Connective Tissue Histology Slides Flashcards
Unlike epithelia which is composed of many cells with little ECM, CT is composed of a few cells with lots of ECM. On an H&E slide, this is readily apparent by comparing….
the number of nuclei in epithelia and CT
epithelia line a lumen or space
…
epithelia tend to have more what than CT? (besides nuclei)
more cytoplasm - which stains eosinophilic, while CT cytoplasm is pale or sparse
what are the three components of CT?
fibers
cells
matrix
fibers in CT?
collagen - thick and pink
reticular - not visible w/o special stains
elastic - thin and purple (not visible with H&E but is with resorcin)
cells in CT?
fibroblast often indicated - has a tapered appearance
WBCs - military formation
matrix in CT?
clear spaces
contain water, ions, GAGs, etc
called “ground substance”
proteins making up reticular fibers are homologous…
to proteins that make up collagen fibers!!
how do reticular fibers show up on H&E?
not visible!
special stains - silver stains - are used
in tissues with large elastic art tiers, elastic fibers form prominent sheets that are readily apparent on H&E
..
elastic tissue is amorphous in shape. it has dark microfibrils within a pale elastin core
..
almost all CT tissues are derived from…
mesenchyme (embryonic precursor tissue)
tissue is composed of mesenchymal cells surrounded by a matrix with very few fibers
fibroblasts are derived from..
mesenchymal cells and are “resident” generic connective tissue cells that produce most, if not all, of the fibers and matrix
in EM, what do fibroblasts look like?
look like spindle-shaped cells
active fibroblasts have lots of RER/golgi
quiescent fibroblasts have less RER/golgi (most cells)
Most of the cells in CT are not permanent residents but immune cells that are “visiting” aka basophiol, eosinophil, neutrophil, mast cell, plasma cell, T cells, macrophages
…
macrophages are derived from…
monocytes!
mast cells
immune cells that play a role in inflamm
have secretory granules (heparin and histamine)
metachromasia seen where?
mast cell granules turn dye purple (really blue)
ECM varies widely! accounts for the fact that some tissues are fluid and others solid!
…
CT can be classified into generic and specialized.
Generic connective tissue types?
1) loose (aka areolar - includes reticular, elastic, maybe mesenchyme)
2) dense irregular
3) dense regular
the density and thickness of the extracellular fibers tells us if its loose or dense
the orientation of the fibers tells us if it is irregular or regular
…
Loose connective tissue (Areolar)
appearance?
function?
appearance - more space than collagen or reticular, fibers thin, so its loose; fibers are oriented in all directions
function - not very strong, but usually is well vascularized; found as filler; ESPECIALLY useful right under epi which has no blood vessels of its own
all of the epi shown have loose connective tissue under them! good for delivering nutrients to the epi
…
reticular tissue (version of loose CT)
reticular fibers stain black
elastic tissue (version of loose CT)
elastic fibers look shinier than collagen
Mesenchyme is NOT loose CT! And loose CT is NOT mesenchyme!
…
Dense irregular CT
appearance?
function?
appearance - less space, many (type I) collage fibers, many are thick, so it is DENSE collagen fibers oriented in all directions ,so it is IRREGULAR
function - strong in multiple directions, but usually is not as well vascularized as loose
dense irregular connective tissue - the fibroblast cells are more spread out than in the loose tissue
…
dense regular CT
appearance?
function?
appearance:
- no space, many thick (type I) collagen fibers packed so tightly, it’s hard to see individual fibers, so it is DENSE
- collagen fibers are hard to see, but look how the fibroblast nuclei have to orient and narrow to accommodate, so it is REGULAR
function:
- strong in one direction (e.g. tendon/ligament) but usually VERY poorly vascularized, so it take a long time to heal
