CT proper and cartilage 2

90% is type 1 collagen with high tensile strength and high flexibility

TEM: fibrils look banded, and fibers look like collections of fibrils

LM: red or pink stain with eosin in H/E and look wavy and unbranched

Fibroblasts -> procollagen (triplet polypeptide chain) rich in hydroxyproline and hydroxylysine

-procollagen secreted by exocytosis to extracellular space, peptidases cleave terminal ends of molec to form tropocollagen

tropocollagen self-assembles into fibrils which become fibers

type 2 and 3 collagen are other types of fibrillar collagen

type 4 collagen is nonfibrillar collagen in the basal lamina

composed of elastin rich in desmosine and isodesmosine, fibrillin, and other glycoproteins

-has little hydroxyproline and no hydroxylysine

-elastin = gives elasticity, fibrillin acts as structural and organizing element, desmosine and isodesmosine bind adjacent elastin molec together to allow stretch and recoil

orcein - dark brown

resorcin- fuchsin: purple/black

aldehyde fuchsin - purple

verhoeff's stain - black

dominated by type 1 collagen made by fibroblasts with fewer cells than loose CT

-mechanically links other tissues or supports other tissues

major tissue component = fibrous with little ground substance

fibroblasts = elongated

some elastic fibers produced but less than collagen

• location: tendons/ligs
• -Type 1 collagen fibers = aligned to run in same direction

tissue = poorly vascularized and appears white

location: dermis of skin and organ capsules

layers of collagen, each layer has fibers in same dir but oblique to other layers

vitamin C deficiency leads to reduced collagen 1 synthesis (dense irreg CT)

common in periodontal lig anchoring teeth in bone sockets -> loose teeth

composition: type 3 collagen fibers

• functions: delicate framework to allow cells and fluid to move within an organ
• -supports blood vessel walls and forms supporting network around fat cells/nerve fibers/ and skeletal and
• smooth musc fibers

1) forms stroma of bone marrow, liver, and lymphatic organs except thymus

2) associated with basal lamina of epithelia, around blood vessels, muscles, nerve fibers, in loose and dense CT and around adipose cells

type 3 collagen produced by reticular cells in lymph. organs by same method as type 1 collagen by fibroblasts

fibrils form small, delicate bundles (string bag) to organize tissue of organs while allowing interchange of cells/fluid

TEM: type 3 fibers look like type 1 but very thin

LM: stained by silver salts, fibers = thin and highly branched

-type 3 collagen also stained by periodic acid schiff technique for carbs

insufficient synthesis of type 3 collagen (prominent in aorta and intestines) can lead to rupture

this CT domintaed by elastic fibers to provide stretch and elasticity

components: fibroblasts or smooth musc cells dominate, ECM is dominated by elastic fibers

Fiber organization: elastic fibers as loose branching, bundled network, or fenestrated laminae or lamellae (sheets with holes)

mixed with loose and dense irreg CT in skin (long, thin, branching fibers)

must use special stains for elastin fibers

in vessels- one or more thin layers in in arteries and large veins

for elastic CT

mutations in gene for microfibrillar component affects large blood vessels.

normally thick aortic wall gets thin and can rupture

well vascularized and dominant cell = unilocular adipocyte

ECM: reticular fibers secreted by adipocytes with little ground substance

in adipose CT

adipose tissue secretes leptin that goes to hypothalamus where it regulates food intake and metabolism

problems in pathway may lead to obesity