connective tissue: collagen and the eye

Question 1

what are the four types of embryonic connective tissue?

Answer 1

1. mesenchymal
2. mucous
3. supporting
4. hematopoietic

Question 2

what is mesenchymal connective tissue?

Answer 2

• contains ground substance

- is capable of differentiating into different kinds of connective tissues

Question 3

what kind of connective tissue is the main constituent of the umbilical cord?

Answer 3

mucous connective tissue (Wharton jelly)

-cannot differentiate into different connective tissues

Question 4

what kind of connective tissue is related to cartilage and bone?

Answer 4

-supporting connective tissue

Question 5

what kind of connective tissue is suspended in intercellular fluid?

Answer 5

hematopoietic tissue

Question 6

what are fixed cells?

Answer 6

-fibroblasts that are formed and reside in the connective tissue

Question 7

what are wandering cells?

Answer 7

• cells that are not fixed and can travel within the tissue

- eosinophils, mast, and plasma cells

Question 8

what are the predominant cells in connective tissue?

Answer 8

fibroblasts

Question 9

what do fibroblasts produce?

Answer 9

-procollagen and other components of the extracellula matrix

Question 10

what are the principle fibers that are most predominant in connective tissue?

Answer 10

collagen fibers

Question 11

collagen fibers are ________ and have high _________

Answer 11

-they are flexible and have high tensile strength

Question 12

describe the collagen structure

Answer 12

• procollagen single strands combine to form triple helix collagen fibril
• multiple collagen fibrils combine to make a collagen fiber

Question 13

how many different types of collagen are recognized and what type comprises 90% of all collagen in the body?

Answer 13

• 16 types

- type 1

Question 14

what are the three categories of collagen based on molecular structure?

Answer 14

1. fibrous collagen
2. non-fibrous collage
3. filamentous collagen

Question 15

what collagen types (numbers) are included in fibrous collagen?

Answer 15

1,2,3

Question 16

are fibrous collagen thick or thin fibers?

Answer 16

thick

Question 17

what is the diameter of fibrous collagen?

Answer 17

• varies from 200nm thick on skin to 25nm thick on cornea

- the range of sizes is larger in skin than in the cornea

Question 18

what type of collagen (number) is included in non-fibrous collagen?

Answer 18

type IV

Question 19

where is non-fibrous collagen found?

Answer 19

basement membranes (cappilaries and golmerulus)

Question 20

are non-fibrous collagen thick or thin?

Answer 20

thin

Question 21

what type of collagen (number) is included in filamentous collagen?

Answer 21

types VI, VII, IX, X

Question 22

how can filamentous collagen be subdivided?

Answer 22

-into pericellular and matrix collagen

Question 23

what kind of fibers are filamentous collagen

Answer 23

-loosely aggregated fibers with little or no periodicity

Question 24

what is the cornea?

Answer 24

transparent tissue with collagen fibers that are uniform in diameter and spacial orientation

Question 25

what is the sclera?

Answer 25

- opaque tissue with thick interwoven collagen fibers - protects - collagen is structural

Question 26

what is the vitreous body?

Answer 26

-polysaccharide gel with fine collagen fibers

Question 27

why is the cornea transparent?

Answer 27

- due to the precise packing of collagen fibers or uniform diameter at a fixed distance apart - fibers are arranged in sheets and each layer sits at right angles to the next layer

Question 28

what type of collagen primarily makes up the cornea?

Answer 28

type 1 (fibrous)

Question 29

why is the sclera so strong?

Answer 29

- close interlacing of the collagen fibers - diameter of fibers vary greatly NON UNIFORMITY - DENSE IRREGULAR CONNECTIVE TISSUE

Question 30

why is the sclera so elastic?

Answer 30

-presence of small proportion of elastin fibers

Question 31

what types of collagen primarily make up the sclera?

Answer 31

type 1 and a small amount of type 3

Question 32

what contributes to structural changes in sclera to play a role in myopia and glaucoma?

Answer 32

- changes in the proportion of types of fibers by aging | - loses structural integrity

Question 33

what is the diameter of the collagen fibers in the vitreous?

Answer 33

7-13nm | -tiny tiny tiny

Question 34

what is the collagen of the vitreous embedded in?

Answer 34

hyaluronate gel

Question 35

what does the collagen of the vitreous contribute to the maintenance of?

Answer 35

- intraocular pressure | - acts as a shock absorber

Question 36

what is the function of the fine collagen fibers in the vitreous?

Answer 36

- stabilize the shape of the gel | - reduce the compressibility of the gel when exposed to external pressure

Question 37

what type of collagen primarily makes up the vitreous?

Answer 37

type 2

Question 38

what type of collagen primarily makes up the lens capsule?

Answer 38

type IV (non fibrous)

Question 39

where is descemet's membrane located?

Answer 39

under the corneal stroma

Question 40

what are the proportions/ types of collagen found in descenmet's membrane?

Answer 40

90% type 4 10% type 5 -NO FIBERS

Question 41

what is bruchs membrane?

Answer 41

-supportive structure for the retina

Question 42

what are the two basement membranes of bruchs membrane?

Answer 42

- pigment epithelial membrane on retinal side | - endothelial membrane on choroidal side

Question 43

what is between the two basement membranes of brucjs membrane?

Answer 43

loose connective tissue

Question 44

what type of collagen primarily makes up retinal basement membranes?

Answer 44

type IV

Question 45

type VI collagen is a major component of the ___________ of the ____________

Answer 45

-major component of the extracellular matrix of the human cornea

Question 46

type VI collagen is distributed throughout what?

Answer 46

corneal stroma

Question 47

where is type VIII found? what does it play a role in?

Answer 47

- found in vivo in descemet's membrane | - plays a role in structure of basement membrane

Question 48

what synthesizes type VIII collagen?

Answer 48

-corneal endothelial cells

Question 49

the vitreous contains about three times more type ____ collagen than cartilage?

Answer 49

IX

Question 50

what is keratoconus?

Answer 50

- problems with collagen of the cornea - weakened cornea bulges - reduced VA

Question 51

the size of the diameter of the collagen fibers plays and important role in...

Answer 51

the transparency of the corneal tissue

Question 52

what plays an important role in corneal strength?

Answer 52

- cross linking of the collagen fibers | - more cross linking=stronger