University:
American Career College
Course:
MICR112 | General Microbiology
Academic year:

2019
Views:

433

Pages:

63
Author:

astralniew2

Connective Tissue Functions  Mechanical support  Material that connects and binds cells into tissues  Binds tissues to each other  Serving as a medium for exchange  Aiding in the defense and protection  Internal support for organs/tissues  Forming a site for storage of energy and water Connective Tissue  Connective tissue is composed of mostly extracellular matrix, and few cells  Tendons, Ligaments, Areolar tissue and Adipose tissue are different kind of CT  Bone,Cartilage and Blood are specialized forms of connective tissue Connective Tissue Composition Fibers (collagen, elastic, reticular) Cells (fibroblasts, immune, vascular) Ground substance (glycosaminoglycans, proteoglycans, glycoproteins) Connective Tissue Cells The cells are two groups fixed cells and transient cells Fixed cells:  Mesenchymal cells  Fibroblasts  Macrophages  Mast cells  Adipose cells  Pericytes Transient cells:  WBC of Blood  Plasma cells  Macrophages Mesenchymal cells Small fusiform or stellate cells Not easily distinguished from fibroblasts Have coarser chromatin pattern Fewer mitochondria and little or no ER Pluripotential Fibroblast and Fibrocyte  Fibroblasts are most common cells of connective tissue  Produce and secrete fibers and ground substance  Active fibroblast has more cytoplasm include of developed RER, Golgi apparatus and euchromatic nucleus = activated (wound healing)  Inactive fibroblast (Fibrocyte) has flattened nuclei, sparse cytoplasm  Fibroblasts may differentiate to adipose cells or chondrocytes Myofibroblast Myofibroblast are modified fibroblasts Myofibroblast have bundle of actin and dense bodies similar to smooth muscle cells Nucleus is also similar to the nucleus of smooth muscle Unlike to smooth muscle have not external lamina (Basal lamina) Abundant in wound healing and periodontal ligament Pericytes Pericytes surround endothelial cells of capillaries and small venules They posses their own basal lamina Technically these cells reside outside the CT compartment They may differentiate into other cells Macrophage Stem cell in bone marrow, circulating form in blood is monocyte  Irregular membrane surface; nucleus may be oval and is eccentric  Phagocytosis of cell debris and microorganisms  Presenting antigens to lymphocytes  RBC turnover in spleen  Two categories: Resident and Elicited  Resident macrophages reside normally in CT  Elicited macrophages develop as a result of an exogenous stimulus and migrate to particular site of CT  In chronic inflammation form Epitheloid cells  Foreign body giant cells in response to excessively large materials form from many macrophages  Mast Cell • “Masten” (Ger) = to feed/fatten • Cytoplasm full of granules containing heparin, histamine, proteases, chemotactic factors • Originate from bone marrow stem cell • Delayed hypersensitivity (allergy) • Widespread in CT, concentrated along small blood vessels contain heparin • Mucosal mast cells are located in alimentary tact mucosa contain chondroitin sulfate White Blood Cells  Attracted to areas of inflammation  Neutrophils phagocytose bacteria in site of inflammation  Eosinophils – combat parasites and phagocytose ag-ab complex  Basophils – control of inflammation allergic response  Lymphocytes - small, heterochromatic nucleus – T- lymphocytes: cell-mediated immune response – B - lymphocytes: divide and differentiate into plasma cells producing antibody Plasma Cell • Common in intestinal lamina propria and glands secreting immunoglubulins such as lacrimal glands, salivary glands, and mammary gland • Oval cell with basophilic cytoplasm, pale centrosome, clockface nucleus • Differentiate from B - lymphocytes • Life span 10-20 days Connective Tissue Fibers Connective Tissue Fibers are consists of: Collagen fibers Elastic fibers Reticular fibers Collagen  Most abundant protein, 30% dry weight  More than 19 types  Type I most abundant, triple helix  Types I,II and III form fibers  Types IV and V are amorphous  Types VII attaches basal lamina to the lamina reticularis  Collagen fibrils 50-300 nm diameter  Grouped together as fibers  Eosin - pink; Mallory’s - blue; Masson’s - green Reticular Fibers (Collagen type III) Bundles are 0.5-2 mm diameter  Not stained by H&E, stained by silver (Argyrophilic) and periodic acid-Schiff (PAS)  45 nm fibrils made of collagen  Abundant in smooth muscle, nerves, spleen, lymph nodes, bone marrow  Form network around cells of liver, kidney, and endocrine organs  Elastic Fibers Stretch and return to original length Form branched fibers in areolar spread Large elastic arteries Not stained by H & E; use resorcin-fuchsin, aldehyde fuchsin or orcein Elastic Fibers • Thinner than collagen fibers • Arranged in a branching pattern – form a three dimensional network • Limit the distensibility of the tissue • Prevent tearing from excessive stretching • Staining: – Orcein & resorcin-fuchsin Elastic fibers component • 1) Central core: elastin • 2) surrounding network: fibrillin microfibrils Elastin • Rich in proline and glycine • Poor in hydroxyproline and completely lacks hydroxylysine • Elastin contains desmosine & isodesmosine – Responsible for the covalent bonding of elastin molecules to one another Fibrillin-1 • Glycoprotein • Forms fine microfibrils measuring 10 to 12 nm in diameter • In elastogenesis: – fibrillin-1 microfibrils are used as substrates for the assembly of elastic fibers Emilin-1 (elastin microﬁ bril interface-located protein) • another glycoprotein found at the elastin– ﬁbrillin microﬁbril interface • most likely regulates the deposition of elastin during the formation of ﬁbers Elastic ligaments • Consists of thick fibers • Interspersed with collagen fibers • E.g: – Ligamenta flava – Ligamentum nuchae – Vocal folds (Finer fibers) The cell s produce elastic fibers • 1- fibroblasts • 2- Smooth muscle cells EXTRACELLULAR MATRIX • 1) Fibers • 2) Ground substance ground substance • Proteoglycans • Multiadhesive glycoproteins • Glycosaminoglycans (GAGs) Glycosaminoglycan(GAG) • The GAGs: – Most abundant heteropolysaccharide components of ground substance – Long unbranched polysaccharid – Compose of repeat disaccharide units: – N- acetylgalactosamine – N- acetylglucosamine – Highly Negative charge: – sulfate, carboxyl group GAGs • Hyaluronan • Chondroitin 4, 6 sulfate • Dermatan sulfate • Keratan sulfate • Heparan sulfate • heparin proteoglycan aggregates • Abundant in the ground substance of cartilage • Act as: – Excellent shock absorbers – Resist compression without inhibiting flexibility proteoglycans • The majority of GAGs in the connective tissue – Linked to core proteins, forming proteoglycans – GAGs extend perpendicularly from the core in a brushlike structure • Linkage of GAGs to the protein core: – Specific trisaccharide: – Composed of two galactose residues and a xylulose residue Multi adhesive glycoproteins • Important role in stabilizing the ECM • Linking it to the cell surface • Possess binding sites for a variety of ECM proteins • Regulate and modulate functions of the ECM related to: – Cell movement and cell migration – Stimulate cell proliferation and differentiation • 1) Fibronectin: – Most abundant glycoprotein in connective tissue – Important role in cell attachment to the ECM • 2) Laminin: – Present in basal and external laminae – It possesses binding sites for: • • • • • Collagen type IV molecules, Heparan sulfate, heparin, entactin laminin receptor on the cell surface • 3) Tenascin: – Appears during embryogenesis – Synthesis is switched off in mature tissues – It eappears: – During wound healing and is – Musculotendinous junctions – Malignant tumors • 4) Osteopontin : – Present in the ECM of bone – It binds to osteoclasts and attaches them to the underlying bone surface Connective Tissue Classification 1) Embryonic Connective Tissue ⊗Mesenchymal connective tissue ⊗Mucous connective tissue 2) Connective Tissue Proper Loose connective tissue (Areolar CT) Dense connective tissue  Dense irregular connective tissue  Dense regular connective tissue  1- Collagenous  2- Elastic Reticular connective tissue Adipose connective tissue Connective Tissue Classification 3- Specialized connective tissue Cartilage Bone Blood Lymphoid myeloid Mesenchymal Connective Tissue • • • • Only in embryo and tooth pulp of adult Undifferentiated Mesenchymal cells No fibers or scattered reticular fiber Amorphous ground substance Mucous Connective Tissue  Abundant amorphous ground substance  Jelly-like with collagen type I & III, elastic  Many fibroblasts  Umbilical cord, subdermal CT of embryo Loose Connective Tissue Fills spaces outside many cells Papillary layer of dermis, hypodermis, Surrounds lymph and blood vessels, below mesothelium and mucous membranes Well vascularized Abundant ground substance and tissue fluid Fibroblasts/fibrocytes & macrophages common Loosely woven collagen type I&III and elastic fibers Dense Connective Tissue Dense connective tissue contains abundance of fibers but fewer cells When collagen bundle are arranged randomly it is called dense irregular When fiber bundles arranged in parallel or organized the tissue called dense regular Cells and ground substances are sparse Dense Irregular Connective Tissue  Many collagen fibers, less ground substance  Collagen bundles lack defined orientation  Resists stress from all directions  Reticular layer skin, submucosa of digestive tract, capsule of spleen and lymph node, testis , ovary, kidney Dense Regular Collagenous Connective Tissue Collagen bundles have parallel orientation Resists tensile forces Tendons join muscle to bone surrounded by loose connective tissue with ground substance for low friction Ligaments connect bones together Dense Regular Elastic Connective Tissue  Elastic fibers arranged parallel to each other to form sheets or fenestrated membranes  Bundles of branching elastic fibers surrounded by loose connective tissue  Yellow color  Ligamentum flava of vertebral column,Large arteries, Suspensory ligament of penis Reticular Tissue Specialized form of loose connective tissue The major fiber component is type III collagen Reticular cells (specialized fibroblast & macrophages) interspersed between a mesh-like network of fibers Trabecular system - sponge-like Supports bone marrow, lymphoid tissues, and hemopoietic organs, liver sinusoids, Adipose Tissue A kind of connective tissue with many adipocytes Forms one of the largest “organs” of body  15-20% of body weight in men  20-25% of body weight in women Over 2 times as much stored energy as glycogen Subcutaneous adipose shapes body Shock absorber in soles of feet and palms Thermal insulation Fills space between organs Two Types of Adipose Tissue Yellow, White or unilocular cells with one large fat droplet in cytoplasm Brown or multilocular cells with numerous smaller lipid droplets in cytoplasm and many mitochondria Unilocular Adipose Tissue White to dark yellow depending on diet Most common form in adults Cells 50-150 mm diameter Nuclei eccentric and flattened Lipid droplet has no membrane Heavily vascularized Cell number constant after early postnatal period Multilocular Adipose Tissue  Fat cells store fat in multiple droplets  Brown fat, color due to vascularization and many mitochondria, Central nucleus  Has a lobular organization like glands  Production of body heat by many mitochondria  In human neonate, produces heat