Lecture 4 - Connective Tissue

Question 1

What are the three types of connective tissue?

Answer 1

Embryonic, CT Proper, Specialized

Question 2

What are the two types of Embryonic CT?

Answer 2

Mesenchymal and Mucous

Question 3

Mesenchymal Embryonic CT

Answer 3

primarily found in embryo and derived from mesoderm. Amorphous matrix with few scattered reticular fibers and star-shaped pale staining mesenchymal cells (pluripotential)

Question 4

Mucous Embryonic CT

Answer 4

found in umbilical cord “Wharton’s jelly;” jelly-like matrix with some collagen fibers and large fibroblasts embedded.

Question 5

CT proper

Answer 5

• Loose irregular CT- loosely arranged fibers + abundant cell types; around blood vessels & below membrane.
• Dense irregular connective tissue: Abundant fibers and few cells. Pretty strong & amorphous. Few fibroblasts.
• Dense regular connective tissue: Main component of tendons, ligaments, and aponeuroses. Parallel fibers.

Question 6

Elastic tissue

Answer 6

few branching elastic fibers, sparse collagen fibers, some fibroblasts filling interstitial space; dermis, lungs, elastic cartilage, elastic ligaments, large blood vessels (forms fenestrated sheaths)

Question 7

Reticular tissue

Answer 7

network of reticular fibers (type III collagen); liver sinusoids, smooth muscle, fat, stroma of lymphatic organs, bone marrow, endocrine glands, reticular lamina of basal lamina.

Question 8

What three things make up the extracellular matrix?

Answer 8

1. Ground substance
2. Fibers
3. Tissue fluid

Question 9

Ground Substance

Answer 9

colorless, transparent gel-like mixture of glycosaminoglycans, proteoglycans, and glycoproteins; occupy space between cells and fibers; lubricant, invasion protection, compression resistant.

Question 10

Glycosaminoglycans

Answer 10

long, unbranced polysaccharides, Sulfated (-); attract H2O and provide structure and support

Question 11

Hyaluronan

Answer 11

proteoglycan monomers attach to it via link proteins = huge, hydrophilic macromolecule

Question 12

Proteoglycans

Answer 12

formed by linking GAGs with core proteins, forms a brush-like structure

Functions: water attraction and communication, different types: Aggrecan (more GAGs, holds more water), Versican (less GAGs, found in most other CT), Syndecan (Inside cell membrane)

Question 13

Multiadhesive glycoproteins

Answer 13

stabilize ECM, link it to cell surface, participate in signaling pathways of CT

• binding sites for ECM proteins.

Question 14

BM (epithelium) attaches to CT via…

Answer 14

Laminin, fibronectin, osteopontin

Question 15

Fibroblasts

Answer 15

principal cell of CT that makes collagen, elastic, and reticular fibers (reside closer to collagen)

Question 16

Which type of collagen fibers are most common in CT?

Answer 16

Type I and III

Question 17

What type of collagen is in reticular fibers?

Answer 17

Type III

Question 18

Reticular fibers

Answer 18

very thin, primarily composed of type III collagen, higher carbohydrate content than collagen fibers; framework for organs and glands; bind silver moelcules and stains black!

Question 19

Elastic fibers

Answer 19

coiled branching fibers that form loose networks; stretch 150%; composed of elastin and microfibrils of fibrillin; need special staining.

Question 20

Collagen

Answer 20

3 molecules form triple helix, assemble into fibril (not seen by LM), then fiber made of many fibrils (seen by LM)

Tensile strength

Question 21

Which Collagen type is most common?

Answer 21

Type I

Question 22

Fibrillar Collagen

Answer 22

most common (1, 2, 3, 5, 6) 68 nm banded fibers

Question 23

FACITS

Answer 23

Fibril-associated collagens with interrupted triple-helixes. Need to be present to form fibrillar collagens (IX, XII, etc). Have interruptions in their triple helixes that provide flexibility to the molecule

Question 24

Transmembrane collagen

Answer 24

Collagen XVII - Hemidesmosomes anchor epithelium to CT

Question 25

Basement membrane type of collagen

Answer 25

Type IV superstructure, Type VII anchoring

Question 26

What two things does laminin attach to?

