LEARNING OBJECTIVES :
Connective Tissue :
At the end of the lecture, student should be able to :
· Define the connective tissue .
· Explain the components of connective tissue.
· Classify the different types of connective tissue.
· Recognize the different types of connective tissue under the microscope.
LECTURE OUTLINE
CONNECTIVE TISSUE
DEFINITION:
CONNECTIVE TISSUE:
It is characterized by the presence of relatively fewer cells and a large amount of intercellular substance, called “ matrix ”.
§ It is derived largely from embryonic mesoderm.
§ It plays both structural and defensive roles in the body.
§ Matrix binds the cells and organs and ultimately gives mechanical support to the body.
§ Unlike the other tissues (epithelium, muscle and nerve ) which are formed mainly by the cells, the major constituent of connective tissue is matrix.
BASIC COMPONENTS OF CONNECTIVE TISSUE :
Basically all types of connective tissue consists of 3 components :
ý Cells .
ý Fibers.
ý Ground Substance.
Fibers and ground substance are collectively known as Matrix.
CELLS OF THE CONNECTIVE TISSUE:
Connective Tissue can be conveniently separated into :
§ The resident cell population.
§ A fluctuating population of immigrants, visitors or wandering cells.
ý THE RESIDENT CELL POPULATION :
a) Fibroblast :
§ Usually most numerous cells.
§ They are flattened and regular in outline, with branching processes.
§ Synthesize most of the extra cellular matrix of connective tissue.
§ Usually adherent to the collagen and elastin fibers.
b) Adipocytes,
c) Persistent mesenchymal stem cells .
ý A FLUCTUATING POPULATION OF IMMIGRANTS,
VISITORS OR WANDERING CELLS.
They have defensive function.
a) Macrophages
b) Lymphocytes
c) Mast cells
d) Neutrophils and
e) Eosinophils.
FIBRES OF THE CONNECTIVE TISSUE:
§ They are formed by proteins that polymerize into elongated structures .
§ They are present in variable proportion in different types of Connective tissue.
TYPES OF FIBRES :
a) Collagen Fibers.
b) Reticular Fibers.
c) Elastic Fibers.
§ Collagen Fibers:
Collagen fibers form the predominant fibrous component of ordinary connective tissue , cartilage, bone, cornea, sclera, and vitrous body of the eye and nucleus pulposus of the intervertebral discs and notochordal tissue.
These are flexible but have a high tensile strength with only a little elastic recoil. Unlike elastin fibers, collagen fibers do not branch.
Under electron microscope, collagen fibers are seen to be composites of narrower collagen fibrils and these in turn consist of fine mircofibrils, which are aggregates of filamentous tropocollagen molecules..
§ Reticular Fibers:
a) Fine, branching and anastomosing reticulin fibres.
b) Form the supporting framework of many glands, the kidney , the lympho reticular tissues ( lymph nodes, spleen etc. )
§ Elastic Fibers :
a) Less frequent than collagen fibers.
b) Branch and rejoin freely and usually thinner than collagen Fibers .
GROUND SUBSTANCE :
It is a colloidal gel-like material, in which cells and fibers are embedded.
It is composed of proteoglycan, glycoprotein, water and salts.
CLASSIFICATION OF CONNECTIVE TISSUE :
TWO MAIN GROUPS :
a) EMBRYOLOGICAL CONNECTIVE TISSUE.
b) ADULT CONNECTIVE TISSUE
a) EMBRYOLOGICAL CONNECTIVE TISSUE:
§ Mesenchymal tissue .
§ Mucous (muciod) tissue .
§
b) ADULT CONNECTIVE TISSUE :
1) C.T PROPER .
a) Loose C.T b) Dense
i) Areolar i) Regularly Arranged.
ii) Reticular ii) Irregularly Arranged .
iii) Adipose.
2) CARTILAGE
a) Hyaline
b)Elastic.
c)Fibro cartilage.
3) BONE.
a) Compact b) Spongy.