Histo Lecture 6

• -Provide and maintain form in the body
• -Provide a matrix that connects and binds cells and tissues together
• -Serve as a reservoir for hormones controlling cell growth and differentiation
• -Medium through which nutrients and metabolic wastes are exchanged between cells and their blood supply

• -Cells
• -Fibers (protein polymers)
• -Ground substance

Many different cell types among various tissues

Predominately collagen fibers, also reticular and elastic fibers

Viscous mixture of water, proteoglycans, glycoasminoglycans, and glycoproteins (laminin, fibronectin)

-Ground substance and fibers = extracellular matrix (ECM)

-Fibroblasts, chondrocytes, osteoblasts, adipocytes, endothelial cells, smooth muscle cells

-Mast cells, basophils, eosinophils, neutrophils, macrophages, lymphocytes (T&B cells), red blood cells (RBC)

Monocytes (blood), macrophage (tissue), multinuclear giant cell (CT), Kupffer cell (liver), microglia (CNS), Langerhans cell (skin), dendritic cell (lymph nodes), oseoclast (bone)

Tendons, ligaments, aponeuroses, dermis, organ capsules, stroma of organs, covering of muscles and nerves and membranes (meninges) surrounding CNS

• -Polymer of collagen protein molecules, typically arranged in fiber bundles
• -Each monomer collagen fiber is made of bundled collagen fibrils
• -More than 25 "collagen types"; types I, II, III, and IV are most abundant
• -Collagen provides resistance to tensile forces

Strongest, largest collagen fibers; most abundant collagen type

Found in articular cartilage and fibrocartilage

Synonymous with reticular fibers; found in skin, artery wall, scar tissue

Major filament of basement membranes (basal lamina)

• -Composed of type III collagen fibrils
• -Small diameter and "loosely" arranged (flexible network for organs)
• -Abundant in smooth muscle, endoneurium (neurons), and framework for hemtopoietic organs
• -Also located in papillary layer of the dermis

• -Oxytalan
• -Elaunin
• -Elastin

Small fibers that do not actually contain elastin protein but are resistant to tensile forces

Mixture of elastin protein and oxytalan fibers

Polymers of elastin aggregate in the center of elastic fibers and are surrounded by network of oxytalan and elaunin fibers

Viscous, hydrophilic substance with many macromolecules; occurs "between" cells

• -Glycoasminoglycans, proteoglycans, glycoproteins
• -Bind cell surface receptors to fiber components of ECM
• -Ancher cells within ECM; provides tissue strength and rigidity
• (ECM = fibers + ground substance)

• Keratan Sulfate = cartilage, nucleus pulposus, annulus fibrosus
• Hyaluronic acid - articular cartilage
• Chondroitin 4-sulfate = cartilage, bone, skin
• Chondroitin 6-sulfate = cartilage, skin, aorta
• Dermatan sulfate = skin, tendons
• Heparan sulfate = lung, liver, basement membrane

• -Loose CT
• -Dense CT (regular or irregular)

Adipose, elastic, hematopoietic (blood), and mucous tissue (umbilical cord)

Cartilage and bone

• -Supports structures that are normally uner low pressure and low frictions forces
• -Flexible tissue, well vascularized, not very resistant to tensile stress
• -Contains mainly fibroblasts and collagen, with lesser amounts of elastic and reticular fibers
• -Very common; found in many tissues (epithelium, dermins, blood vessels, lining cavities)

• -Main function is to offer resistance to tensile force and protection of tissues
• -Fewer cells (fibroblasts) and predominance of collagen fibers compared to loose CT
• -Minimally flexible and highly resistant to stress (especially tension)
• -composed of irregular and regular types, depending on arrangement of collagen fibers of the ECM

• -Collagen bundles arranged into a definitive, linear pattern
• -Linear orientation of fibers (and fibroblasts) is designed to withstand prolong stresses exerted in the direction of fiber alignment
• -Ex. - tendons, ligaments

• -Collagen fibers are arranged in bundles without a definite orientation
• -Provide resistance to stress in all directions
• -Ex. - Dermis

• -Composed of thick, parallel elastic fiber bundles, and fibroblasts
• -Thin collagen fibers are scattered among the elastic fiber bundles
• -Abundant elastic content confers yellow color
• -tissue is designed to provide elasticity to tissues; found mainly in ligaments of vertebral column (ligamentum flavum)

• -Specialized loose connective tissue
• -Provides architectural framework for bone marrow, lymph nodes, spleen, and liver
• -Matrix of intertwined, branched network of reticular fibers secreted by reticular cells (specialized fibroblasts that produce reticular fibers)
• -Reticular fibers and cells form a sponge-like structure where ells and fluids can move easily