Topic 5 anatomy of muscles.doc

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Anatomy and Physiology
Jacqueline Carnegie

Topic 5 Anatomy of the Muscular Systema muscle fibre is the name of a single muscle tissue cella muscle fibre contains several different levels of connective tissue wrapping1 endomysium a fine layer of connective tissue that surrounds each muscle fibre2 perimysium the sheath around a fascicle cluster of muscle fibres 3 epimysium dense fibrous CT that surroundsholds together a group of fascicles outside layer of a single muscle4 deep fascia layer of dense CT that binds muscles into functional groups ie hamstrings quadriceps etc most muscles all skeletal muscles are attached to bone or other connective tissue structures at atleast 2 pointsthe muscles origin is attached to the immovable or less movable bonethe other end of the muscle is attached to the movable bone known as the insertion most attachments are indirect attachments the muscles connective tissue wrappings extend beyond the muscle either as a roplelike tendon or a sheetlike aponeurosis muscles can only pull they never pushas a muscle shortens its insertion moves towards ots originwhatever one musclemuscle group can do another musclemuscle group can undomuscles are classified into 4 functional groups1 Prime Moversmajor responsibility is to produce a specific movementalso called an agonisteg the biceps brachii is a prime mover of elbow flexion2 Antagonistsmuscles that oppose or reverse a particular movement when a prime mover is active the antagonist muscles may be stretched or remain relaxed antagonists usually help regulate the action of a prime mover by contracting slightly to provide some resistancethis helps prevent the muscle from overshooting and acts to slow or stop movement prime movers and antagonists are located on opposite sides of the joint across which they actantagonists can also be prime moverseg the triceps brachii is an antagonist to the flexion of the forearm by the biceps brachii and is the prime mmover for extending the forearm 3 Synergistshelp prime movers by either adding a little extra force to the same movement or reducing undesirable or unnecessary movements that might occur as the prime mover contracts when a muscle crosses two or more joints its contraction causes movement at all of the spanned joints unless other muscles act as joint stabilizerseg the finger flexor muscles cross both the wrist and the interphalangeal joints but you can make a fist without bending your wrists because synergistic muscles stabilize the wrist synergists allow all of the prime movers force to be exerted in the desired direction 4 Fixators involve synergists that immobilize a bone or a muscles origin so that the prime mover has a stable base on which to act eg fixator muscles that run from the axial skeleton to the scapula can immobilize the scapula so that only the desired movements occur at the mobile shoulder joint muscles that help to maintain upright posture are also fixatorsa muscle may act as a prime mover in one movement an antagonist for another movement a synergist for another movement etc Naming Skeletal Musclesnames of skeletal muscles describes the muscle in some way1 Location of the Musclesome muscle names indicate the bond or body region with which the muscle is associatedeg the temporalis muscle overlies the temporal boneeg intercostal muscle runs between ribs2 Shape of the Musclesome muscles are named for their distinctive shapeeg deltoidtriangular muscleeg left and right trapezius from a trapezoid3 Relative Size of Musclemaximus largest minumus smallest longus long and brevis shorteg gluteus maximus and gluteus minimus 4 Direction of Muscle Fibressome names reveal the direction in which the muscle fibres and fascicles run in reference to an imaginary line usually the midline of the body or the longitudinal axis of a limb bone rectus straight refers to fibers that run parallel to the imaginary line or axis
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