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67 Cards in this Set
- Front
- Back
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2 Components of Connective Tissue
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cells
extracellular matrix |
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Specialized Connective Tissues
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Bone, cartilage, blood
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Connective tissue proper
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Nonspecialized connective tissue. Classified as loose or dense.
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loose (areolar) connective tissue
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Low # fibers, lots of cells.
Found where little stress resistance is needed, functions as stroma (supports epithelial parenchyma) |
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Dense connective tissue
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High # fibers, few cells.
Functions where stress is high. |
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Dense irregular tissue
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Complex meshwork of fibers (ex. dermis of skin)
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dense regular tissue
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Fibers are straight and parallel.
Sustain force (ex. tendon) |
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Functions of Connective Tissue
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Maintain gross form of body
Carry vascular and lymphatic vessels of an organ Protect vs. infection Repair after injury Store metabolic energy as triglycerides |
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Components of Extracellular Matrix
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Glue holding cells and tissues together.
Collagen, elastin, ground substance (proteglycans), glycoproteins |
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Collagen
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Main protein of body.
Gives strength and rigidity. |
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Collagen monomer
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300 nm long.
Triple helix of alpha-chains. Every 3rd residue = glycine. Some hydroxylated prolines and lysines. |
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Collagen polymer
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Striped appearance due to staggered monomers.
Crosslinking between molecules increases strength |
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Collagen Synthesis Events
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Intracellular
1. Signal peptide on pro-alpha-chains that allow insertion into RER Extension peptides (propeptides) on both ends...guide triple helix formation, prevent polymerization in cell Post-translational hydroylation of lysines and prolines Hydroxyprolines = H bonds between chains (stability) Secreted to ECM Extracellular Enzymatic removal of propeptides Tropocollagen (mature) now forms fibrils Crosslinking for more stability |
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tropocollagen
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mature collagen
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propeptides
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Extension peptides on ends of collagen fiber before secretion into the ECM
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Fibril-Forming Types of Collagen
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I, II, III
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Fibril-Associated Collagens (FACIT)
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Do not form fibrils. Bind the surface of fibrils. Help organize the fibrils in the matrix.
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Network-Forming Collagen Types
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IV, VII
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Type IV Collagen
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Key component of basal lamina. Supports epithelial cells
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Type I Collagen
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Most common! Skin, bone.
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Type II Collagen
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Cartilage
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Type III Collagen
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Reticular fibers. Delicate networks supporting glandular, lymphoid organs. Underlies basal lamina.
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Elastin
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Branched, anastomosed fibers.
Tissue recoil. Crosslinking via lysine residues Lots of hydrophobicity |
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myofibrils
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Glycoprotein on the surface of elastin (fibrillin). Organize elastin molecules
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Ground substance
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Matrix/gel. Porous, stuff diffuses through it. Lots in cartilage.
Components: proteoglycans, glycoproteins, hyaluronic acid. |
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Proteoglycans
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GAGs covalently linked to protein.
Secreted from cell, full extracellular space. |
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Glycoasminoglycans (GAGs)
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Negatively charged polymers of sulfated or carboxylated disaccharide units
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hyaluronic acid
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Long carb chains of repeating disaccharide units. Attracts water. Cell migration during wound repair.
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Adhesive Glycoproteins
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Help cells attach to the ECM.
fibronectin: Bind collagen, heparin, cell surface, etc. Adhesion of cells to matrix. Laminin as well. Bind via integrins to collagen (ECM) and actin (IC) |
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2 Types of Cells Found in Connective Tissue
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fixed/resident: fibroblasts and adipocytes
Transient/wandering: Motile, short life, response to injury, bacterial invasion, or part of immunological response |
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fibroblasts
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Fixed cells.
Produce ECM and enzymes that break it down (collagenase and elastase) Occur along bundles of collagen fibers Rarely divide...divide more after injury |
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adipocytes
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Fat cells. Synthesize and store lipids
Many = adipose tissue formation |
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White fat
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Most of the body's fat.
20%+ body weight Near blood capillaries |
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Brown Fat
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Heat production (uncouples oxidation and phophorylation)
Lots in newborns and hibernating bears Brown color from cytochromes in mitochondria |
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macrophages
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Motile, phagocytosis.
