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Muscles
function, actions and
identification of
major superficial muscles, some
conditions and treatments
types of muscles
Three structurally and functionally
distinct types of muscle are found in
vertebrates:
1. smooth muscle,
2. skeletal muscle and
3. cardiac muscle.
functions of skeletal muscles
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movement
posture
heat production
shape
facial expressions
chewing, swallowing
reflexes
naming skeletal muscles
Skeletal muscles are named according to
structural and/or functional characteristics.
• Location - temporalis (temporal bone) and
tibialis anterior (front of tibia)
• Size - maximus (largest), minimus (smallest),
longus (longest), brevis (shortest)
• Shape – deltoid (triangular), trapezius
(trapezoid), serratus (saw-like edge)
more on naming muscles
• Direction of fibers – rectus (parrallel to
midline), transverse (perpendicular to
midline), oblique (diagonal to midline)
• Number of origins – biceps (2), triceps (3),
quadriceps (4)
• Origin and insertion – sternocleidomastoid is
named for the two places of origin as well as
its insertion.
• Action – what the muscle does when “at
work.”
actions of
skeletal muscles
• flexion-movement
that decreases
the angle @ a
joint
• extensionmovement that
increases the
angle @ a joint.
abd and add
• abductionmovement of an
appendage away
from the midline.
• adductionmovement of an
appendage towards
the midline.
rotation
• rotation -turning
around the
longitudinal axis @ a
joint. Can only occur
at a pivot (radio-ulna /
neck) or ball & socket
(shoulder / hip) joint.
• circumduction-Is a
movement found @
ball & socket (hip &
shoulder) and
condyloid joints (wrist
/ ankle / knuckles).
supination - pronation
• supination -medial
rotation of the
forearm at the Radio
Ulna joint, so the
palms face up.
• pronation -Lateral
rotation of forearm
at the Radio Ulna
joint, so the palms
face down.
inversion - eversion
• inversion - twisting of the
foot so that the sole faces
inward.
• eversion - Twisting of the
foot so that the sole faces
outward.
dorsiflexion and
plantar flexion
dorsiflexion – toe
towards the knee
using tibialis
anterior
plantar flexion –”point
toes” using
gastrocnemius
shoulder girdle
movements
elevation - Upward movement of the
shoulder girdle.
depression - Downward movement of
the shoulder girdle..Depression
protraction and retraction are all
movements associated with the
shoulder girdle.
movements
1. Lateral rotation
2. medial rotation
3. Supination
4. Pronation
5. Eversion
6. Inversion
7. Adduction
8. Abduction
What do you know
about these muscles?
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Flexor carpi ulnaris
Extensor carpi radialis
Latissimis dorsi
Transversus abdominis
Rectus femoris
Deltoid
Trapezius
Orbicularis oris, Orbicularis oculi
Sternocleidomastoideus
skeletal muscle facts
• Skeletal muscle consists of very long
tubular cells. The average length of skeletal
muscle cells in humans is about 3 cm
(sartorius muscle up to 30 cm, stapedius
muscle only about 1 mm). Their diameters
vary from 10 to 100 µm.
• Skeletal muscle fibres contain many
peripherally placed nuclei.
Up to several hundred rather small nuclei with
1 or 2 nucleoli are located just beneath the
plasma membrane.
facts, continued
• Skeletal muscle fibres show in many
preparations characteristic crossstriations. It is therefore also called
striated muscle.
• Skeletal muscle is innervated by the
somatic nervous system.
• Skeletal muscle makes up the
voluntary muscle.
what students of anatomy
learn about the skeletal
muscles
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over 600 named muscles in human
makes up 40-50% of body weight
the physiology of muscle action
name, location, action, origin, insertion
and often the nerve that serves the
muscle
striated
muscle tissue
the players
myofibrils contract
instantly if ATP and
Ca2+ is added to them,
meaning that it is these
single myofibrils which
are the force
generators in muscle
cells.
sarcomere
Striated sarcomeres are separated by Z-discs. Two Z-discs
bound a sarcomere in the direction of stretching. Thin
filaments made of Actin are attached to each of these discs
and extend towards each other inside the sarcomere. They
do not overlap in the sarcomere’s striated form. In this case
there is a dark band visible between the Z-discs. This is
made up of the thick Myosin filaments which overlap
partially with the thin Actin filaments which extend into a
light half of the I-Band region left and right of the dark Aband.
