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Chapter 11:

The Muscular System
There is 700 muscles in the human body

11-1
Fascicle arrangement is correlated with muscle power and range
of motion
Muscle fibers in skeletal
muscle form bundles of fascicles
...

Based on the patterns of
fascicle organization, we can
classify skeletal muscle as parallel
muscles, convergent muscles,
pennate muscles, and circular
muscles
...
Most of the muscles in the
body are parallel muscles
...
Aponeuroses) flat bands with broad attachments at each end
...
Such a muscle is a spindle shaped, with a central body, also
known as the belly
...

When a parallel muscle contracts, it shortens and gets larger in diameter
...
The muscle may pull on a tendon, an aponeurosis, or a slender band of
collagen fibers known as a raphe (e
...
pectoral muscle)
...

1

Chapter 11:

Pennate Muscles
Pennate muscle) (penna, feather) the fascicles form a common angle with the tendon
...
For this reason, they produce more tension
...

When contracted the diameter becomes smaller
...


11-2
The 3 classes of levers increase muscle efficiency
Lever) is a ridged structure-such as a board, a crowbar, or a bone
...
A lever moves by pressure (applied force)
...
Muscles provide the applied force
...
the direction of an applied force
2
...
the effective strength of an applied force
...
First-class lever: (E
...
(a pry bar) the fulcrum (F) lies between the applied force (AF) and
the load (L)
...

2
...
G
...
The weight is the load and the upward lift on the handle is the applied force
...
Third-class lever: (E
...
(a catapult) the applied force is between the load and the fulcrum
...


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Chapter 11:

11-3
Muscle origins are at the fixed end of muscles, and insertions are
at the moveable end of muscles
Origin) of the muscle
...
Typically, proximal to the insertion
...
the site where the moveable end attaches to another structure
...
Most muscles originate at a bone, but some originate at a connective tissue sheath or band
...
In complex movements,
muscles commonly work in groups rather than individually
...


•

Antagonist: is a muscle whose action opposes that of a particular agonist
...


•

Synergist: when this contracts, it helps a larger agonist work efficiently
...


•

Fixator: is a synergist that assists an agonist by preventing movement of another joint, thereby
stabilizing the origin of the agonist
...

Descriptive info for naming muscles is based on:
•

Location in the body

•

Origin and insertion

•

•

Position

•

Structural characteristics •

Fascicle organization
Action
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Chapter 11:

Location in the Body
Useful summary the designates specific regions of the body
...
Usually when a muscle is such a prominent feature
of a body region that a name referring to the region alone will identify it
...
In such case the 1st part of the name indicates the origin, the 2nd part the insertion
...
Rectus means “straight,” and rectus muscles are parallel muscles whose fibers run along the
long axis of the body
...
Deeper muscles
are termed internus or profundus
...
Muscles located entirely within an organ are intrinsic
...
Bi=2, Tri=3, Quad=4
...
For example, trapezius=triangle,
rhomboid=rhomboid, and orbicularis= circle
...
Teres muscles are both
long and round
...
Large ones are called magnus (big), major (bigger),
or maximus (biggest)
...


Action
Many muscles are named for flexor, extensor, pronator, abductor, and so on
...
For example, the extensor carpi radialis longus muscle is a long muscle along the radial
(lateral) border of the forearm, when it contracts its primary function is extension at the carpus (wrist)
...
the Axial muscles: 60% of the skeletal muscles in the body
...
the Appendicular muscles: the remaining 40% of skeletal muscle in the body
...


Reflected) term used to describe cutting pulling muscles out of the way in order to see deeper
layers of muscle tissue
...

Plexus) refers to a complex network
...
The
groups do not always have distinct anatomical boundaries
...
The Muscles of the Head and Neck
...
They are responsible for both verbal and nonverbal communication
...

2
...
This group includes numerous flexors, extensor, and
rotators of the vertebral column
...
The Oblique and rectus Muscles
...

4
...
These muscles extend between the sacrum and the pelvic
girdle
...


Muscles of the Head and Neck
We can divide muscles in the head and neck into several functional groups
...

Extrinsic eye muscles- those associated with movement of the eye
...
They are interwoven with the fibers of the
epiphysium and dermis resulting in why the skin moves when they contract
...


These

muscles restrict the opening, and other muscles move the lips or the corners of the mouth
...
(chewing, and suction)
Smaller groups of muscle control movements of the eyebrows and eyelids, the scalp, nose, and
the external ear
...
The bellies are separated by the

Epicranial aponeurosis, which is a thick, collagenous sheet
...
It extends from the base of the neck to the
periosteum of the mandible and the fascia at the corner of the mouth
...


