Chapter 11
Muscular System
I.
Lever systems: bone-muscle
relationships
The joints act as a fulcrum (a fixed point
at which a lever moves) the bones
act as levers (rigid bars) and the
muscle contraction provides the
effort (force in opposing direction to
the load). What ever weight or
object the muscle is trying to move
is the load.
A. The distance of the load and
effort from the fulcrum determines if
there is mechanical advantage (not
much effort is needed) or
mechanical disadvantage (much
effort is needed).
B. See page 257 on the types
of levers.
Effort is farther from the joint
and load= mechanical
advantage. Average speed
and mobility.
Effort (muscle
insertions) is further
from the joint than is
the load. Slow,
stable, and can bear
a lot of weight.
Effort lies between the
joint and the load. Fast
and moveable but less
force. Most common
body lever system.
• II. Arrangement of fascicles in muscles
– Fascicles can be seen with the naked eye, these are arranged
in different patterns, this pattern influences the muscles
function.
• A. Parallel-fascicle axis is parallel to muscle, belly is flanked
by tendons. The muscle may be strap like
(sternocleidomatoid) or fusiform (biceps)
• B. Convergent-broad muscle origin with fan shaped fascicles
that converge at one tendon and resemble a triangle
(Pectoralis major)
• C. Pennate- fasciles are arranged along the length of a
tendon, structure resembles a feather.
1. unipennate- fascicles are on one side of the tendon
only(flexor pollicis longus)
2. bipennate-fascicles are on both sides and the
tendon runs down the middle (bicep femoris), also
one of the strongest types of muscles.
3. multipennate- multiplebipennates arranged side by
side and end up connecting to one tendon. Is
considered one of the strongest types of muscles.
• D. Circular- fascicles are arranged in concentric rings, these
are found at the opening of an organ, may be called
sphincter or orbicularis
• IV. Naming the skeletal musclesA. Location- names relates to region of the body in
which the muscle is located.
B. Shape- some muscle are named after geometric
figures they resemble
C. Relative size of the muscle- muscle length or
relative size may make up the name such as maximus,
minimus, longus, breves.
D. Diretion of the fascicles and muscle fibers- the
name may refer to the direction of the fibers in
relationship to the body midline (rectus- parallel,
oblique- at a right angle)
E. Location of attachment- name may incorporate
the origin and insertion (sternohyoid)
F. Number of origins- a name that has a numerical
prefix refers to the number of origins, such as the biceps,
triceps, quadriceps, ect.
G. Action- name may reveal the action the muscle
takes at that joint such as flexor, extensor.
III. Interactions of skeletal muscles in
the body
Muscles work in opposing groups and
are arranges in opposite sides around
a joint. The action they perform
determines their functional types.
A. Agonist (prime mover)produces the movement (example:
joint flexor-bicep).
B. Antagonist- performs that
opposite action as the agonist but
remains relaxed or stretched while
agonist is contracting (example: joint
extensor-tricep)
C. Synergest- a muscle that
works with an agonist to stabilize a
joint or reduce unnecessary action at a
particular joint. Fixators hold a bone in
place to provide a stable base for an
agonist.
• V. A development-based organization of muscles• All muscles develop from the mesoderm germ layer which folds into
sections called myotomes and somitomeres. There are four major
groups:
• 1. visceral organ musculature- this includes the development of
smooth and cardiac muscle. Most often smooth muscle is called
visceral muscle because it is found in abdominal viscera. However
cardiac muscle also makes up an organ and thus is visceral muscle.
• 2. pharyngeal arch muscles- these developed around the embryonic
pharynx and include muscles of facial expression, chewing,
swallowing, and some head neck muscles.
• 3. axial muscles- these developed from some somitomeres and
myotomes they include all throrax and abdominpelvic muscles as
well as back, neck, and eye muscles.
• 4. limb muscles-developed from myotomes near the budding limbs,
includes all muscles of superior and inferior limbs.
• MUSCLE FIGURES
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HEAD
FACE
NECK
ANTERIOR THORAX
POSTERIOR THORAX
Web link on muscle
drawings:
www.gpc.edu/~jali
ff/anahumus.htm
Anterior View of Facial Muscles
Muscles that move the eye
Chapter 16 picture- pg 486
Muscles used for mastication and jaw movement
Muscles that move the tongue for ingestion and
speech
Muscles involved in swallowing
Anterior View of Neck Muscles
Cadaver picture showing neck muscles
Lateral view of neck muscles
The largest and most superficial back muscles are the
trapezius and latissimus dorsi. The Rhomboids are
superficial to the erector spinae muscles.
Anterior Thorax: Chest
Serratus Anterior and Intercostal muscles
Subscapular Fossa
Serratus
Anterior
Top view of the pelvic floor and other
muscles inside the pelvic bone
SHOULDER, ARM, AND FOREARM
• Muscles that move the scapula (shoulder movement)
– Pectoralis minor, Serratus anterior,
– Trapezius, Levator scapulae, Rhomboid major and minor,
• Muscle that move the humerus (arm movement)
– Subscapularis, pectoralis major, deltoid, coracobrachialis,
– Latissimus dorsi, Teres major & minor, Supraspinatus, Infraspinatus
• Muscles that move the ulna & radius(forearm movement)
– Biceps Brachii, Brachialis, Brachioradialis, pronator teres, pronator
quadratus
– Triceps Brachii, anconeus, supinator,
• Muscles that move the carpals, metacarpals, & phalanges
(hand movement)
– Flexor carpi radialis, plamaris longus, flexor carpi ulnaris, flexor
digitorum superficialis and profundus, flexor pollicis longus
– Extensor Carpi radialis longus and breves, Extensor digitorum, Extensor
carpi ulnaris, abductor pollicis, extensor pollicis longus flexor pollicis, and
brevis, Extensor indicis
Muscles that move the scapula and arm at the
shoulder
Bicep Brachii and Brachialis
www.rci.rutgers.edu/~uzwiak/AnatPhys/
APFallLect15.html
www.rci.rutgers.edu/~uzwiak/AnatPhys/APFallLect15.html
www.american.edu/adonahue/m9arm.htm
Supinator, Pronator Teres, Pronator
Quadratus
Extensor Muscles- Posterior View
of forearm
Hip, Knee, Ankles, and Toes
•
•
•
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HIP or THIGH
Knee or LEG
Ankle
Toes
Adductor
Brevis
Gracilis
Gluteal
Muscles
www.preventdisease.com/home/muscleatlas/214.html
Deep Hip muscles