It connects between the different types of tissues and organs, carrying their blood and nerve supply. It is derived mainly from the mesoderm. It has connective tissue proper and specialized connective tissue (blood, cartilage and bone). It is composed of cell and extra-cellular matrix which consists of ground substance and fibers. According to the amount and role of these three components (cells, fibers and ground substance), there are many types of connective tissue. It connects between the different types of tissues and organs, carrying their blood and nerve supply. It is derived mainly from the mesoderm. It has connective tissue proper and specialized connective tissue (blood, cartilage and bone). It is composed of cell and extra-cellular matrix which consists of ground substance and fibers. According to the amount and role of these three components (cells, fibers and ground substance), there are many types of connective tissue.

Functions of Connective Tissue  Support.  Medium for exchange.  Defense and protection.  Storage of fat.  Support.  Medium for exchange.  Defense and protection.  Storage of fat.

Ground substance Amorphous gel-like material composed of glycosaminoglycans, proteoglycans and glycoproteins. Glycosaminoglycans are of two types: –Sulfated such as: keratin sulfate, heparin sulfate and chondroitin sulfate. –Non-sulfated such as: hyaluronic acid. Proteoglycans are responsible for the gel state of the extra-cellular matrix. Glycoproteins such as: fibronectin, chondronectin and osteonectin. Amorphous gel-like material composed of glycosaminoglycans, proteoglycans and glycoproteins. Glycosaminoglycans are of two types: –Sulfated such as: keratin sulfate, heparin sulfate and chondroitin sulfate. –Non-sulfated such as: hyaluronic acid. Proteoglycans are responsible for the gel state of the extra-cellular matrix. Glycoproteins such as: fibronectin, chondronectin and osteonectin.

Connective Tissue Fibers  Collagen fibers.  Reticular fibers.  Elastic fibers.  Collagen fibers.  Reticular fibers.  Elastic fibers.

Collagen Fibers Tough, firm, inelastic fibers which resists the tensile forces upon the tissues. Most common fibers in connective tissue. Formed of branching bundles of strong flexible collagen fibers. It is formed of tropocollagen units running parallel and overlapping each other. This tropocollagen unit is formed of 3 polypeptide chains rich in proline, glycine, hydroxyproline and hydroxylysine. Vitamin C is important in collagen synthesis. Tough, firm, inelastic fibers which resists the tensile forces upon the tissues. Most common fibers in connective tissue. Formed of branching bundles of strong flexible collagen fibers. It is formed of tropocollagen units running parallel and overlapping each other. This tropocollagen unit is formed of 3 polypeptide chains rich in proline, glycine, hydroxyproline and hydroxylysine. Vitamin C is important in collagen synthesis.

Collagen Fibers Are synthesized mainly by fibroblasts. Chondroblasts, osteoblasts and smooth muscle fibers also synthesize collagen. There are many types of collagen fibers (depending on their amino acid sequence): –Type I: in connective tissue, bone, dentine. –Type II: in hyaline and elastic fibers. –Type III (reticular fibers): lymphatic system, spleen, skin and vessels. –Type IV: in basal lamina. –Type V: with type I and placenta. –Type VI: in basal lamina. Are synthesized mainly by fibroblasts. Chondroblasts, osteoblasts and smooth muscle fibers also synthesize collagen. There are many types of collagen fibers (depending on their amino acid sequence): –Type I: in connective tissue, bone, dentine. –Type II: in hyaline and elastic fibers. –Type III (reticular fibers): lymphatic system, spleen, skin and vessels. –Type IV: in basal lamina. –Type V: with type I and placenta. –Type VI: in basal lamina.

Reticular Fibers Thin collagen fibers arranged in framework instead of bundles. Synthesized by the fibroblasts. They form the reticular network of some organs such as lymph nodes and bone marrow. They present also in basement membrane. Thin collagen fibers arranged in framework instead of bundles. Synthesized by the fibroblasts. They form the reticular network of some organs such as lymph nodes and bone marrow. They present also in basement membrane.

Elastic Fibers Slender, long and branching fibers in loose connective tissue, but coarse bundles in elastic ligaments. Formed by the fibroblasts and smooth muscle cells. Composed of protein elsatin and can be stretched to one and half times its original length. It is present in large arteries, larynx and trachea, ligamentum flavum and framework of the spleen. Slender, long and branching fibers in loose connective tissue, but coarse bundles in elastic ligaments. Formed by the fibroblasts and smooth muscle cells. Composed of protein elsatin and can be stretched to one and half times its original length. It is present in large arteries, larynx and trachea, ligamentum flavum and framework of the spleen.

