connective tissue

THE CONNECTIVE TISSUES
1-These tissues arise from the mesoderm only and, in contrast to the epithelia tissues. 2-They have a large amount of intercellular substance or matrix among their cells. 3- They are never to be found on surface . 4- They do not rest on a basement membrane. 5- Their main function is to connect other tissues or organ together or support them. 6- Their ground substance is either solid or fluid .

Their ground substance is either solid or fluid and accordingly they are classified into three main groups: 1// The connective tissues proper. I) Ioose connective tissue
(a) Areolar connective tissue (b) Reticular connective tissue (c) Adipose connective tissue (d) Mucous connective tissue
II) Dense connective tissue 1-Dense irregular connective tissue 2-Dense regular connective tissue
(a) Fibrous connective tissue (b) Elastic connective tissue
2// The skeletal tissues. 3// The vascular tissues.

1// The Connective Tissues Proper
The tissues that belong to this category are divided into two general subtypes :• I) Loose connective tissue
Is characterized by loosely arranged fibers and an abundance of cells, there are four subtypes in this category; (a) Areolar connective tissue. Note the white or collagenous fibers which are wavy , do not branch and run in bundles; and the yellow or elastic fibers which are thinner, run singly and branch to form a network . the following cell types : • The fibrocytes which secrete the fibers and have branched irregular forms and clear cytoplasm ; • The mast cells which secrete the ground substance and have a distinctly granular cytoplasm ; the large amoeboid • macrophages . • The fat cells : full of fat droplets • The small plasma cells : with eccentric nuclei . Some white blood cells , such as some eosinophils and lymphocytes , may also be found in small numbers . Note the clear, amorphous and homogeneous matrix

(b) Reticular connective tissue. Examine a section of the spleen or of a lymph gland and note the reticular tissue in it , with branching and anastomosing reticular fibers .

(c) Adipose connective tissue.
Examine a section of the fat body of the toad and note the adipose connective tissue with predominant fat cells loaded with fat globules .

(d) Mucous connective tissue.
Examine a T.S. of the umbilical cord of a placental mammal and not the mucous connective tissue with few white fibers and stellate cells or fibroblasts, all lying embedded in an extensive semifluid or gelatinous matrix.

II-Dense connective tissue
Can further subclassified into:
1-Dense irregular connective tissue
which characterized by an abundance of fibers and few cells (example the dermis in skin)
1-Dense irregular connective tissue
2-Dense regular connective tissue which characterized by ordered and densely packed in parallel arrays of fibers .This can subdivided into:
(a) Fibrous connective tissue.
Examine an L.S. of a tendon and note the dense connective tissue in it with white fibers running in bundles along the length of section. The yellow fibers are few.
(b) Elastic connective tissue.
Examine an L.S. of the ligamentum nuchae of and note the numerous branching yellow fibers ;the white fibers are few .
2-Dense regular connective tissue
Fibrous connective tissue
Elastic connective tissue