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Flashcards in Connective Tissue Histology Deck (46):
1

connective tissue functions

connect bones via ligaments

forms capsules of rogans and their supporting framework

forms protective barriers from the external environment

transduction in muscles via tendons

controlled moedeling and remodeling processes such as wound healing and growth

pathological processes such as inflammation

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regular connective tissue

varying amounts of fiber, classified as dense or loose dependingo nthe proportion of fibers

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special connective tissue

includes cartilage, bone, fat, and blood

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dense regular connective tissue

dense with parallel collagen fibers, closely packed around fibroblast such as in tendons, compressed nuclei

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dense irregular connective tissue

irregular arrangement of collagen fibers, refers to the meshwork orientation of fibers as in the dermis of the skin, etc.

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loose connective tissue

more cellular, relatively fewer fibers, often has high fat content, serves as packing material throughout the body with a variety of cell and fiber types

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embryonic connective tissue

mesenchyme - a loose connective tissue derived from mesoderm

mucouse connective tissue - fills umbilicord, has mucous, ECM is a gelatinous Wharton's jelly, ground substance and fine collagen fibers

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ground substance

consists of GAGs, proteoglycans, and glycoproteins

strong negative charges on the GAGs hydrate the connective tissue and the clycoproteins link the cells, fibers, and matrix molecules to each other

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connective tissue fibers

classified as collagen, elastic, and reticular fibers

composed of fibrils, aggregates of long molecules

can fibers can be in the form of thick or thin filaments arranged in a meshwork, in patches, or in dense sheets

produced by fibroblasts, smooth muscle cells, and some others

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organization of collagen

alpha1 and  alpha2 chains form triple helices, which form moelecules that are packed into fibrils

regularly repeating lysines, one polypeptide can go from 600 to 1000 amino acids long

gaps are staggered, tensile strength of steel due to hydrogen bonding and disulfide bonds

even repeates of glycines in a glycine,proline-hydroxyproline sequence

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procollagen

collagen before leaving, inactivated by two globular ends on either side

assembled in the ER and fibrils completed extracellularly

vitamin C is required for the hydrogen bonds to form between alpha chains to stabilize the triple helix of the collagen molecule

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collagen assembly - nucleus

transcription and post-transcriptional modifications

mRNA formed

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collagen assembly - rER membrane

pro-alpha chain translation

single alpha chain polypeptides formed with globular heads at each end

hydroxylation of proline and lysine, vitamin C necessary

sugar groups added

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collagen assembly - rER lumen

procollagen molecule assembled

triple helix formed from the C-terminal end to the N-terminal

hydrogen and disulfide bonds form

procollagen molecule transported to the golgi

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collagen assembly - golgi

procollagen transport to the cell membrane

procollagen molecules associate into bundles

bundles of procollagen packed into vesicles that release them to extracellular coves bounded by fibroblast cell membrane

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collagen assembly - extyracellular "coves of fibroblasts

completion of collagen molecule, assembly into fibrils

globular ends cleaved, molecules align and assembled head to tail in quarter stagger to form fibrils

molecules cross-linked with covalent bonds at lysine-hydroxylysine aldehyde groups

other collagen types added to the fibril

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type I collagen

[(a1(I)2)(a2(I)]

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type II collagen

[a1(II)]3

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fibril-associated collagens with interrupted triple helices (FACITs)

have stretches without triple helices, can bend there

usually involved in connecting the fibril to intracellular matrices

role is to connect one fibril to another

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elastic connective tissue

thin fiber meshwork in loose connective tissue

denser fibers in ligamentum flava of the vertebral column and vocal cords

fenestrated elastic plates interspersed with smooth muscle layers in elastic arteries

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elastin

molecule that allows for elasticity by coiling up and attaching each other

when stretched, molecules straighten out

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desmosine and isodesmosine

large amino acids unique to elastic connective tissue, interconnect elastin molecules in a somewhat random pattern

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fibrillin

part of an elastic fibril, both in its interior and on its surface, forms very fine microfibrils that are depositied first as a template for elastic fibril assembly

without fibrilin, elastin molecules will form sheets rather than fibrils

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Marfan's syndrome

defect in the autosomal dominant fibrillin gene, resulting in dysfunctional elastic tissue throughout the body

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reticular fibers

named for arrangement as a reticulum, a branched, interconnecting meshwork in the loose connective tissue stroma of lyphatic tissues and hemopoietic tissues

surround blood vessels, nerves, fat cells, and mucle cells, at the interface between epithelia and underlying connective tissue

also prominent in the embryo and early wound healing

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reticular fibrils

composed of type III collagen and have the same banding pattern as type I collagen fibrils, form fibers that are narrower in diameter, wavy, and have a higher sugar content than type I collagen fibers

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reticular cells

in lymphatic and blood-forming tissues, given name because of their unique relationship to retiucal fibers, surround the fibers they produce with their cytoplasm

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GAGs

repeating, unbranched disaccharides with negative charges, longest GAG is hyaluronan, gives gel-like quality to connective tissue, cartilage matrix, synovial fluid, and vitreous humor in the eye

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proteoglycans

GAGs attached to a linear core protein to make a brush-like structure

often linked to hyaluronan to help stiffen cartilage matrix or can be smaller transmembrane molecules that function in cell-matrix interactions

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multiadhesive glycoproteins

small proteins with a variety of configurations that have binding sites for most components of connective tissues and basal cell membranes of epithelia, help stabilize connective tissues

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connective tissue cells

most varied in loose connective tissue, can be classified as permanent or transient

responsible for manufacturing and maintining the connective tissue fibers and matrix molecules, wound healing, inflammatory response to injury, participation in immune response

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fibroblasts

connective tissue workhorse cells that produce all of the fiber and matrix component molecules

myofibroblasts have secretory properties of fibroblasts and contractile properties of smooth muscle

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macrophages (histiocytes)

phagocytic cells derived from monocyte blood cells

have indented nuclei like monocytes and cellular features characteristic of their function such as numerous lysosomes and endocytotic vesciles with produces of ingestion/digestion

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mononuclear phagocytic system

consists of phagocytic cells throughout the body that are derived from monocytes

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mast cells

connective tissue equivalent of basophils in blood, involved in immune responses where the cells release histamine that causes edema from increased permeability of small blood vessels, the anticoagulant heparin, and other factors

36

Name the different resident cells in connective tissue.

fibroblasts, macrophages, mast cells, adipocytes, and adult stem cells

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monocytes

cells that migrate into connective tissue and differentiates into macrophages

stands for mononuclear leukocyte or a white blood cell with a nucleus that is not lobed

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plasma cells

differentiate from B-lymphocytes to secrete antibodies into the blood during an immune response

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lymphocytes

involved in the immune response, migrate into connective tissue in response to antigen presentation, some places they have a more permanent residence

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B lymphocytes

differentiate into plasma cells that secrete antibodies for a humoral immune response (antibodies in bloodstream)

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T lymphocytes

participate in cell-mediated immune response where they become killer T-cells that attack bacteria, etc.

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granulocytes

cells that have lobed nuclei

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neutrophils

have multilobed nuclei and granules, and are named for their lack of staining

motile phagocytes and the most numerous white blood cells

first wave of cells to leave the blood stream at sites of injury, edema, infection, etc.

ingest and dsestroy infectious agents

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eosinophils

named for eosinophilic granules, function in allergic reactions, parasitic infections, and sites of chronic inflammation

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basophils

blood equivalent of mast cells in connective tissue

secrete histamine that increases vascular permability

secretes anticoagulant heparin

46

What are the three major transient cells in connective tissue?