Unit 2 Review: Lymphatic, Immune, and Respiratory Systems

Chapter 20: The Lymphatic System and Lymphoid Organs and Tissues

Key Terms

• Lacteals: Specialized lymphatic capillaries in the small intestine that absorb dietary fats.

• Lymph: Clear fluid derived from interstitial fluid, transported by lymphatic vessels.

• Immunocompetent: The ability of lymphocytes to recognize and respond to antigens.

• Antigen: Any substance that can provoke an immune response.

• Immunogenicity: The ability of an antigen to stimulate an immune response.

• Defensins: Antimicrobial peptides produced by epithelial cells.

• Pattern recognition receptors: Receptors on immune cells that detect pathogen-associated molecular patterns.

• Margination: The process by which leukocytes adhere to blood vessel walls during inflammation.

• Diapedesis: The movement of leukocytes out of blood vessels into tissues.

• Natural Killer (NK) cells: Lymphocytes that destroy virus-infected and cancerous cells.

• Effector cells: Activated immune cells that carry out responses to pathogens.

• Surfactant: A substance produced by alveolar cells that reduces surface tension in the lungs.

Structure and Function of Lymphatic Capillaries

Lymphatic capillaries are highly permeable vessels that collect excess interstitial fluid and transport it as lymph.

• Permeability: Endothelial cells overlap to form one-way mini-valves, allowing entry of fluid, proteins, and cells.

• Example: Lacteals absorb chylomicrons (fat droplets) in the small intestine.

Major Lymphatic Trunks and Ducts

Lymphatic trunks collect lymph from large regions and drain into ducts, which return lymph to the venous system.

• Trunks: Jugular, subclavian, bronchomediastinal, lumbar, and intestinal trunks.

• Ducts: Right lymphatic duct (drains right upper body), thoracic duct (drains rest of body).

Primary and Secondary Lymphoid Organs

Lymphoid organs are classified by their role in lymphocyte development and immune response.

• Primary: Bone marrow (B cell maturation), thymus (T cell maturation).

• Secondary: Lymph nodes, spleen, tonsils, Peyer's patches.

Lymph Node Structure and Function

Lymph nodes filter lymph and house immune cells.

• Structure: Cortex (contains follicles with B cells), medulla (contains macrophages and plasma cells).

• Function: Filtration of pathogens, activation of lymphocytes.

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

Innate Defenses

Innate immunity provides immediate, non-specific protection against pathogens.

• 1st Line: Physical barriers (skin, mucous membranes), chemical barriers (acid, enzymes, defensins).

• Toll-like receptors: Recognize pathogen molecules and activate immune responses.

Phagocytic Cells and Phagocytosis

Phagocytes engulf and destroy pathogens.

• Types: Neutrophils, macrophages, dendritic cells.

• Steps: 1. Chemotaxis 2. Adherence 3. Ingestion 4. Digestion 5. Exocytosis

• Phagocytic Mobilization: Margination, diapedesis, chemotaxis.

Stages of Inflammation

Inflammation is a protective response to injury or infection.

• 1. Vasodilation

• 2. Increased vascular permeability

• 3. Phagocyte mobilization

• 4. Tissue repair

• 5. Resolution

Interferons

Interferons are proteins released by virus-infected cells to inhibit viral replication.

• Function: Activate antiviral defenses in neighboring cells, enhance phagocytosis.

Complement System

The complement system is a group of plasma proteins that enhance immune responses.

• Functions: Opsonization, cell lysis, inflammation.

Fever

Fever is an elevated body temperature that enhances immune function.

• Mechanism: Pyrogens reset hypothalamic thermostat.

Humoral vs Cellular Immunity

Adaptive immunity is divided into humoral (antibody-mediated) and cellular (T cell-mediated) responses.

• Humoral: B cells produce antibodies.

• Cellular: T cells attack infected cells.

Complete vs Incomplete Antigens

Antigens vary in their ability to provoke immune responses.

• Complete: Have both immunogenicity and reactivity.

• Incomplete (Hapten): Reactive but not immunogenic unless attached to a carrier.

Antigenic Determinants

Antigenic determinants (epitopes) are specific regions of an antigen recognized by antibodies.

Major Histocompatibility Complex (MHC)

MHC molecules present antigens to T cells.

• MHC I: On all nucleated cells; present endogenous antigens to CD8+ T cells.