contraction = shorten
When Myofibrils contract the thin and thick filaments move
past each other. Each sarcomere unit of the myofibrils
shortens proportionally to the muscle contraction. Upon
contraction, it is the light bands which shorten whereas
the dark bands do not change in length. This is explained
by the Actin filaments sliding into the dark region of
Myosin filaments.
thick and thin
Actin - the thin
filaments
Myosin - the thick
filaments
structure
of skeletal muscle
contraction
During contraction, actin fibers are
pulled inward
a) pulling is by "hooks" on myosin
(myosin heads)
b) hooks bend, using energy of ATP
c) each hook pulls, releases, pulls
again until muscle is contracted
d) calcium (Ca2+) ions signal this to
start
-Ca2+ into muscle starts
contraction
-during relaxation, Ca2+ is
transported out
nerves
and muscles
muscle ends
• origin-stationary
end, the anchor
• insertion- moved
end
• belly- the area in
between
CAUTION
NOTE: These pictures are intended to
provide a virtual tour of the lab models and
specimens. They are not intended to
substitute for classroom/lab learning. They
are simply supplemental material for you
to use as reminders of what you should
study or have already studied.
superficial muscles
Muscles which occupy the layer closest
to the surface of the skin are called
superficial muscles. These are easily
displayed on a person who has
developed their physique for show or
physical performance.
major muscles of face
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frontalis
orbicularis oculi
nasalis
temporalis
orbicularis oris
zygomaticus major
masseter
mentalis
levator labii superioris
Facial muscles around the mouth,
directions of muscle contraction
A levator labii superioris
B zygomaticus minor
C zygomaticus major
D risorius
E depressor anguli oris
F labii inferioris,
G orbicularis oris
muscles of mastication
• temporalis
• medial and lateral
pterygoids
• masseter
masseter
masseter and
directions of the lower
jawbone movement
sternocleidomastoid
sternocleidomastoid
muscle is the main
muscle on the side of
the neck.
neck pain
The trapezius muscle is the one
that tenses up most often. When
you see people reaching back to
massage their shoulders, it is the
trapezius muscle that they are
trying to loosen.
The other two muscles that have a
tendency to tighten up are the
sternocleidomastoid (often called
the sterno-mastoid) and the
scalene muscles.
Keep it Moving! The neck is by far
the most mobile portion of the
spine. Its ROM is generally 70 to 90
degrees.
bones of the neck, review
The bones of the neck are called the cervical
vertebrae.
Every mammal on earth, even the giraffe, has
7 of them. In humans, the cervical vertebrae
are obviously a lot smaller than those of
giraffes. They are also a lot smaller than the
vertebrae of the other areas of the human
spine.
neck pain?
Our necks need to use their mobility in order
to maintain it. They work best when they can
consistently move into and out of their full
range of motion in a gentle - that is, not a
jarring - way.
non-used necks = injuries
We rotate our necks fully when we look over our
shoulder and then back the car down the driveway.
We extend our necks completely when we look up
at the ceiling.
The fact that we do not do these things often is one
of the major reasons why our necks cause us
problems. On occasion, when it’s essential for the
neck to move to an extreme range of motion, it
can’t cope with the job. That’s when injuries occur.
muscles of the back
trapezius
The trapezius covers a
large section of the
upper back. It conceals
the upper part of the
shoulder blade.
latissimus dorsi
• The latissimus
dorsi occupy the
middle back on
either side.
• The gluteus
maximus make up
the back of the
buttocks.
abdominal muscles
4 muscles of the abdominal
area
rectus abdominis
external oblique
internal oblique NS
transversus abdominis NS
muscles of the arm
superficial muscles of the
chest and front of the arm.
• The shoulder muscles are
called deltoids. These
triangular muscles define
the upper shoulders
• biceps brachii are easily
recognizable large bumps
on the upper inside of the
arm
• The pectoralis muscles
span the chest
superficial muscles of the
posterior arm
triceps brachii –
extends the arm,
straightening the
elbow
leg muscles
anterior muscles of the thigh
• Quads: extensor of
knee
rectus femoris
vastus lateralis
vastus medius
vastus intermedialis
• sartorius: cross leg
• gracilis: adducts
leg
posterior muscles of the thigh
The hamstring muscle
group comprises three
muscles –
1. biceps femoris
2. semitendonosus
3. semimembranosus
The action of these
muscles is to bend the
knee and extend the
hip.
adductors of the thigh
adductor magnus,
longus, brevis and the
pectineus, make up the
adductor group.
