Connective Tissue Histology Slides

Question 1

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….

Answer 1

the number of nuclei in epithelia and CT

Question 2

epithelia line a lumen or space

Answer 2

…

Question 3

epithelia tend to have more what than CT? (besides nuclei)

Answer 3

more cytoplasm - which stains eosinophilic, while CT cytoplasm is pale or sparse

Question 4

what are the three components of CT?

Answer 4

fibers
cells
matrix

Question 5

fibers in CT?

Answer 5

collagen - thick and pink
reticular - not visible w/o special stains
elastic - thin and purple (not visible with H&E but is with resorcin)

Question 6

cells in CT?

Answer 6

fibroblast often indicated - has a tapered appearance

WBCs - military formation

Question 7

matrix in CT?

Answer 7

clear spaces
contain water, ions, GAGs, etc
called “ground substance”

Question 8

proteins making up reticular fibers are homologous…

Answer 8

to proteins that make up collagen fibers!!

Question 9

how do reticular fibers show up on H&E?

Answer 9

not visible!

special stains - silver stains - are used

Question 10

in tissues with large elastic art tiers, elastic fibers form prominent sheets that are readily apparent on H&E

Answer 10

..

Question 11

elastic tissue is amorphous in shape. it has dark microfibrils within a pale elastin core

Answer 11

..

Question 12

almost all CT tissues are derived from…

Answer 12

mesenchyme (embryonic precursor tissue)

tissue is composed of mesenchymal cells surrounded by a matrix with very few fibers

Question 13

fibroblasts are derived from..

Answer 13

mesenchymal cells and are “resident” generic connective tissue cells that produce most, if not all, of the fibers and matrix

Question 14

in EM, what do fibroblasts look like?

Answer 14

look like spindle-shaped cells
active fibroblasts have lots of RER/golgi
quiescent fibroblasts have less RER/golgi (most cells)

Question 15

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

Answer 15

…

Question 16

macrophages are derived from…

Answer 16

monocytes!

Question 17

mast cells

Answer 17

immune cells that play a role in inflamm

have secretory granules (heparin and histamine)

Question 18

metachromasia seen where?

Answer 18

mast cell granules turn dye purple (really blue)

Question 19

ECM varies widely! accounts for the fact that some tissues are fluid and others solid!

Answer 19

…

Question 20

CT can be classified into generic and specialized.

Generic connective tissue types?

Answer 20

1) loose (aka areolar - includes reticular, elastic, maybe mesenchyme)
2) dense irregular
3) dense regular

Question 21

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

Answer 21

…

Question 22

Loose connective tissue (Areolar)
appearance?
function?

Answer 22

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

Question 23

all of the epi shown have loose connective tissue under them! good for delivering nutrients to the epi

Answer 23

…

Question 24

reticular tissue (version of loose CT)

Answer 24

reticular fibers stain black

Question 25

elastic tissue (version of loose CT)

Answer 25

elastic fibers look shinier than collagen

Question 26

Mesenchyme is NOT loose CT! And loose CT is NOT mesenchyme!

Answer 26

…

Question 27

Dense irregular CT
appearance?
function?

Answer 27

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

Question 28

dense irregular connective tissue - the fibroblast cells are more spread out than in the loose tissue

Answer 28

…

Question 29

dense regular CT
appearance?
function?

Answer 29

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