Fixed Cells 1. Fibroblasts. 2. Adipose cells. 3. Pericytes. 4. Mast cells. 5. Fixed macrophages (histiocytes). 1. Fibroblasts. 2. Adipose cells. 3. Pericytes. 4. Mast cells. 5. Fixed macrophages (histiocytes).

Transient Cells 1. Plasma cells. 2. Lymphocytes. 3. Neutrophils. 4. Eosinophils. 5. Basophils. 6. Monocytes. 7. Transient macrophages. 1. Plasma cells. 2. Lymphocytes. 3. Neutrophils. 4. Eosinophils. 5. Basophils. 6. Monocytes. 7. Transient macrophages.

FibroblastsFibroblasts  They are derived from the undifferentiated mesenchymal cells.  They synthesize the extra-cellular matrix.  They occur either in active state or inactive state (fibrocytes).  Present nearby the collagen fibers.  Elongated fusiform cells with pale staining cytoplasm and large granular, ovoid nucleus.  They are derived from the undifferentiated mesenchymal cells.  They synthesize the extra-cellular matrix.  They occur either in active state or inactive state (fibrocytes).  Present nearby the collagen fibers.  Elongated fusiform cells with pale staining cytoplasm and large granular, ovoid nucleus.

Adipose Cells  They are derived from undifferentiated mesenchymal cell.  They synthesize, store and release fat.  They are two types of adipose cells:  Unilocular fat cells: from white adipose tissue.  Multilocular fat cell: from brown adipose tissue.  They are derived from undifferentiated mesenchymal cell.  They synthesize, store and release fat.  They are two types of adipose cells:  Unilocular fat cells: from white adipose tissue.  Multilocular fat cell: from brown adipose tissue.

PericytesPericytes  They surround the endothelial cell of capillaries.  They are derived from undifferentiated mesenchymal cell.  After injury they may differentiate to form endothelial cell and smooth muscle cells.  They surround the endothelial cell of capillaries.  They are derived from undifferentiated mesenchymal cell.  After injury they may differentiate to form endothelial cell and smooth muscle cells.

Mast cells  They are derived from precursors in bone marrow.  Found near blood vessels and body surfaces (dermis of skin and digestive and respiratory tract).  They are large ovoid cell with central spherical nucleus.  Their cytoplasm have large metachromatic granules containing heparin, histamine and many other mediators.  They are derived from precursors in bone marrow.  Found near blood vessels and body surfaces (dermis of skin and digestive and respiratory tract).  They are large ovoid cell with central spherical nucleus.  Their cytoplasm have large metachromatic granules containing heparin, histamine and many other mediators.

MacrophagesMacrophages  They may be fixed or transient.  They are active phagocytes removing cell debris and protecting the body against foreign invaders.  They are derived from monocytes (transient) or from UDMC (histiocytes).  Highly motile, irregular in shape with pseudopodia.  Have dark nucleus and basophilic cytoplasm containing numerous lysosomes, vacuoles and residual bodies.  They may be fixed or transient.  They are active phagocytes removing cell debris and protecting the body against foreign invaders.  They are derived from monocytes (transient) or from UDMC (histiocytes).  Highly motile, irregular in shape with pseudopodia.  Have dark nucleus and basophilic cytoplasm containing numerous lysosomes, vacuoles and residual bodies.

Plasma Cells  They are derived from B-lymphocytes.  Large ovoid cells with eccentrically placed nucleus.  Its cytoplasm is intensely basophilic (RER).  Its nucleus has the characteristic “clock- face” or “radial spoke” appearance.  They present in areas of chronic inflammation and foreign bodies, where they manufacture and secrete antibodies.  They are derived from B-lymphocytes.  Large ovoid cells with eccentrically placed nucleus.  Its cytoplasm is intensely basophilic (RER).  Its nucleus has the characteristic “clock- face” or “radial spoke” appearance.  They present in areas of chronic inflammation and foreign bodies, where they manufacture and secrete antibodies.

