Lymphatic, Immune, Respiratory, and Digestive Systems

A comprehensive set of flashcards covering key terminology and concepts related to the lymphatic, immune, respiratory, and digestive systems.

Lymphatic System

Network of vessels, organs, and tissues that transport lymph fluid, filter pathogens, absorb fats, and support immune function.

Lymph

Clear, watery fluid derived from interstitial fluid; contains white blood cells, proteins, and cellular waste.

Lymphatic Vessels

Thin-walled vessels that collect and transport lymph from tissues back to the bloodstream.

Lymph Nodes

Small, bean-shaped organs that filter lymph and contain immune cells; found in clusters throughout the body.

Thoracic Duct

Largest lymphatic vessel; drains lymph from most of the body into the left subclavian vein.

Right Lymphatic Duct

Drains lymph from the right upper body into the right subclavian vein.

Thymus

Primary lymphoid organ in the mediastinum where T cells mature; largest in children, atrophies with age.

Spleen

Largest lymphoid organ; filters blood, removes old red blood cells, stores platelets, and mounts immune responses.

Tonsils

Lymphoid tissue in the pharynx that traps pathogens entering through the mouth and nose.

MALT (Mucosa-Associated Lymphoid Tissue)

Lymphoid tissue in mucous membranes of digestive, respiratory, and urogenital tracts.

Lacteals

Specialized lymphatic capillaries in the small intestine villi that absorb dietary fats and fat-soluble vitamins.

Edema

Swelling caused by excess fluid accumulation in tissues; can result from lymphatic obstruction.

Afferent Lymphatic Vessels

Vessels that carry lymph into a lymph node.

Efferent Lymphatic Vessels

Vessels that carry filtered lymph away from a lymph node.

Cisterna Chyli

Dilated sac at the origin of the thoracic duct; receives chyle from the intestines.

Immune System

Body's defense network against pathogens, foreign substances, and abnormal cells.

Immunity

The ability to resist infection and disease.

Pathogen

Disease-causing microorganism (bacteria, virus, fungus, parasite).

Antigen

Any substance that triggers an immune response; typically foreign proteins or polysaccharides.

Antibody (Immunoglobulin)

Y-shaped protein produced by B cells that binds to specific antigens.

Innate Immunity

Non-specific, immediate defense mechanisms present from birth; includes barriers and phagocytes.

Adaptive Immunity

Specific, slower immune response that develops after exposure to antigens; provides immunological memory.

Cell-Mediated Immunity

Adaptive immune response involving T cells that directly attack infected or abnormal cells.

Humoral Immunity

Adaptive immune response involving B cells and antibody production.

B Cells (B Lymphocytes)

Lymphocytes that mature in bone marrow and produce antibodies.

T Cells (T Lymphocytes)

Lymphocytes that mature in the thymus and mediate cell-mediated immunity.

Helper T Cells (CD4+)

T cells that activate other immune cells and coordinate immune responses.

Cytotoxic T Cells (CD8+)

T cells that directly kill infected, cancerous, or foreign cells.

Memory Cells

Long-lived B and T cells that provide rapid response upon re-exposure to the same antigen.

Phagocytes

Cells that engulf and destroy pathogens through phagocytosis (neutrophils, macrophages).

Neutrophils

Most abundant white blood cells; first responders to bacterial infection.

Macrophages

Large phagocytes that engulf pathogens, dead cells, and debris; also present antigens.

Antigen-Presenting Cells (APCs)

Cells that display antigens on their surface to activate T cells (dendritic cells, macrophages, B cells).

MHC (Major Histocompatibility Complex) Molecules

Cell surface proteins that display antigens to T cells and identify 'self'.

Complement System

Group of plasma proteins that enhance immune responses through pathogen lysis, opsonization, and inflammation.

Inflammation

Localized protective response to tissue injury or infection; characterized by redness, heat, swelling, and pain.

Primary Immune Response

Initial adaptive immune response to first antigen exposure; slow, produces mainly IgM.

Secondary Immune Response

Faster, stronger adaptive response upon re-exposure to same antigen; produces mainly IgG.

Active Immunity

Immunity developed when the body produces its own antibodies (through infection or vaccination).

Passive Immunity

Immunity acquired by receiving antibodies from another source (maternal antibodies, immunoglobulin injection).

Immunoglobulin Classes: IgG

Most abundant; provides long-term immunity; crosses placenta.

Immunoglobulin Classes: IgM

First antibody produced in primary response.

Immunoglobulin Classes: IgA

Found in body secretions (tears, saliva, mucus, breast milk).

Immunoglobulin Classes: IgE

Mediates allergic reactions.

Immunoglobulin Classes: IgD

Functions in B cell activation.

