3- Connective Tissues.pdf

Histology 0308211 Connective Tissue Department of Clinical Laboratory Sciences  Connective Tissue Provide a matrix to support and connect other tissues and maintain the water required for metabolite diffusion to and from cells. Connective tissues...

Histology 0308211 Connective Tissue Department of Clinical Laboratory Sciences  Connective Tissue Provide a matrix to support and connect other tissues and maintain the water required for metabolite diffusion to and from cells. Connective tissues all consist primarily of extracellular material rather than cells. Within most organs connective tissue proper forms the supportive stroma, which supports the organ’s unique functional components or parenchyma. Connective Tissue  Connective Tissue All adult connective tissues are derived from an embryonic form of connective tissue called mesenchyme, which contains uniformly undifferentiated cells scattered in a gel-like matrix. Originate from Mesoderm. Connective Tissue  Connective Tissue Abundant and found all over the body Consists of cell separated by extracellular matrix Diverse Performs variety of important functions  Functions of Connective Tissue Enclosing and separating as capsules around organs Connecting tissues to one another as tendons and ligaments Supporting and moving as bones Storing as fat Cushioning and insulating as fat Transporting as blood Protecting as cells of the immune system  Connective tissue Structure Fibroblast, myofibroblast, Cells Resident cells Macrophages, Adipose, Mast, Connective Tissue Lymphocytes, Plasma cells Wandering cells Neutrophils, Eosinophils, Basophils, Monocytes Fibres Collagen Reticular Elastic Matrix Ground substance GAGs proteoglycans Glycoproteins Tissue fluid  Connective Tissue Cells Specialized cells produce the extracellular matrix – Suffixes -blasts: create the matrix -cytes: maintain the matrix -clasts: break the matrix down for remodeling 4-9  Connective Tissue Cells Fibroblasts The major cells of connective tissue proper Are active permanent cells that synthesize all collagen, reticular, and elastic connective tissue fibers Synthesize glycosaminoglycans, proteoglycans, and glycoproteins of ground substance. Targets of many growth factors that influence cell growth and differentiation.  Connective Tissue Cells Fibrocytes Smaller than fibroblasts Inactive or resting connective tissue cells  Connective Tissue Cells White Adipose (Fat) Cells Occur singly or in groups. When adipose cells predominate, the connective tissue is adipose tissue. Store fat (lipid) as single large droplet primarily as tryglycerides.  Connective Tissue Cells Macrophages Most numerous in loose connective tissue. Ingest bacteria, dead cells, cell debris, and foreign matter. Are antigen-presenting cells to lymphocytes for immunologic response Derived from circulating blood monocytes. Called Kupfer cells in liver, osteoclasts in bone, and microglia in central nervous system  Connective Tissue Cells Lymphocytes Most numerous in loose connective tissues of respiratory and gastrointestinal tracts. Produce antibodies and kill virus-infected cells. Plasma Cells Characterized by chromatin distributed in radial pattern. Derived from lymphocytes exposed to antigens. Produce antibodies to destroy specific antigens.  Connective Tissue Cells Mast Cells Closely associated with blood vessel Found in skin, respiratory, and digestive system connective tissue Release histamine when exposed to allergens, causing allergic reactions Connective Tissue Cells  Connective Tissue Cells The first exposure to an antigen results in production of the (IgE) by plasma cells. IgE is avidly bound to the surface of mast cells. A second exposure to the antigen results in binding of the antigen to IgE on the mast cells. This event triggers release of the mast cell granules, liberating histamine, leukotrienes, chemokines, and heparin  Connective Tissue Cells Neutrophils Active phagocytes; engulf and destroy bacteria Eosinophils Increase after parasitic infestation Phagocytize antigen–antibody complexes during allergic reactions  Connective tissue Structure Fibroblast, myofibroblast, Cells Resident cells Macrophages, Adipose, Mast, Connective Tissue Lymphocytes, Plasma cells Wandering cells Neutrophils, Eosinophils, Basophils, Monocytes Fibres Collagen Reticular Elastic Matrix Ground substance GAGs proteoglycans Glycoproteins Tissue fluid  Extracellular Matrix Components – Protein fibers Collagen which is most common protein in body Reticular fill spaces between tissues and organs Elastic returns to its original shape after distension or compression – Ground substance Shapeless background – Tissue Fluid  Connective tissue fibres They are long, slender protein polymers Types: - Collagen - Reticular - Elastic Collagen & reticular fibres are formed of collagen protein Elastic fibres are composed of elastin protein  Types of Collagen Most abundant protein in the human body, Produced by fibroblasts, chondroblasts, osteoblasts and odontoblast Classification 1- Fibril-forming collagens (type I, II, III, V and XI) - Type I, most abundant 2- Fibril-associated collagens (type IX and XII) - Short structures that bind collagen fibrils to one another and other components of matrix.  Types of Collagen 3- Network-forming collagen (IV collagen) - Build basal lamina 4- Anchoring collagen (VII collagen) - Present in the anchoring fibrils that bind collagen fibres to the basal lamina  Reticular Fibers Vey fine delicate short collagen fibers. Branch to form networks Found in delicate connective tissue of many organs (e.g spleen, liver and red bone marrow). Consist mainly of collagen type III. Reticular fibers contain up to 10% carbohydrate as opposed to 1% in most other collagen fibers.  