Circulatory System Overview

Circulatory System Overview

• The circulatory system, also known as the cardiovascular system, is responsible for distributing essential nutrients, oxygen, and other substances to all parts of the body.
• The heart is a hollow muscular organ about the size of a clenched fist, located behind the sternum and between the lungs.

The Heart

• The heart pumps over 500 million liters of blood throughout a person's life.
• The average heart beats 2400 million times in a person's lifetime.
• The heart is enclosed in a protective sac called the pericardium.
• The heart wall is called myocardium. The myocardium's contraction and relaxation creates a definite cycle.
• The heart has four chambers: two atria (upper chambers) and two ventricles (lower chambers).

Blood Vessels

• Blood vessels are responsible for carrying blood throughout the body. They are mainly arteries, capillaries, and veins.
• Arteries carry oxygen-rich blood away from the heart.
• Veins carry oxygen-poor blood back to the heart.
• Capillaries have very thin walls and exchange materials between blood and cells. They also help regulate body temperature.
• Arteries have thicker walls than veins to withstand higher blood pressure.
• Veins have valves to prevent blood from flowing backward.

Blood Composition

• Blood is referred to as the "red river of life" because it delivers vital nutrients and oxygen to body parts and removes waste products.
• Blood is composed of two parts:
  • Solid part or cellular: This part consists of blood cells (red blood cells, white blood cells, and platelets) and accounts for approximately 45% of blood volume.
  • Liquid part or plasma: This is composed mainly of water and proteins, and carries nutrients, hormones, and waste products. It makes up approximately 55% of blood volume.

Blood Components

• Red blood cells (erythrocytes): Carry oxygen from the lungs to tissues and carbon dioxide from tissues to the lungs. They contain hemoglobin, which gives blood its red color.
• White blood cells (leukocytes): Protect the body from disease. They are part of the immune system
• Platelets (thrombocytes): Crucial for blood clotting. They are cell fragments that assist in preventing blood loss when a blood vessel is damaged. They help form clots.

Circulation Pathways

• Systematic circulation: Blood flow from the heart to the body and back to the heart, excluding the lungs.
• Pulmonary circulation: Blood flow between the heart and the lungs. This is where oxygen is picked up and carbon dioxide is released.
• Coronary circulation: Blood flow to the heart muscle itself. Brings oxygen and nutrients to heart tissue.

Common Circulatory System Ailments

• Hypertension: High blood pressure, often caused by narrowed arteries.
• Stroke: Blood clot blocks blood flow to the brain, potentially causing brain damage.
• Rheumatic heart disease: Repeated throat infections can lead to heart lining inflammation/weakening of the heart's valves.
• Leukemia: Cancer of the blood, characterized by the overproduction of immature white blood cells in bone marrow.
• Anemia: Decrease of hemoglobin in red blood cells reduces oxygen delivery to cells.

Caring for the Circulatory System

• Eat a balanced diet.
• Avoid too much fat and salt.
• Avoid smoking and alcohol.
• Exercise regularly.
• Manage stress.
• Get adequate rest.
• Never self-medicate without consulting a doctor.

(Questions for Page 123)

• 1. The heart is considered a powerful machine due to its continuous, forceful pumping action that delivers blood throughout the body.
• 2. Atria are thin-walled, receiving chambers. Ventricles are thick-walled, pumping chambers. Their function differences reflect the different pressures required.
• 3. Blood vessels carry blood throughout the body, delivering oxygen, nutrients, and removing waste products.
• 4. Arteries carry oxygenated blood away from the heart, while veins carry deoxygenated blood back to the heart. Artery walls are thicker.
• 5. Platelets are essential for blood clotting, stopping bleeding and preventing blood loss.