Masseter) is large, and the strongest jaw muscle
Temporalis) this muscle assists in elevation of the mandible
...
These movements are important in making efficient use of the
teeth while chewing on various consistencies
...
Palatoglossal: originates at the palate

2
...
Genioglossus: the muscle at the chin

4
...


Pharyngeal constrictor) muscles (superior, middle, and inferior) move food (in the form of
bolus) into the esophagus by constricting the pharyngeal walls
...


Laryngeal elevator) elevate the larynx
...


Anterior Muscles of the Neck
The anterior muscles of the neck include (1) five muscles that control the position of the larynx,
(2) muscles that depress the mandible and tense the floor of the mouth, and (3) muscles that provide a
stable foundation for muscles of the tongue and pharynx
...
The other
continues from the hyoid bone to the mastoid portion of the temporal bone
...

Stylohyoid) forms a muscular connection between the hyoid bone and the styloid process of the
skull
...


Omohyoid) attaches to the scapula, the clavicle and 1st rib, and the hyoid bone
...

The superficial layer can be divided into spinalis, longissimus, and ilocostalis groups
...
When
contracting together, the erector spinae extend the vertebral column
...
In various combos, they produce slight
extension or rotation of the vertebral column
...

The muscles of the vertebral column include many posterior extensors, but few anterior flexors
...
In the neck, the longus capitis
and the longus colli muscles rotate or flex the neck, depending on whether the muscles of 1 or both sides are
contracting
...


Oblique and Rectus Muscles
These muscles lie within the body wall, between the spinous processes of the vertebrae and the ventral
midline
...

The oblique group includes scalene muscles of the neck
...

(anterior, middle, and posterior) elevate the 1st two pair of ribs and assist in flexion of the neck
...
Both groups of the
intercostal muscles aid in respiratory movements of the ribs
...

The basic pattern of musculature extends unbroken across the abdominopelvic surface
...
The rectus abdominis inserts at the xiphoid process and originates near the pubic symphysis, this muscle is
longitudinally divided by the linae alba (white line), a median collagenous partition
...

Each segment extends longitudinally, originating and inserting on the tendinous inscriptions
...


The Diaphragm
The term diaphragm refers to any muscular sheet that forms a wall
...

These muscles (1) support the organs of the pelvic cavity, (2) flex the sacrum and coccyx, and (3)
control the movement of materials through the urethra and anus
...
Its boundaries are formed by the inferior
margins of the pelvis
...
They
cover the deeper muscles that strengthen the pelvic floor and encircle the urethra
...


Urogenital diaphragm) a deep muscular layer that extends between the pubic bones
...


Pelvic diaphragm) forms the muscular foundation of the anal triangle
...


11-6
Appendicular muscles are muscles of the shoulders, upper limbs,
pelvis, and lower limbs
The appendicular musculature positions and stabilizes the pectoral and pelvic girdles and moves the
upper and lower limbs
...
the muscles of the shoulders (pectoral girdles) and upper limbs
2
...
muscles that position the pectoral girdle
2
...
muscles that move the forearm and hand
4
...
Cover the back and portions of the neck, reaching to the base of
the skull
...
They are inverted by more than 1 nerve, and for this reason specific regions can be made to
contract independently
...
It originates along the anterior surfaces of several ribs
...
It abducts
(protracts) the scapula and swings the shoulder anteriorly
...
The
subclavius muscle inserts on the inferior border of the clavicle, when contracted it depresses and
protracts the scapular end of the clavicle
...
Contraction of this muscle
generally complements that of the subclavius muscle
...
These muscles are attached posteriorly to the surfaces of the cervical and thoracic
vertebrae
...
Contraction of a rhomboid muscle adducts (retracts) the scapula on that side
...


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Chapter 11:

Muscles That Move the Arm
The muscles that move the arm are easiest to remember when they are grouped by their actions
at the shoulder joint
...


Subscapularus and the Teres major) these muscles produce medial rotation at
the shoulder
...

The deltoid, subscapularis, teres major, infraspinatus, the teres minor all originate on the
scapula
...


Pectoralis major) this muscle extends between the anterior portion of the chest and the crest of
the greater tubericle of the humerus
...


Lattissimus dorsi) extends between the thoracic vertebrae at the posterior midline and the
intertubericle groove of the humerus
...

