muscloskeletal system
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- 5 primary functions of the skeleton?
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1) support
2) protection
3) movement
4) storage
5) blood cell production - rigid, strong bone
-
well suited for bearing weight
the major supporting tissue of the body - function of cartilage?
- provides a firm, yet flexible support within certain structures (nose, external ear, rib cartilages, trachea)
- What are ligaments?
- strong bands of fibrous connective tissue that attach to bones and hold them together
- What three things include in support system of the skeleton?
-
1) rigid, strong bone
2) cartilage
3) ligaments - bone : protenction
- bone is hard and protects the organs it surrounds
- skull
- encloses and protects the brain
- vertebrae
- surround the spinal cord
- rib cage
- protects the heart, lungs, and other organs of the thorax
- What are the four things importnat in the skletal movement?
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1) skeletal muscles
2) joints
3) smooth cartilage
4) ligaments - skeletal muscles
- attach to bones by tendons
- tendons
- strong bands of connective tissue
- contraction of the skeletal muscle
- moves the bones, producing body movements
- Where are joints formed?
- where two or more bones come together
- function of joints?
- permit and control the movement between bones
- smooth cartilage
- covers the ends of bones within some joints, allowing the bones to move freely
- function of ligaments?
- allow some movement between bones but prevent excessive movements
- What are two principle minerals stored into bone?
- calcium and phosphorus
- Where is fat (adipose tissue) stored?
- within bone cavities
- many bones contain cavities filled with?
- bone marrow
- bone marrow gives rise to?
- blood cells and platelets
- three types of bone cells?
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1) osteoblasts
2) osteocytes
3) osteoclasts - What are osteoblasts?
- bone-forming cells
- primary function of osteoblasts?
- to lay down new bone
- after forming new bone, osteoblsats become what?
- osteocytes
- What does an osteoblast produce?
- type one collagen & osteocalcin
- type I collagen is responsive to?
- PTH (parathyroid hormone)
- When osteoblasts produce osteocalcin?
- when stiumulated by 1,25-dyhydroxyvitamin D
- osteocalcin
-
a calcium-binding protein
inhibit Ca-Phosphate precipitation
promotes bone resorption - osteoblasts are active on?
- on the outer surface of bones, where they form a SINGLE layer of cells
- osteoblasts bring about the formation of new bone by?
- by their synthesis of OSTEOID (non-mineralized bone matrix)
- What is osteoid?
- a protein mixture composed mainly of collagen that is secreted by osteoblasts and becomes mineralized to form bone
- What are osteocytes?
- are osteoblasts that have become imprisoned within the mineralized bone matrix
- function of osteocytes?
- help maintain bone by synthesizing new bone matrix molecules
- function of osteocytes? #2
-
not fully known
synthesize certain matrix molecules assisting bone calcification - osteocytes : nutrients
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osteocytes obtain nutrients from capillaries in the CANALICULI
help concentrate them in the matrix
help synthesize and replace needed elements of the matrix - obtaining nutrients from calillaries in the canaliculi help what?
- help to maintain mineral homeostasis with the help of the PTH and osteoblast cells
- definition of osteocyte?
- is a transformed osteoblast that is trapped or surrounded in OSTEOID as it hardens from minerals that enter during calcification
- What are osteoclasts?
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the major resorptive cells of bone
large, multinucleated cells
short life span - osteoclasts develop from?
-
1)from the hematopoietic stem cells in the bone marrow stroma and adjacent vessels
2) from mononuclear phagocytic cells - function of osteoclasts?
- to resorb (remove) bone during of growth and repair
- osteoclasts contain what?
- lysosomes (digestive vacuoles) filled with hydrolytic enzymes
- long bone
-
femur
thigh bone
humerus of arm - flat bone
- parietal bone of skull
- short bone
-
carpals of wrist
wrist bone - irregular bone
-
sphenoid bone from skull
vertebra - muscle
- consists of hundreds to thousands of muscle cells, plus connective tissue wrappings, blood vessels, and nerve fibers
- muscle are covered externally by?
- the epimysium
- fascicle
- discrete bundle of muscle cells, segregated from the rest of the muscle by a connective tissue sheath
- fascicle are surrounded by?
- perimysium
- muscle fiber
- elongated multinucleate cell; has a banded (striated) appearance
- muscle fiber are surrounded by?
- endomysium
- motor units are composed of what?
- lower motor neurons, which extend to skeletal muscles
- another name for motor unit?
- the functional unit of the neuromuscular system
- motor unit behaves as?
- a single entity and contracts as a whole when it receives an electrical impulse
- whole muscle may be controlled by?
- several motor nerve axones, which innervate many motor units within the muscle
- Does the # of motor units per individual muscle vary?
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varies greatly
(Ex) Calf - one motor axon will innervate appro. 2000 muscle fibers, out of a total of 1,200,000 muscle fibers - 2 types of muscle contraction
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1) isometric contraction
2) isotonic contraction - isometric contraction
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static or holding contraction
the muscle maintains constant length as tension is increased - example of isometric contraction
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when the arm or leg is pushed against an immovable object
the muscle contracts, but the limb does not move - isotonic contraction
- the muscle maintains a constant tension as it moves
- 2 types of isotonic contractions
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1) eccentric (lengthening)
2) concentric (shortening) - eccentric isotonic contraction
- the muscle lengthens and absorbes energy
- concentric isotonic concentration
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positive work is accomplished
energy is released to exert force or lift a weight - Do actin and myosin myofillaments change length during contraction of skeletal muscle fibers?
- NO! Instead, actin and myosin myofillaments slide past one another in a way that causes the sarcomeres to shoten.
- Whar happens during contraction?
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1) actin myofillaments at each end of the sarcomere slide past the myosin myofilaments toward the H zone
2) I bands shorten
3) A bands do not chenge - H zone during the contraction?
- the H zone narrows or even disappears as the actin myofilaments meet at the center of the sarcomere
- the last step of contraction
- as the actin myofilaments slide over the myosin myofilaments, the Z disks are brought closer together, and the sarcomere is shortened
- contracting muscle
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1) sarcomere shortens
2) actin myofilaments move toward H zone - fully contracted muscle
- sarcomere is shortened but A band width is unchanged