Connective Tissue Histology Flashcards
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
regular connective tissue
varying amounts of fiber, classified as dense or loose dependingo nthe proportion of fibers
special connective tissue
includes cartilage, bone, fat, and blood
dense regular connective tissue
dense with parallel collagen fibers, closely packed around fibroblast such as in tendons, compressed nuclei
dense irregular connective tissue
irregular arrangement of collagen fibers, refers to the meshwork orientation of fibers as in the dermis of the skin, etc.
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
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
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
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
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
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
collagen assembly - nucleus
transcription and post-transcriptional modifications
mRNA formed
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
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
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
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
type I collagen
[(a1(I)2)(a2(I)]
type II collagen
[a1(II)]3
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
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
elastin
molecule that allows for elasticity by coiling up and attaching each other
when stretched, molecules straighten out
desmosine and isodesmosine
large amino acids unique to elastic connective tissue, interconnect elastin molecules in a somewhat random pattern
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
Marfan’s syndrome
defect in the autosomal dominant fibrillin gene, resulting in dysfunctional elastic tissue throughout the body
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
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
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
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
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
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
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
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
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
mononuclear phagocytic system
consists of phagocytic cells throughout the body that are derived from monocytes
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
Name the different resident cells in connective tissue.
fibroblasts, macrophages, mast cells, adipocytes, and adult stem cells
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
plasma cells
differentiate from B-lymphocytes to secrete antibodies into the blood during an immune response
lymphocytes
involved in the immune response, migrate into connective tissue in response to antigen presentation, some places they have a more permanent residence
B lymphocytes
differentiate into plasma cells that secrete antibodies for a humoral immune response (antibodies in bloodstream)
T lymphocytes
participate in cell-mediated immune response where they become killer T-cells that attack bacteria, etc.
granulocytes
cells that have lobed nuclei
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
eosinophils
named for eosinophilic granules, function in allergic reactions, parasitic infections, and sites of chronic inflammation
basophils
blood equivalent of mast cells in connective tissue
secrete histamine that increases vascular permability
secretes anticoagulant heparin
What are the three major transient cells in connective tissue?
