronchioles compared with some other species, and alveoli arise directly from terminal bronchioles over a short distance.

Pulmonary acini, the functional units of gas exchange, consist of respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli. The alveolar epithelium comprises type I pneumocytes, which cover approximately 95 percent of the alveolar surface and provide an extremely thin barrier for gas diffusion, and type II pneumocytes, which synthesise and secrete pulmonary surfactant. The blood-gas barrier is conserved across vertebrate species, being thin enough to permit efficient gas exchange yet strong enough to withstand the distension forces of breathing. Pulmonary surfactant, a complex mixture of phospholipids and proteins, lines the air-liquid interface and varies surface tension with changing lung volume, preventing alveolar collapse at end-expiration.

Surfactant and the Air-Liquid Interface

Pulmonary surfactant is established, maintained, and dynamically regulated by surfactant proteins, with a mixed phospholipid and neutral lipid interfacial film. The hydrophobic surfactant protein B is essential for the formation and stability of the surfactant film, and its deficiency is lethal in mammals. Oxidative stress to surfactant protein B is particularly detrimental to biophysical function, as oxidised surfactant constituents lose their ability to reduce surface tension effectively.

Inhaled oxidants interact primarily with the epithelial lining fluid, a thin layer covering the epithelial cells of the lung that contains surfactant and antioxidants. In the upper airways, this layer is thick and rich in antioxidants, so oxidant injury is uncommon there. In the lower airways, where the lining fluid is thin and antioxidant concentrations are lower, oxidant exposure can impair surfactant function, promote inflammation and edema, and further compromise the surfactant system. These mechanisms are relevant to smoke inhalation injury, oxygen toxicity, and the pulmonary consequences of systemic inflammatory states.

Lymphatic Drainage and Thoracic Duct

The lung has a rich lymphatic network that drains interstitial fluid and particulate matter from the alveolar interstitium toward the hilar lymph nodes. The thoracic duct transports lymph from the body to the venous system at the lymphovenous junction in the neck. The ostial valve at this junction regulates lymph flow in relation to the respiratory cycle. During inspiration, central venous pressure falls, the valve cusps collapse, and lymph flows antegrade into the vein. During early expiration, rising central venous pressure closes the valve and halts lymph flow. This respiratory phasing of lymphatic drainage is clinically relevant in chylothorax, where disruption of the thoracic duct or elevated venous pressures can impair lymph clearance from the pleural space.

Applied Clinical Assessment of the Canine Respiratory Tract

Signalment, History, and Localization

The first decision point in evaluating a canine respiratory patient is anatomic localization. The clinician must determine whether the problem originates in the upper airway (nasal cavity, pharynx, larynx, cervical trachea), the lower airway (intrathoracic trachea, bronchi), the pulmonary parenchyma, or the pleural space. Localization changes the diagnostic plan, the urgency of intervention, and the likely differential list.

Signalment narrows the differential set before the examination begins. Brachycephalic breeds present with stertor, exercise intolerance, and sleep-disordered breathing attributable to stenotic nares, elongated soft palate, and hypoplastic trachea. Young, large-breed dogs with acute respiratory distress and a history of vigorous exercise or vomiting are candidates for aspiration pneumonia or spontaneous pneumothorax. Middle-aged to older dogs with progressive cough and weight loss raise concern for primary or metastatic neoplasia. Breed predispositions for specific conditions, such as laryngeal paralysis in Labrador Retrievers and collapsing trachea in toy breeds, should be considered but must not anchor the diagnosis.

Historical features that refine the differential include cough character, timing, and triggers. A honking, goose-honking cough that worsens with excitement, leash pressure, or eating suggests tracheal collapse. A soft, moist cough that worsens after recumbency or in the morning is more consistent with bronchopneumonia or cardiogenic pulmonary edema. Hemoptysis, though uncommon in dogs, points toward severe pneumonia, pulmonary thromboembolism, neoplasia, or coagulopathy. Nasal discharge that is unilateral and mucopurulent or sanguinous suggests foreign body, neoplasia, or fungal rhinitis, whereas bilateral serous discharge is more typical of viral or allergic rhinitis.

