Download Musculoskeletal System C Background

Musculoskeletal System C Background
1.
The skeletal system
1.
Bones
1.
Axial, appendicular skeleton (Fig.36-4)
(1)
Axial = 80 bones; skull, vertebral column, thorax
(2)
Appendicular = 126 bones; upper, lower extremities; shoulder, pelvis
2.
Bones can be long, short, flat, irregular (Fig 36-2,3)
(1)
Long have diaphysis (shank), epiphysis (end); surrounded by periosteum
(2)
Diaphysis contains marrow cavity w/ fatty tissue; blood supply
(3)
Epiphysis contains red marrow (blood forming tissue)
3.
Cells of bone (Fig 36-1; Table 36-1)
(1)
Osteoblasts C form new bone
(1)
Responsive to parathyroid hormone (PTH), Vitamin D, growth factors
(2)
Mature to osteocytes
(2)
Osteocytes C surrounded by hard bone matrix
(1)
Maintain bone matrix by concentration of nutrients
(3)
Osteoclasts C major resorptive (break down + reabsorb) cells of bone
(1)
Contain lysosomes, acids that break down old bone, collagen
(2)
Important for reshaping bone
4.
Ossification = inorganic ions deposited as matrix
(1)
Calcium, phosphate, hydroxide ions form hydroxyapatite
(1)
Water-insoluble
(2)
Deposited on tensile (strong) collagen frame
(2)
Bone formation prior to birth, through growth/development
(1)
Elongation of long bones by ossification near ends
(2)
Epiphyseal plate = cartilage structure at end
(1)
ASealed@ when growth complete
(3)
Bones continually modified during life (Fig.36-5)
(1)
Result of altered patterns of weight-bearing, different stresses during
growth/development
(2)
Change in tensions generated by muscle tissue attached also affect need to
modify bone shape/strength
5.
Bones serve as source of Ca storage in body
(1)
Has exchangeable Ca (about 1% of total bone Ca)
(2)
Released w/ PTH C produced by parathyroid
(1)
PTH stimulates osteoclasts to break down bone, release Ca to blood
(2)
PTH also promotes reabsorption of Ca through kidneys
(3)
PTH also affects Vitamin D
(3)
Vitamin D (actually produced in body as hormone)
(1)
Produced in skin through UV light  activates enzyme  Vit D
(2)
Processed through liver, kidney to most active form
(3)
Promotes absorption of Ca in intestine
(4)
Depending on level, promotes bone deposition (low levels) or may
activate bone resorption (breakdown & reabsorption of bone molecules)
(high levels)
(4)
Calcitonin C produced by thyroid
(1)
Opposes PTH effects
(2)
Promotes Ca into bone from blood
(3)
Also promotes excretion of Ca through kidney
2.
Joints = articulations C where bones meet (or bone/ligament) (Fig.36-7)
1.
2.
2.
May be immovable, slightly movable, freely movable (diarthrosis)
Diarthroses are synovial (most complex). Main structures: (Fig.36-6)
(1)
Fibrous joint capsule (= articular capsule)
(1)
Made of connective tissue; innervated; vascularized
(2)
Synovial membrane C lines inner surface of joint capsule
(1)
Helps secrete synovial fluid
(3)
Joint cavity (= synovial cavity) C space formed by capsule
(4)
Synovial fluid C fills joint cavity; lubricates joint surface
(5)
Articular cartilage C covers, pads bony surfaces
(1)
Collagen, proteins, cartilage cells
The muscular system
1.
Anatomy
1.
Types
(1)
Skeletal C striated due to thick/thin filaments organized into sarcomeres; long
fibers; voluntary
(2)
Cardiac C striated; branched fibers w/ gap junctions; involuntary
(3)
Smooth C not striated with additional filament structures; long fibers; involuntary
2.
Cellular (Fig.36-12,14)
(1)
Thin filaments made of large proteins: actin, tropomyosin, troponin in helical
structure
(2)
Thick filaments made of long protein myosin; has Ahead@ region
(3)
Thick, thin filaments arranged as sarcomeres
(4)
Sarcomeres appear at intervals to make up myofibriles
(5)
Myofibriles + other organelles + sarcolemma make up muscle cell = muscle fiber
3.
Attachments
(1)
Muscle fibers bundled into fascicles, surrounded by connective tissue
(2)
Fascicles bundled into muscles, surrounded by fascia
(3)
Fascia continues beyond muscle to become tendon
(4)
Tendon attaches to bone, skin (Fig.36-16)
(1)
Attachment to 2 bones which make up joint
(1)
Muscle contraction  movement of one bone relative to the other
(so joint flexes)
(2)
Bone of muscle origin is stationary
(3)
Bone of muscle insertion moves by joint movement
(2)
Usually two muscles lie along bone
(1)
One is agonist  specific movement with contraction
(2)
Anagonist opposes; relaxes when agonist contract
2.
Physiology
1.
Neurological input (Fig.36-13)
(1)
Muscle contraction stimulated by neurological signal
(2)
Neuromuscular junction includes axon of neuron, synapse, sarcolemma with
chemical gated channels includes receptor for neurotransmitter
(3)
ACh common neurotransmitter
(1)
When bound to muscle cell receptor, signals opening of Na+ channels
(2)
Inflow of Na+  change in membrane potential of muscle  action
potential along muscle fiber
2.
Contraction (Fig.36-15)
(1)
Action potential along muscle fiber causes increased Ca inside muscle cell
(2)
When Ca incr=d in cell (enters from outside cell (cardiac, smooth) and/or released
from stores in cell (skeletal, cardiac)) it binds troponin  shift of protein
structures of thin filaments  actin binding regions exposed
(3)
Myosin Ahead@shifts, causing thick, thin filaments to slide toward each other
(activated by ATP)
(5)
Sarcomere contracts
Movement
(1)
By agonist muscle contraction coupled w/ antagonist muscle relaxation 
movement of skeletal muscles
(2)
Controlled by somatic nervous system
(4)
3.
Myosin Ahead@ binds actin in binding regions