Lymphatic, Immune, and Respiratory Systems: Study Guide

LYMPHATIC AND IMMUNE SYSTEMS

Components of the Lymphatic System

The lymphatic system is a network of vessels, nodes, and organs that helps maintain fluid balance and contributes to immune defense.

• Lymphatic vessels: Thin-walled tubes that transport lymph throughout the body.

• Lymph: A clear fluid derived from interstitial fluid, containing water, proteins, lymphocytes, and sometimes pathogens or debris.

• Lymph nodes: Small, bean-shaped structures that filter lymph and house immune cells.

• Lymphoid organs: Includes the spleen, thymus, and tonsils, each with specialized immune functions.

Chemical components of lymph: Water, electrolytes (e.g., Na+, K+), proteins (mainly albumin), lymphocytes, and sometimes lipids (chyle), cellular debris, and pathogens.

Functions of the Lymphatic System

• Fluid balance: Returns excess interstitial fluid to the bloodstream.

• Fat absorption: Absorbs dietary fats from the intestine via lacteals.

• Immune defense: Filters pathogens and foreign particles, and supports immune cell maturation and activation.

Clinically Important Groups of Lymph Nodes

• Cervical lymph nodes: Located in the neck; filter lymph from the head and neck.

• Axillary lymph nodes: Located in the armpits; filter lymph from the upper limbs and breast.

• Inguinal lymph nodes: Located in the groin; filter lymph from the lower limbs and external genitalia.

Lymphoid Organs: Location and Function

• Spleen: Located in the upper left abdomen; filters blood, removes old red blood cells, and mounts immune responses.

• Has two main components: 

  1. White pulp: where immune functions take place made mostly of lymphocytes on suspended reticular fibers

  2. Red pulp: where worn out red blood cell and bloodborne pathogens are destroyed contains large numbers of red blood cells and macrophages that engulf them; made up of splenic cords (reticuolar tissue) that separate blood filled splenic sinusoids

  Main function: lymphocyte proliferation, immune surveillance & response and blood cleansing functions

• Tonsils: Located in the pharyngeal region; trap pathogens entering through the mouth and nose.

  • Paird palatine tonsils: located on either side of the posterior end of the oral cavity largest and most often infected 

  • Linguinal tonsil: a lumpy collection of lymphoid follicles at the base of the tongue

  • Pharyngeal tonsil: posterior wall of the nasophaynx

  • Tubal tonsil: small, surround the opening of the auditory tubes into the pharynx

• Thymus: Located in the anterior mediastinum (above the heart); site of T-cell maturation, most active in childhood.

Formation and Flow of Lymph

• Formation: Lymph forms when interstitial fluid enters lymphatic capillaries due to pressure gradients.

• Flow factors: Lymph moves via skeletal muscle contraction, respiratory movements, and one-way valves preventing backflow.

Specific vs. Non-Specific Immunity

• Non-specific (innate) immunity: General defenses such as skin, mucous membranes, phagocytes, inflammation, and fever.

• Specific (adaptive) immunity: Targeted responses involving lymphocytes (T-cells and B-cells) and the production of antibodies.

• Examples: Non-specific: skin barrier, macrophage phagocytosis. Specific: antibody production against a virus.

Functions of T-cells and B-cells

• T-cells: Develop in the thymus; responsible for cell-mediated immunity. Types include helper T-cells (activate other immune cells), cytotoxic T-cells (destroy infected cells), and regulatory T-cells (modulate immune response).

• B-cells: Mature in bone marrow; responsible for humoral immunity by producing antibodies.

• Antigen presentation: Process by which cells display antigens on their surface for recognition by T-cells.

• Humoral immunity: Involves B-cells and antibody production to neutralize pathogens in body fluids.

• Cell-mediated immunity: Involves T-cells directly attacking infected or abnormal cells.

• Antibodies: Proteins produced by B-cells that specifically bind to antigens.

RESPIRATORY SYSTEM

Organs of Respiration and Their Functions

• Nose and nasal cavity: Warm, moisten, and filter incoming air.

• Larynx: ContPharynx: Passageway for air and food; involved in swallowing.

  • Nasopharynx: the portion of the pharynx located posterior to and continuous with the nasal cavity; serves only as an air passageway 

  • Oropharynx: the portion of the pharynx located posterior to and continuous with the oral cavity; serving as passageway for both food and air

  • Laryngopharynax: the portion of the pharynx located posterior to the larynx; serving as a passageway for both food and air

• Larynx: contains vocal cords; routes air and food into proper channels.

• Trachea: Windpipe; conducts air to bronchi.