Physical Examination and Point-of-Care Testing

The physical examination should proceed from observation to auscultation in a systematic manner. Respiratory rate and effort are assessed first, ideally before handling causes excitement. Normal resting respiratory rate in the dog ranges from 10 to 30 breaths per minute, with brachycephalic breeds often at the higher end. Increased inspiratory effort with stertor or stridor localizes disease to the upper airway. Prolonged or labored expiration with wheezes suggests small airway disease. Rapid, shallow breathing with normal or quiet lung sounds raises suspicion for pleural space disease or restrictive parenchymal processes.

Auscultation is performed over the trachea, the hilar region, and the peripheral lung fields on both sides. Bronchial sounds are normally heard over the hilar region, whereas vesicular sounds are quiet at the periphery. Increased bronchial sounds in the peripheral fields indicate consolidated or edematous lung. Crackles are generated by the sudden opening of collapsed small airways and are heard in pneumonia, pulmonary edema, and pulmonary fibrosis. Wheezes indicate narrowing of airways and are heard in bronchitis, asthma, and dynamic airway collapse. Absent or markedly reduced lung sounds in one hemithorax with dullness on percussion suggest pleural effusion, whereas hyperresonance suggests pneumothorax.

Point-of-care testing adds immediate diagnostic information. Pulse oximetry estimates hemoglobin oxygen saturation, with values below 94% at sea level indicating impaired oxygenation. Capnography provides a continuous reading of end-tidal carbon dioxide, which approximates arterial PCO2 in dogs with normal ventilation-perfusion matching. A widened arterial to end-tidal CO2 gradient suggests increased dead space ventilation, as occurs with pulmonary thromboembolism or hypovolemia. Arterial blood gas analysis remains the reference standard for assessing oxygenation and ventilation, but it requires technical skill and is not always available in first-opinion practice.

Diagnostic Imaging and Sampling

Thoracic radiographs are the first-line imaging modality for suspected lower respiratory disease. Two orthogonal views, right lateral and dorsoventral or ventrodorsal, are required. The right lateral view minimizes magnification of the cardiac silhouette and is preferred for evaluating the caudal lung lobes. Radiographic patterns guide the differential diagnosis. An alveolar pattern with air bronchograms in the cranioventral lung fields is typical of aspiration pneumonia. A diffuse interstitial to alveolar pattern with cardiomegaly and pulmonary venous distension supports cardiogenic pulmonary edema. A peribronchial pattern with bronchial wall thickening is seen in chronic bronchitis. A miliary or nodular interstitial pattern raises concern for metastatic neoplasia or fungal disease.

The radiographic appearance of the canine lung differs from that of other species. The dog has relatively complete lobar fissures, and the accessory lobe of the right lung projects into the caudal mediastinum. Radiographic interpretation must account for the phase of respiration, as the cranioventral lung fields appear more opaque during expiration. The normal canine lung has a thin, sharp silhouette at the periphery, and blunting of the costophrenic angles suggests pleural effusion.

Airway sampling is indicated when imaging identifies a focal or diffuse parenchymal pattern and the clinical picture does not respond to empirical therapy. Transtracheal wash is performed in the standing or sternal recumbent dog with a sterile catheter passed through the cricothyroid membrane. It samples the trachea and mainstem bronchi and is well suited for diagnosing bacterial tracheobronchitis and bronchopneumonia. Bronchoalveolar lavage via bronchoscopy samples the alveolar space and is preferred when the disease is diffuse or when cytologic evaluation of alveolar macrophages is needed. The two techniques are complementary, and the choice depends on the suspected disease location and the availability of equipment.

Respiratory Parameters and Monitoring

Serial monitoring of respiratory parameters is essential for tracking disease progression and response to therapy. The following table summarizes the key parameters, their normal ranges in the resting dog, and the clinical significance of abnormalities.

The choice of monitoring modality depends on patient status and available equipment. Pulse oximetry is noninvasive and widely available but is unreliable in the presence of severe anemia, hypothermia, or poor peripheral perfusion. Capnography requires an intubated patient or a tightly fitting mask and is most useful during anesthesia or mechanical ventilation. Arterial blood gas analysis is the most accurate method but is invasive and requires immediate sample processing. In the unstable patient, serial physical examination with attention to respiratory effort, mucous membrane color, and lung auscultation remains the most practical monitoring approach.

