Exam 2 Study Guide: Blood Vessels, Circulation, and Lymphatic System (Chapters 21 & 22)

Blood Vessels and Circulation

Structure of Arteries and Veins

Arteries and veins are the main types of blood vessels, each with distinct structural features suited to their functions.

• Arteries: Thick, muscular walls; carry blood away from the heart under high pressure.

• Veins: Thinner walls, larger lumen; carry blood toward the heart under lower pressure; contain valves to prevent backflow.

• Example: The aorta is a large artery, while the vena cava is a large vein.

Structure of Capillaries

Capillaries are the smallest blood vessels, facilitating exchange between blood and tissues.

• Single layer of endothelial cells allows for efficient diffusion.

• Types: Continuous, fenestrated, and sinusoidal capillaries.

• Example: Fenestrated capillaries are found in kidneys for rapid filtration.

Components of Circulatory Pressure

Circulatory pressure is essential for blood flow throughout the body.

• Blood Pressure: Force exerted by blood on vessel walls.

• Capillary Hydrostatic Pressure: Drives fluid out of capillaries into tissues.

• Venous Pressure: Pressure within veins, much lower than arterial pressure.

Resistance to Blood Flow

Resistance opposes blood flow and is influenced by several factors.

• Vascular Resistance: Determined by vessel diameter and length.

• Viscosity: Thickness of blood; higher viscosity increases resistance.

• Turbulence: Irregular flow increases resistance, often at vessel branches.

Arterial Blood Pressure

Arterial blood pressure is measured in terms of systolic and diastolic values.

• Systolic Pressure: Maximum pressure during heart contraction.

• Diastolic Pressure: Minimum pressure during heart relaxation.

• Pulse Pressure: Difference between systolic and diastolic pressures.

• Mean Arterial Pressure (MAP): Average pressure in arteries during one cardiac cycle.

Formula:

$\text{MAP} = \text{Diastolic Pressure} + \frac{1}{3}(\text{Systolic Pressure} - \text{Diastolic Pressure})$

Capillary Exchange

Capillary exchange involves movement of substances between blood and tissues.

• Filtration: Movement of fluid out of capillaries due to hydrostatic pressure.

• Reabsorption: Movement of fluid into capillaries due to osmotic pressure.

• Forces: Hydrostatic and osmotic pressures.

Factors Assisting Venous Blood Propulsion

Several mechanisms help return blood to the heart through veins.

• Valves: Prevent backflow.

• Skeletal Muscle Pump: Muscle contractions push blood upward.

• Respiratory Pump: Changes in thoracic pressure during breathing assist venous return.

Cardiovascular Regulation

The cardiovascular system is regulated by multiple mechanisms.

• Autoregulation: Local adjustments in blood flow.

• Neural Mechanisms: Baroreceptors and chemoreceptors adjust heart rate and vessel diameter.

• Hormonal Regulation: Hormones like epinephrine and angiotensin II affect blood pressure.

Effect of Exercise

Exercise increases cardiac output and blood flow to muscles.

• Heart rate and stroke volume increase.

• Vasodilation in active muscles.

Baroreceptor and Chemoreceptor Reflexes

These reflexes help maintain homeostasis in blood pressure and gas levels.

• Baroreceptors: Detect changes in blood pressure.

• Chemoreceptors: Detect changes in blood O2, CO2, and pH.

Circulatory Shock

Shock occurs when blood flow is insufficient to meet tissue needs.

• Types: Hypovolemic, cardiogenic, obstructive, and distributive shock.

Arteriosclerosis

Arteriosclerosis is the hardening and thickening of arterial walls.

• Can lead to hypertension and reduced blood flow.

Major Blood Vessels

Major vessels include arteries, veins, and capillaries throughout the body.

• Examples: Aorta, carotid arteries, jugular veins, femoral arteries.

Lymphatic System and Immunity

Functions of the Lymphatic System

The lymphatic system maintains fluid balance and provides immune defense.

• Returns excess tissue fluid to the bloodstream.

• Absorbs fats from the digestive tract.

