B. Connective Tissues Made up of: – Cells, which are further apart than epithelial cells – Fibers – Matrix: intercellular material Major cell types: 1.Fibroblasts – large, fixed, star-shaped cell that secretes fibers 2.Macrophages – wandering scavenger cells that defend against infection 3.Mast cells – large cells, located near blood vessels, that secrete heparin and histamine

Connective Tissues (cont.) Connective tissue fibers: 1.Strong, collagenous fiber (white fiber), made of the protein collagen; adds strength 2.Stretchy, elastic fiber (yellow fiber), made of the protein elastin; adds ____________. 3.Reticular fibers – thin collagenous fibers that form supportive networks in tissue

Connective Tissues (cont.) 1.Loose Connective Tissue (“areolar tissue”) – Cells are some distance apart; separated by gel- like matrix – Forms delicate, thin membranes – Binds skin to underlying organs, fills space between muscles

Connective Tissues (cont.) 2. Adipose Tissue – fat – Large fat droplets in cells push nuclei close to the cell membranes. – Beneath the skin, between muscles, around kidneys, behind eyeballs, on heart, around joints

Connective Tissues (cont.) 3. Dense Connective Tissue – closely packed, thick collagenous fibers + elastic fibers – Strong! – Binds organs together – Found in tendons, ligaments, deep skin layers

Connective Tissues (cont.) 4. Cartilage – a rigid connective tissue – Chondrocyte: cartilage cell – Perichondrium: around cartilage; membrane surrounding cartilage; contains blood vessels to supply nutrients – Three types of cartilage, distinguished by intercellular (???) matrix: a)Hyaline cartilage b)Elastic cartilage c)Fibrocartilage

Connective Tissue (cont.) a)Hyaline cartilage – Very fine collagenous fibers in matrix – White glass appearance – Ends of bones in joints, soft part of nose b)Elastic Cartilage – Dense network of elastic fibers = more flexible – Framework for external ears and parts of larynx c)Fibrocartilage – Very tough; many collagenous fibers – Forms intervertebral discs and pads between bones in knees and pelvic girdle

Connective Tissue (cont.) 5. Bone – the most rigid connective tissue – Matrix made of mineral salts and collagen fibers – Osteocyte: bone cell 6. Blood See Table 5.4, p.105!!!