Oxygen Therapy and Ventilatory Support

Supplemental oxygen is indicated when SpO2 falls below 94% or when the patient shows clinical signs of respiratory distress. The method of delivery depends on the patient's size, temperament, and oxygen requirement. Flow-by oxygen delivered at 50 to 150 mL/kg per minute is well tolerated but achieves a low inspired oxygen fraction. An oxygen cage provides a controlled environment with inspired oxygen fractions up to 50% but limits patient access for monitoring and nursing care. Nasal oxygen cannulas deliver higher inspired oxygen fractions and allow continuous patient access, but they require sedation in some dogs and can cause nasal irritation.

The response to oxygen therapy must be reassessed within 15 to 30 minutes. If hypoxemia persists despite an adequate inspired oxygen fraction, the clinician should consider mechanical ventilation. Indications for mechanical ventilation include refractory hypoxemia, progressive hypercapnia with respiratory acidosis, and severe respiratory fatigue. The decision to ventilate is influenced by the underlying disease, the anticipated duration of support, and the owner's goals and resources. Mechanical ventilation requires continuous monitoring of airway pressures, tidal volume, and blood gases, and it is best performed in a referral setting with 24-hour staffing.

Species and breed differences affect the approach to oxygen therapy. Brachycephalic dogs have upper airway obstruction that may worsen with sedation, and they may require a temporary tracheostomy tube to bypass the obstruction. Dogs with pleural effusion require thoracocentesis before oxygen therapy is maximally effective, as the effusion mechanically restricts lung expansion. In all cases, the underlying cause of hypoxemia must be addressed, as oxygen therapy is supportive instead of curative.

Recognized Complications and Failure Modes

The canine respiratory system fails in predictable patterns, and early detection depends on knowing which clinical sign corresponds to which structural or functional breakdown. Upper airway obstruction, typically laryngeal paralysis or brachycephalic syndrome, presents with inspiratory stertor, increased respiratory effort, and normal to low PaCO₂ until fatigue supervenes. Lower airway disease, by contrast, produces expiratory wheeze and hyperinflation. Parenchymal disease, whether pneumonia, pulmonary edema, or neoplasia, causes tachypnoea, hypoxemia, and often a normal or low PaCO₂ until ventilation-perfusion mismatch becomes extreme.

Pleural space disease deserves particular attention because it can mimic parenchymal disease while requiring a different intervention. A dog with a tension pneumothorax shows progressive inspiratory and expiratory effort, auscultatory silence dorsally, and deteriorating perfusion. The discriminating finding is absent lung sounds with normal or hyperresonant percussion, whereas consolidated lung yields dull percussion with bronchial breath sounds. Ultrasonography, specifically the presence of a glide sign, distinguishes these rapidly at the point of care.

Surfactant dysfunction constitutes a less visible but equally important failure mode. Oxidant injury to the epithelial lining fluid can inactivate extracellular surfactant constituents, impairing surface tension regulation and promoting edema and inflammation that further degrade surfactant function. This sequence matters clinically in dogs with smoke inhalation, sepsis, or prolonged oxygen therapy, where progressive atelectasis and hypoxemia may develop despite apparently adequate ventilation. Serial arterial blood gas measurement and lung ultrasound for B-lines provide the earliest objective evidence of this deterioration.

Common Errors in Assessment and Corrective Action

Less experienced clinicians frequently misattribute respiratory noise to the wrong anatomical site. Stertor, a low-pitched snoring sound, originates in the nasopharynx, stridor, a high-pitched musical sound, originates in the larynx or extrathoracic trachea. Failing to distinguish these leads to inappropriate imaging and delayed diagnosis of laryngeal paralysis. The corrective action is disciplined auscultation over the nose, larynx, trachea, and chest during both inspiration and expiration, with the stethoscope bell placed directly over each site.

A second recurring error is interpreting a normal resting respiratory rate as evidence of adequate gas exchange. Dogs with early pulmonary parenchymal disease may maintain a normal rate at rest while showing increased effort, abdominal component, or prolonged expiratory phase. The converse error, attributing tachypnoea to pain or anxiety without checking pulse oximetry or blood gases, delays recognition of hypoxemia. Capnography provides waveform morphology, also numeric end-tidal CO₂, and an abnormal waveform may reveal obstruction or rebreathing before oxygen saturation falls.

