Connective tissue TYPES: 1-CT. proper. 2.Specialized CT (cartilage, bone and blood).

Connective tissue proper Components of CT: 1-Cells. 2-Extracellular matrix (ground substances and fibers). Functions of CT: a. Structural support b. A medium for exchange. c. Helps in defense & protection of the body. d. A site for storage of fat.

Extracellular Matrix I-Ground substance It is a hydrated, amorphous material that is composed of: Glycosaminoglycans, proteoglycans and adhesive glycoproteins. II-Fibers Collagen fibers, are inelastic and possess great tensile strength. Each fiber is composed of fine subunits called tropocollagen molecule. Most of the fibers show axial periodicity by EM. There are six major collagen types: Type I: in CT proper, bone, dentin.

Elastic fibers: Type II: In hyaline and elastic cartilage. Type III: reticular fibers.( stroma of spleen & lymph nodes) Elastic fibers: Structure of Elastic Fiber the fiber branch and anastomose with each other they run singly and not in bundles but forming a membrane. Stretchable Fibers.

Collagen type I

CT.Cells 1.Fibroblasts 2.Adipose cells. 3.Pericytes. 4.Mast cells. 5.Macrophages. 6.Plasma cells. 7.leukocytes.

I- Fibroblasts They are the most abundant CT. cells and derived from undifferentiated mesenchymal cells. Types: 1- Active fibroblasts: are elongated, fusiform cells with dark-staining cytoplasm rich in RER with large ovoid nucleus containing well-defined nucleolus. 2- Inactive fibroblasts (fibrocytes): are smaller and are more ovoid with more acidophilic cytoplasm. Fibrobalsts are responsible for the synthesis of almost of extracellular matrix. can close wound during injury.

II-Adipose cells (fat cells or adipocytes): They are derived from undifferentiated mesenchymal cells. They are fully differentiated and do not undergo cell division. There are 2 types: A-Unilocular fat cells, form white adipose tissue: they are large cells, they store fat as one droplet, which enlarge pushing the cytoplasm and the nucleus peripherally against cell membrane (signet-ring appearance). They have few mitochondria. The fat droplet is not bounded by a membrane. Present in: under the skin especially in females, it is more considered in the mammary glands and gluteal region. B-Multilocular adipocytes, form brown adipose tissue: Are small cells with multiple fat droplets, central spherical nucleus and many mitochondria. Present In: new born. * They function in the synthesis, storage and release of fat.

Adipocytes

III- Pericytes Function: They surround capillaries and small venules. They have multiple processes that wrap around the endothelium of blood capillaries and small venules. Function: 1.Important in the healing of CT of blood vessles where ever wound presents 2. give raise to smooth muscle cell 3. can modified for smooth muscle cells which can contract.

The granules contain heparin, histamine. IV. Mast cells: Their cytoplasm is rich in membrane-bound granules that stained metachromatically with toluidine blue. The granules contain heparin, histamine. Histamine causes vasodilatation and increase permeability of blood vessels. It causes bronchospasm and increase mucus production.

Mast Cell

V- Macrophages Derived from blood monocytes after migrate from blood from C.T. Some are fixed and others are transient . They are irregular in shape due to the present of filopodia. They have branched cell with many process. Their cytoplasm Is basophilic, prominent RER, well developed Golgi and an abundance of lysosomes. They derived from monocytes.

Macrophage

VI- Plasma cells They are derived from B-lymphocytes after exposure to an antigen. They secrete antibodies. They are large ovoid cells with intensely basophilic cytoplasm that is rich in RER and Golgi (pale-staining region adjacent to the nucleus that has chromatin radiating out from the center (clock-face appearance).

VII- Leukocytes: They are white blood cells that circulate in blood stream then migrate through capillaries to enter CT. during inflammation, invasion by foreign elements and immune response. In the present of infection.

Connective tissue proper 1- Loose (areolar CT): It fills in the spaces of the body just deep to the skin, The loose CT of mucous membranes is called lamina propria. It is characterized by abundant ground substance and tissue fluid housing the fixed CT. cells, undifferentiated cells and collagen, reticular and elastic fibers. Its ground substance loose.

2. Reticular CT: 3. Adipose tissue: Type III collagen is its major component. Collagen forms mesh-like networks It forms the framework of liver, lymph nodes, spleen, 3. Adipose tissue: It is divided into white (unilocular) adipose tissue and brown (multilocular) adipose tissue. It is rich in blood vessels.

Adipose CT.

b. Dense regullar collagenous CT: 4. Dense CT: It has many more fibers and fewer cells than ordinary CT.It is formed of three types: a. Dense irregular collagenous CT: it is formed of randomly arranged collagen fibers, few ground substances and fibroblasts scattering between collagen fibers. It form the dermis of skin, b. Dense regullar collagenous CT: it is composed of coarse collagen bundles that oriented into parallel sheets. It has few ground substances and fibroblasts between collagen bundles.Ex. Tendons.

Dense irregular CT. Dense regular CT

c. Dense regular elastic CT: it has coarse branching elastic fibers and scattered fibroblasts. Elastic fibers are arranged parallel to one another and form either thin sheets or fenestrated membranes as in large blood vessels (aorta).

Practical slides

Elastic connective tissue

Dense regular fibrous connective tissue

Reticular connective tissue (silver stain)

Adipose connective tissue

Loose (areolar connective tissue)