Histology of Connective Tissues PDF

Connective Tissues - Introduction 4 Types of Tissues q Epithelial n Covers body surfaces and lines hollow organs, body cavities, duct, and forms glands q Connective n Protects, supports, and binds organs. n Stores energy as fat, provides immunity q Muscular n G...

Connective Tissues - Introduction 4 Types of Tissues q Epithelial n Covers body surfaces and lines hollow organs, body cavities, duct, and forms glands q Connective n Protects, supports, and binds organs. n Stores energy as fat, provides immunity q Muscular n Generates the physical force needed to make body structures move and generate body heat q Nervous n Detect changes in body and responds by generating nerve impulses Development of Tissues n Tissues of the body develop from three primary germ layers: n Ectoderm, Endoderm, and Mesoderm q Epithelial tissues develop from all three germ layers q All connective tissue and most muscle tissues drive from mesoderm q Nervous tissue develops from ectoderm Connective Tissue n Most abundant and widely distributed tissues in the body n Numerous functions q Binds tissues together q Supports and strengthen tissue q Protects and insulates internal organs q Compartmentalize and transport q Energy reserves and immune responses Extracellular matrix of Connective Tissue n Extracellular matrix is the material located between the cells q Consist of protein fibers and ground substance n Connective tissue is highly vascular n Supplied with nerves q Exception is cartilage and tendon. Both have little or no blood supply and no nerves Cells and Fibers in Connective Tissue Connective Tissue Cells n Fibroblasts q Secrete fibers and components of ground substance n Adipocytes (fat cells) q Store triglycerides (fat) n Mast cells q Produce histamine n White blood cells q Immune response q Neutrophil and Eosinophils n Macrophages q Engulf bacteria and cellular debris by phagocytosis n Plasma cells q Secrete antibodies Connective Tissue Extracellular Matrix n Ground substance q Between cells and fibers n Fluid, semifluid, gelatinous, or calcified q Functions to support and bind cells, store water, and allow exchange between blood and cells q Complex combination of proteins and polysaccharides Fibers q Collagen fibers q Elastic fibers q Reticular fibers Classification of Connective Tissues n Embryonic connective tissue q Mesenchyme and mucous connective tissue n Mature connective tissue (proper) q Loose connective tissue n Areolar, adipose, and reticular q Dense connective tissue n Dense regular, dense irregular, and elastic q Cartilage n Hyaline, fibrocartilage, and elastic cartilage q Bone tissue q Liquid connective tissue n Blood and lymph Embryonic Connective Tissue q Mesenchyme n Gives rise to all other connective tissues q Mucous (Wharton’s Jelly) n Found in umbilical cord of the fetus Embryonic Connective Tissue n Mesenchyme q Found in the embryo q Small, spindle shaped cells, uniform appearance q Cells extend processes to form networks q A viscous ground substance between cells with paucity of collagen Embryonic Connective Tissue n Mucous Connective Tissue (Wharton’s) q Present in cord q A specialized unique ECM that is gelatin-like q Wharton’s jelly q Spindle-shaped fibroblasts that are seperated by large intercellular spaces Loose Connective Tissue n A cellular CT with thin and relatively sparse collagen fibers n Abundant ground substance with viscous consistency n Facilitates diffusion of O2 and nutrients from circulation n Located primarily beneath epithelia at body surfaces n Surrounds glands and blood vessels Loose Connective Tissue n The initial site of pathogen encounter if epithelia are breached n Contains resident and wandering immune cell populations n Site of inflammation Loose Connective Tissue: Areolar Connective Tissue q Most widely distributed in the body q Contains several types of cells and all three fibers Loose Connective Tissue: Adipose Tissue q Contains adipocytes q Insulation and energy reserves q Hormone production and proinflammatory cytokines q White (common) and brown adipose tissue Loose Connective Tissue: Reticular Connective Tissue q Fine interlacing reticular fibers and cells q Forms the stroma of liver, spleen, and lymph nodes Dense Connective Tissue n Dense connective tissue q Contains numerous, thicker, and denser fibers q Packed closely with fewer cells than loose connective tissue n Dense regular connective tissue q Bundles of collagen fibers are regularly arranged in parallel patterns for strength q Tendons and most ligaments Types of Mature Connective Tissue: Dense Irregular Connective Tissue q Collagen fibers are usually irregularly arranged q Found where pulling forces are exerted in many directions q Dermis of skin and heart Dense Connective Tissue: Elastic Connective Tissue q Contain branching elastic fibers q Strong and can recoil to original shape after stretching q Lung tissue and arteries Types of Mature Connective Tissue: Cartilage n Cartilage is a dense network of collagen fibers and elastic fibers firmly embedded in chondroitin sulfate q Chrondrocytes n Cartilage cells found in the spaces called lucunae q Pericondrium n Covering of dense irregular connective tissue that surrounds the cartilage n Two layers: outer fibrous layer and inner cellular layer q No blood vessels or nerves, except pericondrium Cartilage n Composed of chondrocytes (cells) located in matrix- surrounded spaces called lacunae. n Type of cartilage determined by components of the matrix. n Firm consistency. n Ground substance: Proteoglycans and hyaluronic acid complexed together trap large amounts of water Allows tissue to spring back after being compressed.. n Perichondrium. Dense irregular connective tissue that surrounds cartilage. Fibroblasts of perichondrium can differentiate into chondroblasts (cartilage-forming cells) n Types of cartilage q Hyaline q Fibrocartilage q Elastic Hyaline cartilage q Most abundant cartilage in the body q Surrounding by perichondrium (some exceptions like articular cartilage) q Provide flexibility and support. Reduces friction Copyright 2009, John Wiley & Sons, Inc. Fibrocartilage q Chondrocytes are scattered among bundles of collagen fibers within the extracellular matrix q Lack a perchondrium q Strongest type of cartilage q Found in intervertebral disc (between vertebrae) Elastic Cartilage q Chrondrocytes are located within a threadlike network of elastic fibers q Pericondrium is present q Provides strength and elasticity Repair and Growth of Cartilage n Cartilage grows slowly n When injured or inflamed, repairs is slow due to its avascular nature. n Two patterns of cartilage growth: q Interstitial growth n Growth from within the tissue q Appositional growth n Growth at the outer surface of the tissue Bone tissue n Bones are organs composed of several different connective tissues: bone (osseous) tissue, periosteum, and endosteum. n Compact or spongy n Osteon or haversian system q Spongy bone lacks osteons. They have columns called trabeculae Fluid Connective Tissue n Blood tissue q Connective tissue with liquid extracellular matrix called blood plasma n Lymph