The S1 heart sound (sometimes referred to as "lub") is caused by the sudden snapping-shut of the tricuspid and mitral valves during systole, when the heart contracts and tension on the chordae tendinae is released. No sound is produced on the opening of these or any other valves in the heart.

The contraction rate for the heart is set by the cells of the sinoatrial node, also known as the pacemaker cells of the heart. These cells have membranes that are especially permeable to ions, and are able to depolarize on their own at a rate of 70-100 beats per minute. All the other areas listed do have their own spontaneous contractility, but their rates are slower than that of the sinoatrial node. Thus, the sinoatrial node is the pacemaker in a healthy heart.

The proper unit when recording a patient's blood pressure is mmHg, or millimeter of mercury. This is derived from a historical measurement of how many millimeters of mercury in a mercury manometer were able to be elevated by a particular pressure. Due to it's toxicity,  are longer used in medical equipment, though the  unit remains in use.

The left ventricle is the most commonly enlarged heart structure seen in chronic hypertension. The left ventricle must overcome the afterload of the arterial system by becoming hypertrophied. As a result, the heart gets remodeled to overcome the systemic high blood pressures. The left ventricle directly pumps blood from the heart to the systemic circuit.

T-cell maturation occurs in the thymus, a small organ located in the upper part of the mediastinum, between the heart and the sternum. Mature T cells then may either circulate in the lymph or blood or reside in lymph nodes. The spleen is not a site of T cell maturation, though it does have other important immune functions, such as the production of antibodies and the removal of antibody-coated pathogens. The cisterna chyli is a part of the lymphatic system that is involved in lipid digestion.

Dietary fat is absorbed via lacteals, small lymph vessels contained within the body of the intestinal villi. Microvilli, tiny projections covering the surface of the villi, help with the absorption of minerals, vitamins, and other micronutrients. The cisterna chyli is a dilated pouch at the lower end of the thoracic duct that serves as a collection point for fatty chyle from the intestinal lacteals.

The lymphatic system has several roles in the body, including drainage of interstitial fluid from tissues, transportation and activation of lymphocytes, and absorption and transportation of dietary fats. Red blood cells, however, are unable to enter lymph vessels, and so the lymphatic system does not participate in any type of gas exchange.

Each heme group in hemoglobin encloses a single iron atom in the center of a protoporphyrin, a tetrapyrrol composed of four pyrrole rings linked together by four methyl groups, two vinyl groups, a methane bridge, and two propinoic acid side chains.

The average lifespan of a red blood cell is 4 months, after which it is phagocytosed by macrophages the spleen, liver, or lymph nodes. White blood cells, on the other hand, live for only about 3-4 days.