Chapter 20 – Lymphatic System

Main Functions and Components of the Lymphatic System

The lymphatic system is essential for fluid balance, immune defense, and absorption of dietary fats. It consists of several organs and vessels that transport lymph throughout the body.

• Main functions: Fluid recovery, immunity, lipid absorption.

• Main components: Bone marrow, thymus, lymph nodes, lymphatic vessels.

Major Areas of Lymph Nodes

Lymph nodes are distributed throughout the body, with major clusters in specific regions.

• Cervical lymph nodes: Located in the neck.

• Axillary lymph nodes: Located in the armpits.

• Inguinal lymph nodes: Located in the groin.

General Anatomy of the Lymph Node

Lymph nodes filter lymph and are sites of immune cell activation.

• Afferent vessels: Enter the lymph node at the convex surface.

• Efferent vessels: Exit the lymph node at the concave surface (hilum).

Major Lymphoid Tissues and Tonsils

Tonsils are lymphoid tissues located in the pharynx and oral cavity, protecting against inhaled or ingested pathogens.

• Palatine tonsils: Located on either side of the oropharynx.

• Pharyngeal tonsil (adenoid): Located in the nasopharynx.

• Lingual tonsils: Located at the base of the tongue.

• Histology: Tonsils contain germinal centers for B cell division, covered by stratified squamous non-keratinized epithelium.

Other Lymphatic Tissues

• Peyer's patches: Located in the small intestine, important for gut immunity.

Thymus

The thymus is the site of T lymphocyte development and immunocompetence.

• Location: Thorax, largest in children, atrophies with age.

• Histology: Contains a cortex and medulla with corpuscles called thymic corpuscles.

Spleen

The spleen filters blood, recycles RBCs, and supports immune functions.

• Location: Left hypochondrium, lateral to the stomach.

• Structure: Contains red pulp (RBC recycling) and white pulp (lymphocyte activation).

Lymphatic Vessels

Lymphatic vessels drain lymph from tissues and return it to the bloodstream.

• Right lymphatic duct: Drains right upper torso into the junction of the right internal jugular and subclavian veins.

• Thoracic duct: Drains the left side of the body, lower limbs, abdomen, and thorax into the left subclavian vein.

Chapter 21 – Immune System

Lines of Defense

The immune system protects against pathogens through innate (nonspecific) and adaptive (specific) defenses.

• First line of defense: Physical and chemical barriers (skin, mucous membranes, secretions).

• Second line of defense: Internal defenses (phagocytes, inflammation, fever, antimicrobial proteins).

Inflammation

Inflammation is a response to injury or infection, characterized by redness, heat, swelling, and pain.

• Key events: Physical trauma, intense heat, redness, swelling.

• Complement activation: Causes cell lysis.

Immunity Types

Immunity can be classified as humoral or cellular, and as active or passive.

• Humoral immunity: Involves B lymphocytes and antibody secretion.

• Cellular immunity: Involves T lymphocytes and direct attack on infected cells.

• Active immunity: Body produces its own antibodies (e.g., infection, vaccination).

• Passive immunity: Antibodies are received from another source (e.g., maternal antibodies, antibody injection).

Antibodies

Antibodies are proteins produced by B lymphocytes in response to antigens.

• Function: Bind to antigens, neutralize pathogens, and facilitate their destruction.

• Types: IgM, IgA, IgG, IgE, IgD (each with specific roles).

Immune Responses

• Primary response: First exposure to antigen, slower and less robust.

• Secondary response: Subsequent exposure, faster and stronger due to memory cells.

Mechanisms of Antibody Action

• Neutralization

• Agglutination

• Precipitation

• Complement fixation and cell lysis

Immune System Disorders

• Autoimmune diseases: Immune system attacks self tissues (e.g., rheumatoid arthritis, lupus, multiple sclerosis, Type 1 diabetes).

• Hypersensitivity reactions: Allergic reactions involving mast cells and basophils releasing histamine.

• Immunodeficiency: Example: AIDS (Helper T lymphocytes are destroyed).

Chapter 22 – Respiratory System

Structure and Function of the Respiratory System

The respiratory system is responsible for gas exchange, supplying oxygen, and removing carbon dioxide.

• Major parts: Nasal cavity, pharynx, larynx, trachea, bronchi, lungs.

• Conducting zone: Nasal cavity, pharynx, trachea, bronchi, bronchioles, terminal bronchioles.

• Respiratory zone: Alveolar duct and alveoli.

Nasal Cavity and Sinuses

• Epithelium: Roof of the nose (olfactory epithelium).

• Septum: Cartilage and bone (vomer and part of the ethmoid bone).

• Sinuses: Frontal, sphenoid, ethmoid, maxillary (open spaces in these bones).

Pharynx and Larynx

• Pharynx divisions: Nasopharynx, oropharynx, laryngopharynx.

• Larynx: Contains vocal cords, cartilage (e.g., thyroid, cricoid, arytenoid), and is responsible for sound production.

• Paired cartilage: Arytenoid cartilage.

• Elastic cartilage: Prevents food from entering the airway.

• Narrowest region: Between the vocal folds.

Bronchi and Lungs

• Bronchi: Right bronchus is shorter, wider, and more vertical (food more likely to lodge).

• Carina: Cartilage at the bifurcation of the trachea.

• Lung hilum: Indentation where vessels and bronchi enter the lung.

Respiratory Physiology

• Inspiration: Volume increases, intrapulmonary and intrathoracic pressure decreases.

• Expiration: Volume decreases, pressure increases.

• Muscles: External intercostals and diaphragm (inspiration); internal intercostals and diaphragm (expiration).

Gas Exchange and Blood pH

• Partial pressure of CO2 (): As increases, pH decreases (blood becomes more acidic).

• Hyperventilation: Decreases , increases pH (blood becomes more alkaline).

• Equation for CO2 conversion:

• Enzyme: Carbonic anhydrase (present in RBCs).

Respiratory Volumes

• Tidal volume (TV): Amount of air inhaled or exhaled in one breath (about 500 mL).

• Exchangeable air volumes: Inspiratory reserve volume (IRV) and expiratory reserve volume (ERV), normally 3100 mL and 1200 mL in men, respectively.

Table: Comparison of Lymphatic Organs

Table: Types of Immunity

Additional info: Academic context and definitions have been expanded for clarity and completeness. Tables have been recreated and summarized for comparison and classification purposes.