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how many muscles are there?
about 600
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how much of our body weight are our muscles?
about half
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what are the three kinds of muscle tissue?
skeletal, cardiac, smooth
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what are muscles specialized to do?
converting the chemical energy in ATP into the mechanical energy of motion
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what is the study of the muscular system?
myology
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what are the functions of the muscles?
movement, stability, control of openings and passageways, heat production by skeletal muscles
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Muscles and movement:
- –move from place to place, movement of body parts and body contents in breathing, circulation, feeding and digestion, defecation, urination, and childbirth–role in communication
- –speech, writing, and nonverbal communications
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Muscles and stability:
- –maintain posture by preventing unwanted movements
- –antigravity muscles
- –resist the pull of gravity and prevent us from falling or slumping over
- –stabilize joints
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Muscles and control over openings and passageways:
–sphincters-internal muscular rings that control the movement of food, bile, blood, and other materials
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Muscles and heating the body:
as much as 85% of our body heat
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endomysium
- –thin sleeve of loose connective tissue surrounding each muscle fiber
- –allows room for capillaries and nerve fibers to reach each muscle fiber
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perimysium
- –slightly thicker layer of connective tissue
- –fascicles–bundles of muscle fibers wrapped in perimysium
- –carry larger nerves and blood vessels, and stretch receptors
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Epimysium
- –fibrous sheath surrounding the entire muscle
- –outer surface grades into the fascia
- –inner surface sends projections between fascicles to form perimysium
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fascia
sheet of connective tissue that separates neighboring muscles or muscle groups from each other and the subcutaneous tissueConnective
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–the effects produced by a muscle
–to produce or prevent movement
action
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muscle that produces most of force during a joint action
prime mover (agonist)
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muscle that aids the prime mover–stabilizes the nearby joint–modifies the direction of movement
synergist
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opposes the prime mover
–relaxes to give prime mover control over an action
–preventing excessive movement and injury
–antagonistic pairs-muscles that act on opposite sides of a joint
antagonist
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muscle that prevents movement of bone
fixator
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intrinsic muscle
- entirely contained within a region, such as the hand
- –both its origin and insertion there
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extrinsic muscle
act on a designated region, but has its origin elsewhere–fingers –extrinsic muscles in the forearm
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suprahyoid group
digastric, geniohyoid, mylohyoid, stylohyoid
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opens mouth widely
digastric
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depresses mandible
geniohyoid
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elevates floor of mouth at beginning of swallowing
mylohyoid
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elevates hyoid
stylohyoid
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infrahyoid group
omohyoid, sternohyoid, thyrohyoid, sternothyroid
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depresses hyoid after elevation
omohyoid, sternohyoid
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depresses hyoid and elevates larynx
thryhyoid
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depresses larynx after elevation
sternothyroid
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–encircle pharynx forming a muscular funnel
–during swallowing drive food into the esophagus
the three pairs of pharyngeal constrictors
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the three functional groups for muscles in the trunk
- –muscles of respiration
- –muscles that support abdominal wall and pelvic floor
- –movement of vertebral column
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External intercostals
- –elevates ribs
- –expand thoracic cavity
- –create partial vacuum causing inflow of air
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internal intercostals, Innermost intercostals
- –depresses and retracts ribs
- –compresses thoracic cavity
- –expelling air
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external abdominal oblique
- •Most superficial of lateral abdominal muscles
- •Supports abdominal viscera against pull of gravity
- •Stabilizes vertebral column during heavy lifting
- •Maintains posture
- •Compresses abdominal organs
- •Aids in forced expiration•Rotation at waist
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internal abdominal oblique
- •Intermediate layer of lateral abdominal muscles
- •Unilateral contraction causes ipsilateralrotation of waist
- •Aponeurosis–tendons of oblique and transverse muscles
- –broad, fibrous sheets
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transverse abdominal
- •Deepest of lateral abdominal muscles
- •Horizontal fibers
- •Compresses abdominal contents
- •Contributes to movements of vertebral column
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rectus abdominis
- •Flexes lumbar region of vertebral column
- •Produces forward bending at the waist
- •Extends from sternum to pubis
- •Rectus sheath encloses muscle
- •Three transverse tendinousintersections divide rectus abdominisinto segments –“six pack”
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Perineum
- diamond-shaped region between the thighs
- –bordered by four bony landmarks
- •pubic symphysis anteriorly
- •coccyx posteriorly
- •ischialtuberosities laterally
- –urogenitaltriangle –anterior half of perineum
- –anal triangle –posterior half of perineum
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Three layers or compartments of the perineum:
- –superficial perinealspace –three muscles•ischiocavernosus, bulbospongiosus, superficial transverse peritoneal
- –middle compartment -spanned by urogenitaldiaphragm•composed of a fibrous membrane and two or three muscles•deep transverse perinealmuscle, external urethral and anal sphincters•compressor urethraein females only
- –pelvic diaphragm–deepest layer consists of two muscle pairs•levatoraniand coccygeusSuperficial
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Male muscles-perineum
- •ischiocavernosus–maintains erection
- •bulbospongiosus–aids in erection, expels remaining urine
- •superficial transverse perineal–not always present
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Female muscles-perineum
- Middle layer of pelvic floor contains urogenitaldiaphragm and external urethral and anal sphincters
- •Deepest compartment of the perineum
- •Pelvic diaphragm –two muscle pairs
- –levatorani-supports viscera and defecation
- –coccygeus-supports and elevates pelvic floor
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STUDY
fascicle orientation of muscles, muscle attachments, facial muscles, muscles for chewing and swallowing, muscles acting on the head, etc
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