ECM and Connective Tissue Flashcards
connective tissue
tissue that connects, supports, binds, or separates other tissues or organs, typically having relatively few cells embedded in an amorphous matrix, often with collagen or other fibers, and including cartilaginous, fatty, and elastic tissues.
types of connective tissue
proper or specialized
proper CT
loose or dense
specialized CT
bone, blood, cartilage
loose CT
areolar, adipose, or reticular
dense CT
regular, elastic, or irregular
bone CT
spongy or compact
cartilage CT
elastic, hyaline, or fibrocartilage
Resident CT
Live in that particular area;
fibroblasts (chondroblasts, osteoblasts, odontoblasts) or adipocytes
Type 1 collagen
fibers; skin, bone, ubiquitous
Type II collagen
network of fibrils; hyaline cartilage, elastic cartilage
Type III collagen
fibers; reticular fibers
not present in h&e staining- have to do silver stain in order to visualize
during remodeling they are the first type of collagen to be laid down
type 4 collagen
network (no fibers); basement membranes
assembly of type 1 collagen
1) 3 precursor alpha chains assemble and become procollagen (triple helix with loose ends)
2) procollagen peptidase cleaves and it becomes collagen molecule (insoluble and occurs in extracellular domain)
3) assembly–> collagen fibril
4) assembly–> collagen fiber
LOX
lysyl oxidase
oxidizes primary amines on collagen and elastin substrates to reactive semialdehydes that condense to form covalent cross-linkages to make collagen fibrils
tendon
attaches to muscle at one end and bone or skin at the other end; transfers mechanical energy from muscle;
consists of dense regular connective tissue composed of primarily type 1 collagen
skin
dense, irregular connective tissue; type 1 collagen
epithelial lining CT
loose connective tissue supports epithelial linings of GI, GU, and respiratory tracts and is found as packing tissue in many organs
space between type 1 collagen filled with ground substance
ground substance
gel like amorphous material; composed of large proteoglycans, glycosaminoglycans, glycoproteins, and WATER; growth factors are pround and presented to cells
reticular fibers
supporting framework for highly cellular organs such as spleen and liver and lymph nodes,
type 3 collagen;
only seen under silver staining;
commonly in places where cells are loosely held together and cells are coming in and moving out
composition of elastic fibers
tropoelastin, fibrillin I and II, microfibril associated glycoprotein (MAGP)
also assembled in extracellular environment;
flexible fibers due to cross-linking
can be present as fibers or sheets
synthesis of elastic fibers
1) rough ER–> synthesis of proelastin (desmosine and isodesmosine), MAGP, and fibrillin 1 and 2
2) golgi apparatus–> packaging and secretion of protein
3) extracellular space–> coassembly of MAGP and tropoelastin to produce immature elastic fibers; fibrillin 1- force bearing structural support; fibrillin 2- regulates assembly of elastic fiber
LOX does linking here as well
Defect in elastic fibers
Marfan’s syndrome (abraham lincoln)- aorta
Basement membrane
bulletin board; mechanical support and relays cellular signals to epithelia, muscle cells, or endothelium
Stained well by PAS
PAS
Periodic acid–Schiff (PAS) is a staining method used to detect polysaccharides such as glycogen, and mucosubstances such as glycoproteins, glycolipids and mucins in tissues;
stains sugar moieties
3 zones of basement membrane
lamina lucida (rara), lamina densa, lamina reticularis
RGD domain
Proteins that contain the Arg-Gly-Asp (RGD) attachment site, together with the integrins that serve as receptors for them, constitute a major recognition system for cell adhesion. The RGD sequence is the cell attachment site of a large number of adhesive extracellular matrix, blood, and cell surface proteins, and nearly half of the over 20 known integrins recognize this sequence in their adhesion protein ligands.
Laminin
lamina rara composed primarily of laminin network;
laminin composed of three peptides: alpha, beta, gamma
alpha- laminin
heparan sulfate binding site
beta- laminin
HS binding site and proteoglycan binding site on top, integrin binding sites on bottom (RGD)
gamma- laminin
HS and proteoglycan binding site and entactin attachment site with RGD domain
2 networks that make basal lamina
type 4 collagen sheets and laminin
entactin
binds collagen and laminin together; also known as nidogen
fibronectin
present on basement membrane; bind to collagen and integrins on cell surface
proteoglycan
will bind to laminin network and act as signaling molecules; can bind and present other growth factors
growth factors
sequestered by proteoglycan GAG chains;
once sequestered, growth factor is held in place and keeps binding so that the receptor is constantly activated;
glomerular basement membrane
specialized BM that is part of filtration barrier; basal lamina- produced by endothelial cells and epithelial cells;
GBM consists of subendothelial and subepithelial lamina rara and in between the two is the lamina densa; there is no lamina reticularis
diabetic GBM
thickening of BM
transient CT
visitors;
macrophages, plasma cells, mast cells, lymphocytes, eosinophils
diapedesis
The movement or passage of blood cells, especially white blood cells, through intact capillary walls into surrounding body tissue.
how do lymphocytes move into connective tissue?
rolling adhesion, tight binding (through integrin to ICAM-1) , diapedisis, and migration
macrophage
phagocytose;
stained blue by trypan blue dye
differentiation of lymphocytes
differentiate into plasma cells which result in conversion of quiescent cells into cells active synthesizing protein (immunoglobulin)
plasma cell
“cartwheel” configuration created by distribution of heterochromatin
mast cell
release histamines and heparin in response to allergen;
1) Ag bridges two adjacent IgE receptors
2) bridging induces signaling cascade resulting in mobilization of cytosolic calcium
3) cascade triggers release of granules and cytokines
granules (mast cell)
in mast cells containing histamines, proteases, proteoglycans, and cytokines
eosinophil
first line of defense in parasitic infection;
red staining granules (eosin) and bilobed nucleus
granules (eosinophil)
eosinophil peroxidase; major basic protein; eosinophil cationic protein
eosinophil peroxidase
binds to microorganisms facilitating their killing by macrophages
major basic protein
MBP; major component of crystallin center of eosiniphil; binds and disrupts membrane of parasites
eosiniphil cationic protein
together with MBP causes fragmentation of parasites
4 S’s of connective tissue
support-mechanical (type 1)
storage- of energy (adipose)
signaling- GF, apical identity, matrix bulletin board
sifting- filtering in glomerulus
what do fibroblasts synthesize?
proteoglycans, collagen, elastin;
tendon and skin
chondroblasts
fibroblast in cartilage; synthesizes type 2 collagen
osteoblasts
fibroblast in bone; synthesizes bone (type 1 collagen)
odontoblasts
fibroblast in teeth; synthesizes dentin (type 1 collagen)
type II collagen present in
hyalin and elastic cartilage
type 3 collagen present in
bone marrow and lymphoid organs; synthesized by fibroblasts called reticular cells;
movement in and out
type 4 collagen synthesized
by epithelial cells;
forms basal lamina with laminin
