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Lecture 4

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Biological Sciences
Connie Potroff

1 Lecture 4 Foundations: Connective Tissues (Chapter 3) Connective Tissues Tissues that connect or form structures Most diverse, abundant, widely distributed and microscopically variable All derived from mesoderm Examples of connective tissue: bone, cartilage, blood, connective tissue proper – ligament, tendon, fibrous tissue, loose connective tissue, dense connective tissue, fat Functions of Connective Tissue Physical protection – bones of cranium, sternum, vertebral column, thoracic cavity, fat surrounding organs Support and structural framework of the body – bones provide framework and support soft tissues; cartilage supports body structures such as trachea, bronchi, nose and ears; sheets of connective tissue form capsules to support such organs as spleen and kidneys Transporting fluid and dissolved materials – blood carries nutrients, gases, hormones, wastes and blood cells between different regions of the body Connecting other tissues – ligaments bind bone to bone; tendons bind muscle to bone; dense irregular tissue (fascia) binds skin to underlying muscle and bone Storing energy – fat is major energy reserve in the body, bones are a large reservoir for calcium and phosphorus Immune protection – much connective tissue contains white blood cells (leukocytes) which protect the body against disease and mount an immune response against foreign material; the viscous nature of the extracellular matrix interferes with the movement and spread of disease causing organisms Elements of Connective Tissues • Cells spaced far apart (unlike epithelium) • Lots of extracellular matrix (ECM) between cells Matrix is the collective term for the extracellular component of any connective tissue that is made of protein fibers and the ground substance  ECM is secreted from cells of connective tissue by proteins in fibrous tissues called fibroblasts TERMINOLOGY - ______cyte – a generic cell type (eg. osteocyte in bone, adipocyte in fat) -_______blast – produces something, lays down some foundation (eg. osteoblast is a cell that lays down (makes) bone matrix, fibroblasts in connective tissue proper) © 2012 Pearson Education, Inc. 2 -______clast – reabsorbs/breaks down something (eg. osteoclast breaks down bone)  ECM composed of: o Ground substances – sugary water and protein and carbohydrate molecules (gelatin-like), proteins help to keep water in o Fibers:  COLLAGEN – for tensile strength and stretch resistant  ELASTIC –which are flexible and resistant  RETICULAR – which form an interwoven network Classification of Connective Tissues: based on type of extracellular matrix: Connective tissue proper - has a matrix of fibers (loose and dense) in a syrupy ground substance (kind of like “jello” with fruit in it) • Different types have different numbers of cell types and different relative proportions of fibers and ground substance (examples include: adipose (fat), ligaments, tendons) Fluid connective tissue - has a matrix of watery liquid than contains dissolved proteins (examples are: blood and lymph) Supporting connective tissue - has a matrix consisting of a gel (densely packed fibers), cartilage or a solid (matrix is calcified of mineral deposits of predominantly calcium), bone Connective Tissue Proper Types with Loose fibers: Areolar tissue, Adipose tissue, Reticular tissue (LAAR) Types with Dense fibers: Dense regular, Dense irregular, Elastic Cells of Connective Tissue Proper contain various types of FIXED (stationary cells involved primarily with local maintenance/energy storage) and WANDERING cells (cells that require movement for defense and repair of damaged tissues) Fixed Cells: Fibroblasts – produce connective tissue fibers (collagen, elastic, reticular) Fibrocytes – maintain connective tissue fibers and matrix Fixed macrophages – phagocytize pathogens and damaged cells Adipocytes – store lipid reserves Mesenchymal cells – connective tissue stem cells that can differentiate into other cell types Melanocytes – synthesize melanin Wandering Cells: Free Macrophages – mobile/travelling phagocytic cells (derived from monocytes of the blood) Mast Cells – stimulate local inflammation Lymphocytes – participate in immune response – can develop into plasmocytes which produce antibodies (proteins involved in defending the body against disease) © 2012 Pearson Education, Inc. 3 Neutrophils and Eosinophils (white blood cells) – small phagocytic blood cells that mobilize during infection or tissue injury Loose Connective Tissue Areolar Tissue Location - deep to the dermis, covered by epithelial lining, between muscles, around blood vessels, nerves and around joints *Function - connects skin to muscle, cushions organs, provides support but with movement Matrix – abundant collagen fibers, thin irregularly arranged elastic fibers, small fibroblast cells, adipocyte (fat) cells and abundant gel-like ground substance Adipose Tissue Location – hypodermis, buttocks, breasts, around eyes, surrounds organs Function – provides padding and cushions shocks, insulates and stores energy Matrix – predominantly adipocytes, inside each cell is drop of fat surrounded by plasma membrane, pushed nucleus and organelles to the side, absence of fibers, little ground substance Reticular Tissue Location - liver, spleen, kidney, lymph nodes, tonsils, appendix, bone marrow Function - supporting framework Matrix – predominantly reticular fibers and fibrocytes Dense Connective Tissue Dense Regular Connective Tissue • The collagen fibers are packed tightly and aligned parallel to applied force (like a group of cables), able to withstand stress in ONE direction, almost no ground substance and fibroblast nuclei are squeezed between layers of fibers Location and Function tendons – cords of dense regular connective tissue attach muscles to bone and cartilage *aponeuroses - cartilaginous sheets that resemble broad tendons, may cover muscles or attach muscle to muscle or another structure (eg. on diaphragm and abdominal muscles ligaments - between bones or stabilizing positions of organs, stabilizes the vertebrae  elastic tissue – large number of elastic fibers, tissue is springy and allows some stretch, found in elastic walls of arteries, trachea, bronchial tubes, vocal cords and suspensory ligaments of the penis Dense Irregular Connective Tissue Location - nerve and muscle sheaths, capsules of visceral organs, joint capsule of synovial joint, dermis, periosteum covering bones Function - provides strength and can withstand stress in multiple directions Matrix – unorganized fibers Fluid Connective Tissue Blood Location: circulatory system Erythrocytes (erythro = red) - transport oxygen and carbon dioxide Leukocytes (leuko = white) - fight infections (monocytes, eosinophils, neutrophils, basophils, lymphocytes) © 2012 Pearson Education, Inc. 4 Platelets - blood clotting Matrix - liquid (plasma) Lymph Location - lymphoid system (lymphatic vessels that run alongside the cardiovascular system) Cells – Lymphocytes - develop into T cells and B cells (for example) Function - involved with the immune system Supporting Connective Tissue Cartilage and Bone - provide a strong fram
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