Connective Tissue.pdf

Week 3: Connective Tissue James Inno Guanzon, RMT Connective Tissue provide form and support to the body and organs; connect and anchor parts exchange of nutrients, oxygen, and waste products between other tissues stores fat for cushioning and thermoregulation...

Week 3: Connective Tissue James Inno Guanzon, RMT Connective Tissue provide form and support to the body and organs; connect and anchor parts exchange of nutrients, oxygen, and waste products between other tissues stores fat for cushioning and thermoregulation 2 Connective Tissue types include: ○ connective tissue proper ○ specialized almost all arise embryonically from the mesoderm 3 Connective Tissue consist of: ○ cells ○ extracellular matrix cells include: ○ fibroblasts ○ mast cells ○ macrophages ○ plasma cells ○ adipocytes ○ pericytes 4 Connective Tissue functions depend on the properties of the ECM can be classified as: ○ loose (areolar) ○ dense 5 General Classification Adult Specialized Embryonic Connective Adipose Mesenchyme Tissue Elastic Mucous Loose Reticular Dense ○ Regular ○ Irregular 6 Loose Connective Tissue (Areolar) is the most widespread; has the greatest variety of cells and fibers highly cellular with few fibers much of the body’s tissue fluid is found within this tissue type 7 Loose Connective Tissue (Areolar) well vascularized, flexible, not very resistant to stress located in ○ mesenteries ○ lamina propria ○ blood vessels function: inflammatory and immune reactions 8 Dense Connective Tissue has a greater proportion of fibers, fewer cells, and less ground substance categorized according to the orientation of fibers 9 Dense Regular Connective Tissue fibers appear parallel can withstand stress from one direction located in: ○ tendons ○ ligaments 10 Tendons connect muscle to bone arrangement is more regular than ligaments 11 Ligaments connect bone to bone contents less regularly arranged collagen fibers 12 Dense Irregular Connective Tissue has randomly oriented, interwoven fibers can withstand stress in many directions located in: ○ dermis ○ capsule of many organs 13 Elastic Connective Tissue has a predominance of elastic fibers allow structures in which they are found to expand considerably and return to their original shape elastic fiber contain: ○ microfibrils ○ fibrillin ○ elastin 14 Elastic Connective Tissue located in: ○ lungs ○ skin ○ urinary bladder 15 Reticular Connective Tissue is a specialized loose connective tissue fibers appear long and thin fibers appear to branch are made up of type III collagen fibers 16 Extracellular Matrix is an organized meshwork of macromolecules consists of an amorphous ground substance ○ Glycosaminoglycans (GAGs) ○ Proteoglycans ○ Glycoproteins 17 Glycosaminoglycans (GAGs) repeating identical disaccharide units possess uronic acid sugar have a strong negative charge ○ create an aqueous diffusion pathway through connective tissues 18 Hyaluronic Acid aka Hyaluronan are very large molecules that can hold a large volume of water ○ excellent shock absorber 19 Proteoglycans composed of core proteins serve as binding sites for growth factors and signalling molecules 20 Glycoproteins have multiple binding sites for cell surface receptors e.g. are ○ Fibronectin ○ Laminin 21 Cells in Connective Tissue Mesenchymal cells Fibroblasts ○ collagen synthesis Mast cells Plasma cells Macrophages 22 Cells in Connective Tissue Resident (Fixed) Wandering (Transient) fibroblasts lymphocytes macrophages plasma cells adipocytes neutrophils mast cells eosinophils basophils monocytes 23 Mesenchymal Stem Cells are primitive stem cells derived mostly from the mesoderm differentiate into various cell types during embryonic development are often used as a source of pluripotential stem cells for tissue repair 24 Mesenchymal Stem Cells resemble fibroblasts but appear smaller have the ability to invade and migrate through the ECM can also be found in walls of capillaries 25 26 Fibroblasts main cell type of connective tissue are the most common cells of loose connective tissue only type of cell found in dense regular connective tissue 27 Fibroblasts function in synthesis and secretion of ground substance produce connective tissue fibers in mature connective tissue, these cells are relatively inactive and immobile → fibrocytes 28 Fibroblasts appear ovoid or stellate have one elliptical nucleus with one or more distinct nuceloli 29 Major Steps in Collagen Formation 1. Transcription 7. Procollagen Formation 2. mRNA Export 8. Packaging 3. Ribosome Attachment 9. Secretion 4. Translation 10. Enzymatic Cleavage 5. Polypeptide Chain 11. Tropocollagen Aggregation Assembly 12. Fiber Formation 6. Hydroxylation 30 Intracellular Events mRNA is synthesized from a template of DNA mRNA molecules enter the cytoplasm and attach to the ribosomes of the RER ○ a polypeptide chain of several amino acids is assembled 31 32 33 34  amino acid sequence hydroxylation of proline and lysine + ascorbic acid (cofactor) 3 alpha chains → triple helix procollagen 35 Intracellular Events packaging of procollagen occurs in the Golgi complex procollagen is released to the cell surface through exocysosis 36 Extracellular Events procollagen procollagen peptidase tropocollagen molecules collagen fibrils collagen fibers 37 Collagen Fibers most abundant structure contains: ○ 3 polypeptide chains bound into a triple helix ○ triple helices are assembled into collagen microfibrils that can be viewed microscopically 38 Important Notes each polypeptide chain that makes up the triple helix consists of amino acids that are arranged in groups of 3 (triplets) each triplet contains: ○ glycine ○ 2 variable amino acids; can be hydroxyproline/hydro xylysine or proline 39 Collagen is the most abundant, ubiquitous structural protein occurs in all of the ordinary and specialized connective tissues 40 Type I Collagen most common located in the dermis, tendons, ligaments, fascia, bone, fibrocartilage, dentin, capsules of organs, and sclera 41 Type II Collagen has a slightly different molecular composition occurs in hyaline cartilage and the vitreous body of the eye 42 Type III Collagen makes up reticular fibers found in several tissues 43 Type IV Collagen is associated with basal laminae 44 Mast Cells are normal elements of the connective tissues and lamina propria of mucous membranes trigger or maintain inflammatory and immune responses derive from bone marrow precursors 45 Mast Cells located near blood vessels usually contain large, abundant granules: ○ histamine ○ heparin ○ chemotactic factors ○ cytokines granules exhibit metachromasia when stained with cationic dyes 46 Plasma Cells are mature B lymphocytes that are specialized for antibody (immunoglobulin) production are distributed widely throughout the body, especially in the lamina propria of the gastrointestinal tract and in lymphatic organs 47 Plasma Cells cytoplasm is deeply basophilic has an ovoid nucleus and a prominent nucleolus 48 Macrophages are the most numerous cells after fibroblasts belong to monocyte-derived cells; referred to as: ○ Kupffer cells ○ dust cells ○ microglia ○ Langerhans cells ○ dendritic cells ○ osteoclasts 49 Macrophages are phagocytic cells ○ engulf or digest particulate matter, infectious microorganisms may be fixed or wandering are attracted to sites of inflammation and are involved in the immune response by antigen processing and presentation 50