Lymphatic and Immune System

Main functions of the lymphatic system

Return extra fluid, protect from infections, destroy harmful organisms, remove damaged cells, transport fats, and activate immune cells.

Lacteals

Special lymphatic vessels in the small intestine that absorb dietary fats.

Afferent lymphatic vessels

bring lymph into a lymph node (arrives)

Efferent lymphatic vessels

carry lymph away from it (exits

Right lymphatic duct

Drains right upper body.

Thoracic duct

drains most of the rest of the body

Cortex of a lymph node

Outer region containing many lymphocytes, especially B cells.

Medulla of a lymph node

Inner region containing lymphocytes, plasma cells, and macrophages.

Thymus function

Lymphatic organ where immature T cells mature and are tested.

Spleen function

Largest lymphatic organ that filters blood, removes old red blood cells, and monitors for pathogens.

Nonspecific (Innate) Defenses

General, pre-existing defenses that respond broadly to pathogens (e.g., skin, phagocytes, fever).

Specific (Adaptive) Defenses

Targeted defenses against specific antigens involving B and T cells with memory.

Mechanical barriers

Physical barriers preventing pathogen entry, such as skin, mucus, cilia, and flushing actions.

Phagocytes

Cells like neutrophils and macrophages that engulf and destroy foreign material (phagocytosis).

Natural Killer (NK) cells

Cells that destroy virus-infected cells, abnormal cells, and some cancer cells.

Interferons

Signaling proteins released by virus-infected cells to warn nearby cells and create an antiviral state.

Complement system

Blood proteins that help destroy pathogens, increase inflammation, and form membrane attack complexes (MAC).

Inflammation signs and function

Response marked by redness, heat, swelling, and pain to bring immune cells and chemicals to damaged areas.

Fever function

Elevated body set point that makes conditions less favorable for pathogens and boosts immune reactions.

Antigen

A foreign substance or molecule recognized by the immune system to trigger a response (ID tag).

Three complement pathways

Classical (antibody-activated), Lectin (carbohydrate-activated), and Alternative (pathogen-surface activated).

Membrane Attack Complex (MAC)

A structure formed by complement proteins that creates holes in a target pathogen's membrane.

T cells origin and maturation

Produced in bone marrow; mature in the thymus.

Helper T cells (CD4)

Coordinate the immune response by releasing signals to activate B cells, cytotoxic T cells, and macrophages.

Cytotoxic T cells (CD8)

Directly destroy virus-infected or abnormal cells.

Regulatory T cells

Control the immune response and prevent excessive or unnecessary aggression.

Memory T cells

Cells remaining after an immune response to provide faster reactions upon re-exposure.

B cells origin and maturation

Produced and mature in the bone marrow.

Plasma cells

Activated B cells whose main job is to produce and release large amounts of antibodies.

Cell-mediated immunity

Adaptive immunity primarily controlled by T cells directly interacting with and destroying infected cells.

Humoral (Antibody-mediated) immunity

Adaptive immunity involving B cells and circulating antibodies in body fluids.

Antibody structure

Y-shaped proteins with two heavy and two light chains, featuring antigen-binding tips and a constant region.

IgG antibody

Most common blood antibody; provides long-term systemic protection and crosses the placenta.

IgM antibody

First major antibody produced during a primary immune response; highly effective at activating complement.

IgA antibody

Found in body secretions like saliva, tears, mucus, and breast milk for mucosal protection.

IgE antibody

Associated with allergic reactions and defense against parasites.

IgD antibody

Found on B-cell surfaces, functioning as a receptor for B-cell activation.

Secondary immune response

Faster and stronger due to memory cells.

Primary immune response

slow upon first exposure

Autoimmune disorder

A condition where the immune system mistakenly attacks the body's own tissues (loss of self-tolerance).

Rheumatoid arthritis

Autoimmune disease attacking joint tissues, causing inflammation, pain, and damage.

Type 1 diabetes mellitus

Autoimmune attack on pancreatic beta cells, leading to insufficient insulin and high blood glucose.

Multiple sclerosis (MS)

Autoimmune attack on myelin in the central nervous system, interfering with nerve signaling.

Classical pathway

Usually activated when antibodies are attached to an antigen.

Lectin pathway

Activated when complement proteins recognize certain carbohydrates on pathogens.

Alternative pathway

Can be activated directly by surfaces of pathogens.

Complement Pathways

can result in;

Inflammation

Increased phagocytosis

Destruction of pathogens

Formation of the membrane attack complex (MAC)