Cardiovascular System

Blood Vessels and Circulation

The cardiovascular system consists of the heart and blood vessels, which transport blood throughout the body. Blood vessels are classified based on their structure and function.

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

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

• Capillaries: Microscopic vessels; site of exchange between blood and tissues.

Key Terms:

• Vasoconstriction: Narrowing of blood vessels, increasing blood pressure.

• Vasodilation: Widening of blood vessels, decreasing blood pressure.

• Blood Pressure: The force exerted by circulating blood on the walls of blood vessels.

Example: Blood pressure is highest in arteries and lowest in veins.

Blood Flow and Pressure Regulation

Blood flow is regulated by vessel diameter, blood volume, and cardiac output. Blood pressure is determined by cardiac output and resistance.

• Cardiac Output (CO): The amount of blood pumped by the heart per minute.

• Resistance: Opposition to blood flow, mainly due to vessel diameter.

Equation:

Example: Vasoconstriction increases resistance and blood pressure.

Lymphatic System

Functions and Components

The lymphatic system returns excess tissue fluid to the bloodstream and provides immune defense. It consists of lymph, lymphatic vessels, and lymphoid organs.

• Lymph: Fluid similar to plasma, but with fewer proteins.

• Lymphatic Vessels: Transport lymph; contain valves.

• Lymphoid Organs: Include lymph nodes, spleen, thymus, tonsils.

Example: Lymph nodes filter lymph and trap pathogens.

Lymphoid Tissue Structure

Lymphoid tissue consists of reticular fibers and lymphocytes. It is found in lymphoid organs and mucosa-associated lymphoid tissue (MALT).

• Primary Lymphoid Organs: Thymus and bone marrow (site of lymphocyte production).

• Secondary Lymphoid Organs: Lymph nodes, spleen, MALT (site of immune responses).

Example: The spleen filters blood and removes old red blood cells.

Immune System

Innate vs. Adaptive Immunity

The immune system protects the body from pathogens through innate (nonspecific) and adaptive (specific) defenses.

• Innate Immunity: Present at birth; includes barriers (skin, mucous membranes), phagocytes, inflammation, fever.

• Adaptive Immunity: Develops after exposure; involves lymphocytes (B cells and T cells); specific to antigens.

Example: Skin acts as a physical barrier; antibodies target specific pathogens.

Cells of the Immune System

Immune cells include lymphocytes, macrophages, dendritic cells, and others.

• B Lymphocytes (B cells): Produce antibodies; responsible for humoral immunity.

• T Lymphocytes (T cells): Responsible for cell-mediated immunity; include helper, cytotoxic, and regulatory T cells.

• Macrophages: Engulf and destroy pathogens; present antigens to T cells.

Example: Helper T cells activate B cells and cytotoxic T cells.

Inflammatory Response

Inflammation is a protective response to injury or infection, characterized by redness, heat, swelling, and pain.

• Steps: Vasodilation, increased permeability, migration of phagocytes, tissue repair.

Example: Inflammation helps isolate and destroy pathogens.

Respiratory System

Structure and Function

The respiratory system provides oxygen to the body and removes carbon dioxide. It consists of the airways, lungs, and respiratory muscles.

• Upper Respiratory Tract: Nose, pharynx, larynx.

• Lower Respiratory Tract: Trachea, bronchi, lungs.

Example: The alveoli are the site of gas exchange in the lungs.

Mechanics of Breathing

Breathing involves inspiration (inhalation) and expiration (exhalation), driven by changes in thoracic volume and pressure.

• Inspiration: Diaphragm contracts, thoracic volume increases, pressure decreases, air flows in.

• Expiration: Diaphragm relaxes, thoracic volume decreases, pressure increases, air flows out.

Equation:

Example: During exercise, respiratory rate and depth increase.

Gas Exchange and Transport

Oxygen and carbon dioxide are exchanged in the alveoli and transported in the blood.

• Oxygen Transport: Mostly bound to hemoglobin in red blood cells.

• Carbon Dioxide Transport: Dissolved in plasma, bound to hemoglobin, or as bicarbonate ions.

Equation:

Example: Increased CO2 levels lower blood pH (respiratory acidosis).

Table: Comparison of Blood Vessel Types

Table: Innate vs. Adaptive Immunity

Additional info: Some details and examples were expanded for clarity and completeness based on standard Anatomy & Physiology curriculum.