Cardiovascular System Overview

Definition and Main Functions

The cardiovascular system consists of the heart, blood vessels, and blood. Its primary function is to transport nutrients, gases, hormones, and waste products throughout the body, maintaining homeostasis and supporting cellular function.

• Transport: Delivers oxygen and nutrients to tissues; removes carbon dioxide and metabolic wastes.

• Protection: Circulates immune cells and antibodies.

• Regulation: Maintains body temperature, pH, and fluid balance.

Blood: Composition and Function

Definition and Constituents

Blood is a specialized connective tissue composed of plasma and formed elements. It serves as the medium for transport within the cardiovascular system.

• Plasma: The liquid component, making up about 55% of blood volume. Contains water, proteins (albumin, globulins, fibrinogen), electrolytes, nutrients, hormones, and waste products.

• Formed Elements: Includes erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets).

Blood as Connective Tissue: Blood is considered a connective tissue because it consists of cells suspended in a liquid matrix (plasma) and performs functions of support, transport, and protection.

Physiological Roles of Blood

• Transport of gases (O2, CO2), nutrients, and hormones

• Regulation of pH and electrolyte composition

• Protection against pathogens (immune response)

• Clotting to prevent blood loss

Blood Vessels: Types and Functions

Major Types of Blood Vessels

• Arteries: Carry blood away from the heart; usually oxygenated except for pulmonary arteries.

• Veins: Carry blood toward the heart; usually deoxygenated except for pulmonary veins.

• Capillaries: Microscopic vessels where exchange of gases, nutrients, and wastes occurs between blood and tissues.

Capillaries: Structure and Function

Capillaries have very thin walls (one cell thick) to facilitate efficient exchange of substances between blood and tissues.

• Allow diffusion of oxygen, carbon dioxide, nutrients, and waste products.

• Thin walls are crucial for rapid and efficient exchange.

Blood Vessel Size and Oxygenation

• Veins carrying deoxygenated blood from the body to the heart become larger as they approach the heart (e.g., vena cava).

• Blood in most veins has low oxygen content, but some oxygen remains.

Heart: Structure and Function

Location and Function

The heart is a muscular organ located in the thoracic cavity, slightly left of center. Its function is to pump blood throughout the body via the circulatory system.

• Receives deoxygenated blood from the body and pumps it to the lungs (pulmonary circulation).

• Receives oxygenated blood from the lungs and pumps it to the rest of the body (systemic circulation).

Chambers of the Heart

• Atria: Right and left atria receive blood returning to the heart.

• Ventricles: Right and left ventricles pump blood out of the heart.

Valves and Blood Flow

• Valves prevent backflow of blood, ensuring unidirectional flow through the heart and vessels.

• Important for maintaining efficient circulation and preventing mixing of oxygenated and deoxygenated blood.

Control of Heartbeat

• The sinus rhythm is the normal regular rhythm of the heart, initiated by the sinoatrial (SA) node.

• Electrical impulses from the SA node coordinate contraction of cardiac muscle cells.

Cardiac Muscle Cells

• Contractile cells: Responsible for the forceful contraction of the heart.

• Pacemaker cells: Generate and conduct electrical impulses; found in the SA and AV nodes.

• Contractile cells differ from pacemaker cells in their function and electrical properties.

Circulatory Pathways

Pulmonary vs. Systemic Circulation

The cardiovascular system has two main circuits:

• Pulmonary circulation: Carries deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the left atrium.

• Systemic circulation: Carries oxygenated blood from the left ventricle to the body and returns deoxygenated blood to the right atrium.

Comparison Table:

Coronary Circulation

• Coronary arteries supply oxygenated blood to the heart muscle (myocardium).

• Coronary veins return deoxygenated blood from the myocardium to the right atrium.

Transported Substances

• Gases: Oxygen and carbon dioxide

• Nutrients: Glucose, amino acids, fatty acids

• Hormones: Chemical messengers

• Waste products: Urea, creatinine

Cardiovascular Diseases and Risk Factors

Cardiovascular Disease (CVD)

Cardiovascular disease refers to a group of disorders affecting the heart and blood vessels, including coronary artery disease, stroke, and hypertension.

• Leading cause of mortality worldwide.

• Common risk factors: hypertension, high cholesterol, smoking, diabetes, obesity, sedentary lifestyle.

Coronary Artery Disease

• Occurs when coronary arteries are narrowed or blocked, reducing blood flow to the heart muscle.

• Examples: Angina pectoris, myocardial infarction (heart attack).

Stroke

• Occurs when blood flow to part of the brain is interrupted, causing tissue damage.

• Ischemic stroke: Caused by blockage of a blood vessel.

• Hemorrhagic stroke: Caused by rupture of a blood vessel.

Blood Pressure

• Systolic pressure: The higher number; pressure during heart contraction.

• Diastolic pressure: The lower number; pressure during heart relaxation.

• Normal adult blood pressure: approximately 120/80 mm Hg.

• High blood pressure (hypertension) increases risk for CVD.

Equation:

Pathology and Precursor Conditions

• Atherosclerosis: Build-up of plaque in arteries, leading to narrowing and reduced blood flow.

• Hypertension: Chronically elevated blood pressure.

Common plaque components: cholesterol, fatty substances, calcium.

Comparisons and Classifications

Arteries: Coronary vs. Pulmonary vs. Systemic

Clinical Conditions

Anemia

• Reduction in red blood cells or hemoglobin, leading to decreased oxygen transport.

• Symptoms: weakness, fatigue.

Heart Failure vs. Cardiac Arrest

• Heart failure: Chronic condition where the heart cannot pump enough blood.

• Cardiac arrest: Sudden loss of heart function; immediately life-threatening.

• Cardiac arrest is more serious and requires immediate intervention.

Summary Table: Circulatory Pathways

Additional info:

• Some explanations and tables have been expanded for clarity and completeness.

• Equations and physiological details have been added to support exam preparation.