Chapter 38: Tissues of the Musculoskeletal System

Question 1

Where do mesenchymal cells come from?

Answer 1

Embryonic mesoderm

Question 2

What is the most abundant protein in the body?

Answer 2

Collagen

Question 3

What is the difference between a homotypic and heterotypic collagen?

Answer 3

Homotypic (2/3) - 3 identical alpha chains
Hetero (5) - 3 different alpha chains

Question 4

What is the most abundant GAG in the body?

Answer 4

chondroitin

Question 5

MMP are a large family of endopeptidases that are dependent on what element?

Answer 5

Zinc

Question 6

What is the monometric component of elastin?

Answer 6

Tropoelastin

Question 7

Incorporation of tropoelastin into nascent elastic fibers involves what two process?

Answer 7

coacervation and cross-linking

Question 8

What is coacervation?

Answer 8

Temperature dependent alignment and macromolecular assembly of tropoelastin monomers

Question 9

Elastic fibers can undergo elastic deformation to what % of their resting length?

Answer 9

70%

Question 10

Elastic fibers can undergo maximal extension of what % before loss of strength?

Answer 10

220%

Question 11

What cells are a common source of elastase activity and elastic fiber degradation?

Answer 11

Neutrophils - hence why degredation occurs commonly in the setting of acute inflammation

Question 12

How many latent transforming growth factor (TGF)-B binding proteins (LTBPs) are there?

Answer 12

4

Question 13

Cartilage is what % collagen by dry weight? What type of collagen is predominant?

Answer 13

50%!
Type II collagen most common

Question 14

Bone matrix is 90% what type of collagen?

Answer 14

Type 1

Question 15

What are the zones of cartilage from surface to deep?

Answer 15

(surface)
Zone 1 / superficial
Zone 2 / transitional
Zone 3/ radiate
Tide Mark
Zone 4 / mature, calcified cement line

Question 16

Fibrocartilage is mostly what type of collagen?

Answer 16

Type 1 with small amounts proteoglycans

Question 17

What are tendons?

Answer 17

Dense bands of collagen rich fibers that connect muscle to bone or muscle to muscle

Their function is to transfer force of muscle contracture to skeleton
Some have a vascular synovial sheath and some do not

Question 18

What are the three forms of tendons?

Answer 18

Aponeuroses - flattened structures that connect muscles to bones or other fascial elements (fascia of biceps femoris)
Positional tendons - discrete and stiff structures that transfer muscular forces to bones (infraspinatus, DDF)
Energy storing tendons - have a greater elastic content to respond to weight bearing by elastic recoil (common calcanean tendon)

Question 19

What are ligaments?

Answer 19

Connective tissue bands that connect bone to bone.

Question 20

Are the components of tendons and ligaments similar?

Answer 20

Yes.
Elongated fibroblastic cells aligned with collagen fibers interconnected through cytoplasmic connections
Extracellular matrix is dense type I collagen
Very strong longitudinally but not stiff in transverse loading

Question 21

How are larger diameter collagen fibers different from smaller diameters?

Answer 21

Larger dia. = stiffer
Smaller dia. = viscoelastic

** healed tendons have more small fibers = less strong

Question 22

True or false: Skeletal muscle is the largest organ in the body?

Answer 22

True

Question 23

The basic unit of skeletal muscle is the myofiber. Describe it’s composition?

Answer 23

Made of myofibrils that are tandem arrays of contractile units called sarcomeres.
Sarcomeres are made of parallel arrays of overlapping actin and myosin filaments
Individual sarcomeres are terminated by Z bands with a central A band composed of tails of myosin proteins.
The sarcolemma is the cell membrane of the myofiber.

Question 24

The I-band of the sarcomere is made up of what?

The Z and A bands?

Answer 24

I band: terminal portions of the actin filaments on adjacent sarcomeres

Z and A- bands: myosin

Question 25

What are the two basic muscle fiber types?

Answer 25

Type I - slow twitch, rich in mitochondria, for sustained low-force contraction and oxidative metabolism

Type II - Fast twitch, fewer mitochondria, more myofibrils, for transient high-force contraction, glycolysis