A third error involves sedation for imaging. Brachycephalic dogs and dogs with laryngeal disease tolerate sedation poorly, and a routine pre-imaging sedative can convert marginal upper airway patency into complete obstruction. The corrective action is to assess upper airway function before sedation, use minimal doses of reversible agents, and maintain the patient in sternal recumbency with the head extended throughout the procedure.

Limitations of Current Evidence

Several areas of canine respiratory physiology rest on extrapolation from other species. The bitter taste receptor literature, for example, demonstrates that T2R activation produces bronchodilation in human airway smooth muscle and that T2R38 polymorphism influences chronic rhinosinusitis susceptibility in people. Whether these receptors contribute meaningfully to canine airway tone or disease susceptibility remains unstudied, and clinical application in dogs would be speculative. Similarly, much surfactant biology derives from laboratory rodents and human preterm infant research, and while the fundamental biophysics of the air-liquid interface is conserved across air-breathing vertebrates, the specific vulnerability of canine surfactant to oxidant injury has not been quantified.

Anatomical variability also limits generalization. The thoracic duct shows marked variation in its terminal course in humans, with multiple terminations in roughly 13% of cases. Comparable data in dogs are sparse, which matters for surgical planning of chylothorax management. Expert opinion still differs on whether thoracic duct ligation alone, or with pericardectomy, offers the best outcome for idiopathic chylothorax, and the evidence base does not currently resolve this question.

Referral, Consultation, and Reporting

Referral to a specialist is warranted when the diagnosis remains uncertain after basic imaging and sampling, when the patient requires mechanical ventilation, or when the suspected condition needs advanced intervention such as bronchoscopy, thoracic surgery, or interventional procedures. A dog with progressive hypoxemia despite supplemental oxygen, a suspected mediastinal mass, or recurrent aspiration pneumonia should be referred before respiratory fatigue develops. Specialist consultation is also appropriate for chronic cough that fails to respond to empirical therapy, because the differential list, including bronchomalacia, eosinophilic bronchopneumopathy, and neoplasia, requires advanced diagnostics.

Laboratory involvement extends beyond routine hematology and biochemistry. Arterial blood gas analysis is essential for quantifying gas exchange and guiding oxygen therapy. Cytological evaluation of tracheal wash or bronchoalveolar lavage fluid distinguishes septic from eosinophilic or neoplastic inflammation. Fungal serology and antigen testing are indicated for dogs with compatible travel history or radiographic patterns.

Regulatory reporting obligations vary by jurisdiction. Suspicion of a notifiable respiratory disease, such as canine influenza in regions where it is reportable, should prompt immediate contact with the relevant veterinary authority. The WOAH terrestrial animal health standards provide the international framework for disease notification, and the AVMA practice resources offer guidance on professional obligations and public health considerations. Clinicians should confirm the current list of reportable diseases in their own jurisdiction instead of rely on memory.

Frequently Asked Questions

How do I perform a respiratory assessment when advanced imaging is unavailable?

When computed tomography or bronchoscopy is not accessible, a structured approach using radiography, ultrasonography, and clinicopathologic data remains reliable. Obtain orthogonal thoracic radiographs with inspiratory and expiratory views when possible. Thoracic ultrasound can identify pleural fluid, pulmonary consolidation, and diaphragmatic integrity. Arterial blood gas analysis or venous blood gas with lactate provides objective ventilation and perfusion data. Pulse oximetry and capnography offer continuous monitoring where available. If sampling is needed, ultrasound-guided fine needle aspiration or blind tracheal wash can yield diagnostic material. The MSD Veterinary Manual provides guidance on interpreting these modalities in practice. Document the limitations of each technique and communicate diagnostic uncertainty clearly to the owner.

What are the practical limits of oxygen therapy in a general practice setting?

Flow-by oxygen, mask delivery, and oxygen cages remain the mainstay when mechanical ventilation is unavailable. Flow-by administration at 50 to 100 mL/kg per minute achieves modest inspired oxygen fractions, often below 40%. Oxygen cages allow higher fractions but require frequent opening for patient care, which causes rapid oxygen washout. Humidification becomes essential beyond 12 hours of therapy to prevent airway drying and impaired mucociliary clearance. Patients with severe hypoxemia, progressive hypercapnia, or fatigue require referral for mechanical ventilation. The MSD Veterinary Manual outlines monitoring parameters for oxygen therapy. Reassess arterial oxygenation within 30 minutes of any delivery change and adjust the fraction accordingly.

