no AIR AIR 🎶
This is the primary physiological route of breathing in most domestic species , which allows proper humidification and filtration of inspired air.
What is the one species that this is the ONLY option?
What is nasal breathing?
Starting at the cricoid cartilage of the larynx, name the next two major airway segments in order as air travels toward the lungs.
What are the trachea and then the principal (primary) bronchi?
List the three bony boundaries that define the thoracic inlet
What are the first pair of ribs, the body of the first thoracic vertebra, and the manubrium of the sternum?
This muscle is the primary inspiratory muscle in mammals and provides most of the work of quiet inspiration.
What is the diaphragm?
These epithelial cells, which have motile apical structures, form the major cell type in the conducting airways and are essential for mucociliary clearance.
What are ciliated epithelial cells?
Because the upper airways have a relatively small total cross-sectional area, airflow here tends to have this character, which explains why abnormal sounds like stertor and stridor are heard at this level.
What is high-velocity, turbulent airflow with high resistance?
These airways are termed “conducting airways” because they carry air but do not participate directly in gas exchange.
What are the primary/principal bronchi, secondary (lobar) bronchi, tertiary (segmental) bronchi, subsegmental bronchi, bronchioles, and terminal bronchioles?
Name the four lobes of the right lung in the dog.
What are the cranial lobe, middle lobe, caudal lobe, and accessory lobe?
During quiet inspiration in a healthy dog, how do intrapleural pressure and alveolar (intrapulmonary) pressure change relative to atmospheric pressure to draw air into the lungs?
Intrapleural pressure becomes more negative, and alveolar pressure falls slightly below atmospheric; this pressure gradient (Patm > Palv) causes air to flow into the lungs.
Name two of the three key functions of the respiratory tract epithelium that help maintain a healthy airway environment.
Any two of:
Physical barrier function
Innate immune defense (e.g., cytokines, chemokines)
Mucociliary clearance of inhaled particles
Name two general functions of the respiratory tract (any two are fine) that are primarily carried out by the upper airways before air reaches the lungs.
Any two of:
Warming inspired air
Humidifying inspired air
Filtering/protecting against particles, aerosols, pathogens
Thermoregulation (e.g., panting, condensation)
Transport of odorants for smell
Facilitating vocalization
In ruminants and pigs, a special bronchus arises before the tracheal bifurcation. Name this bronchus and the lung region it ventilates.
What is the tracheal bronchus, which ventilates the right cranial lung lobe?
Define lobation versus lobulation of the lungs, and give one species example that is well lobated but poorly lobulated, and one that is well lobated and well lobulated.
Lobation is division of the lung into gross lobes; lobulation is further subdivision into small lobules by connective-tissue septa. Dogs and cats are well lobated but not well lobulated, while ruminants and pigs are both well lobated and well lobulated.
Define transpulmonary pressure and explain what happens to it in an open pneumothorax.
Transpulmonary pressure is the difference between alveolar pressure and intrapleural pressure (Palv – Ppl). In an open pneumothorax, air enters the pleural space and intrapleural pressure equilibrates with atmospheric, so the transpulmonary pressure falls toward zero, and the lung collapses.
In chronic rhinitis, explain how persistent epithelial activation and increased permeability can actually contribute to disease rather than protect the animal.
Chronic activation and increased permeability allow more allergens and pathogens to cross the epithelium, driving ongoing inflammation and tissue remodeling (e.g., goblet cell hyperplasia, edema). Instead of resolving the insult, this perpetuates chronic mucosal disease and can impair normal barrier and clearance functions.
During quiet nose breathing, inspired air is warmed and humidified on the way in, cooling the mucosal walls. On the way out, this cooled mucosa alters the expired air. Describe this exchange, what its called and what it conserves.
Inspired air gains heat and moisture from the mucosa (cooling the mucosal surface); during expiration, the now-cool mucosa reclaims heat and water from the warm, saturated exhaled air, so less heat and moisture are lost to the environment.countercurrent exchanger, conserves heat and water for the animal.
Compare the wall structure of a typical intrapulmonary bronchus with that of a bronchiole in terms of cartilage, glands, and epithelium.
