Lecture 7: Connective Tissue (Hayward) Flashcards
main type of connective tissue in the MS system*
dense connective tissue (esp. dense REGULAR CT)
2 main classifications of connective tissue*
ordinary and specialized CT
“ordinary” CT consists of what 2 types of CT?*
loose and dense CT
“specialized” CT includes:*
cartilage and bone
2 types of dense CT*
regular and irregular CT
difference b/w loose and dense CT*
dense CT has larger # of fibers compared to # of cells
characteristics of regular dense CT*
parallel bundles of fibers. Present in tendons, ligaments, and aponeurosis
chars. of irregular dense CT*
Allow more stretch and distension than regular dense CT. Present in dermis, submucosa of digestive tract, and fascia.
3 types of fibers secreted by fibroblasts*
collagen, elastic fibers, reticular fibers
role of amorphous ground substance in connective tissue**
imparts “spongyness” and capacity of connective tissue to take on compressive forces. Its negative charge draws Na+ and subsequently H2O towards it, giving it a characteristic gel-like property. Common in loose connective tissue
which are more active: fibroblasts or fibrocytes?*
fibroblasts; they are actively producing intercellular fibers
role of reticular fibers*
act as supportive meshwork/anchoring system between collagen and adjacent cells in the lamina
general role of tendons and ligaments*
absorb stretching forces
why does collagen have a banded appearance at light microscopic lvl?*
due to interconnection of individual filaments
type 1 collagen fibers are present in:*
tendons, ligaments, bone, and fibrocartilage,
type 2 collagen fibers are present in what type of connective tissue?*
Hyaline and elastic cartilage. (i.e. intervertebral discs)
type 3 collagen fibers are present in:*
loose connective tissues, reticular fibers, blood vessels
what are reticular fibers composed of?*
type III collagen with polysaccharide coating in a basal lamina
How are elastic fibers able to undergo expansion and recoil?*
They have strong interfiber crosslinking which is mediated by LYSYL OXIDASE. They also automatically recoil when they don’t have any stretch on them.
what are elastic fibers composed of?*
elastin and fibrillin
role of fibrillin in elastic fiber composition*
help mold elastin molecules into elastic fibers
Marfan’s syndrome*
a deficiency or defect in fibrillin. Leads to underdevelopment of elastin. Patient is predisposed to aortic rupture and joint instability
Composition of amorphous ground substance**
glycosaminoglycans and proteoglycan. Has high neg. charge which attracts Na+ and thus H2O into it. High negative charge of GAGs imparts compressive strength to connective tissue**
what is basal lamina? What is it composed of?
interface between conncective tissue and adjacent layer. Composed of type 4 and 7 collagen, laminin (which binds cell membrane to collagen and proteoglycans of laminae), and fibronectin (which attaches cell to basal laminae)
where are fibroblasts, chondroblasts, and osteoblasts found?
fibroblasts: ordinary connective tissue (i.e. fascia, ligaments, tendons)
chondroblasts: cartilage
osteoblasts: bone
3 main components of extracellular matrix
extracellular fibers, ground substance, and tissue fluid
2 principal classes of intercellular substances that constitute the extracellular matrix
intercellular fibers and amorphous ground substances
3 main types of intercellular fibers
collagen fibers, reticular fibers, and elastic fibers
steps of collagen formation*
1) alpha chains are made in rough ER and transported to Golgi where they are packaged into procollagen triple alpha helix structure
2) procollagen excreted into extracellular space
3) procollagen cleaved by extracellular pepsidases, which allows for inter-chain bonding b/w collagen fibers
4) fibers combine together to form a fibril, which band together into larger fibers
what enzyme allows for cross linking between adjacent collagen molecules?*
lysyl oxidase
periodicity of collagen fibers under electron microscope. What is it caused by?
67nm. Created by alternating pattern of gap regions and overlap regions of collagen molecules
most common type of collagen
type I
what do elastin polymers form in the absence of fibrillin?
lamina
what surrounds all muscle fibers, Schwann cells, endothelial cells, and adipocytes?
external lamina
laminin
adhesive glycoprotein that binds the cell membrane of type IV collagen and heparin sulfate proteoglycans of the laminae
fibronectin
adhesive glycoprotein that attaches the cell to the laminae as well as reticular fibers that project into the lamina from the underlying connective tissue
6 principal glycosaminoglycans of connective tissue
1) hyaluronic acid
2) chondroitin-4-sulfate
3) chondroitin-6-sulfate
4) dermatan sulfate
5) keratan sulfate
6) heparin sulfate
how are proteoglycan aggregates formed?*
via the attachment of numerous proteoglycan molecules to hyaluronic acid via linking proteins
