Chapter 38: Tissues of the Musculoskeletal System Flashcards
Where do mesenchymal cells come from?
Embryonic mesoderm
What is the most abundant protein in the body?
Collagen
What is the difference between a homotypic and heterotypic collagen?
Homotypic (2/3) - 3 identical alpha chains
Hetero (5) - 3 different alpha chains
What is the most abundant GAG in the body?
chondroitin
MMP are a large family of endopeptidases that are dependent on what element?
Zinc
What is the monometric component of elastin?
Tropoelastin
Incorporation of tropoelastin into nascent elastic fibers involves what two process?
coacervation and cross-linking
What is coacervation?
Temperature dependent alignment and macromolecular assembly of tropoelastin monomers
Elastic fibers can undergo elastic deformation to what % of their resting length?
70%
Elastic fibers can undergo maximal extension of what % before loss of strength?
220%
What cells are a common source of elastase activity and elastic fiber degradation?
Neutrophils - hence why degredation occurs commonly in the setting of acute inflammation
How many latent transforming growth factor (TGF)-B binding proteins (LTBPs) are there?
4
Cartilage is what % collagen by dry weight? What type of collagen is predominant?
50%!
Type II collagen most common
Bone matrix is 90% what type of collagen?
Type 1
What are the zones of cartilage from surface to deep?
(surface)
Zone 1 / superficial
Zone 2 / transitional
Zone 3/ radiate
Tide Mark
Zone 4 / mature, calcified cement line
Fibrocartilage is mostly what type of collagen?
Type 1 with small amounts proteoglycans
What are tendons?
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
What are the three forms of tendons?
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)
What are ligaments?
Connective tissue bands that connect bone to bone.
Are the components of tendons and ligaments similar?
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
How are larger diameter collagen fibers different from smaller diameters?
Larger dia. = stiffer
Smaller dia. = viscoelastic
** healed tendons have more small fibers = less strong
True or false: Skeletal muscle is the largest organ in the body?
True
The basic unit of skeletal muscle is the myofiber. Describe it’s composition?
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.
The I-band of the sarcomere is made up of what?
The Z and A bands?
I band: terminal portions of the actin filaments on adjacent sarcomeres
Z and A- bands: myosin
What are the two basic muscle fiber types?
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
