Connective Tissue

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Connective Tissue

Characteristics of connective tissues
Extracellular matrix separates cells
Most widely variable of tissues
Many varied functions
Common (mesenchyme) origin
Degrees of vascularity

Functions
Binding
Suport
Protection
Insulation
Transport

Structural Elements
Fibers
Collagen (white) fibres
Elastin (yellow) fibers
Reticular fibers
Ground substance
Amorphous material fills space between cells and contains fibers
Holds fluids
Acts as molecular sieve
Consists of interstitial fluid, cell adhesion proteins "glue", proteoglycans
Cells
Each class of connective tissue has a fundamental cell type that exists in an immature and mature form
Undifferentiated cell gets suffix "blast" i.e chronoblast, they are actively mitotic, secrete fibers and ground subtance
Once the cells synthesise the matrix they assume their less active mature mode indicated by suffix "cyte" i.e. lymphocyte

Summary
Fibers
Ground Substance
Cells
Collagen
Interstitial fluid
Immature form "blast"
Elastin
Cell adhesion proteins "glue"
Mature form "cyte"
Reticular
Proteoglycans

Types of connective tissue
All consist of cells surrounded by matrix
Differences reflect cell type, finer type and the proportion of matrix contributed by fivers
These differences determine connective tissue classes and their subgroups
General (fibrous) connective tissue "proper"
Specialised Connective tissues (skeletal - bone and cartilage, adipose, lymphoid, blood)

Cells found in 'Prototype' Connective Tissue
FIbroblasts
Adipocytes (fat cells)
Cells which migrate from blood
WBC
Other cells concerned with tissue response to injury

Connective Tissue Proper
Two subgroups - classification mainly based on finer arrangement and density:
Loose CT
Areolar
Reticular
Dense CT
Dense regular
Dense irregular

Connective Tissue Proper
Sub groups
Characteristics/Structural elements
Loose
Areolar
Semi fluid
Gelatinous ground substance
Collagen, elastin, reticular loosely distributed
Fibroblasts and macrophages are abundant
Occasional adipocytes (fat cells)
Widely distributed packing material of body
Loose
Reticular
Matrix contains reticular fibers
Reticular fibers form network of reticular cells (fibroblasts)

Dense
Regular
Closely packed collagen fibers orientated in same direction
Mainly fibroblasts
Poorly vascularised (no blood vessels)
White, flexible tissue with great tensile strength in one direction Wavy fivers - allow minimal 'give' until fibbers are straightened Elastic CT has high elastic content
i.e. ligaments and tendons
Dense
Irregular
Closely packed collagen fibers orientated in same direction
Mainly fibroblasts
Poorly vascularised (no blood vessels)
Collagen bundles are orientated in MANY directions
Forms sheets where tension is exerted in from many directions i.e. dermis of skin, fibrous joint capsules, fibrous capsules of many organs (kidneys, testis, bone, muscles)

Blood
Classified as a connective tissue
Cells in matrix (plasma)
Fibers are soluble proteins which only become visible during clotting
Functions
Transport of nutrients (glucose, oxygen)
Transport of wastes (CO2)
Transport of gases (oxygen, CO2)
Hormones

Cartilage
Somewhere between dense CT and bone
Tough but flexible
Cartilage cells "chondro" prefix
Ground substance has firmly bound collagen fivers
Contains lots of tissue fluid (80% water)
No blood vessels or nerves (good for joints)
Perichondrium (dense irreg. CT) surrounds most cartilage
Growth both interstitial and appositional
Types:
Hyaline
Elastic
Fibrocartilage

Bone
"Bone" can refer to:
Osseous tissue (type of CT)
Organs of the body i.e. humerus (consisting of several tissue types)

Bone as a tissue
Bone is connective tissue...
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