BI233 Midterm Exam #1 Study Guide: Blood, Lymphatic System, and Immunity

Chapter 17: Blood - White Blood Cells

General Structural and Functional Characteristics of the Five White Blood Cells

White blood cells (WBCs), or leukocytes, are crucial components of the immune system, each with distinct structures and functions.

• Neutrophils: Multi-lobed nucleus; cytoplasmic granules stain light purple. Function as phagocytes, especially effective against bacteria and fungi.

• Lymphocytes: Large, round nucleus with a thin rim of cytoplasm. Involved in adaptive immunity; B cells produce antibodies, T cells mediate cellular immunity.

• Monocytes: Largest WBC, kidney-shaped nucleus. Differentiate into macrophages in tissues; phagocytize pathogens and debris.

• Eosinophils: Bi-lobed nucleus, red-orange granules. Combat parasitic infections and modulate allergic responses.

• Basophils: Bi-lobed or S-shaped nucleus, large blue-purple granules. Release histamine and heparin during inflammatory and allergic reactions.

Example: Neutrophils are the first responders to bacterial infection, engulfing and destroying pathogens.

Chapter 19: Capillary Exchange and Bulk Flow

Fluid Movement Across Capillary Walls (Bulk Flow)

Bulk flow refers to the movement of fluid and solutes across capillary walls, driven by pressure differences.

• Hydrostatic Pressure: The force exerted by fluid pressing against a wall; pushes fluid out of capillaries into tissues.

• Colloid Osmotic Pressure: The pulling force exerted by plasma proteins (mainly albumin); draws fluid back into capillaries.

Equation:

$Net\ Filtration\ Pressure = (HP_c + OP_{if}) - (HP_{if} + OP_c)$

Where HP = hydrostatic pressure, OP = osmotic pressure, c = capillary, if = interstitial fluid.

Example: At the arterial end of a capillary, hydrostatic pressure exceeds osmotic pressure, resulting in net filtration (fluid leaves the capillary).

Chapter 20: The Lymphatic System and Lymphoid Organs and Tissues

Structure and Function of Lymphatic Capillaries

• Modified Features:

  • Endothelial cells overlap loosely, forming one-way minivalves that allow interstitial fluid to enter but not exit.

  • Anchoring filaments attach capillaries to surrounding tissue, preventing collapse and opening minivalves when interstitial pressure increases.

Example: During inflammation, increased interstitial fluid opens minivalves, allowing more fluid and debris to enter lymphatic capillaries.

Pathway of Lymphatic Fluid

1. Interstitial fluid enters lymphatic capillaries.

2. Lymph flows through collecting vessels, passing through lymph nodes.

3. Lymphatic trunks collect lymph from large regions of the body.

4. Lymph is delivered to one of two ducts:

   • Right lymphatic duct: Drains right upper limb, right side of head and thorax.

   • Thoracic duct: Drains the rest of the body.

5. Both ducts empty into the subclavian veins, returning lymph to the bloodstream.

Lymphoid Cells and Their Functions

• Lymphocytes: Main warriors of the immune system; B cells (produce antibodies), T cells (cell-mediated immunity).

• Macrophages: Phagocytize foreign substances and help activate T cells.

• Dendritic Cells: Capture antigens and present them to lymphocytes.

• Reticular Cells: Produce the stroma (network) that supports other cells in lymphoid organs.

Protective Functions of Lymph Nodes

• Filter lymph, removing debris and pathogens.

• Site of immune cell activation and proliferation.

Primary vs. Secondary Lymphoid Organs

Primary Lymphoid Organs	Secondary Lymphoid Organs
Bone marrow, thymus	Lymph nodes, spleen, tonsils, MALT
Site of lymphocyte development and maturation	Site of immune response activation

Lymphatic Fluid vs. Blood

• Lymphatic fluid: Clear, contains less protein, no red blood cells.

• Blood: Contains red and white blood cells, platelets, and plasma proteins.

Lymphatic Vessels vs. Blood Vessels

• Lymphatic vessels: Thin-walled, contain valves, carry lymph one-way toward the heart.

• Blood vessels: Thicker walls, carry blood in a closed circuit (arteries and veins).

Lymph Node Structure, Function, and Pathway

• Structure: Encapsulated, bean-shaped; cortex (with follicles), medulla (cords and sinuses).

• Function: Filter lymph, immune surveillance.

• Pathway: Lymph enters via afferent vessels, percolates through cortex and medulla, exits via efferent vessels.

Spleen Structure, Function, and Blood Pathway

• Structure: Surrounded by a capsule; contains white pulp (lymphoid tissue) and red pulp (blood-filled sinuses).

