Connective Tissue

Seite 1

Connective Tissue/supporting tissue: Basic tissue structure of mesodermal origin which provides structural support as well as metabolic support for other tissues and organs throughout the body.

There are three types of connective tissue:

Connective tissue proper (focus on this one)

Fluid connective tissue: Blood and lymphatic fluid

Supporting Connective tissue: Cartilage and Bone

General Structure

Cells

MESENCHYMAL STEM CELLS: differentiate to replace connective tissue after injury.

FIBROBLAST: Synthesize and maintain extracellular fluid

ADIPOCYTES: storage and metabolism of lipids

CELLS with defense and immune function

Extracellular material

GROUND SUBSTANCE

FIBRES: collagen (reticulin) and elastin

STRUCTURAL GLYCOPROTEINS: cell adhesion proteins and proteoglycans

It differs from other tissues in three ways:

It is cell poor and matrix rich

Diverse cellular components (4 cell types)

No basement membrane

It is never exposed to the external enviroment as it's not robust enough, it sits below the basement membrane and has blood vessels within

Functions

Establish structural framework

Transport fluid and dissolved materials

Support, surround and interconnect tissues

Store energy reserves

Insulate the body

Defend against pathogens

Classification:

Loose (areolar): most common and least specialized.

Located beneath epithelial tissue and surrounds blood vessels and nerves. It has an open framework consisting mainly of GROUND SUBSTANCES. It acts as a shock absorber and reservoir for salt and water as well as forming the stroma/non functioning parts of most organs.

Dense: divided into regular and irregular froms consists mainly of FIBRES

Irregular: found in the dermis of SKIN and capsule of ORGANS, it is a mesh of fibres that provide physical support.

Regular: found in LIGAMENTS and TENDONS formed of bundles of fibres.

Specialized forms

Fibroblasts:

Spindle-shaped cells that align with connective tissue fibres. They produce fibrous componets and ground substance key for the healing of wounds. Tissue damage causes Fibrocytes to activate to Fibroblasts. Specialised forms are found in cartilage and bone.

Collagen fibres: Main fibre in most connective tissue.

It is unbranched filaments/fibrils meshwork. There are 29 types but 1-4 are the most important. Retiulin fibres (type III) are branched and important in disease diagnosis.

Elastic Fibres:

They are short branched fibres that fuse with each other and are found in skin lung stomach and bladder.

Adipose tissue: (fat) unicellular and multicellular are both composed of adipocyte cells.

Unicellular (white) adipose tissue: found throughout the body espicailly in deep skin. The cells are arranged in sheets or present as single/groups of cells. They are for: energy stores; thermal insulation and cushioning. Microdroplets of triglyceride fuse to form a single droplet ths toccupies the cell cytoplasm.

Multicellular (brown): adipose tissue: the most prominent in the foetus and newborns but also found in adults neck, shoulders and back. It contains small lipid droplets. Its function is to metabolise fat, produce heat and maintain temp.

Cells with defence and immune function

Fixed (intrinsic) tissue is fixed macrophages (histocytes) and mast cells which are found in all connective tissue.

Wandering (extrinsic) white blood cells.

Basement Membrane

Boundary between epithelial tissue and connective tissue composed of 3 layers. Special techniques are required to visualize it. Its functions are:

Structural support

Anchor epithelium to connective tissue

Control Epithelium growth

Diffusion/permeability barrier

Malignant epithelial cells breach the basement membrane.