Histology: Connective Tissue- Embryonic Connective Tissue

Question 1

What is the main embryonic tissue?

Answer 1

mesenchyme

Question 2

Where is the mesenchyme primarily found?

Answer 2

in the embryo

Question 3

What is the structure of the mesenchyme?

Answer 3

• small, spindle shaped cells
• uniform appearance
• processes extend from these cells and contract similar processes of neighbouring cells (forming a three-dimentional cellular network)
• the extracelular space is occupied by a viscous ground substance

Question 4

What is the extracellular space of mesenchyme occupied by?

Answer 4

the extracelular space is occupied by a viscous ground substance

viscous- thickk consistency

Question 5

What do spindle shaped cells create when they connect to each other by their ‘endings’?

Answer 5

a three-dimentional cellular network

Question 6

Why are the mesenchyme cells an exception to connective tissue?

Answer 6

It does not have any fibers. (It is composed only of ground substance and mesenchyme cells).

Question 7

What happens to mesenchymal cells as they develop?

Answer 7

Mesenchymal stem cells first proliferate and then differentiate into adult connective tissue cells.
eg.
osteoblasts
chondrocytes
adipocytes
fibroblasts

proliferate= multiply

Question 8

What are the primary bone cells?

Answer 8

osteocytes (created through osteoblasts from mesenchymal stem cells)

Question 9

What are the primary cartilage cells?

Answer 9

chondrocytes (created through transitory chondrocytes from mesenchymal stem cells)

Question 10

What are the primary adipose tissue cells?

Answer 10

adipocytes (created through pre-adipocytes from mesenchymal stem cells)

Question 11

What are the primary connective tissue proper cells?

Answer 11

Fibrocytes created through transitory fibroblasts.

Question 12

What is another example of embryonic connective tissue?

Answer 12

Mucous connective tissue

Question 13

Where is mucous connective tissue found?

Answer 13

in the umbillical chord

Question 14

What does the mucous connective tissue consist of?

Answer 14

• specialized, almost gelatin like ECM,
• its ground substance is referred to as “Whartons Jelly”,
• spindle shaped cells
• widely seperated
• appear like fibroblasts in the near-term umbillical chord

Question 15

What is the ground substance of mucous connective tissue cells referred to as?

Answer 15

Whartons Jelly

Question 16

What are “Wharton’s jelly mesenchymal stem cells”?

Answer 16

Cells which are isolated from Whartons jelly, expressing significant amounts of mesenchymal stem cells and having the ability to differentiate under adequate condition into cells such as:
- osteocytes
- chondrocytes
- adipocytes
- neural-like cells

Question 17

What is the difference between mucous and mesenchyme connective tissue?

Answer 17

The embryo or fetus is mostly filled with mesenchyme in all of its capacity.
The umbillical chord is filled with mucous connective tissue.

Question 18

What can the Wharton Jelly do in particular cases eg. damage of mesenchymal cells)?

Answer 18

In some particular substances (such as damage or lack of mesenchymal cells) Wharton jelly can act in the same manner as mesenchymal cells (can support the mesenchyme).

Question 19

What is the common precursor tissue of all connective tissues?

Answer 19

mesenchyme

Question 20

How is the mesenchyme formed?

Answer 20

Cells migrating from the germimal layers in the embryonic body (from the mesoderm and ectoderm).

Question 21

What type of nucleus do most mesenchyme cells have? What does this mean/allow for?

Answer 21

nucleus filled with euchromatin, indicating their high transcriptional activity.

Question 22

What do mesenchyme cells produce?

Answer 22

the extracellular matrix

Question 23

What do mesenchymal cells differentiate into?

Answer 23

individual types of connective tissue, cartilage, bone, hematopoietic and endothelial cells.

Question 24

What property of mesenchymal cells decreases during their maturation?

Answer 24

• ability to produce the cellular matrix
• ability to undergo mitosis

Question 25

What is the intermediary fillament of connective tissue called?

Answer 25

vimentin