  • Carina: point of branching of trachea and leads to 3 primary bronchi

    Secondary bronchi: 1st branch in the lungs

    Tertiary bronchous: stems off secondary bronchi

    Respiratory bronchioles and alveoli: are also a part of bronchioles tree; however they are in the respiratory zone

• Bronchi (primary, secondary, tertiary): Branching airways conducting air to lungs.

• Bronchioles (terminal, respiratory): Smaller airways leading to alveoli.

• Alveolar ducts, sacs, and alveoli: Sites of gas exchange.

• Lungs: Main organs of respiration; house alveoli and conduct gas exchange.

Pharynx and Larynx: Structure and Function

• Pharynx: Divided into nasopharynx, oropharynx, and laryngopharynx; conducts air and food, aids in speech.

• Larynx: Cartilaginous structure; protects airway, produces sound, and prevents food entry into trachea.

Airway Anatomy: Conducting vs. Respiratory Zones

Structure	Zone	Function
Trachea	Conducting	Air passage
Primary bronchi	Conducting	Air passage
Secondary bronchi	Conducting	Air passage
Tertiary bronchi	Conducting	Air passage
Terminal bronchioles	Conducting	Air passage
Respiratory bronchioles	Respiratory	Some gas exchange
Alveolar ducts	Respiratory	Gas exchange
Alveolar sacs & alveoli	Respiratory	Main site of gas exchange

Respiratory Membrane

• Composed of alveolar epithelium, capillary endothelium, and their fused basement membranes.

• Thin barrier (about 0.5 μm) allowing efficient gas exchange between air and blood.

Anatomy of the Lungs

• Location: Thoracic cavity, flanking the mediastinum.

• Pleurae: Double-layered serous membranes (parietal and visceral pleura) surrounding each lung.

• Lobes: Right lung has 3 lobes (superior, middle, inferior); left lung has 2 lobes (superior, inferior).

• Fissures: Oblique and horizontal fissures separate the lobes.

• Blood supply: Pulmonary arteries (deoxygenated blood to lungs), pulmonary veins (oxygenated blood to heart).

Diaphragm and Muscles of Ventilation

• Diaphragm: Dome-shaped muscle separating thoracic and abdominal cavities; primary muscle of inspiration.

• Other muscles: External intercostals (inspiration), internal intercostals (forced expiration), accessory muscles (e.g., sternocleidomastoid, scalenes) during deep breathing.

Respiratory Pressures

• Atmospheric pressure (Patm): Pressure of air outside the body.

• Intrapulmonary (alveolar) pressure (Palv): Pressure within the alveoli.

• Intrapleural pressure (Pip): Pressure within the pleural cavity; always slightly negative relative to Palv.

Respiratory Cycle: Events and Pressure Changes

• Inspiration: Diaphragm contracts, thoracic volume increases, Palv drops below Patm, air flows in.

• Expiration: Diaphragm relaxes, thoracic volume decreases, Palv rises above Patm, air flows out.

Lung Volumes and Capacities

• Tidal volume (TV): Volume of air inhaled or exhaled in a normal breath (~500 mL).

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

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

• Vital capacity (VC): Maximum air exhaled after maximum inhalation. $VC = TV + IRV + ERV$

• Minute respiratory volume (MRV): Total air breathed per minute. $MRV = TV \times \text{respiratory rate}$

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

• Total lung capacity (TLC): Total volume in lungs after maximal inspiration. $TLC = VC + RV$

• Anatomical dead space: Volume of air in conducting airways not involved in gas exchange (~150 mL).

Respiratory Gases: Pressures and Transport

• Partial pressures: Each gas in a mixture exerts its own pressure (e.g., O2, CO2).

• External respiration: Gas exchange between alveoli and blood.

• Internal respiration: Gas exchange between blood and tissues.

• Transport: O2 mainly carried by hemoglobin; CO2 transported as bicarbonate, dissolved in plasma, or bound to hemoglobin.

Oxygen-Hemoglobin Dissociation Curve and Exercise

• Shows relationship between O2 partial pressure and hemoglobin saturation.

• During exercise, increased CO2, temperature, and acidity shift the curve right (Bohr effect), promoting O2 release to tissues.

Control of Respiration

• Respiratory centers: Located in the medulla oblongata and pons; regulate rate and depth of breathing.

• Voluntary control: Cerebral cortex can override automatic centers (e.g., holding breath).

• Chemical factors: CO2, O2, and pH levels detected by chemoreceptors influence respiratory rate.

• Physical factors: Stretch receptors, pain, and temperature can also affect breathing.