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Tissues and tissue types Tissues are: Collections of specialized cells and cell products organized to perform a limited number of functions Histology = study of tissues The four tissue types are: Epithelial Connective Muscular Nervous Epithelial tissue Includes glands and epithelium Glands are secretory Is avascular Forms a protective barrier that regulates permeability Cells may show polarity Functions of epithelium Physical protection Control permeability Provide sensation Produce specialized secretions Specializations of epithelium Perform secretory functions Perform transport functions Maintain physical integrity Ciliated epithelia move materials across their surface The Polarity of Epithelial Cells Maintaining the integrity of epithelium Cells attach via cell adhesion molecules (CAM) Cells attach at specialized cell junctions Tight junctions Desmosomes Gap junctions Intercellular connections Structure of typical epithelium Basal lamina attaches to underlying surface Lamina lucida Lamina densa Germinative cells replace short-lived epithelial cells Classification of epithelia Number of cell layers Simple Stratified Shape of apical surface cells Squamous Cuboidal Columnar Squamous Epithelia Cuboidal Epithelia Cuboidal Epithelia Columnar Epithelia Columnar Epithelia Columnar Epithelia Transitional Epithelium Glandular epithelia Exocrine glands Secrete through ducts onto the surface of the gland Endocrine glands Release hormones into surrounding fluid Glandular secretions can be: Merocrine (product released through exocytosis) Apocrine (involves the loss of both product and cytoplasm) Holocrine (destroys the cell) Mechanisms of Glandular Secretion Glands Unicellular Individual secretory cells Multicellular Organs containing glandular epithelium Classified according to structure A Structural Classification of Exocrine Glands Connective tissue functions: Establishing a structural framework Transporting fluids and dissolved materials Protecting delicate organs Supporting, surrounding and interconnecting tissues Storing energy reserves Defending the body from microorganisms A Classification of Connective Tissues Connective tissues contain Specialized cells Matrix Composed of extracellular protein fibers and a ground substance Connective tissue proper Contains varied cell populations Contains various fiber types A syrupy ground substance Fluid connective tissue Contains a distinctive cell population Watery ground substance with dissolved proteins Two types Blood Lymph Supporting connective tissues Less diverse cell population Dense ground substance Closely packed fibers Two types Cartilage Bone Connective tissue proper Contains fibers, a viscous ground substance, and a varied cell population. The ground substance is the non-living material in which the cells and protein fibres are found. Can contain varying amounts of water. Can be of viscous (blood), semi-solid (cartilage) or solid (bone). The ground substance and the extracellular proteins form the matrix. Types of cells found in connective tissue: Macrophage Adipocytes Mesenchymal cells Fibroblasts Melanocytes Mast cells Lymphocytes Microphages Connective tissue proper Three types of fiber Collagen fibers Reticular fibers Elastic fibers Connective tissue proper Classified as loose or dense Loose Embryonic mesenchyme, mucous connective tissues Areolar tissue Adipose tissue Reticular tissue Dense Dense regular CT Dense irregular CT The Cells and Fibers of Connective Tissue Proper Connective Tissue in Embryos Adipose and Reticular Tissues Dense Connective Tissues Dense Connective Tissues Dense Connective Tissues Fluid connective tissues Distinctive collections of cells in a fluid matrix Blood Formed elements and plasma Red blood cells, white blood cells and platelets Arteries carry blood away, veins carry to the heart Capillaries allow diffusion into the interstitial fluid Lymph Interstitial fluid entering the lymphatic vessels Formed Elements of the Blood Supporting connective tissues Cartilage and bone support the rest of the body Cartilage Grows via interstitial and appositional growth Matrix is a firm gel containing chondroitin sulfate Cells called chondrocytes Cells found in lacunae Perichondrium separates cartilage from surrounding tissues Three types: hyaline, elastic and fibrocartilage The Perichondrium and Types of Cartilage The Perichondrium and Types of Cartilage II The Perichondrium and Types of Cartilage III Bone, or osseus tissue Has osteocytes Depend on diffusion through canaliculi for nutrients Little ground substance Dense mineralized matrix Surrounded by periosteum Bone Membranes are simple organs Form a barrier Composed of epithelium and connective tissue Four types Cutaneous Synovial Serous Mucous Membranes Mucous membranes Line cavities that communicate with the exterior Contain lamina propria Serous membranes Line sealed internal cavities Form transudate Cutaneous membrane Covers the body surface Synovial membrane Incomplete lining within joint cavities Organs and systems are interconnected Network of connective tissue proper consisting of Superficial fascia Deep fascia Subserous fascia The Fasciae Muscle tissue Specialized for contraction Three types Skeletal Cardiac Smooth Muscle Tissue Muscle Tissue Muscle Tissue Skeletal muscle Cells are multinucleate Striated voluntary muscle Divides via satellite cells Cardiac muscle Cardiocytes occur only in the heart Striated involuntary muscle Relies on pacemaker cells for regular contraction Smooth muscle tissue Non-striated involuntary muscle Can divide and regenerate Neural tissue Conducts electrical impulses Conveys information from one area to another Neural tissue cells Neurons Transmit information Neuroglia Support neural tissue Help supply nutrients to neurons Neural Tissue Neural anatomy Cell body Dendrites Axon (nerve fiber) Carries information to other neurons Inflammation and regeneration Injured tissues respond in coordinated fashion Homeostasis restored by inflammation and regeneration Inflammatory response Isolates injured area Damaged cells, tissue components and dangerous microorganisms removed Infection avoided Regeneration restores normal function An Introduction to Inflammation Aging and tissue repair Change with age Repair and maintenance less efficient Structure altered Chemical composition altered Aging and cancer incidence Incidence of cancer increases with age 70-80% of all cases due to exposure to chemicals or environmental factors Changes in a Tissue under Stress