Histology Guide

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Chapter 3 - Connective Tissue

Connective tissue provides support, binds together, and protects tissues and organs of the body.

Connective Tissue Fibers

The three types of connective tissue fibers are:

CONNECTIVE TISSUE CELLS

Connective tissue cells are usually divided into two types:

FIXED CELLS

Fixed cells are normal components of connective tissue.

Fibroblasts

Fibroblasts produce and maintain the extracellular matrix. They are the most common cell type in connective tissue.

Adipocytes

Adipocytes (fat cells) are specialized for storage of fats. They also function as a cushion for organs and insulate the body.

Macrophages

Macrophages are phagocytic cells that engulf and digest microbes, cellular debris, and foreign substances. Monocytes develop in bone marrow, circulate in the bloodstream, and migrate into connective tissue, where they differentiate into macrophages.

Mast Cells

Mast cells release molecules that dilate blood vessels and recruit more immune cells to a site of mast cell activation. Progenitor mast cells (agranular) develop in bone marrow, circulate in the bloodstream, and migrate into connective tissue, where they proliferate and differentiate into mature mast cells (granular).

Mast cells undergo rapid degranulation during an anaphylactic reaction.

TRANSIENT CELLS

Transient cells are leukocytes (white blood cells) that circulate in the bloodstream and migrate into connective tissue at sites of an immune response. These include neutrophils, eosinophils, basophils, lymphocytes, and monocytes.

Plasma Cells

Plasma cells are mature B lymphocytes that produce large quantities of antibodies. They are abundant wherever antigens may enter the body, such as the gastrointestinal tract and the respiratory system.

Eosinophils

Eosinophils are involved in many inflammatory processes, including parasitic infections, allergic diseases, and asthma.

Lymphocytes

Lymphocytes develop the ability to recognize and respond to antigens. Their number increases dramatically at sites of inflammation.

Mast Cell/Plasma Cells/Eosinophils

Example of multiple types of immune cells in connective tissue.