Classification of C.T. 1. Embryonic C.T.: 1.Mesenchymal 2.Mucous (mucoid) 2. Specialized C.T.: 1.Cartilage. 2.Bone. 3.Blood. 3. Mature C.T. proper: 1.Loose areolar 2.Dense 1.Dense regular 2.Dense irregular 1.Collagenous 2.Elastic 3.Reticular 4.Adipose

Mucous C.T.  Present in the umbilical cord and subdermal C.T. of the embryo.  Loose amorphous C.T. with a jelly-like matrix containing hyaluronic acid and little amounts of collagen types I and III and fibroblasts.  This type of C.T. is called Wharton’s jelly.  Present in the umbilical cord and subdermal C.T. of the embryo.  Loose amorphous C.T. with a jelly-like matrix containing hyaluronic acid and little amounts of collagen types I and III and fibroblasts.  This type of C.T. is called Wharton’s jelly.

Loose areolar C.T.  Contains abundant ground substance and tissue fluid, nearly all type of C.T. cells and less amounts of fibers.  Located in subcutaneous tissue, lamina propria of gastrointestinal & respiratory tracts, around blood vessels & organs and under serous membranes.  In inflammatory condition it swells because of increased extra-cellular fluid (Edema).  Contains abundant ground substance and tissue fluid, nearly all type of C.T. cells and less amounts of fibers.  Located in subcutaneous tissue, lamina propria of gastrointestinal & respiratory tracts, around blood vessels & organs and under serous membranes.  In inflammatory condition it swells because of increased extra-cellular fluid (Edema).

Dense regular C.T.  Contains abundant amounts of fibers with less cells and ground substances.  Has tightly packed coarse collagen bundles arranged in parallel fashion to form cord- like cylinders (tendons & ligaments) or sheets (aponeurosis).  Fibroblasts are arranged between the collagen fibers so they appears elongated with their dash-like elongated nuclei.  It is also called white fibrous C.T.  Contains abundant amounts of fibers with less cells and ground substances.  Has tightly packed coarse collagen bundles arranged in parallel fashion to form cord- like cylinders (tendons & ligaments) or sheets (aponeurosis).  Fibroblasts are arranged between the collagen fibers so they appears elongated with their dash-like elongated nuclei.  It is also called white fibrous C.T.

Dense irregular C.T.  Contains abundant amounts of fibers with less cells and ground substances.  Has tightly packed coarse collagen bundles arranged randomly in all directions, with few elastic fibers.  Fibroblasts and other less cells are arranged between the collagen fibers.  They are found in dermis of skin, capsule of organs, sheaths around nerves and dura mater.  Contains abundant amounts of fibers with less cells and ground substances.  Has tightly packed coarse collagen bundles arranged randomly in all directions, with few elastic fibers.  Fibroblasts and other less cells are arranged between the collagen fibers.  They are found in dermis of skin, capsule of organs, sheaths around nerves and dura mater.

Elastic C.T.  Composed mainly of elastic fibers with little amounts of collagen fibers and few cells and ground substance.  The elastic fibers are arranged in sheaths or fenestrated lamellae.  They are present in the wall of large arteries, ligamentum flavum, trachea and larynx, and suspensory ligament of penis.  Composed mainly of elastic fibers with little amounts of collagen fibers and few cells and ground substance.  The elastic fibers are arranged in sheaths or fenestrated lamellae.  They are present in the wall of large arteries, ligamentum flavum, trachea and larynx, and suspensory ligament of penis.

Reticular C.T.  Composed mainly of type III collagen fibers in a form of network or mesh, fibroblasts and macrophages.  It forms the architectural framework of liver sinusoids, bone marrow, lymph nodes, spleen, smooth muscles, islet of Langerhans and adipose tissues.  Composed mainly of type III collagen fibers in a form of network or mesh, fibroblasts and macrophages.  It forms the architectural framework of liver sinusoids, bone marrow, lymph nodes, spleen, smooth muscles, islet of Langerhans and adipose tissues.

Adipose C.T.  Loose C.T. very rich in adipocytes.  Two types of adipose C.T.  Unilocular (white fat) C.T.: its fat cells are of unilocular type, present in subcutaneous tissue, around organs and blood vessels.  Multilocular (brown fat) C.T., present in infants and hibernating animals, cells are rich in mitochondria, supply heat.  Loose C.T. very rich in adipocytes.  Two types of adipose C.T.  Unilocular (white fat) C.T.: its fat cells are of unilocular type, present in subcutaneous tissue, around organs and blood vessels.  Multilocular (brown fat) C.T., present in infants and hibernating animals, cells are rich in mitochondria, supply heat.

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