Muscular System: Gross Anatomy of Skeletal Muscles

connective tissue sheaths

endomysium, perimysium, epimysium

-all come together to form attachment to bone

-tendons are dense regular CT

endomysium

loose connective tissue wrapping each muscle fiber

perimysium

dense regular connective tissue that surrounds each fascicle (group of muscle fibers)

epimysium

dense irregular connective tissue surrounding entire muscle

nerves and blood vessels of a skeletal muscle

-each skeletal muscle is supplied by branches of one primary nerve, one primary artery, and one or more veins

-smallest nerve branches serve individual muscle fibers to form the neuromuscular junction

muscle attachments

-most skeletal muscles run from one bone to another

-one bone will move (insertion) the other remains fixed (origin)

-attach to origin and insertion by connective tissue (direct or indirect)

origin

less movable attachment

insertion

more moveable attachment

movement/action of muscle

insertion bone pulled into origin bone

direct (fleshy) attachments

epimysium directly attached to periosteum

indirect attachments

-tendon

-aponeurosis (sheet-like tendon, ie. thoracolumbar fascia)

-raphe (seam-like tendon, ie. linea alba)

fascicle arrangements

-bundles of muscle fibers

-arrangement tells about the action of a muscle: amount of movement, amount of force

-includes: circular, convergent, parallel (strap-like or fusiform), pennate (uni, bi, multi)

circular fascicle arrangement

-surround external body openings

-sphincter = general name for circular muscle

-ex: orbicularis oris and oculi

convergent fascicle arrangement

-origin of muscle is broad, fibers taper as approach insertion

-both force and range of motion benefit

-ex: pectoralis major

parallel fascicle arrangement: strap-like

-every fiber parallel and about the same length

-range of motion benefit

-ex: SCM, gracilis, sartorius

parallel fascicle arrangement: fusiform

-with expanded central belly

-range of motion and force production benefit

-ex: biceps brachii

pennate fascicle arrangement

-feather-like, short fascicles attach obliquely to tendon

-unipennate, bipennate, multipennate

pennate fascicle arrangement: unipennate

-fibers come from one side

-ex: flexor pollicis longus

-range of motion and force benefit

pennate fascicle arrangement: bipennate

-fibers anchor to both sides

-ex: rectus femoris

-range of motion and force benefit

pennate fascicle arrangement: multipennate

-multiple bipennate arrangements

-ex: deltoid

-force benefit

functional groups of skeletal muscles

prime mover, antagonist, synergist

prime mover (agonist)

major responsibility for certain movement

antagonist

opposes or reverses a movement

synergist

helps prime mover

-adds extra force

-reduces undesirable movements

-fixator (holds bone firmly in place)

a muscle that crosses on the anterior side of a joint produces...

flexion

-exception: knee

a muscle that crosses on the posterior side of a joint produces...

extension

a muscle that crosses on the lateral side of a joint produces...

abduction

a muscle that crosses on the medial side of a joint produces....

adduction

skeletal muscles can be named according to....

location, shape, relative size, direction of fascicles and muscle fibers, location of attachments, number of origins, actions

naming: location

ex: brachialis on the arm, intercostals between ribs

naming: shape

ex: quadratus femoris is 4-sided, deltoid triangular

naming: relative size

ex: maximus, minimus,

ex: longus, brevis

naming: direction of fascicles and muscle fibers

-oblique: lie at oblique angle to midline (ex: external oblique)

-transversus: lie at right angle to midline (ex: transversus abdominis)

-rectus (straight): parallel to the body midline (ex: rectus abdominis)

naming: location of attachments

-name reveals point of origin and insertion

-ex: coracobrachialis

naming: number of origins

-ex: biceps- two origins

naming: actions

-indicates type of muscle movement

-flexor, extensor, adductor, abductor