Cardiovascular System

Heart Anatomy

The heart is a muscular organ responsible for pumping blood throughout the body. Its structure includes chambers, valves, major vessels, and accessory features that support its function.

• Chambers: The heart has four chambers: two atria (upper) and two ventricles (lower).

• Valves: Valves (tricuspid, bicuspid/mitral, pulmonary, aortic) ensure unidirectional blood flow and prevent backflow.

• Major Vessels: Includes the aorta, pulmonary arteries and veins, superior and inferior vena cava.

• Accessory Structures: Includes the septa (interatrial and interventricular), chordae tendineae, and papillary muscles.

Heart Physiology

The heart's function is regulated by electrical conduction and the cardiac cycle, which coordinates contraction and relaxation.

• Cardiac Cycle: Sequence of events in one heartbeat, including systole (contraction) and diastole (relaxation).

• Electrical Conduction Pathway: Involves the sinoatrial (SA) node, atrioventricular (AV) node, bundle of His, bundle branches, and Purkinje fibers.

• Blood Flow: Blood enters the right atrium, passes to the right ventricle, is pumped to the lungs, returns to the left atrium, and is pumped out to the body via the left ventricle.

Blood

Plasma

Plasma is the liquid component of blood, making up about 55% of its volume.

• Dissolved Substances: Includes proteins (albumin, globulins, fibrinogen), nutrients (glucose, amino acids), electrolytes, hormones, and waste products.

Formed Elements

Formed elements are the cellular components of blood, including red blood cells (RBCs), white blood cells (WBCs), and platelets.

• RBCs (Erythrocytes): Specialized for oxygen transport; contain hemoglobin. Most abundant formed element.

• WBCs (Leukocytes): Involved in immune defense. Several types exist, each with specific functions.

• Platelets (Thrombocytes): Cell fragments essential for blood clotting.

Structure and Function of Blood Cells

• RBCs: Biconcave shape increases surface area for gas exchange; lack nuclei in mammals.

• WBCs: Types include neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Each type has unique roles in immunity.

• Platelets: Initiate clotting by adhering to damaged vessel walls and releasing clotting factors.

Vascular System

Types of Vessels

The vascular system consists of arteries, veins, and capillaries, each with distinct structural and functional characteristics.

• Arteries: Carry blood away from the heart; thick muscular walls; high pressure.

• Veins: Carry blood toward the heart; thinner walls; contain valves to prevent backflow.

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

Functional Differences and Classification

Pressure

• Blood Pressure: The force exerted by circulating blood on vessel walls. Measured in mmHg.

• Control: Regulated by cardiac output, vessel diameter, and blood volume.

• Pathology: Hypertension (high BP) and hypotension (low BP) are common disorders.

Blood Flow

• How Controlled: By heart rate, vessel resistance, and blood viscosity.

• Equation:

Where = blood flow, = pressure difference, = resistance.

Capillaries

• Function: Site of exchange for gases, nutrients, and wastes.

• Fluid Loss/Absorption: Governed by hydrostatic and osmotic pressures.

Lymphatic System

Anatomy and Physiological Role

The lymphatic system is a network of vessels and organs that returns excess tissue fluid to the bloodstream and plays a key role in immune defense.

• Lymphatic Vessels: Collect and transport lymph (fluid) from tissues to veins.

• Lymph Nodes: Filter lymph and house immune cells.

• Other Organs: Spleen, thymus, tonsils.

Comparison to Cardiovascular System

Cells of the Lymphatic System

• Lymphocytes: Key immune cells (B cells and T cells) responsible for adaptive immunity.

• Macrophages: Engulf pathogens and debris.

• Dendritic Cells: Present antigens to lymphocytes.

Additional info: Academic context and definitions have been expanded for clarity and completeness.