How does respiratory assessment differ in brachycephalic breeds?

Brachycephalic dogs present a unique challenge because upper airway obstruction alters every component of the respiratory examination. Stridor, stertor, and increased respiratory effort may reflect anatomical obstruction instead of parenchymal disease. Sedation for imaging carries higher risk due to collapsing airways and laryngeal dysfunction. Pulse oximetry readings may be falsely reassuring during periods of compensatory hyperventilation. Blood gas analysis often reveals chronic respiratory acidosis with compensatory metabolic alkalosis. Assess these patients before and after exercise, and consider dynamic airway evaluation under light sedation. The NCBI Bookshelf comparative physiology texts describe breed-related anatomical variation in the upper airway. Surgical correction of obstructive anatomy frequently improves both clinical signs and diagnostic accuracy.

What should I document in the medical record for a respiratory case?

Record the respiratory rate, effort, and pattern at presentation and after each intervention. Document thoracic auscultation findings by region, including the presence and character of crackles, wheezes, or absent sounds. Note the fraction of inspired oxygen and the delivery method for every blood gas or oximetry reading. Record the response to bronchodilators, diuretics, or oxygen therapy with specific time points. Include images or detailed descriptions of endoscopic and radiographic findings. The AVMA practice resources emphasize the importance of contemporaneous, objective documentation for continuity of care and medicolegal protection. Serial measurements of body weight, mucous membrane color, and capillary refill time provide objective trends that support treatment decisions.

How do I explain a respiratory diagnosis to a client without causing undue alarm?

Use anatomical language the owner can visualize, such as describing the airways as branching tubes that narrow with inflammation. Distinguish between conditions that are manageable at home and those requiring hospitalization. Explain the diagnostic plan in sequence, with estimated costs and expected outcomes for each step. Be explicit about prognostic uncertainty, particularly for conditions such as pulmonary fibrosis or neoplasia where response to therapy varies. Provide written instructions for medication administration and parameters that warrant immediate recheck. The AVMA practice resources offer guidance on client communication and informed consent. Offer a follow-up telephone call within 48 hours to review progress and answer emerging questions.

When should I refer a respiratory case to a specialist?

Refer when the patient requires mechanical ventilation, when diagnostic imaging beyond radiography is needed, or when the condition fails to improve despite appropriate first-line therapy. Refer early in cases of suspected foreign body, laryngeal paralysis, or tracheal collapse where interventional procedures are likely. Patients with progressive dyspnoea despite oxygen therapy, or those requiring escalating sedation for diagnostic procedures, benefit from specialist care. The WOAH terrestrial animal health standards address transport considerations for compromised animals. Provide the receiving facility with radiographs, blood work, and a summary of treatments attempted. Stabilize the patient before transport and ensure oxygen is available during the journey.

Related Clinical & Scientific Guides

• Comparative Anatomy of the Mammalian Kidney
• Feline Cardiopulmonary Physiology: Heart-Lung Interactions
• Equine Ocular Anatomy: Adnexa and Globe Structures

References and Further Reading

• Bitter taste receptors: Extraoral roles in pathophysiology.. 2016.
• Toxic oxidant species and their impact on the pulmonary surfactant system.. 1997.
• The anatomy and physiology of the terminal thoracic duct and ostial valve in health and disease: potential implications for intervention.. 2018.
• The anatomy, physics, and physiology of gas exchange surfaces: is there a universal function for pulmonary surfactant in animal respiratory structures?. 2007.
• Use of three-dimensional organoids and lung-on-a-chip methods to study lung development, regeneration and disease.. 2018.
• The anatomy and physiology of the bovine respiratory system relating to pulmonary disease.. 1978.
• NCBI Bookshelf: Veterinary and Comparative Biomedical Sciences. NCBI Bookshelf.
• MSD Veterinary Manual, Professional Edition. MSD Veterinary Manual.
• American Veterinary Medical Association Practice Resources. American Veterinary Medical Association.

Related Articles

• Canine Lymphatic System: Anatomy and Function
• Bovine Respiratory System: Anatomy and Clinical Examination
• Canine Endocrine System: Glands and Hormonal Regulation
• Canine Heart Anatomy: Chambers, Valves, and Conduction System
• Canine Skeletal System: Axial and Appendicular Overview

This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.