Autoimmune Disease

Condition where the immune system attacks the body's own tissues.

Immunodeficiency

Condition of weakened or absent immune function.

Respiratory System

Organ system responsible for gas exchange between the body and external environment.

Respiration

Process of gas exchange; includes pulmonary ventilation, external respiration, and internal respiration.

Pulmonary Ventilation (Breathing)

Movement of air into and out of the lungs.

External Respiration

Gas exchange between alveoli and blood.

Internal Respiration

Gas exchange between blood and body tissues.

Upper Respiratory Tract

Nose, nasal cavity, pharynx, and associated structures.

Lower Respiratory Tract

Larynx, trachea, bronchi, and lungs.

Nasal Cavity

Hollow space behind the nose; warms, filters, and humidifies incoming air.

Pharynx (Throat)

Muscular tube serving both respiratory and digestive systems.

Larynx (Voice Box)

Cartilaginous structure containing the vocal cords; connects pharynx to trachea.

Epiglottis

Leaf-shaped cartilage that covers the larynx during swallowing to prevent aspiration.

Trachea (Windpipe)

Tubular airway extending from larynx to primary bronchi; reinforced with C-shaped cartilage rings.

Bronchi

Airways branching from the trachea (primary, secondary, tertiary).

Bronchioles

Small airways lacking cartilage; lead to alveoli.

Alveoli

Microscopic air sacs where gas exchange occurs; ~300 million per lung.

Type I Alveolar Cells

Thin cells forming the alveolar wall; site of gas exchange.

Type II Alveolar Cells

Cuboidal cells that secrete pulmonary surfactant.

Pulmonary Surfactant

Lipoprotein mixture that reduces surface tension in alveoli, preventing collapse.

Respiratory Membrane

Thin barrier where gas exchange occurs; consists of alveolar epithelium and capillary endothelium.

Lungs

Paired organs in the thoracic cavity; site of gas exchange.

Pleura

Double-layered serous membrane surrounding each lung (visceral and parietal).

Pleural Cavity

Potential space between visceral and parietal pleura containing serous fluid.

Diaphragm

Dome-shaped skeletal muscle separating thoracic and abdominal cavities; primary muscle of inspiration.

Inspiration (Inhalation)

Active process of drawing air into the lungs; diaphragm contracts and moves downward.

Expiration (Exhalation)

Process of air leaving the lungs; passive during quiet breathing.

Tidal Volume (TV)

Volume of air inhaled or exhaled during normal quiet breathing (~500 mL).

Vital Capacity (VC)

Maximum amount of air that can be exhaled after maximal inspiration.

Residual Volume (RV)

Air remaining in lungs after maximal expiration.

Total Lung Capacity (TLC)

Total volume of air lungs can hold.

Respiratory Control Centers

Groups of neurons in the brainstem that regulate breathing rhythm.

Chemoreceptors

Receptors that monitor blood chemistry (O₂, CO₂, H⁺) to regulate ventilation.

Hypoxia

Inadequate oxygen supply to tissues.

Hypercapnia

Elevated carbon dioxide levels in blood.

Hemoglobin

Protein in red blood cells that binds and transports oxygen and some carbon dioxide.

Digestive System

Organ system that breaks down food, absorbs nutrients, and eliminates waste.

Digestion

Mechanical and chemical breakdown of food into absorbable molecules.

Mechanical Digestion

Physical breakdown of food (chewing, churning, segmentation).

Chemical Digestion

Enzymatic breakdown of food into smaller molecules.

Absorption

Process by which nutrients pass from the digestive tract into blood or lymph.

Gastrointestinal (GI) Tract

Continuous muscular tube from mouth to anus.

Peristalsis

Wave-like muscular contractions that propel food through the GI tract.

Segmentation

Mixing contractions that churn food in the small intestine.

Mouth (Oral Cavity)

Opening where food enters; begins mechanical and chemical digestion.

Saliva

Watery secretion containing enzymes, antibodies, and mucus; moistens food and begins starch digestion.

Salivary Amylase

Enzyme in saliva that begins starch digestion.

Pharynx

Throat; passageway for food and air.

Esophagus

Muscular tube connecting pharynx to stomach; transports food via peristalsis.

Stomach

J-shaped organ that mechanically and chemically digests food; secretes gastric juice.

Gastric Juice

Acidic fluid containing HCl, pepsinogen, and intrinsic factor.

Hydrochloric Acid (HCl)

Acid that activates pepsinogen, kills bacteria, and denatures proteins.

Pepsin

Active enzyme that digests proteins into smaller peptides.

Intrinsic Factor

Glycoprotein necessary for vitamin B12 absorption in ileum.

Chyme

Semifluid mixture of partially digested food and gastric juice.