• Function: Filters blood, recycles old red blood cells, stores platelets and monocytes.

• Pathway: Blood enters via splenic artery, passes through white and red pulp, exits via splenic vein.

Major Functional Difference: Lymph Node vs. Spleen

• Lymph node: Filters lymph.

• Spleen: Filters blood.

White Pulp vs. Red Pulp of the Spleen

White Pulp	Red Pulp
Lymphocyte-rich; immune functions	Removes old RBCs, stores platelets

Chapter 21: The Immune System: Innate and Adaptive Body Defenses

Innate vs. Adaptive Immunity

• Innate immunity: Non-specific, immediate response; includes barriers and internal defenses.

• Adaptive immunity: Specific, slower to respond; involves lymphocytes and memory cells.

First vs. Second Lines of Defense (Innate Immunity)

• First line: Physical and chemical barriers (skin, mucous membranes, secretions).

• Second line: Internal defenses (phagocytes, natural killer cells, inflammation, antimicrobial proteins, fever).

Chemicals and Secretions of Physical Barriers

• Acid mantle: Skin and stomach acidity inhibits microbial growth.

• Enzymes: Lysozyme in saliva, tears, and mucus destroys bacteria.

• Mucin: Traps microorganisms in mucus.

• Defensins: Antimicrobial peptides in skin and mucosae.

Antimicrobial Proteins (Second Line Defense)

• Interferons: Proteins released by virus-infected cells; help protect neighboring cells.

• Complement: Group of plasma proteins that enhance inflammation, promote phagocytosis, and lyse pathogens.

• Transferrins: Bind iron, limiting bacterial growth. Additional info: Some sources may list other proteins such as defensins or collectins.

Phagocyte Mobilization and Phagocytosis

1. Leukocytosis: Increased production of neutrophils.

2. Margination: Neutrophils cling to capillary walls.

3. Diapedesis: Neutrophils squeeze through capillary walls into tissues.

4. Chemotaxis: Neutrophils migrate toward chemical signals at infection site.

5. Phagocytosis: Engulfment and digestion of pathogens by phagocytes.

Humoral vs. Cell-Mediated Immunity (Adaptive Immunity)

Humoral Immunity	Cell-Mediated Immunity
B cells, antibodies in body fluids	T cells, direct cellular attack
Effective against extracellular pathogens	Effective against intracellular pathogens

MHC Class I vs. MHC Class II Receptors

• MHC Class I: Found on all nucleated cells; present endogenous antigens to CD8+ cytotoxic T cells.

• MHC Class II: Found on antigen-presenting cells; present exogenous antigens to CD4+ helper T cells.

Lymphocyte Development, Maturation, Activation, Proliferation, and Differentiation

• Development: Originates from hematopoietic stem cells in bone marrow.

• Maturation: B cells mature in bone marrow; T cells mature in thymus.

• Activation: Encounter with specific antigen triggers activation.

• Proliferation: Activated lymphocytes divide rapidly.

• Differentiation: B cells become plasma cells or memory cells; T cells become helper, cytotoxic, or memory T cells.

Major Antigen Presenting Cells (APCs) and Their Functions

• Dendritic cells: Capture antigens, migrate to lymph nodes, present to T cells.

• Macrophages: Phagocytize pathogens, present antigens to T cells, secrete cytokines.

• B cells: Present antigens to helper T cells, differentiate into plasma cells.

Primary vs. Secondary Immune Responses

• Primary response: First exposure to antigen; slower, lower antibody production.

• Secondary response: Subsequent exposure; faster, stronger, longer-lasting due to memory cells.

Antibody Classes and Their Roles

Class	Main Function
IgM	First antibody produced; effective in agglutination and complement activation
IgG	Main antibody in blood; crosses placenta; provides long-term immunity
IgA	Found in mucosal areas and secretions; protects body surfaces
IgD	Functions as B cell receptor
IgE	Involved in allergic reactions and defense against parasites

Active vs. Passive Immunity (Humoral Immunity)

• Active immunity: Body produces its own antibodies after exposure to antigen (infection or vaccination).

• Passive immunity: Antibodies are transferred from another source (maternal antibodies, antibody injection); no memory cells produced.

Laboratory Activities

Laboratory Preparation

• Review laboratory worksheets, illustrations, course images, and virtual slides from Weeks 1-2.

• Revisit extra credit study guides, journal article annotation project, and lab exam practice assignments.

• Consult notes and materials from in-person tutoring sessions if attended.

Additional info: Laboratory activities reinforce concepts from lectures and readings, focusing on identification of blood cells, lymphatic structures, and immune responses.