Connective Tissue

1. Occurs throughout the body, represents most abundant tissue type by weight.
2. Cells are far apart.
3. Abundance of intercellular matrix between cells
4. Cells are able to reproduce and usually have a good blood supply.

   Major Cell Types

   • Fibroblast: most common type of cell, quite large, usually star shaped. function is to produce fibres.
   • Macrophages: Almost as numerous as fibroblasts. Cells can move about and engulf and destroy foreign cells. Important defence against infectious agents.
   • Mast: Widely distributed. Function not completely understood, but release substances important for the defence against foreign cells and particles.

   Connective tissue fibre types

   • Collagen: Quite thick, made of the protein collagen. Major structural protein of the body, flexible but only slightly elastic. Great tensile strength.
   • Elastic: Made up of protein bundles (microfibrils) embedded in a protein called elastin. Less strength than collagen but very elastic. Easily stretched, but will resume original length and shape.
   • Reticular: Very thin fibres made of collagen. Form delicate supporting networks.

   Functions of Connective Tissue

   • Bind structures together
   • Support and protection
   • Store fat
   • produce blood cells

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   Loose aerolar Connective

   

   Identifying Features

   • Nuclei visible -belong mainly to fibroblasts.
   • Thick fibres visible are collagen.
   • Thin fibres visible are elastic.
   • All the above embedded in a gel like ground substance (not stained here)

   Functions

   • Binds organs together
   • Holds tissue fluids, provides a reservoir of water and salts
   • Universal packaging material between other tissues

   Locations

   Between muscles, forms subcutaneous tissues of skin, wraps small blood vessels and nerves, surrounds glands, forms laminar propria of mucous membranes.

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   Dense Fibrous

   

   Identifying Features

   • Nuclei visible -belong to fibroblast cells
   • Dense, closely packed thick collagen fibres

   Function

   Binds organs together.

   Locations

   Ligaments, tendons, skin.

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   Elastic

   

   Identifying Features

   • abundance of elastic fibres, note the wavy appearance
   • few nuclei

   Function

   Gives elastic quality.

   Location

   Between adjacent vertibrae, walls of airways.

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   Adipose

   

   Identifying Feature

   Large fat filled cells (nuclei not visible here, but usually squished to outside of cell). Compared to other connective tissues it is very cellular.

   Functions

   • Insulation
   • Protection
   • Storage of fat
   • Provides reserve food supplies

   Location

   Under the skin (subcutaneous tissue), around kidneys, bone marrow (yellow), behind the eyeballs, breasts.

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   Hyaline Cartilage

   

   Identifying Features

   • Cells called chondrocytes found in spaces called lacunae
   • Background matrix contains no visible fibres (collagen fibres are actually present, but not visible)

   Functions

   • Provides pliable support
   • Protection
   • Provides framework

   Locations

   Ends of bones, parts of nose, walls of trachea, connects ribs to sternum, forms part of larynx, forms part of bronchial tree, epiphyseal plates.

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   Fibro Cartilage

   

   Identifying Features

   • Fewer chondrocytes
   • Abundance of collagen fibres

   Functions

   • Support that can withstand heavy pressures
   • Protection

   Location

   Pubis symphysis of pelvic girdle, intervertebral disks, knee.

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   Elastic Cartilage

   

   Identifying Features

   • Chrondrocytes
   • Abundance of elastic fibres (looks messy)

   Functions

   • Support with great ability to bend
   • Protection
   • Provides framework

   Location

   Makes up framework for parts of the ear, larynx and epiglottis.

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   Reticular

   

   Identifying Features

   • Reticular Fibres present
   • Cell nuclei visible belonging to reticular cells (a type of fibroblast)

   Function

   Support

   Location

   Walls of liver and spleen

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   Blood

   

   Identifying Features

   • Abundance of cells. Most cells are biconcave discs lacking nuclei (erythrocytes). Also visible is one white blood cell, this is the most common type of leucocyte called a neutrophil (note the lobed nucleus).
   • Clear background matrix is the plasma, lacks any visible fibres.

   Functions

   • Transport of gases
   • Fights infection
   • Blood clotting

   Location

   Inside blood vessels

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   Bone

   Note: This is compact bone.

   Identifying Features

   • Large cylindrical structures (Osteons or haversian systems)
   • Smaller concentric layers (lamellae)
   • In centre of haversian systems are canals (haversian canals). These appear as solid black circles.
   • Small cells (osteocytes).

   Functions

   • Provide framework
   • Site of attachment of tendons
   • Storage site of calcium
   • Protection
   • Red marrow is site of blood cell production

   Location (Compact bone)

   This bone is found in the shafts of long bones.
   Tissue Index

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