Bronchi have ciliated pseudostratified columnar epithelium with goblet cells, a lamina propria with elastic fibers, mixed seromucous glands in the submucosa, and cartilage plates in the wall. Bronchioles have simple columnar/cuboidal ciliated epithelium, no cartilage and no submucosal glands, a thinner lamina propria, and a continuous smooth-muscle ring.
Describe how diaphragm contraction and external intercostal muscle contraction together change thoracic volume and pressures to produce inspiration.
Contraction of the diaphragm pulls it caudally and flattens it, increasing the vertical dimension of the thorax; contraction of the external intercostals lifts and rotates the ribs outward, increasing the lateral dimension. Together they increase thoracic volume, making intrapleural pressure more negative and dropping alveolar pressure below atmospheric so air flows into the lungs.
Using Laplace’s law, explain why small alveoli would be prone to collapse without surfactant, and how surfactant changes this relationship.
Laplace’s law states ΔP = 2T/r, so for a given surface tension (T), smaller radius (r) means higher collapsing pressure—small alveoli would tend to empty into larger ones and collapse. Surfactant reduces surface tension, and its concentration increases as alveolar radius decreases, so T falls more in smaller alveoli, equalizing pressures and helping prevent collapse.
Outline the reflex arc of sneezing, including the receptor location, afferent nerve, central integration site, and the general efferent response.
Receptors in the upper airway/nasal mucosa detect irritation; signals travel via the trigeminal nerve (afferent) to the medulla oblongata “sneeze center”; efferent signals go through multiple motor nerves to respiratory, pharyngeal, and laryngeal muscles, producing an initial deep inspiration followed by a forceful expiratory blast through the nose with depressed soft palate and increased nasal secretions.
A dog switches from normal nasal breathing to intense panting during exercise. Explain how panting changes the pathway of airflow and heat exchange compared with quiet nasal breathing, and why this is such an effective thermoregulatory strategy.
In panting, air is still warmed/humidified on inspiration, but it is exhaled mainly through the mouth, so the heat and moisture carried in the air are not returned to the nasal mucosa. Instead, evaporation from the moist tongue and oral tissues plus exhalation of “hot air” continually dumps heat and water to the environment, making panting an efficient way to cool the body.
Explain the functional transition from terminal bronchioles → respiratory bronchioles → alveolar ducts → alveoli, and why we say that the “respiratory airways” begin at the respiratory bronchiole.
Terminal bronchioles are the last purely conducting tubes. At the respiratory bronchioles, alveoli begin to bud from their walls, so gas exchange starts here—this is why they mark the start of respiratory airways. These lead into alveolar ducts, which are essentially tubes whose walls are almost entirely alveoli, and finally into clusters of alveoli, where most gas exchange occurs.
In a normal dog at rest, why do the lungs not simply collapse away from the thoracic wall, despite their natural elastic recoil? Include the roles of the closed thorax and transpulmonary pressure.
The lungs have an elastic tendency to collapse, but the tight, closed thoracic cage prevents air from entering the pleural space, and opposing elastic recoils of lung and chest wall create a sub-atmospheric intrapleural pressure. The resulting transpulmonary pressure (alveolar minus intrapleural) is positive and holds the lungs expanded against the thoracic wall, preventing collapse.
Explain hysteresis in the lung pressure–volume curve and relate it to respiratory work and surface tension, including what changes when the lung is filled with saline instead of air.
Hysteresis is the phenomenon where the inflation and deflation curves of the lung do not overlap; at the same pressure, lung volume differs during inspiration vs expiration. This is largely due to surface tension at the air–liquid interface in alveoli. About 2/3 of respiratory work is used to overcome surface tension, and 1/3 to overcome elastic tissue forces. When the lung is filled with saline, the air–liquid interface and surface tension are removed, hysteresis disappears or is greatly reduced, and much less work is required to inflate the lung.
Compare sneezing and coughing in terms of:
Where the stimulus originates (upper vs lower airway),
The afferent cranial nerve involved, and
The primary route of expelled air.
Sneezing: stimulus is in the nasal mucosa/upper airway, afferent via the trigeminal nerve (CN V), and air is expelled primarily through the nose.
Coughing: stimulus is in the larynx, trachea, or bronchi (lower airways), afferent via the vagus nerve (CN X), and air is expelled mainly through the mouth after a brief glottic closure and high-pressure release.