Lab 3 - Connective Tissue

Question 1

5 common characteristics of CT

Answer 1

-there are no free surfaces, CT fills spaces with a mixture of cells and extracellular material

-CT underlies epithelia and surrounds muscle and nervous tissues, thus providing structural integrity and support to an organism

-CT also provides chemical support to other tissues; blood vessels and nerves run though CT to reach their destinations

-the ECM is the most abundant component of most CT and the properties of different types of CT are primarily determined by the composition of the ECM

-CT cells are often not connected to each other by cell-cell junctions

Question 2

what are the two components of CT

Answer 2

cells and the ECM

Question 3

what are the two types of cells in CT

Answer 3

-the fibroblast family makes and maintains this tissue. various cells will have different appearancs and names depending on location and activity

-bone marrow derived (immune system) cells are concerned with immune surveillance and defense. they travel through and reside in CT but dont contribute to its formation

Question 4

what makes up the ECM (4)

Answer 4

• collagen fibers = most abundant protein type in mammalian body, primarily collagen type 1 or 2. eosinophilic in H+E and provide tensile strength

-reticular fibers = are actually collagen type 3 thin fibers that stain poorly with H+E. they form supporting network in some organs

-elastin fibers = usually stain very pale with H+E unless in large sheets, but have light refractive properties. they provide stretch-recoil function to CT

-ground substance = composed of water, PG, GAG, soluble proteins and other water soluble molecules. can appear as empty spaces because they dont stain well with H+E, and the spaces are often enlarged by shrinkage during processing

Question 5

what is the main cell type we see in dense CT

Answer 5

fibroblasts

Question 6

why does loose CT tend to have more cells compared to dense

Answer 6

because there are numerous immune system cells moving throughout

Question 7

what is a special type of loose fibrous CT

Answer 7

reticular tissue

Question 8

why dont reticular fibers (collagen type 3) react well with eosin

Answer 8

they are very thin and highly glycosylated

Question 9

how are adipose cells connected

Answer 9

-NOT by cell to cell junctions but rather they are held in densly packed arrays of reticular fibers/collagen type 3 fibers

Question 10

what type of adipose tissue has chicken wire type appearance

Answer 10

unilocular/white adipose tissue

Question 11

what is the territorial matrix

Answer 11

more dense staining around the lacunae - it contains more GAGs

Question 12

what are some types of cartilage? what is the most common

Answer 12

-hyaline cartilage is most common
-fibrocartilage
-elastic cartilage

Question 13

what is on both sides of the cartilage? how does it stain and why

Answer 13

perichondrium - stains more eosinophilic compared to the cartilage because there is more collagen present

Question 14

what is another name for perforating canal

Answer 14

volkmans canal

Question 15

when are you able to see the interstitial lamellae

Answer 15

in cross sections of ground bone only

Question 16

what do mesenchymal cells differentiate into? and what does that do?

Answer 16

they differentiate into osteoblasts that synthesize bone ECM

Question 17

what are the 5 zones in endochondral ossification and what happens in each

Answer 17

• the reserve zone = contains chondrocytes that are not currently dividing
• zone of proliferation = consists of rapidly dividing chondrocytes. axis of cell division is oriented along the direction of cartilage growth so instead of small clumps of chondrocytes, we see long rows of chondrocytes in isogenic chains

-zone of hypertrophy = chondrocytes start to enlarge

• zone of calcification = the cartilage ECM becomes mineralized and the chondrocytes eventuall die leaving empty lacunae space
• zone of ossification =

Question 18

what do osteoclasts do?

Answer 18

degrade immature woven bone and some of the remaining mineralized cartilage to remodel it into mature lamellar bone

Question 19

osteoblasts vs osteocytes vs osteoclasts

Answer 19

osteoblasts = immature baby cells
osteocytes = mature cells that are trapped in the lacunae
osteoclasts = cells that degrade for remodeling

Question 20

at what point is it impossible for bone to grow any longer

Answer 20

when the epiphyseal plate cartilage stops proliferating, endochondral ossification converts the remaining portion of cartilage in the plate into bone and forming the bone marrow cavities becomes connected.

however it can still continue to thicken