Chronic Inflammation Overview

Study Notes

Chronic Inflammation Overview

Chronic inflammation is a prolonged response to tissue or organ injury lasting weeks to months, involving simultaneous active inflammation, tissue destruction, and healing efforts.

Cells Involved in Chronic Inflammation

Key cells: Monocytes, Macrophages, Lymphocytes, Plasma cells, Eosinophils.

Morphologic Patterns of Chronic Inflammation

Non-Specific Chronic Inflammation: Characterized by diffuse accumulation of macrophages and lymphocytes (e.g., chronic pancreatitis).
Granulomatous Inflammation: Defined by granuloma formation—a collection of modified macrophages (epitheloid cells) surrounded by lymphocytes, plasma cells, and giant cells.

Granuloma Formation

Granulomas are tumor-like nodules with epitheloid cells arranged in clusters and surrounded by a rim of various immune cells.
Giant Cells: Formed through the fusion of macrophages, these large cells contain multiple nuclei and resemble epithelial cells.
Tuberculosis Granulomas: Exhibit follicular collections of epitheloid histiocytes and multinucleated giant cells with peripheral small lymphocytes.

Granulation Tissue and Healing Process

Granulation tissue displays fibroblast proliferation and delicate capillary growth within a loose extracellular matrix along with inflammatory cells, primarily macrophages.
The extent of granulation tissue correlates with the size of the tissue deficit and injury intensity.

Maturation and Remodeling

Occurs months post-injury, involving collagen synthesis and degradation, enhancing repair strength.
Capillaries diminish, resulting in an avascular scar that never fully regains the original tissue's tensile strength.

Factors Impairing Wound Healing

Malnutrition
Poor blood flow and hypoxia
Impaired immune response
Wound infections
Presence of foreign particles
Aging (decreased immune activity and circulation)

Keloid Scars

Keloids are raised scars resulting from excessive collagen production and insufficient degradation, often extending beyond the original wound boundaries.
There is a familial tendency for keloid formation, with higher prevalence in individuals of African descent.

Types of Wound Healing

Primary Intention: Involves rapid epithelial regeneration with minimal tissue loss and no scar formation; typical in surgical incisions.
Secondary Intention: Applies to larger wounds requiring regeneration and scarring; healing takes longer with significant tissue loss and scar formation.

Stages of Tissue Repair

Inflammatory Stage: Begins with fibrin clot formation, followed by infiltration of neutrophils and macrophages, which promote cell growth and new blood vessel formation.
Proliferative Stage: Occurs within 1-3 days post-injury, marked by fibroblast activity leading to collagen synthesis and granulation tissue formation; wound closure typically happens within 1-2 weeks.

Two Mechanisms of Tissue Repair

Repair by Regeneration: Involves replacement by the same type of cells, allowing full function restoration; occurs in labile cells (e.g., skin) and stable cells (e.g., liver).
Repair by Connective Tissue Replacement: Functional tissue is replaced with collagen, resulting in scar formation and loss of original function, common in fixed cells like nerve and cardiac muscles.

Description

This quiz explores the characteristics and cellular components of chronic inflammation. Understand the various cells involved, such as macrophages and lymphocytes, and the morphologic patterns that define this prolonged response to tissue injury. Test your knowledge on the key aspects of chronic inflammation.