Anatomy of Blood Circulation and Cardiac Health
Characteristics of the Human Circulatory System
- It is closed: The blood flows within blood vessels. When a blood vessel breaks, bleeding occurs.
- It is double: There are two circuits: the systemic circuit (general) that travels around the body and the pulmonary circuit (smaller) that targets the lungs.
- It is complete: There is no mixing of oxygen-rich blood with oxygen-poor blood in the heart.
Lymph and Interstitial Fluid
Lymph: This consists of plasma and lymphocytes. The liver forms urea from uric acid. Interstitial fluid is the plasma medium located in the spaces between cells.
Functions of Blood
The blood carries nutrients and oxygen to the cells and collects waste products formed in cell metabolism, such as urea, uric acid, and CO2. It also handles temperature regulation, as body heat is distributed similarly to a heating system, moving from hot to cold areas.
Composition of Blood
Blood plasma, which has a yellowish color, is comprised of water, mineral salts, nutrients, waste substances, proteins, and hormones.
Blood Cells
- Red blood cells (Erythrocytes): These are the most numerous cells in the blood. They are disc-shaped and have no nucleus. They contain hemoglobin, which is responsible for transporting oxygen from the lung alveoli where it is collected by the blood.
- Leukocytes (White blood cells): These are fewer in number than red blood cells and are responsible for defending the body. Types of leukocytes include granulocytes, agranulocytes, monocytes, and lymphocytes.
- Thrombocytes (Platelets): These are fragments of cells containing substances that enable blood clotting.
The blood cells are formed in the red bone marrow.
Blood Vessels and the Cardiac Cycle
The system includes veins, arteries, and capillaries. The cardiac cycle consists of:
- Atrial systole: The atria contract and the blood is pumped into the ventricles through the atrioventricular valves, which open.
- Ventricular systole: The ventricles contract and the blood contained in them exits through the pulmonary artery and aorta as the semilunar valves open.
- Diastole: The heart relaxes and blood enters the atria, which are filled with blood from the vena cava and pulmonary veins.
The flow follows this path: Veins > Atrium > Ventricle > Arteries.
Common Cardiovascular and Blood Diseases
Heart Diseases
- Myocardial infarction
- Angina pectoris
- Heart failure
- Endocarditis
- Heart valve abnormalities
Blood Diseases
- Anemia
- Leukemia
- Hemophilia
- Thrombosis