The circulatory system's main role is to transport blood, which carries oxygen and essential nutrients to tissues. It does not produce hormones, digest food, or primarily protect from infections.

Carbohydrates are the main source of energy for the body as they are quickly converted into glucose. Proteins, vitamins, and fats serve other essential functions and are not primarily used for immediate energy production.

The kidneys filter blood by removing waste products and excess fluids, which are then excreted as urine. Other organs perform different roles, such as metabolism, gas exchange, or blood circulation.

BMI stands for Body Mass Index, which is used to assess body fat based on a person's weight and height. It is a widely used indicator in health science for evaluating whether an individual's weight is in a healthy range.

Arteries are responsible for carrying oxygenated blood from the heart to the rest of the body. Veins, on the other hand, return deoxygenated blood back to the heart while capillaries facilitate the exchange of substances between blood and tissues.

Red blood cells contain hemoglobin, the protein that binds oxygen and carries it to tissues throughout the body. Their primary role is oxygen transport, unlike white blood cells or platelets which have different functions.

Vitamin D is crucial because it facilitates the absorption of calcium, which is vital for maintaining strong bones. While other vitamins are important, they do not play as significant a role in calcium metabolism and bone health.

Insulin is a hormone that helps lower blood glucose levels by promoting the uptake of glucose into cells for energy production. The other options do not accurately describe insulin's function in regulating blood sugar.

The endocrine system is responsible for producing and releasing hormones that regulate a wide range of body functions including growth and metabolism. Other systems have different primary functions such as signal transmission or circulation.

Type 2 diabetes is primarily caused by insulin resistance, where the body's cells do not respond effectively to insulin. This is distinct from type 1 diabetes, which involves autoimmune destruction of insulin-producing cells.

Skeletal muscle is voluntary and has a striated appearance due to its organized fiber structure. In contrast, smooth muscle is involuntary and cardiac muscle, although striated, is not under voluntary control.

Smoking is a risk factor that individuals can change to reduce their risk of cardiovascular disease. Factors like age, gender, and family history are non-modifiable and cannot be altered through personal behavior.

Epidemiology focuses on understanding how diseases affect populations and identifying factors that influence their distribution. It differs from disciplines that deal with individual treatment or structural anatomy.

Platelets are the blood components that initiate clotting by aggregating at injury sites to form a plug. Red and white blood cells, as well as plasma, have different primary roles in oxygen transport and immune response.

The respiratory system is responsible for the exchange of gases, bringing oxygen into the body and removing carbon dioxide. Other functions such as nutrient circulation and digestion are managed by different bodily systems.

COPD is characterized by the destruction of alveolar walls, which enlarges airspaces and hampers effective gas exchange. This tissue damage leads to reduced respiratory efficiency rather than improved lung function.

A Complete Blood Count (CBC) measures hemoglobin and red blood cell levels, which directly indicates the oxygen-carrying capacity of the blood. Other tests focus on heart structure or lung performance and do not specifically assess oxygen transport.

Allergic bronchospasm is most commonly associated with a Type I hypersensitivity reaction, which is mediated by IgE antibodies. The other hypersensitivity types involve different immune mechanisms that are not typically responsible for immediate allergic responses.

Regular exercise strengthens the heart, leading to an increased stroke volume, which means more blood is pumped with each beat. This adaptation allows the heart to work efficiently at a lower rate during rest.

This intervention is designed to prevent obesity and related diseases before they occur, which is the goal of primary prevention. It focuses on education and lifestyle changes rather than early disease detection or managing existing conditions.