Connective Tissue (Semester 2 - Biomedical science)

There are four 4 classes of tissue:

Tissue = A collection of cells performing a similar function.

Connective Tissue 

In contrast to the densely packed epithelial and muscle tissue, connective tissue are usually

• dispersed population of cells. 
• embedded in an extracellular matrix that they secrete (The extracellular matrix composition and properties differ among different types of of connective tissue).

Connective tissue cells:

If they name ends in '-Blast' 

• Immature, ‘to bud or sprout’ 
• Dividing, matrix-secreting cells 
• Chondroblasts (cartilage) and osteoblasts (bone) 

If the name ends in '-cyte'

• Mature
• Reduced division and matrix formation.
• Matrix maintenance
• Chondrocyte (cartilage) and osteocyte (bone)

FIBROBLASTS ARE THE EXCEPTION!!!!!

Fibroblast:

'A fibroblast is a type of cell that synthesizes the extracellular matrix andcollagen,[1] the structural framework (stroma) for animal tissues, and plays a critical role in wound healing. Fibroblasts are the most common cells of connective tissue in animals.'

-They Secrete fibres and ground substance thus maintain extracellular matrix
-Migrate to sites of damage
Derived from mesenchyme (embryonic cells). Secrete collagen.

Macrophages
They are Phagocytes that engulf pathogens by endocytosis

• Derived from monocytes 
• Phage- eaters 
• Engulf bacteria/debris by phagocytosis 
• Fixed and wandering

Plasma Cells

• They're derived from B-lymphocytes 
• They secrete antibodies
• Reside in connective tissue but migrates.
• Found and transported by blood and lymph. 

Extracellular matrix protien

Protein fibers are an important component in the extracellular matrix,

• The dominant protein is collagen, it makes up to 25% of the bodies protein. 
• Collagen is strong, resistant and stretchy. = Strength to the skin and connection between the bones and muscle.
• Elastin is also in the Extracellular matrix. As you can tell from the name is provides elasticity which means it can stretch to several times its size and then recoil. 

Cartilage and bone are connective tissues that provide rigid structural support. In cartilage a network of collagen fibers is embedded in a flexible matrix consisting of a protein-carbohydrate complex. Along with a specific type of cell called chondrocyte. 

Cartilage lines the joints of vertebrates, is resistant to compressive forces. Because it's flexible it provides structural support for flexible structures i.e. external ears and noses.
The extracellular matrix in bone also contains many collagen fibers, but it's  hardened by the deposition of the mineral calcium phosphate.(I will write more about cartilage bone in much detail in another post).

1. ^ http://ghr.nlm.nih.gov/glossary=fibroblast