• MHC II: On antigen-presenting cells; present exogenous antigens to CD4+ T cells.

Lymphocyte Development, Maturation, and Activation

Lymphocytes undergo development in primary organs, mature, and are activated upon antigen exposure.

• Development: Stem cells in bone marrow.

• Maturation: B cells in bone marrow, T cells in thymus.

• Activation: Occurs in secondary lymphoid organs.

Antigen-Presenting Cells (APCs)

APCs process and present antigens to T cells.

• Function: Initiate adaptive immune responses.

• Types: Dendritic cells, macrophages, B cells.

Antibody Structure

Antibodies are Y-shaped proteins composed of two heavy and two light chains.

• Variable region: Binds antigen.

• Constant region: Determines antibody class.

CD4 vs CD8 T Cells

CD4 and CD8 are surface proteins that distinguish T cell subsets.

• CD4: Helper T cells; activate other immune cells.

• CD8: Cytotoxic T cells; destroy infected cells.

Chapter 22: The Respiratory System

Nose: Structure and Function

The nose filters, warms, and moistens incoming air.

• Structure: External nares, nasal cavity, conchae.

• Function: Olfaction, air conditioning.

Pharynx: Structure, Function, and Regions

The pharynx is a muscular tube connecting the nasal cavity to the larynx and esophagus.

• Regions: Nasopharynx, oropharynx, laryngopharynx.

• Function: Passage for air and food.

Larynx: Function and Vocal Cords

The larynx maintains an open airway and produces sound.

• Vocal cords: Vibrate to produce voice.

Trachea: Structure and Function

The trachea is a cartilaginous tube that conducts air to the lungs.

• Structure: C-shaped cartilage rings, mucosa.

• Function: Air passage, protection.

Alveoli

Alveoli are tiny air sacs where gas exchange occurs.

• Structure: Simple squamous epithelium, surrounded by capillaries.

• Function: Exchange of O2 and CO2.

Gross Anatomy of the Lungs

The lungs are paired organs divided into lobes and supplied by bronchi.

• Right lung: 3 lobes; Left lung: 2 lobes.

Thoracic Cavity: Pressures and Relationships

Pressure differences drive ventilation.

• Atmospheric pressure: Pressure outside the body.

• Intrapulmonary pressure: Pressure within alveoli.

• Intrapleural pressure: Pressure within pleural cavity; always lower than intrapulmonary.

Factors Influencing Pulmonary Ventilation

Three main factors affect breathing efficiency.

• 1. Airway resistance

• 2. Alveolar surface tension

• 3. Lung compliance

Respiratory Volumes and Capacities

Respiratory volumes measure the amount of air exchanged during breathing.

• Tidal volume (TV): Amount of air inhaled or exhaled per breath.

• Inspiratory reserve volume (IRV): Extra air inhaled after normal inspiration.

• Expiratory reserve volume (ERV): Extra air exhaled after normal expiration.

• Residual volume (RV): Air remaining in lungs after maximal exhalation.

O2 Transport to Cells

Oxygen reaches cells by two main mechanisms.

• 1. Bound to hemoglobin in red blood cells

• 2. Dissolved in plasma

CO2 Transport to Lungs

Carbon dioxide returns to the lungs by three mechanisms.

• 1. Dissolved in plasma

• 2. Bound to hemoglobin (as carbaminohemoglobin)

• 3. As bicarbonate ions (HCO3-)

Equation for CO2 transport:

$\mathrm{CO_2 + H_2O \rightarrow H_2CO_3 \rightarrow HCO_3^- + H^+}$

Neural Control of Breathing

Breathing is regulated by neural centers in the brainstem.

• Medullary respiratory center: Controls rhythm.

• Pontine respiratory center: Modifies rhythm.

Summary Table: Lymphatic and Immune System Components

Component	Function	Location
Lymphatic Capillaries	Collect interstitial fluid	Tissues throughout body
Lymph Nodes	Filter lymph, activate immune cells	Along lymphatic vessels
Thymus	T cell maturation	Superior mediastinum
Spleen	Filters blood, immune response	Left upper abdomen
Bone Marrow	B cell maturation, hematopoiesis	Long bones
NK Cells	Destroy abnormal cells	Blood, tissues
Defensins	Antimicrobial action	Skin, mucosa

Additional info: Academic context was added to expand brief points and clarify terms, steps, and mechanisms for self-contained study notes.