Histology - Connective Tissues PDF

Histology Dr. Ayman Sedky Lec.1 Connective tissues are derived from the embryonic connective tissue, primarily from the mesodermal germ layer Connective tissue is comprised of cells and extracellular matrix (ECM) which is formed from fibers and ground substance...

Histology Dr. Ayman Sedky Lec.1 Connective tissues are derived from the embryonic connective tissue, primarily from the mesodermal germ layer Connective tissue is comprised of cells and extracellular matrix (ECM) which is formed from fibers and ground substance. Functions of the connective tissue include: - support and binding the other tissues together. - providing a medium for the passage of metabolites. - serving as a storage site for lipids, water and electrolytes. - aiding in protection against infection by an inflammatory reaction mediated by cells that have migrated into the connective tissue from the blood. - repair by the formation of scar tissue. Histology Dr. Ayman Sedky Lec.1 Connective tissue cells Connective tissue contains a variety of cells, each with distinct roles in maintaining tissue structure and function. The main types of cells in connective tissue include: 1. Fibroblasts: o Function: The most common cell type, responsible for producing the extracellular matrix, including collagen and elastin fibers. They help in wound healing and tissue repair. 2. Adipocytes (Fat Cells): o Function: Store energy in the form of fat and provide insulation and cushioning for organs. 3. Macrophages: o Function: Part of the immune system, these cells engulf and digest pathogens, dead cells, and other debris. They also play a role in inflammation and tissue repair. 4. Mast Cells: o Function: Release histamine during allergic reactions and inflammation. It also secrets heparin (anticoagulant). 5. Plasma Cells: o Function: produce antibodies that help protect the body against infections. 6. Chondrocytes (in cartilage): o Function: Maintain the cartilage matrix and help in tissue repair and resilience in joints and other cartilage-based structures. 7. Osteocytes (in bone): o Function: Mature bone cells that maintain the mineralized bone matrix and regulate calcium levels. 8. Leukocytes (White Blood Cells): o Function: These immune cells help defend the body against infections and foreign invaders. They include neutrophils, lymphocytes, and other immune cells. Histology Dr. Ayman Sedky Lec.1 The main fibers in connective tissues are part of the extracellular matrix and provide strength, flexibility, and support. There are three primary types of fibers: 1. Collagen Fibers: o Structure: Thick, long fibers composed of collagen protein. o Function: Provide tensile strength and resist stretching, making them crucial for supporting tissues like tendons, ligaments, and skin. They are the most abundant fibers in connective tissues. 2. Elastic Fibers: o Structure: Thin, branched fibers composed of elastin protein and surrounded by fibrillin. o Function: Provide elasticity, allowing tissues to stretch and return to their original shape. They are found in tissues that require flexibility, like the lungs, skin, and walls of arteries. 3. Reticular Fibers: o Structure: Thin, delicate fibers composed of collagen (type III collagen) arranged in a mesh-like network. o Function: Provide structural support for soft tissues and organs like the liver, spleen, lymph nodes, and bone marrow. Reticular fibers form a supportive framework for cells within these organs. These fibers work together to give connective tissues their mechanical properties and support functions in various parts of the body. Histology Dr. Ayman Sedky Lec.1 CLASSIFICATION OF CONNECTIVE TISSUE 1. Loose Connective Tissue: o Loose Areolar connective tissues: - Histology Dr. Ayman Sedky Lec.1 o Adipose connective tissues: Stores fat provides insulation and protection, and acts as an energy reserve. Histology Dr. Ayman Sedky Lec.1 o Reticular connective tissues: Supports lymphoid organs like the spleen and lymph nodes with a network of fibers. Histology Dr. Ayman Sedky Lec.1 2. Dense or Fibrous Connective Tissue: Histology Dr. Ayman Sedky Lec.1 Regular Irregular Histology Dr. Ayman Sedky Lec.1 o Dense Regular Tissue: Collagen fibers aligned in parallel, found in tendons and ligaments for strength in one direction. It is mostly made up of collagen fibers (usually type I collagen) o Dense Irregular Tissue: Collagen fibers arranged in multiple directions, providing strength in many directions, found in the dermis of the skin. o Elastic Tissue: rich in elastin fibers, allowing tissues to stretch and recoil, found in walls of large arteries and the respiratory system. Histology Dr. Ayman Sedky Lector: TWO 3. Specialized Connective Tissue: o Cartilage: A semi-rigid tissue providing support and flexibility; includes: § Hyaline Cartilage: Found in joints and respiratory tract. § Elastic Cartilage: Found in the ear and epiglottis. § Fibrocartilage: Found in intervertebral discs and menisci. o Bone: A rigid tissue providing structure, protection, and supporting movement. o Blood: A fluid connective tissue that transports nutrients, gases, and waste throughout the body Histology Dr. Ayman Sedky Lector: TWO Histology Dr. Ayman Sedky Lector: TWO Histology Dr. Ayman Sedky Lector: TWO Histology Dr. Ayman Sedky Lector: TWO Histology Dr. Ayman Sedky Lector: TWO Histology Dr. Ayman Sedky Lector: TWO Histology Dr. Ayman Sedky Lector: TWO Histology Dr. Ayman Sedky Lector: TWO