Unit 3 Pathophysiology - Chapter 44 Structure and fx of musculoskeletal system

Question 1

Bones function

Answer 1

1) support and protect body tissue + organs
2) imporant source of minerals and blood cells

Question 1

Bone formation

Answer 1

• starts in embryonic development with differentiation of mesenchymal cells (multipotent stem cells found in bone marrow that are important for making and repairing skeletal tissues, such as cartilage, bone and the fat found in bone marrow)
• create either chondrocytes (secrete matrix of cartilage and become embedded) and preosteoblasts (precursor to osteoblasts, important for bone formation)
• bone minerals either crystallize on a cartilage framework OR become bone-forming cells w/o cartilage

Question 2

How is bone tissue managed

Answer 2

continuously resorbed (osteoclasts break down tissue in bone and release minerals, result in transfer of calcium from bone tissue to blood) and synthesized by bone-remodeling units of osteoblasts

Question 3

receptor activator of nuclear factor kappa beta ligand (RANKL)

Answer 3

• induces osteoclast activation and bone resorption
• OPG (protein) binds to another protein called OPG ligand; this attachment acts as a decoy receptor for RANKL and blocks osteoclast activity
• results in decreased bone resorption
• BALANCE between RANKL and OPG determines bone quality

Question 4

Bone are made of?…

Answer 4

1) Compact bone tissue; highly organized into haversian (series of microscopic tubes in outermost region of bone [cortical]) that consist of concentric layers of crystallized matrix surround a central canal with blood vessels and nerves [dispered through concentric layers of matrix are small spaces w/ osteocytes – what they become when osteoblasts become embedded in matrix]
* smaller canals called canaliculi — interconnect osteocyte-containing spaces
* the crystallized matrix in spongy bone is arranged in bars or plates (spaces containing osteocytes dispersed between bars or plates and interconnectd by canaliculi)

Question 5

bone morphogenic proteins (BMPs)

Answer 5

• TGF-B superfamily
• involved in crucial fx of skeletal sys => induction, maintenance, repair

Question 6

Total number of bones in body?

Answer 6

206
* axial skeleton (approximately 80 bones; skull [cranial + facial], ears, neck, back [verterae, sacrum, tailbone], and rib cage [sternum and ribs])
* appendicular skeleton (upper and lower extremities, which include shoulder girdle and pelvis)
* bones described as long, short, flat, or irregular
* Long bones have broad end (epiphysis), broad neck (metaphysis, right under epiphysis, circumference?), and narrow mid portion (diaphysis) w/ medullary cavity

Question 7

How are bone injuries repaired?

Answer 7

1) hematoma formation provides fibrin framework for formation and organization of granulation tissue
2) Granulation tissue => provides for cartilage model for formation and crystallization of bone matrix
3) remodeling restores shape and size of injured bone

Question 8

Joint

Answer 8

• site of attachment of two or more bones; provides stability and mobility to skeleton

Classifications
1) synarthroses (immovable fixed joint between bones connected by fibrous tissue [sutures of skull, articulations between teeth and mandible, join found between first pair of ribs and sternum]
2) amphiarthroses (movable joints where surfaces of bones are connected by ligaments or cartilage – vertebral column, pelvis (pubic symphysis) in middle, cartilaginous joint that unite right and left hip bones of pelvis
3) diarthroses (articulation that permits free movement) – elbow, shoulder, ankle, most joints

Question 9

Fibrious joint

Answer 9

connected by
* dense fibrious tissue
* ligaments
* membranes

Question 10

Cartilaginous joints

Answer 10

connected by
* fibrocartilage (white fibrious tissue + cartilaginous tissue // tough and elastic) or hyaline cartilage (lines joints and caps the ends of your bones; articular cartilage; slippery smooth, translucent blue+white

Question 11

Synovial joint

Answer 11

connected by fibrous joint capsulte
* within capsulte contains small-fluid filled space; fluid in space nourishes the articular cartilage that covers ends of bones meeting in in the synovial joint
* articular cartilage is organized system of collagen fibers and proteoglycans (proteins heavily glycosylated

Question 12

Skeletal muscle

Answer 12

• millions of individual fibers
• fusiform (tapering at both ends; spindle)
• pennate (attach in slanting position)

fundamental concept
* motor unit (all muscle fibers innervated by single motor nerve)

Question 13

Muscle fibers contain?..

