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The body
I. Muscle Tissue types
all have contractile proteins in interior of cells that shorten the cell. It
is this shortening that provides the contraction force to move something.
A. Skeletal:
It is striated, multinucleated, and voluntary.
found attached to bone to move body
B. Cardiac:
Striated, uninucleate, involuntary.
Found in myocardium of the heart to move blood.
C. Smooth
Forms sheets, non-striated, involuntary, uninucleate.
Found in walls of hollow organs (blood vessels, respiratory ducts, digestive
organs, urinary organs, reproductive organs, iris of eye to move fluids or substances
in those hollow tubes.
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II. Functions of Skeletal mucular system:
1) Movement: moving the skeleton and other body parts.
2) Maintaining posture
3) Stabilize joints
4) Generate heat by shivering
III. Anatomy of skeletal muscle cell.
1. Muscle cell is covered by a membrane (sarcolemma) and contains bundles of
rod-like myofibrils inside.
2. Each myofibril (cell organelle) is composed of linearly arranged, repeating
units called sarcomeres.
3. Sarcomeres are contractile units of cell and shorten (contract) the cell
(Made up of contractile protein filaments= Actin, thin filaments; Myosin, thick
filaments )
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IV Contraction of skeletal muscle cell sarcomere requirements include:
1) nervous stimulation (electrical signal from outside the cell)
2) calcium (chemical signal throughout the cell)
3) ATP (energy source for contraction)
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Muscle power depends on the total number of muscle cells (sarcomeres) in the
muscle that are contracting at one time.
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V . Anatomy of skeletal muscle organ.
Muscles are organs with muscle cells, connective tissue membranes, nerves, arteries
and veins
A. Muscle cells are organized by connective tissue layers within the muscle.
1. Endomysium: connective tissue layer that surrounds individual muscle cells.
Connects sarcolemma to perimysium.
2. Perimysium: dense fibrous connective tissue, surrounds a group of muscles
cells (fascicle). Connects to epimysium.
3. Epimysium: dense fibrous connective tissue, surrounding the entire muscle. Connects to tendon.
4.Tendon connects to periosteum around bone. Net result-movement of the bone.
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VI. Contraction of muscle cell results in force being applied to body part.
When sarcomeres in muscle cell are contracted (contractile protein Actin sliding
over contractile protein myosin in sarcomere) then sarcolemma is moved. Sarcolemma
movement causes connective tissues layers (endomysium, perimysium, epimysium)
to be moved. Movement of epimysium, surrounding muscle, moves tendon which moves
a body part. (usally the periosteum of bone)
Role of all these layers/structures is to transmit contraction force, generated
in cell sarcomere, to the attached bone.
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VII. Connection of muscles to skeletal system
1) Insertion: the bone that moves.
2) Origin: the immovable or less movable bone.
Contraction is always a movement of insertion towards the orgin.
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VII. Interactions of Skeletal Muscles: Functional Groups
Muscles pull bones. They do not push.
There are groups of muscles with opposing actions:
- flexors and extensors
- adductors and abductors
- pronators and supinators
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A. Prime Mover/Agonist: The muscle that provides the major force
for providing a specific movement.
B. Antagonist: The muscle that opposes, or reverses, a particular movement.
If the prime mover is contracted, the antagonist is relaxed. They are usually
on the opposite side of the bone or joint.
C. Synergist: aids the agonist.
- promotes the same movement
- reduces undesirable or unnecessary movements that might occur
D. Fixator: a synergist that immobilizes a bone.
VIII. Naming Skeletal Muscles:
Information in name may include:
1) Location: (bone or body region)
Frontalis, tibialis, femoris, Temporalis, abdominis, brachialis
Superficial – externus or superficialis
Deep – internus or profundus
2) Shape of the Muscle:
Trapezius, deltoid, Serratus anterior, rhomboids
3) Relative size:
Maximus = largest
minimus = the smallest
medius = mid-size
Longus = long
brevis = short
4) Direction of Fibers:
Rectus – fibers run parallel to midline-straight
Transversus – perpendicular to midline
Oblique – diagonally or at an angle
5) Location of origin and/or insertions:
Sternocleidomastoid: origin – sternum and clavicle, insertion –
mastoid process
Mylohyoid – insertion on hyoid, origin on mandible
6) Action:
Adductor longus and adductor magnus
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Professor Thomas M. Lancraft
Human Anatomy Courses
at St. Petersburg College
St. Petersburg/Gibbs Campus
5/2006