Pneumothorax occurs when air enters the breaking the fluid bond that holds the lungs open.

A. Red blood cells break down in the capillaries: Red blood cells remain intact during internal respiration. Hemolysis does not normally occur in capillaries, and the color change of blood is not due to cellular breakdown but rather changes in hemoglobin’s oxygenation state.

B. The pH of the blood decreases: Although tissue metabolism produces acids that can slightly lower blood pH, the primary cause of color change is not pH itself. Blood color is determined by the oxygen saturation of hemoglobin rather than minor pH fluctuations.

C. Oxygen dissociates from hemoglobin as it diffuses into tissues: As oxygen leaves hemoglobin to enter cells during internal respiration, the hemoglobin transitions from oxyhemoglobin (bright red) to deoxyhemoglobin (darker, burgundy color). This shift in oxygen saturation directly causes the observed color change in venous blood.

D. Hemoglobin binds more carbon dioxide than oxygen: While hemoglobin does carry carbon dioxide, the binding of CO₂ does not cause the immediate color change seen during internal respiration. The color change is primarily due to the release of oxygen from hemoglobin, not CO₂ binding.

A. Producing digestive enzymes: The nasal cavity does not have any role in enzyme secretion for digestion. Digestive enzymes are produced primarily by the salivary glands, stomach, pancreas, and small intestine to facilitate chemical breakdown of food. The nose is part of the respiratory and olfactory systems, not the gastrointestinal system.

B. Housing olfactory receptors: The superior portion of the nasal cavity contains the olfactory epithelium, which houses specialized chemoreceptors responsible for the sense of smell. These receptors transmit impulses via the olfactory nerve (cranial nerve I) to the olfactory bulb and cortex, enabling odor detection and discrimination.

C. Filtering and cleaning air: The nasal cavity plays a critical role in air filtration through vibrissae (nasal hairs), mucus secretion, and ciliated epithelium. These mechanisms trap particulate matter, pathogens, and debris, while coordinated ciliary movement propels contaminants toward the pharynx for elimination.

D. Resonating speech sounds: The nasal cavity contributes to speech by serving as a resonating chamber that modifies sound produced by the larynx. Proper nasal resonance is essential for phonation of certain consonants and overall voice quality; obstruction can result in hyponasal or hypernasal speech patterns.