Answer 13

• myofibrils arranged in parallel along longitudinal axis (stacked tubes); include muscle membrane, myofibrils, sarcotubular system, aqueous sarcoplasm and mitochondria
• type I and II; depend on motor nerve innervation
• type I - slow twitching (contains more mitochondria meaning they can produce more energy and are better for long, aerobic activities
• type 2 - fast twitch, suited for short, fast bursts of activity that doesn’t require as much oxygen

1) motor neuron w/ action potential impulse
2) synaptic vesecle release ACh and reach sarcolemma
3) bind of ACh to receptor opens channel => Na+ enters sarcolemma
4) l/t action potential in sarcolemma => potential travels down t-tubules
5) calcium released from SR into sarcoplasm allowing for binding of actin and myosin
6) ca++ binds to troponin to change structure of actin
7) myosin binding sites exposed
8) binding of myosin head to actin
9) actin gets pulled towards middle of sarcomere (release ADP)
10) New ATP binds to myosin head l/t unbinding of myosin => hydrolyzed ATP => cocking of myosin head in high energy form

Question 14

Myofibrils and myofilaments

Answer 14

• major muscle proteins actin and myosin; interact to form cross-bridges during muscle contraction
• non protein constituents provide energy source for contraction and regulate:
  1) protein synthesis
  2) enzyme systems
  3) membrane stabilization
• cause sarcomere to shorten, a process now known as cross-bridge theory of muscle constraction

Question 15

Muscle contraction consist of…

Answer 15

1) excitation
2) coupling
3) contraction
4) relaxation

Question 16

Muscle strength

Answer 16

• graded by “all or nothing” phenomenon and recruitment
• speed of contraction affected by these factors

1) muscle fiber type
2) temperature
3) stretch
4) weight of load

Question 17

types of muscle contraction

Answer 17

1) isometric (tesnsion increases, muscle length remains the same, important in maintaining posture (antigravity muscle){
2) Isotonic (tension remains the same, muscle shortens, used in movement)

Question 18

skeletal muscle requires

Answer 18

• constant supply of ATP and phosphocreatine to fuel muscle contration + growth/repair
• ATP + phosphocreatine generated aerobically or anaerobically
• Phosphocreatine concentration extremely sensitive indicaotr of muscle fiber activity

Question 19

How is whole-muscle contraction accomplished

Answer 19

• one motor unit creates a phasic contraction d/t a single nerve stimulis (generate a fast transient isometric contraction)
• CNS smoothly grades the force generated by recruiting additional motor units and varying the discharge frequency of each active motor unit

Question 20

How to evaluate bone fx

Answer 20

1) gait analysis
2) urinary bone resorption markers
3) serum calcium and phopshorous levels (Calcium has an inverse relationship to phosphorus. This means that as levels of phosphorus in the blood rise, levels of calcium in the blood fall because phosphorus binds to calcium reducing the available free calcium in the blood)
4) serum bone-specific akalatine phosphate (BAP)
5) x-ray films
6) angiography
7) bone scanning
8) MRI

Question 21

Joint fx eval

Answer 21

1) arthography
2) arthoscopy
3) MRI
4) synovial fluid analysis

Question 22

Serum creatine kinase

Answer 22

• detect muscle damage
• Electromyography – assess muscle membrane’s capacity to fx
• genetic eval — muscular dystrophy

Question 23

Aging and muscle

Answer 23

• muscle bulk and strength slowly decline

Question 24

Bone and aging

Answer 24

bone remodeling cycle takes longer to complete and rate of mineralization slows (deposit into matrix)

Question 25

Exercise and aging

Answer 25

1) improve muscle strength 2) help increase bone mineral density

Question 26

sarcopenia

Answer 26

* age related loss in skeletal muscle * loss of satellite cells plays major role in development of sarcopenia