The “pecs” and “lats” work together to produce adduction and medial rotation of the humerus at
the shouldr
...


Muscles That Move the Forearm and Hand
Most of the muscles that insert on the forearm and hand originate on the humerus, but the
biceps and triceps are noteworthy exceptions
...

the long head of the Triceps
the ulna
...

The flexor carpi ulnaris(flexes and adducts)), flexor carpi radialis,(flexes and abducts) and
palmaris longus muscles are superficial muscles that work together to produce flexion of the wrist
...


Pronator quadratus) originates on the ulna and assists the pronator teres muscle in opposing
the action of the supinator or biceps brachii muscles
...
These
large muscles end before reaching the wrist, and only their tendons croos the articulation
...


Synovial tendon sheaths) elongated bursae that reduce friction, where the tendons that cross
the posterior and anterior surfaces of the wrist pass through
...
Its a
wide band of connective tissue, that holds the tendons of the extensor muscles in place
...
Its the same as
the extensor retinaculum, but it stabilizes the tendons of the flexor muscles
...
muscles that move the thigh
2
...
muscles that move the foot and toes

12

Chapter 11:

Muscles That Move the Thigh
Gluteal muscles cover the lateral surface of the ilia
...
Its origin includes parts
of the ilium; the sacrum, coccyx, and associated ligaments; and the thoracolumbar fascia
...

The gluteus maximus share an insertion with the
...

Together these 2 muscles pull on the
...
Helps balancing on 1 foot
...


Lateral rotators) originate at or inferior to the horizontal axis of the acetabulum
...

• The Adductures originate inferior to the horizontal axis of the acetabulum
...
All the other muscles, which insert on low ridges of the posterior surface
of the femur, produce medial rotation
...

Psoas major) originates alongside the inferior thoracic and lumbar vertebrae
...
Before reaching this insertion its tendons merge with that of the
...

These 2 powerful flexors are often grouped together and collectively referred to as the
iliopsoas
...

Flexors of the knee:

• biceps femoris

┌→ These 3 muscles are often referred to as the Hamstrings

• semimembranous ┤
• semitendonousus
•

┘

They originate on the pelvic surface inferior and posterior to the acetabulum,
their contractions produce not only flexion at the knee, but also extension at
the hip
...
It inserts along the
medial surface of the tibia
...
G
...


Popliteus) small muscle that originates on the femur near the lateral condyle and insert on the
posterior tibial shaft
...

Collectively 4 knee extensors the Quadriceps femoris is made up of the

• 3 Vastus muscles

Originate along the shaft of the femur
...


• Rectus femoris muscle

Originates on the anterior inferior iliac spine and the superior acetabulum
rim—so in addition to extending the knee, it assists in flexion of the hip
...


Muscles That Move the Foot and Toes
Most of the muscles that move the ankle produce the plantar flexion involved with walking and
running movements
...
Its muscle fibers arise
from 2 heads located on the medial and lateral epicondyles of the femur just
proximal to the knee
...


These muscles are best seen in posterior and lateral views
...


Calcaneal tendon) among the largest and strongest tendons in the body
...


Fibularis or peroneus) produce eversion and extension (planter extension) at the ankle
...
The anterior tibilis muscle flexes the ankle and opposes the gastrocnemius
muscle
...
Large synovial
sheaths surround the tendons of the tibialis anterior, extensor digitorum longus, and extensor hallcis
longus muscles, where they cross the ankle joint
...

Intrinsic muscles of the foot originate on the tarsal and metatarsal bones
...


11-7
With advancing age, the size and power of muscle tissue
decreases
•
•
•
•

Summary of effects of aging on the muscular system:
Skeletal muscle fibers become smaller in diameter
Skeletal muscles become less elastic
Tolerance to exercise decreases
The ability to recover from muscular injuries decreases

11-8
Exercise produces responses in multiple body systems
•
•
•
•

The immediate effects of exercise on various body systems:
Cardiovascular system:
Respiratory system:
Integumentary system:
Nervous and Endocrine systems: (responses of other systems are coordinated through these
systems)
15

Chapter 11:

Related Clinical Terms
charley horse: common name for a muscle spasm, especially in the leg
compartment syndrome: condition in which increased pressure within the muscle compartment of a limb produces
ischemis or “blood starvation”

fibromyositis: chronic illness characterized by widespread musculoskeletal aches, pains, and stiffness, and soft tissue
tenderness

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