Groin pulls are a strain at
the attachment of the
adductors to the pubic
bone.
major muscle of lower leg
- anterior
• tibialis anterior: flexes the
foot – pulls foot toward the
knee
muscles of lower leg posterior - calf muscles
gastrocnemius is the
calf muscle which
are each divided into
two hemispheres.
soleus
soleus and Achilles tendon
This picture illustrates
the relationship
between the superficial
gastrocnemius muscle,
the deeper soleus
muscle and the large
Achilles tendon which is
visible attaching to the
heel.
atrophy - hypertrophy
• no use
• average use
• increased use
muscle twitch
• cycle of contraction
and relaxation
• latent phase
tetany
Tetany-stimuli is so fast
that muscle cannot relax
- stays contracted
(tetanus - bacterial toxin
interferes with motor
neuron function,
uncontrolled stimulation)
chondromalacia
(runner's knee)
Wearing away and/or softening of the
articular cartilage, tissue that covers
and protects the underside of the
patella, the bottom end of the femur,
and top end of the tibia. It absorbs
stress to the knee joint and allows the
patella to track smoothly in its femoral
groove.
Causes: Typically, excessive running
Symptoms: Pain around the patella
(kneecap), usually occurring on the
medial (inner) side and below (inferior
aspect of the patella).
doctor and PT
• Recommended Treatment: R.I.C.E. - Rest, Ice,
Compression, Elevation. Reduce activity to promote
healing. Avoid downhill runs especially. Strengthen
surrounding muscles with a professionally
recommended program. Apply Ice for 10-15 minutes
after each workout to reduce inflammation and pain. (If
any skin irritation or adverse reaction occurs due to
icing, see your medical doctor). A proper stretching
(Quadriceps, Iliotibial Band) routine is highly
recommended pre and post workouts. As with any
orthopedic injury, a consultation with a sports medicine
professional is recommended.
hamstring strain/tear
occurs when excessive or repetitive
stress causes tearing of the muscle
fibers in the hamstring.
Causes: Tight hamstring muscles,
muscle imbalance, sudden movement,
and repetitive strain are all common
types of hamstring injuries.
Symptoms: A sharp pain may be felt
in the hamstring when a serious strain
or tear occurs. This often happens
during such action as an explosive
move in basketball or a quick sprint. If
you feel a deep ache in the hamstring
area it may be a less severe strain or
minor tear.
intramuscular injection
intramuscular
injection delivers
medicine directly
into the muscle
deltoid
gluteus medius
injections
Intramuscular injections are the deepest injection
type, delivering the medication into the muscle
tissue. Most vaccines are currently delivered to the
intramuscular depth.
Subcutaneous injections are delivered to the
adipose (fat) layer just below the skin. Many
therapeutic proteins are delivered to the
subcutaneous depth, such as human growth
hormone.
Intradermal injections are very shallow injections
that deposit the medication between the layers of
the skin. Many new DNA-based vaccines are
delivered to the intradermal layer.
muscular disorders
• Atrophy
– decrease in size of muscle fibers
– Disuse atrophy - bedridden individuals, casts
– Denervation atrophy - loss of nerves and muscle
function
• Muscular Dystrophy - (Duchenne MD)
Loss of muscle fibers
Linked to young males (ages 3-5)
Lacking certain protein thus allows too
much Ca+ into cell this leads to cell death
and replacement with scarring
muscular disorders
• Myasthenia gravis
– autoimmune disease
– antibodies bind to ACh receptors
– atrophy of muscle fibers
– drugs that keep levels of ACh high are
used
what happens in rigor mortis?
Ca++ pumps run out of ATP
Ca++ cannot be removed
continuous contraction
eventually tissues break down
muscles of the face, review
references
Link Publishing
www.linkpublishing.com
Texas Tech University
www.biol.ttu.edu/Z2403/large%20A&P%20pics
humanback.htm
PE World
http://www.peworld.org/anatomy/muscles.htm
Pro Tech Athletics
www.pro-tecathletics.com/ kneeinjuries.htm
Insite Fitness
www.insitefitness.com.au/