Unit 3 Pathophysiology - Chapter 44 Structure and fx of musculoskeletal system Flashcards
Bones function
1) support and protect body tissue + organs
2) imporant source of minerals and blood cells
Bone formation
- 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
How is bone tissue managed
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
receptor activator of nuclear factor kappa beta ligand (RANKL)
- 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
Bone are made of?…
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)
bone morphogenic proteins (BMPs)
- TGF-B superfamily
- involved in crucial fx of skeletal sys => induction, maintenance, repair
Total number of bones in body?
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
How are bone injuries repaired?
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
Joint
- 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
Fibrious joint
connected by
* dense fibrious tissue
* ligaments
* membranes
Cartilaginous joints
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
Synovial joint
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
Skeletal muscle
- 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)
Muscle fibers contain?..
- 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
Myofibrils and myofilaments
- 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