Ingest dead, damaged cells First line of defense vs. infection Process/display antigens to lymphocytes Secrete cytokines. Monocytes in bone marrow = precursor. Differentiates in CT |
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mononuclear phagocyte system
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Group of phagocytic cells including macrophages, Knupffer cells of liver, osteoclasts, alveolar phagocytes of lungs
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neutrophils
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Gather @ sites of acute inflammation. Enter from blood...
Phagocytic. Help macrophages |
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eosinophils
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Bone marrow-->blood-->CT
Acidophilic granules! Function as combined lysosomes/peroxisomes Granules defend against parasitic infections |
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lymphocytes
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Occur in small #s in all CT. Patrol to defend against infection
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plasma cells
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Major producers of humoral antibodies. B cells differentiate into these
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mast cells
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Large cells, many granules.
Many where body meets outside. Initiate immediate hypersensitivity reaction |
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immediate hypersensitivity reaction
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1. Antigen binds IgE on mast cells.
2. Exocytosis of mast cell granules (degranulation). ex. histamine IgE from previous response to same antigen |
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gap in collagen fibrils
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Hole zone. Ca deposition
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lysyl oxidase
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Crosslinking extracellular enzyme for collagen
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scurvy
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Vitamin C deficiency.
Vitamin C needed for proline hydroxylation --> crosslinking within triple helix! |
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hyperextensible skin
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deficiency in hydroxylysine (lysyl hydroxylas). No crosslinking between molecules
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Type VII Collegan
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Anchoring fibrils. Attaches basal lamina to underlying CT
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Marfan Syndrome
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Defective fibrillin..defective CT. aortic aneurysm
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Elastin & Microfibrils
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elastin core surrounded by microfibrils.
Microfibrils laid down first. Elastin molecules crosslinked to each other after secretion (via lysine residues) |
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cutis laxa (loose skin)
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Lysyl oxidase deficiency...elastin molecules aren't crosslinked
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CT & Aging
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Elastin damaged (UV, mechanical damage, etc.)
Synthesis slows Old skin is thinner, more fragile |
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Ground Substance Visibility On Slides
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Mostly water, which is extracted. Usually not visible.
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Osteoarthritis
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Degenerate joint disease.
Decreased proteoglycan production in cartilage Decreased water at joints to cushion (proteoglycans draw in less water) |
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Chondronectin
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Binds chondrocytes to Type II collagen in cartilage
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Fibroblast Structure (high synthetic activity vs. low synthetic activity)
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High: lots of cytoplasm, ova nucleus, euchromatic, lots of RER, big Golgi
Low: smaller cell, spindle-shaped, low cytoplasm, long, heterochromatic ncleus, less RER (more acidophilic), small Golgi. Often only see nucleus |
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Myofibroblasts
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During wound healing, these fibroblasts become contractile to pull the wound margins together
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unilocular
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One large lipid droplet. Used to described white fat adipocytes
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multilocular
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Multiple small lipid droplets. Used to describe brown fat
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Microscopic Characteristics of Macrophages
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Indented nucleus, secondary lysosomes, ate something!, active cell surface (villi, lamellopodia)
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Opsonization
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Antibody molecules on bacteria bound by Fc receptor on macrophage, induces phagocytosis
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Microscopic Characteristics of Eosinophils
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Bilobed nucleus, eosinophilic (pink-staining granules), crystalline core.
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Microscopic Characteristics of Lymphocytes
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Small, round, little cytoplasm, heterochromatic nucleus = most of cell
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Microscopic Characteristics of Plasma Cells
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Ovoid, negative Golgi, clockface nucleus, RER
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Microscopic Characteristics of Mast Cells
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Large, MANY metachromatic granules
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What cells cause allergic reactions and how?
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Mast cells. Overreaction of the immediate hypersensitivity response
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anaphylactic shock
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When mast cell response is no longer localized.
Histamine carried throughout body by blood vessel...capillary leakage/permeability, decrease in BP |
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When someone has hives, what is the change in tissue?
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Increased # of cells. many WBCs moved to the area
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