Blood Physiology Anatomy and Its Functions 1. Physiological Functions of Blood for the Body The means of blood circulation in humans is mainly blood. Blood has three main functions for the body, namely as follows: 1) Blood is the main means of transportation for the human body which can transport gases, nutrients and waste products of the body's metabolism. Oxygen (O2) which comes from the lungs will be transported by the blood and will be distributed to the body's cells. Then carbon dioxide (CO2) which is one of the metabolic wastes that is not needed by the body will be removed from the lungs. Apart from that, blood also transports other waste products such as excess nitrogen which is then carried to the kidneys for elimination. Blood as a tool Transport also transports hormones secreted by glands for distribution to body cells that need them. 2) Blood acts as the body's defense system against attacks by pathogens or foreign objects that enter the body and also protects the body from blood loss (in the blood clotting process). 3) Blood plays an important role in maintaining stable body temperature or plays an important role in body homeostasis. 2. Blood Characteristics Blood has several main characteristics, namely as follows: 1) Color, blood in the arteries (veins) is pink because it contains a lot of oxygen (O2). This is related to Hemoglobin (Hb) which has a high ability to bind with oxygen. The blood in the veins (veins) is dark/dark red because it lacks oxygen (rich in CO2) compared to arterial blood. 2) pH (degree of acidity), normal blood pH levels range from 7.35 – 7.45. Meanwhile, if a person has a pH level greater than 7.45, this indicates that the blood is too alkaline and this condition is called alkalosis. 3) Blood Volume, blood volume in humans reaches 5 – 8% of body weight. Newborn babies weighing around 2.6 – 3.6 kilograms only have around 0.2 liters of blood in their bodies. 3. Blood Components Blood is an essential component for the human body. In blood there are two components, namely blood cells and blood fluid called blood plasma which contains various nutrients and other substances. The blood plasma component is around 55%, then the remaining 45% is the blood cell component. The main components of human blood in detail consist of: a. Blood Cells - Erythrocytes (human blood cells) - Leukocytes (white blood cells) - Platelets (blood platelets) b. In blood plasma there are substances that are important for the human body. These substances are albumin proteins, globulins, blood clotting factors, and various electrolytes sodium (Na+), potassium (K+), chloride (Cl-), Magnesium (Mg2+), hormones, and so on.