Study Guide: Lymphatic, Immune, and Respiratory Systems (Chapters 20-22)

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Lymphatic System

Main Functions and Components

The lymphatic system is essential for maintaining fluid balance, defending the body against pathogens, and facilitating the absorption of dietary fats. Its main components include:

Bone marrow: Site of lymphocyte production.
Thymus: Site where T lymphocytes mature and develop immunocompetence.
Lymph nodes: Filter lymph and house immune cells.
Lymphatic vessels: Transport lymph throughout the body.

Major Lymph Node Locations

Cervical lymph nodes: Located in the neck.
Axillary lymph nodes: Located in the armpits.
Inguinal lymph nodes: Located in the groin.

Lymph Node Anatomy

Afferent vessels bring lymph into the node at the convex surface.
Efferent vessels exit at the concave surface (hilum).
Cortex contains lymph follicles with germinal centers (active B cell division).
Medulla contains medullary cords and sinuses.

Tonsils and Lymphatic Nodules

Palatine tonsils: Located in the oropharynx, lined by stratified squamous non-keratinized epithelium.
Pharyngeal tonsil (adenoids): Located in the nasopharynx.
Lingual tonsils: At the base of the tongue.
Tubal tonsils: Around the auditory tube.
Peyer's patches: Isolated lymphatic nodules in the small intestine.

Thymus

Located in the thorax, largest in children, atrophies after adolescence.
Site of T lymphocyte maturation and selection (self-reactive cells are destroyed).
Contains thymic corpuscles (Hassall's corpuscles) in the medulla.

Lymphatic Ducts

Thoracic duct: Begins at the cisterna chyli, drains lymph from the left side of the body into the junction of the internal jugular and subclavian veins.
Right lymphatic duct: Drains lymph from the right upper torso into the same venous junction on the right.

Spleen

Located in the left hypochondrium, lateral to the stomach.
Functions: RBC destruction, immune surveillance, blood reservoir.
Histology: Red pulp (RBC destruction), white pulp (lymphocyte proliferation).

Immune System

Overview of Immune Responses

The immune system protects the body from pathogens using innate (nonspecific) and adaptive (specific) defenses.

Innate (Nonspecific) Defenses

First line of defense: Physical and chemical barriers (skin, mucous membranes, secretions).
Second line of defense: Internal defenses (phagocytes, natural killer cells, inflammation, antimicrobial proteins, interferons, fever).

Examples of First Line Defenses

Intact skin (acid mantle, keratin)
Mucous membranes (mucus, nasal hairs, cilia, gastric juice, vaginal acid mantle, tears, saliva, urine)

Examples of Second Line Defenses

Phagocytes (neutrophils, macrophages)
Natural killer cells
Inflammation (mediated by histamine, kinins, prostaglandins, complement, cytokines)
Antimicrobial proteins (complement, interferons)
Fever

Inflammation

Triggered by trauma, heat, infection.
Signs: Redness, swelling, heat, pain.
Purpose: Isolate and eliminate pathogens, initiate tissue repair.

Antigens and Immunity Types

Antigens: Substances that provoke an immune response (bacteria, viruses, foreign cells).
Humoral immunity: B lymphocytes produce antibodies to target extracellular pathogens.
Cellular immunity: T lymphocytes target intracellular pathogens and abnormal cells.

Cytotoxic T Lymphocytes

Attack infected or abnormal cells (e.g., cancer, virus-infected, graft rejection).
Require antigen presentation via MHC proteins.
Stimulated by helper T cells.

Antibodies

Proteins produced by plasma cells (from B lymphocytes) in response to antigens.
Mechanisms: Neutralization, agglutination, precipitation, complement fixation, cell lysis.

Classes of Antibodies and Functions

Antibody	Function
IgM	First antibody secreted in primary response
IgA	Found in secretions (saliva, sweat, milk, etc.)
IgD	Acts as B cell receptor
IgG	Most abundant in plasma (75-85%)
IgE	Triggers histamine release in allergic reactions

Types of Immunity

Type	How Acquired	Example
Passive, natural	Antibodies from mother	Fetus receives maternal antibodies
Passive, artificial	Injection of antibodies	Antibody shot before travel
Active, natural	Exposure to antigen	Recovering from measles
Active, artificial	Vaccination	Flu shot

Primary vs. Secondary Immune Response

Primary response: First exposure, lag of 3-6 days, slower antibody production.
Secondary response: Subsequent exposure, rapid and stronger due to memory cells.