• Defends against pathogens.

Components of the Lymphatic System

The system consists of vessels, cells, and organs.

• Lymph: Fluid transported by lymphatic vessels.

• Lymphatic vessels: Network transporting lymph.

• Lymphoid organs: Lymph nodes, spleen, thymus, tonsils.

Major Lymphatic Vessels and Areas of Drainage

Lymphatic vessels collect and return lymph to the bloodstream.

• Thoracic duct: Drains most of the body.

• Right lymphatic duct: Drains right upper quadrant.

Types of Lymphocytes and Their Functions

Lymphocytes are key immune cells.

• T cells: Cell-mediated immunity.

• B cells: Produce antibodies.

• NK cells: Destroy abnormal cells.

Major Lymphoid Organs and Their Functions

Lymphoid organs filter lymph and house immune cells.

• Lymph nodes: Filter lymph, activate immune response.

• Spleen: Filters blood, removes old RBCs.

• Thymus: Matures T cells.

• Tonsils: Protect against inhaled/ingested pathogens.

Types of Nonspecific Defenses

Nonspecific defenses protect against a wide range of pathogens.

• Physical barriers: Skin, mucous membranes.

• Phagocytes: Engulf pathogens.

• Immunological surveillance: NK cells.

• Interferons: Antiviral proteins.

• Complement system: Proteins aiding phagocytosis and inflammation.

• Inflammatory response: Localized tissue response.

• Fever: Inhibits pathogens, speeds repair.

Specific Defense Mechanisms

Specific defenses target particular pathogens.

• Cell-mediated immunity: T cells attack infected cells.

• Antibody-mediated immunity: B cells produce antibodies.

Properties of Immunity

Immunity has several key properties.

• Specificity: Targets specific antigens.

• Versatility: Responds to many antigens.

• Memory: Faster response upon re-exposure.

• Tolerance: Does not attack self-antigens.

Types of T Cells and Their Actions

T cells are classified by their functions.

• Helper T cells (CD4): Activate other immune cells.

• Cytotoxic T cells (CD8): Destroy infected cells.

• Regulatory T cells: Suppress immune response.

• Memory T cells: Provide long-term immunity.

Types of Antibodies

Antibodies (immunoglobulins) are classified by structure and function.

• IgG: Most abundant, crosses placenta.

• IgA: Found in secretions.

• IgM: First produced in response.

• IgE: Involved in allergies.

• IgD: Functions mainly as a receptor.

Primary and Secondary Responses to Antigen Exposure

The immune system responds differently to first and subsequent exposures.

• Primary response: Slow, initial exposure.

• Secondary response: Rapid, stronger upon re-exposure.

Hypersensitivities

Hypersensitivity is an exaggerated immune response.

• Immediate: Rapid, e.g., allergies.

• Delayed: Hours to days, e.g., contact dermatitis.

Anaphylaxis

Anaphylaxis is a severe, immediate allergic reaction.

• Can cause shock and requires emergency treatment.

Immunodeficiency Diseases

Immunodeficiency results from impaired immune function.

• Examples: AIDS, SCID.

Active Immunization

Active immunization stimulates the immune system to produce antibodies.

• Vaccines: Provide protection against specific diseases.

AIDS

AIDS is caused by HIV, leading to severe immunodeficiency.

• Destroys helper T cells.

Inflammation

Inflammation is the body's response to injury or infection.

• Signs: Redness, heat, swelling, pain.

• Purpose: Isolate injury, recruit immune cells, promote healing.

Summary Table: Types of Lymphocytes and Their Functions

Type	Main Function
T cells	Cell-mediated immunity; destroy infected cells
B cells	Produce antibodies; humoral immunity
NK cells	Immunological surveillance; destroy abnormal cells

Summary Table: Types of Antibodies

Type	Function
IgG	Most abundant; crosses placenta
IgA	Found in secretions (saliva, tears)
IgM	First produced in response
IgE	Allergic reactions
IgD	Receptor on B cells

Additional info: Academic context and definitions were added to expand brief review points into comprehensive study notes.