block III: CT video 1

Question 1

Which tissues does connective tissue serve to connect?

Answer 1

epithelium, muscle and nerve

Question 2

What are the adult types of Connective tissue?

Answer 2

Connective tissue proper (major type)
Specialized connective tissue

Question 3

What are the embryonic types of Connective tissue?

Answer 3

Messenchymal CT (mesodermal organs)
Mucoid CT (found in umbilical cord)

Question 4

Which is the general diffuse type of connective tissue found all through out the body connecting together the other tissues

Answer 4

Connective tissue proper

Question 5

Which are the specialized connective tissues?

Answer 5

1. Reticular connective tissue (Lymphatic and blood forming organs)
2. Adipose tissue (fat)
3. Cartilage
4. Bone
5. Blood

Question 6

Where are most types of CT derived from?

Answer 6

undifferentiated mesenchymal cells of
the embryonic mesoderm (some CT comes from neural crest [from CT of head[)

Question 7

What characterizes CT histologically in basic characteristics?

Answer 7

presence of cells which are typically widely
separated from each other by extensive
regions of an extracellular matrix
which typically consists of several types of
fibers and a ground substance.

Question 8

Identify

Answer 8

mesentery spread as an example of
connective tissue

Question 9

Identify

Answer 9

Micrograph of epithelium in small intestine showing tight spacing of epithelial cells with only small amounts of extracellular matrix

Question 10

Identify

Answer 10

Micrograph of connective tissue in submucosa of small intestine
showing CT cells widely separated with extracellular space with
fibers and ground substance

Question 11

What are some functions of CT?

Answer 11

• connect together & strengthen the other tissues
• provide a diffusional pathway for the movement of ions, molecules,
  and metabolites to the other tissues. (Blood vessels typically run in the connective tissue)
• immunological defense (immunocompetent cells are typically present. In addition connective tissue acts as a physical barrier to microbes)
• wound healing (scar formation)

Question 12

What are the types of fibers in CT?

Answer 12

1. Collagen fibers
2. Reticular fibers
3. Elastic fibers

Question 13

identify

Answer 13

Micrograph of a mesentery spread showing stained collagen and elastic fibers as well as CT cells

Question 14

What is the size and stain of collagen fibers?

Answer 14

1. 2-30 microns (largest within CT proper)
2. Stain with eosin in H&E preps

Question 15

What are collagen fibers composed of and how do they look in electron microscope?

Answer 15

1. collagen fibrils
2. collagen fibrils are composed of collagen and show distinct 68nm cross striation in EM

Question 16

Functions of collagen fibers

Answer 16

They have extreme tensile strength and depending on the numbers and arrangement they add mechanical strength to surrounding tissues [compared to steel, resist pulling forces]

Question 17

identify

Answer 17

Micrograph of submucosa of small intestine showing collagen fibers
stained with H&E

Question 18

identify

Answer 18

EM showing collagen fibers composed of bundles of collagen fibrils, and a fibroblast cell

Question 19

identify

Answer 19

EM of collagen fibrils in dense irregular CT with and inset showing the cross-banding
structure of the fibrils (striated pattern) [distinct 68nm repeat]

Question 20

identify

Answer 20

Collagen Type I fibrils as seen in atomic
force microscope image. Note the striations [distinct 68nm repeat]

Question 21

WHat is the size of reticular fibers and its stain?

Answer 21

1. about 1.5 microns in diameter
2. not typically seen in routine H&E. Stained with silver metal containing stains

Question 22

What is the arrangement of reticular fibers?

Answer 22

arranged in a delicate meshwork or network of fibrils, rather than the large
bundles seen in collagen fibers

Question 23

Functions of reticular fibers

Answer 23

surround small blood vessels, small nerves, fat cells, and form the CT
framework of liver & most lymphoid and blood-forming tissues.

Question 24

identify

Answer 24

reticular fibers

Question 25

What is the structure of collagen?

Answer 25

linear molecule 1.5 nm diameter by 300nm length composed of three helically arranged polypeptide chains.

Question 26

What is present in the helical regions of collagen?

Answer 26

glycine, every third residue

Question 27

WHta is the percetange of hydroxyproline and hydroxylysine?

Answer 27

10% hydroxyproline 10% hydroxylysine

Question 28

Why are hydroxyproline residues important?

Answer 28

important in forming hydrogen bonds between the polypeptides and stabilize the triple helical structure

Question 29

Why is hydroxylysine important?

Answer 29

important for forming crosslinks between adjacent collagen molecules in the fibril. An enzyme lysl oxidase is required.

Question 30

WHat cofactors are important for hydroxylation reactions?

Answer 30

Vitamin c and iron; Thus diets including a source of vitamin C (fruits and vegetables) and iron (meat for example) are important for proper collagen synthesis.

Question 31

Where does the formation of the triple helical procollagen molecule occur?

Answer 31

RER of cytoplasm

Question 32

What final step forms collagen and where does it occur?

Answer 32

final clipping of the non-helical ends of molecule assembly of the molecules to form the fibril or other arrangements of collagen; occurs extracellularly in association with indentations (coves) of the fibroblast cell surface

Question 33

How many types of collagen are there and which are the most important?

Answer 33

28 types, 4 are most important: 1. Type I 2. Type II 3. Type III 4. type IV

Question 34

Where is collagen type I found?

Answer 34

In dermis, bone, tendons, fibrocartilage, dentin, most organ capsules. Type found in collagen fibers (90% of collagen in body)

Question 35

Where is collagen type II found?

Answer 35

Found in all cartilages. (Fibrocartilage contains both Type II and Type I)

Question 36

Where is collagen type III found?

Answer 36

Found associated with blood vessels, nerves, lymphatic and blood forming tissues, the liver, lung. Type of collagen associated with reticular fibers

Question 37

Where is collagen type IV found?

Answer 37

Associated with basement membranes (non-fibrillar) [blood brain barrier]

Question 38

identify type of collagen present

Answer 38

Collagen Type I fibers in submucosal layer of small intestine

Question 39

identify type of collagen present

Answer 39

Hyaline cartilage containing Type II collagen

Question 40

identify type of collagen present

Answer 40

Reticular fibers with Type III collagen stained with silver in lymph node

Question 41

What collagen is found in type I fibrils? What are they associated with?

Answer 41

Type V, XI, XII & XIV Type V associates with surface of Type I collagen fibrils and type XI forms the initial core of the type I fibril. Small amounts of Type III may also be found Types XII & XIV also attach to Type I fibrils and play a role in their 3D arrangement in CT

Question 42

What collagen is found in Type II fibrils? What are they associated with?

Answer 42

Collagen type IX, Associated with the surface of type II collagen fibrils forms links to other extra-cellular molecules