Circulatory System: Heart, Blood, Vessels, and Function
Circulatory System: Composition and Function
The circulatory system consists of the heart and blood vessels. Blood is composed of 45% blood cells and 55% plasma, which is a liquid.
Blood Plasma
Blood plasma is a yellowish liquid consisting of water and a great variety of dissolved substances.
Blood Cells
Blood cells are formed in the red bone marrow. There are three types:
- Red blood cells: The most abundant cells in the blood.
- White blood cells: Several types of white blood cells exist, and all have a nucleus.
- Platelets: Cell fragments found in small groups.
Transport Function of Blood
Blood, with its high water content, functions as a transport system. Dissolved solids are transported in the plasma. It carries carbon dioxide gas dissolved in water.
Other Functions of Blood
- Distributes body heat.
- Defense: White blood cells defend the body from infection.
- Hemorrhage control: Platelets control blood clotting and stop bleeding.
Diseases Associated with Blood
Most of the diseases associated with blood occur due to a malfunction of the red marrow.
- Anemia: Symptoms include fatigue and loss of vitality. The blood of patients with anemia has a low amount of hemoglobin, often from iron deficiency.
- Leukemia: A cancer affecting the bone marrow, which is responsible for manufacturing blood cells.
- Hemophilia: A hereditary condition manifested by sudden hemorrhage or strokes due to clotting problems.
Types of Blood Vessels
- Arteries: Conduits that carry blood from the heart to all organs. Their walls are strong.
- Veins: Lead blood from the organs to the heart. Their walls are thinner than arteries.
- Capillaries: Small diameter vessels that form walls inside organs, connecting circulatory routes.
The Heart
The heart is an organ located in the center of the chest. Its walls are made of a tissue called myocardium. It is hollow inside and divided into four chambers:
- Two atria: The upper chambers have thin, extensible walls.
- Two ventricles: The lower chambers have thick walls. Blood leaves the heart from the ventricles, driven by the arteries.
Blood Circulation
Blood travels through a double circuit:
- Pulmonary circuit: Blood leaves the right ventricle through arteries and goes to the lungs, where gas exchange occurs with the alveoli.
- Systemic circuit: Blood leaves the left ventricle through the aorta and reaches all the organs.
Four Systems for the Function of Nutrition
Nourishment is more complex than feeding. It involves the digestive, circulatory, respiratory, and urinary systems.
- Circulatory system: Nutrients and wastes are transported by the blood, flowing through blood vessels driven by the heartbeat.
- Digestive system: Responsible for transforming the complex molecules that form food into soluble nutrients.
- Respiratory system: Breathing is not sufficient for nutrient absorption; cells also need oxygen.
- Urinary system: Using nutrients, cells not only generate carbon dioxide as waste but also urea, another nutrient that contains nitrogen.