THE INNATE IMMUNITY & RESPIRATORY SYSTEM

• The innate immune system serves as the first line of defense against pathogens, utilizing physical barriers and immune responses that are non-specific.

• Key components include: Skin and mucous membranes that act as barriers; Inflammation, which increases blood flow and immune cell recruitment; Interferon, proteins that inhibit viral replication; Complement system, a group of proteins that enhance the ability of antibodies to clear pathogens; Fever, which can inhibit pathogen growth; and Natural Killer (NK) cells that target infected or cancerous cells.

Adaptive Immune Mechanisms

• The adaptive immune system is characterized by its specificity and memory, involving B lymphocytes, T lymphocytes, and macrophages.

• B lymphocytes are responsible for humoral immunity, producing antibodies that target specific antigens.

• T lymphocytes are involved in cell-mediated immunity, with CD8 cytotoxic T cells killing infected or abnormal cells, and CD4 helper T cells stimulating other immune cells.

• Macrophages act as antigen-presenting cells (APCs), engulfing pathogens and presenting their antigens to T cells, thus activating the adaptive immune response.

• The concept of immunological memory is crucial, as it allows for a faster and more effective response upon re-exposure to the same pathogen.
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Immunoglobulin Classes and Vaccination

• Immunoglobulins (Ig) are antibodies that play a key role in the immune response, with different classes (IgG, IgA, IgM, IgE, IgD) serving various functions.

• Vaccines work by stimulating the adaptive immune system to produce a memory response without causing disease, leading to long-term immunity.

• Active immunity is established through exposure to antigens, either through infection or vaccination, allowing for the development of immunological memory.

Mechanisms of Antibody Action

• Antibodies do not directly kill pathogens; instead, they tag them for destruction by other immune cells, enhancing the efficiency of the immune response.

• The role of helper T cells is central in mobilizing both humoral and cellular immunity, as they provide necessary signals for B cell activation and antibody production.

Cell-Mediated Immune Response

T-Cell Activation and Function

• T-cells require recognition of processed antigen fragments presented by Major Histocompatibility Complex (MHC) molecules on the surface of other cells for activation.

• CD8 cytotoxic T cells directly kill infected or cancerous cells using perforin, while CD4 helper T cells enhance the immune response by stimulating other lymphocytes.

• Regulatory T cells help to downregulate the immune response, preventing overactivity that could lead to autoimmunity.

Clonal Selection and Memory

• Clonal selection is the process by which specific T-cells are activated and proliferate in response to an antigen, ensuring a tailored immune response.

• The effectiveness of the immune system relies on the ability to recognize foreign antigens and communicate effectively among immune cells.

Role of Macrophages

• Macrophages arise from monocytes and play a crucial role in engulfing pathogens and presenting their antigens to T-cells, thus bridging innate and adaptive immunity.

• They secrete soluble proteins that activate T-cells, creating a feedback loop that enhances the immune response.

Respiratory System Overview

Major Functions and Processes

• The primary functions of the respiratory system include supplying oxygen (O2) to the body and removing carbon dioxide (CO2).

• Four distinct processes are involved: Pulmonary ventilation (air movement), External respiration (gas exchange in alveoli), Transport of respiratory gases (via blood), and Internal respiration (gas exchange at tissue level).

Anatomy of the Respiratory System

• The respiratory system is divided into the conducting zone (passageways) and the respiratory zone (site of gas exchange).

• The conducting zone includes structures such as the nose, nasal cavity, pharynx, larynx, trachea, bronchi, and bronchioles, which cleanse, humidify, and warm incoming air.

• The respiratory zone consists of respiratory bronchioles, alveolar ducts, and alveoli, where gas exchange occurs.

Structure and Function of Key Components

• The nose serves multiple functions including air passage, filtration, and olfactory reception, with its structure influenced by nasal cartilages.

• The pharynx acts as a common pathway for food and air, with distinct regions (nasopharynx, oropharynx, laryngopharynx) serving different roles.

• The larynx is crucial for voice production and acts as a switch between the respiratory and digestive tracts.

Detailed Anatomy of the Respiratory System

The Bronchial Tree

• The bronchial tree consists of a series of branching air passages, with the right primary bronchus being wider and more vertical than the left.

• As one moves through the bronchial tree, changes occur in wall composition: cartilage transitions from rings to plates to none, epithelium changes from pseudostratified columnar to cuboidal, and smooth muscle increases.

Gas Exchange Mechanism

• The respiratory zone, particularly the alveoli, provides a vast surface area for gas exchange, with approximately 300 million alveoli in the lungs.

• The structure of alveoli, including their thin walls and extensive capillary networks, facilitates efficient gas exchange between air and blood.