Reticular Fibers Surround adipocytes, smooth muscle and nerve fibers, and small blood vessels. Delicate reticular constitute a network around the cells of for the parenchymal organs (e.g liver and endocrine glands. Produced by fibroblasts occur in the reticular lamina of basement membranes.  Elastic Fibers Thinner than the type I collagen fibers Composed of three types of fibers: oxytalan, elaunin and elastic. Form sparse networks interspersed with collagen bundles in many organs, particularly those subject to much bending or stretching. Elastic fibers have physical properties similar to those of rubber, allowing tissues to be stretched or distended and return to their original shape.  Elastic Fibers In the wall of large blood vessels, especially arteries, elastin occurs as fenestrated sheets called elastic lamellae. Elastic fibers (and lamellae) are a composite of fibrillin microfibrils embedded in a larger mass of cross-linked elastin. Both components are secreted from fibroblasts (and smooth muscle cells in vascular walls) and produce elastic fibers in a stepwise manner.  Ground substance Formed of: glycosaminoglycans (GAGs), proteoglycans and glycoproteins Watery, largely unstained extracellular material that is more abundant than fibers in some types of connective tissue proper. It is viscous and acts as both a lubricants and a barrier for protection The major types of GAGs are hyaluronic acid (HA or hyaluronan)  Ground substance Proteoglycans attach to polymers of HA via linker proteins to form huge complexes in ground substance that bind water and other substances, including certain polypeptide growth factors that help regulate fibroblast proliferation. Multi-adhesive glycoproteins such as fibronectin and laminin have binding sites for collagens and for integrin proteins in cell membranes, thus allowing temporary attachments between cells and the ECM required for cell migration and positioning. Ground substance  Tissue fluid Tissue fluid is similar to blood plasma found in the ground substance. It passes through the capillary walls by the hydrostatic pressure of blood. Gives metabolic support to cells as the medium for diffusion of nutrients and waste products.  Tissue fluid Two forces act on the water in capillaries: The hydrostatic pressure of the blood caused by the pumping action of the heart, which forces water out across the capillary wall. The colloid osmotic pressure produced by plasma proteins such as albumin, which draws water back into the capillaries.  Connective Tissue Categories Embryonic Connective Tissue - Mesenchyme - Mucoid Tissue Adult Connective Tissue 1- Connective tissue Proper - Loose (areolar) - Dense (Regular, Irregular) 2- Specialized Connective tissue - Elastic Tissue, Adipose Tissue, Cartilage, Bone and Blood 4-33  Embryonic Connective Tissue Mesenchymal Connective Tissue Made up of irregularly shaped fibroblasts Surrounded by abundant extracellular matrix Formed during the third and fourth week of development from mesoderm  Embryonic Connective Tissue Mucoid Connective Tissue Large amount of ground substance composed chiefly of hyaluronic acid Jelly-like tissue containing very few fibers The cells are mainly fibroblasts Found in the umblical cord and its principal component of the umbilical cord, where it is referred to as Wharton’s jelly Supports and cushions large blood vessels  Adult Connective Tissue 1- Connective tissue Proper Loose Connective Tissue Also known as areolar tissue More prevalent in body and exhibits loose, irregular arrangement of cells and fibers. Attaches skin to underlying tissues Contains collagen, reticular, elastic fibers Fibroblasts, adipose cells, mast cells, and macrophages predominate 4-36  Dense Connective Tissue Fibers densely packed with regular, parallel orientation Has abundant collagen fibers Tendons: Connect muscles to bones Ligaments: Connect bones to bones Great resistance to forces pulling along single axis or direction Minimal ground substance; predominant cell is fibroblast 4-37  Dense Irregular Connective Tissue Consists primarily of fibroblasts, and thick and densely packed collagen fibers Fewer other cell types and minimal ground substance Collagen fibers exhibit random orientation and provide strong tissue support Concentrated in areas where resistance to forces from different directions is needed 4-38  Dense Irregular Elastic Connective Tissue Bundles of thick parallel elastic fibers The space between these fibers is filled by thin collagen fibers and flattened fibroblasts Highly elastic Found in wall of elastic arteries  2- Specialized Connective tissue Reticular tissue Consists of type III collagen (reticulin) that form a delicate 3D network, which supports various types of cells. The fibrous network of this specialized connective tissue is produced by modified fibroblasts called reticular cells that remain associated with and partially covering the fibers. Characterized by network of reticular cells and fibers forming a spong-like structure.  Reticular tissue Most abundant in certain lymphoid organs where the fibers form attachment sites for lymphocytes and other immune cells. Macrophages and other cells of the mononuclear phagocyte system are also dispersed within these reticular tissues to monitor cells formed there or passing through and to remove debris. Bone Marrow, spleen, Lymph node, and thymus