Immune Disorders

AIDS: Destroys helper T lymphocytes.
Autoimmune diseases: Immune system attacks self (e.g., rheumatoid arthritis, multiple sclerosis, Graves’ disease, type 1 diabetes, lupus, glomerulonephritis).
Hypersensitivity: Overreaction to harmless antigens (allergies, IgE-mediated histamine release).

Respiratory System

Anatomy of the Respiratory System

Olfactory epithelium: Roof of the nasal cavity.
Nasal septum: Made of cartilage and bone (vomer, ethmoid).
Tonsils: Palatine (oropharynx), pharyngeal (nasopharynx), lingual (base of tongue).
Laryngeal cartilages: Arytenoid (paired), epiglottis (elastic cartilage, prevents food entry).
Trachea: Largest tube, hyaline cartilage rings.
Bronchioles: Small tubes (<1 mm), smooth muscle, no cartilage.
Vocal cords: Shorter/thinner in women (higher pitch).
Pharynx divisions: Nasopharynx, oropharynx, laryngopharynx.
Auditory tube: Connects middle ear to nasopharynx (pathway for infection).
Paranasal sinuses: Frontal, sphenoid, ethmoid, maxillary (in respective bones).

Respiratory Zones

Conducting zone: Nasal cavity, pharynx, trachea, bronchi, bronchioles, terminal bronchioles.
Respiratory zone: Respiratory bronchioles, alveolar ducts, alveoli.

Respiratory Membrane

Composed of alveolar wall, capillary wall, and fused basement membranes.
Site of gas exchange between air and blood.

Lung Anatomy

Hilum: Indentation where vessels, bronchi, lymphatics, and nerves enter/exit lung.
Carina: Cartilage at tracheal bifurcation.
Right primary bronchus: Shorter, wider, more vertical (more likely to lodge foreign objects).

Mechanics of Breathing

Inspiration: Volume increases, intrapulmonary pressure decreases; muscles: diaphragm, external intercostals.
Expiration: Volume decreases, intrapulmonary pressure increases; muscles: internal intercostals, diaphragm (relaxation).
Thoracic diameter increases in transverse and anteroposterior directions during inspiration.

Gas Exchange and Transport

External respiration: Gas exchange between alveoli and blood.
Internal respiration: Gas exchange between blood and tissues.
Oxygen transport: 98.5% bound to hemoglobin, 1.5% dissolved in plasma.
Carbon dioxide transport: 70% as bicarbonate, 20% bound to hemoglobin, 7-10% dissolved in plasma.
CO2 is more soluble in plasma than O2 (20x).

Key Chemical Reaction (in RBCs, catalyzed by carbonic anhydrase):

Respiratory Volumes

Volume	Definition	Typical Value
Tidal Volume (TV)	Air in/out during normal breath	500 mL
Vital Capacity (VC)	Max air exhaled after max inhalation (TV + IRV + ERV)	3100 mL (women), 4800 mL (men)

Partial Pressures of Respiratory Gases

Blood Vessel	O2 (mmHg)	CO2 (mmHg)
Pulmonary arteries	40	45
Pulmonary veins	100	40
Systemic arteries	100	40
Systemic veins	40	45

pH and CO2 Relationship

As PCO2 increases, pH decreases (more acidic).
As PCO2 decreases, pH increases (more basic).
Hyperventilation: CO2 is exhaled rapidly, leading to decreased blood CO2 and increased pH (alkalosis).

Lung Compliance and Surfactant

Lung compliance: Stretchiness of the lungs, determined by tissue distensibility and alveolar surface tension.
Surfactant: Produced by type II alveolar cells, reduces surface tension to prevent alveolar collapse.

Dead Space

Volume of air not involved in gas exchange (conducting zone).
Typical value: 150 mL (1 mL per pound of ideal body weight).
If dead space increases, may indicate damaged alveoli.

Respiratory Chemoreceptors

Located in aortic and carotid bodies, and medulla.
Stimulated by increased H+ or decreased O2 partial pressure.

Clinical Terms

Pneumothorax: Air in the pleural cavity, causing lung collapse.
Sinus infection: Can cause pressure in the frontal sinus, leading to headaches.

Additional info: For a more comprehensive review, consult the chapter summaries and diagrams in your textbook.