Understanding the Human Circulatory System
The Human Circulatory System
The circulatory system consists of a pump (the heart), a liquid (blood), and a series of ducts (blood vessels) through which blood is pumped throughout the body.
Composition of Blood
Blood is composed of a liquid part called plasma and different types of blood cells.
- Blood plasma: A yellowish liquid formed by water.
- Blood cells: Formed in the red bone marrow. There are three types:
- Red blood cells (erythrocytes or RBCs)
- White blood cells (leukocytes)
- Platelets (thrombocytes)
Blood’s Transport Function
Blood, with its high water content, functions as an efficient transport system.
- Carries solid substances dissolved in the plasma, such as nutrients and waste.
- Carries respiratory gases: Carbon dioxide dissolves well in water and is transported by blood plasma, but oxygen is slightly soluble in water.
Other Functions of Blood
Besides transporting substances, blood performs other functions:
- Distributes body heat
- Defense
- Control of bleeding
Diseases of the Blood
- Anemia: Characterized by a low amount of hemoglobin. Symptoms include fatigue and loss of vitality. It is caused by iron deficiency and is corrected with a balanced diet rich in foods that provide iron.
- Leukemia: A form of cancer that affects the bone marrow cells responsible for making blood.
- Hemophilia: An inherited disease manifested by bleeding, which may be spontaneous or caused by a blow or wound. It is due to problems with blood clotting.
Blood Vessels
The tubes that carry blood are called blood vessels. The heart is responsible for pumping blood through them. There are three types of blood vessels: arteries, veins, and capillaries.
The Heart
The heart is an organ, the size of a fist, located in the center of the chest, slightly shifted to the left. Its walls are made of myocardial muscle tissue, and the inside is hollow and divided into four chambers: two atria and two ventricles. Blood enters the atria of the heart driven by the veins and leaves the ventricles through the arteries.
The route: The heart has a few devices or valves that force blood to circulate through the interior in one direction.
The Heartbeat
The heart is the engine of circulation. If it stops, the brain loses its oxygen and dies. In each heartbeat, a series of phenomena occur that constitute a cardiac cycle:
- Atrial systole
- Ventricular systole
- Diastole
The heartbeat is the most perceptible sign of its activity. The frequency with which the heart beats varies according to the needs of the organism.
The Path of Blood
The structure of the heart, which functions as a double pump, has a direct impact on circulation: the blood goes through a double circuit.
- Pulmonary or lesser circuit: Blood travels from the right ventricle to the pulmonary arteries and into the lungs.
- Systemic or greater circuit: Blood travels from the left ventricle through the aorta and reaches all the organs.
In a full stroke, blood passes twice through the heart: once when browsing the pulmonary circuit and the other to cross the systemic circuit.
Cardiovascular Disease
The heart and blood vessels are also known collectively as the cardiovascular system. Diseases affecting the heart are called cardiovascular diseases.
Examples include atherosclerosis and myocardial infarction.
Lifestyle and Cardiovascular Health
- Smoking
- Obesity
- Lack of exercise
Four Systems for Nutrition
Nutrition is one of the processes going on inside our body. Its goal is to make each of our cells receive the nutrients it needs and utilize them. To achieve this objective requires the coordinated operation of four major systems: digestive, respiratory, circulatory, and urinary (or excretory).