The only sinuses that can be assessed on physical exam are the frontal and maxillary sinuses. The sphenoid and ethmoid sinuses are too deep in the skull to be assessed via physical examination.

Gas exchange in the lung occurs exclusively in the alveoli, the tiny grape-like clusters of sacks at the terminus of the bronchioles of the lung. The gas contained in the larger structures of the lung - the trachea, bronchi, and bronchioles, is termed "dead space" as it does not participate in gas exchange.

The main trigger for the impulse to breathe is high carbon dioxide (decreased blood pH). In response to a decrease in blood pH, the medullary respiratory center triggers the diaphragm and the external intercostal muscles to increase breathing rate.

Myoglobin, an oxygen-binding protein in the muscle tissue, can bind with one molecule of oxygen. Hemoglobin, the main oxygen-binding metalloprotein in red blood cells, can bind four molecules of oxygen. 

While hyperventilation or tachypnea may be triggered by various forms of acidosis, they will not cause a decrease in blood pH, but rather push the blood into a more alkaline state. This occurs due to loss of carbon dioxide during respiration, followed by a compensatory decrease in bicarbonate ions. The result is in an elevation in the pH of the blood. This condition is known as respiratory alkalosis.

Many gases, such as room air, are composed of several gasses (in the case of room air, primarily nitrogen, oxygen, and several trace gasses). Partial pressure is the amount of pressure that each gas contributes. To find the total pressure of a gas mixture, one would find the sum of all partial pressures of each individual gas. 

Gas exchange in the alveoli occurs by the process of simple diffusion. The blood that enters the lung capillaries is relatively low in oxygen and high in , in comparison to the room air that is drawn into the alveoli during respiration. The separation between the capillaries and the alveolar epithelium is thin enough that these gasses can exchange across their pressure gradients by the process of simple diffusion.

Increased epinephrine, released either by the adrenal medulla or by myocardial innervation, increases contractility in the heart, which in turn increases stroke volume. 

Blood in the right atrium must pass through the tricuspid valve to enter the right ventricle. The mitral valve is between the left atrium and the left ventricle. The semilunar valves are located at the base of the aorta and the pulmonary trunk, also known as the aortic valve and pulmonary valve. The foramen ovale is a type of shunt that exists in the fetal heart. It's presence in an adult patient is a form of congenital heart defect.

The S2 heart sound (sometimes referred to as the "dub" in "lub-dub") occurs in diastole, during the closing of the aortic and pulmonary valves. When pressure within the aorta and pulmonary arteries exceeds pressure within the heart, the cups of the valves fill with blood and snap shut, causing the "dub" sound.