Answer 26

Integrin receptors in the membrane of the epithelium and the underlying type IV collagen network

Question 27

Invasive breast cancer; what's important enzyme in cancer cells for invasiveness?

Answer 27

Type IV Collagenase! Type IV forms basal lamina, so breaking through the basal lamina indicates cancer cells invading into surrounding connective tissue.

Question 28

Appendectomy and scar forms for tensile strength. What is that tensile strength due to?

Answer 28

Collagen type I! Most common, holds the connective tissue together

Question 29

Where does collagen synthesis occur?

Answer 29

Fibroblasts and then in ECM

Question 30

What is the process of collagen synthesis?

Answer 30

(1) mRNA encodes each alpha chain and finished by ribosomes (2) hydroxylation of proline & lysine residues (vit C required) (3) glycosylation (4) formation of procollagen triple helix in rER and propeptides at ends to protect against degradation (5) golgi sends procollagen into ECM (6) Non-helical ends cut off = tropocollagen in ECM (7) self-polymerization of rod-shaped tropocollagen molecules into collagen fibrils.

Question 31

What causes scurvy?

Answer 31

Vit C. deficiency = poorly hydroxylated tropocollagen, which is unable to form stable triple helix or collage fibril.

Question 32

What causes osteogenesis imperfecta?

Answer 32

Type I collage mutation

Question 33

Type I Collagen

Answer 33

most common, found in connective tissue of skin, bone, tendons, ligaments = scar formation

Question 34

Type II Collagen

Answer 34

found in cartilage (hyaline and elastic), intervertebral disk

Question 35

Type III Collagen

Answer 35

reticular fibers

Question 36

Type IV Collagen

Answer 36

makes up basement membrane = support and filtration

Question 37

Type IX and XII Collagen

Answer 37

makes up FACITS; regulates type II fibrillar collagen

Question 38

Type XVII

Answer 38

Makes up hemidesmosomes

Question 39

Elastic Fibers

Answer 39

synthesized like collagen, but made of elastin and fibrillin microfibrils

Question 40

Elastin

Answer 40

an amorphous structural protein; very stretchy; produced by fibroblasts in elastic ligaments, smooth muscle cells in large arteries, chondrocytes and chondroblasts in elastic cartilage. Attach desmosomes.

Question 41

a glycoprotein that makes hairlike microfibrils; essential for elastin assembly into fibers; forms peripheral microfibrils of elastic fibers. (Can see very well in SEM!)

Answer 41

Fibrillin

Question 42

Where is elastin produced?

Answer 42

Fibroblasts

Question 43

Reticular Fibers are made of?

Answer 43

Type III Collagen

Question 44

Three types of connective tissue proper

Answer 44

1. Loose Connective Tissue 2. Dense Irregular CT 3. Dense Regular CT

Question 45

Loose Connective Tissue

Answer 45

few fibers, many cells, underlies all epithelium. Fills space btwn epithelium and dense CT, also around blood and lymphatic vessels, nerves and glands.

Question 46

Dense Irregular CT

Answer 46

most common, fibers run in different directions, few cells Found in dermis, articular capsules, periosteum, and periochondrium, and big arteries.

Question 47

Dense Regular CT

Answer 47

fiber bundles and fibroblasts in uniform parallel fashion; in tendons and ligaments only

Question 48

Adipose Tissue

Answer 48

important hormone-producing tissue and stores lipids

Question 49

White Adipose Tissue

Answer 49

nucleus squeezed off to one side, produce leptin hormone homeostasis

Question 50

Brown Adipose Tissue

Answer 50

many lipid droplets, found in hibernating animals (neck/heart/scapula)

Question 51

Mast Cells

Answer 51

Contain heparin and histamine (allergic rxns) Found near blood vessels, similar to basophils.

Question 52

Plasma Cells

Answer 52

Antibody manufacturing cells from activated B lymphocytes; responsible for humoral immunity (adaptive immune system, guided by antibodies).

Question 53

Macrophages

Answer 53

eat and present antigens to draw immune response.