Connective Tissue

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Connects, supports, binds or separates other tissues or organs

Provide structural support (fibrous CT, cartilage and bone)

Provide metbolic support (adipose CT & blood)

2 main divisions:

Fibrous CT = proper CT

Special CT = Cartilage, Bone, Blood

3 components:

Cell types(characteristics)

Extracellular matrix (polyzaccharides/glycoproteins)

Fibers

Proportion varies

Connective tissue is derived from the mesoderm (middle)

Types:

Fibroblasts & Fibrocytes

Reticular cells

Adipose cells

Chondroblasts & Chondrocytes

Osteoblasts & Osteocytes

Blood cells

Fibroblasts = immature cells Fibrocytes = mature cells

Occur widely in those supporting tissues that ‘fill spaces’

Also responsible for forming organ capsules, tendons & ligaments

Functions: Produce collagen & elastin fibres

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Reticular cells:

Special type of fibroblast that synthesises reticular fibres (type 3 collagen)

Forms the fine structural network of highly cellular organs such as the liver & lymphoid organs (acts as a scaffold)

Adipose cells: (adipocytes)

Occur more often in aggregates

Assemble and store fat droplets

As fat grows, the nucleas is displaced to one side of the wall

Functions: Fat/energy storage, Insulation, Associate with hormone production (can affect metabolism)

Chondroblasts and Condrocytes:

Chondroblast = immature, Chondrocyte = mature

Found in respiratory tract, nose, ears, joints and rib cage

Act as template for developing skeleton

Produces dense matrix

Functions: Provide semi-rigid supprt which still supplies a degree of flexibility

Osteoblasts and Osteocytes:

Osteoblast=immature, Osteocyte= mature

Found in bone

Functions: support and protection, store calcium and other ions

Blood Cells:

Functions: Defense and immune functions, transport nutrients

Examples: Mast cells, Macrophages, Leukocytes (Usually only see with inflammation, Consist of neutrophils, eosinophils, plasma cells, lymphocytes, etc.)

CT Matrix:

Outside cell

Fibers: Collagen, elastin, reticular

Ground substance: Proteoglycans and glycoproteins, water and dissolved substances (eg. electrolytes and gas)

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Collagen Fibers:

Thick, unbranching fibers, 20 different types (type I most common in bones, ligaments, tendons, fascia), tensile strength, only stretch by 15%

Fibroblasts secrete tropocollagen subunits

Subunits assembled into microfibrils-overlapping subunits cause banding appearance

Microfibrils are organised into fibrils which are subsequently organised into collagen fibres

Elastin Fibers:

Thin, branching fibers, permit stretch up to ~150% of original length, permits recoil

Produced by fibroblasts and in arteries by smooth muscles

Found in lungs, arteries, veins, skin, elastic cartilage

Reticular Fibers:

Secreted by particular fibroblasts named retinacular cells

Fibres form a mesh or framework in a wide variety of tissues including liver, lymphoid organs & glands

Compose of Type III Collagen fibers

Ground substance:

Produced mainly fibroblasts

Also secreted by chondroblasts and osteoblasts

No definitive structure

Consists of large complexes of proteins & polysaccharides (proteoglycans) → made up of smaller molecules called glycoproteins

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Classifications:

Fibrous or proper connective tissue:

Loose connective tissue

Dense irregular connective tissue

Dense regular connective tissue

Reticular Connective Tissue

Adipose Connective Tissue

Special connective tissue:

Cartilage

Bone

Blood

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Loose (areolar):

Supports epithelial cells lining GIT, respiratory and urinary tracts, forms deeper layers of skin

Provides structural support for surrounding tissue and provides a deformable, space-occupying "packing"

Dense irregular:

Found in fermis of skin, sheaths surrounding nerves and tendons, organ capsules and deep fascia

Provide protection and structural support, able to withstand tension from different directions

Dense regular:

Found in tendons and ligaments

Connect muscle to bone or bone to bone

Resist tensile forces generated during movement

Reticular (Type III Collagen):

Found in the stroma (supportive tissue) of highly cellular organs eg. liver, spleen and bone marrow

Provides a branching scaffold to support the cellular component of organs

Adipose:

Surrounds some organs, associated with many systems

Acts as energy storage, protects underlying structures, provides insulation