Chapter 11:
The Muscular System
Biol 141 A&P
The Muscular System
• Consists only of skeletal muscles
• How are fascicles arranged in the
various types of muscles, and what
are the resulting functional
differences?
Muscle Organization
and Function
• Muscle organization affects power, range,
and speed of muscle movement
Fascicles
• Muscle cells (fibers) are organized in
bundles (fascicles)
Classification of Skeletal Muscles
• By the way fascicles are organized
• By relationships of fascicles to tendons
Organization of
Skeletal Muscle Fibers
• 4 patterns of fascicle organization:
• 1) Parallel– Fibers parallel to the long axis of muscle
- e.g., biceps brachii
• 2) Convergent• 3) Pennate• 4) Circular-
Parallel Muscles
Figure 11–1a
Parallel Muscle Body
• The center or body of the muscle thickens
when parallel muscle contracts
• Parallel muscles contract about 30%
Parallel Muscle Tension
• Depends on total number of myofibrils
• Directly relates to cross section of muscle
• 1 in.2 (6.45 cm2) of cross section develops
50 lb (23 kg) of tension
Convergent Muscles
Figure 11–1b
Convergent Muscles
• A broad area converges on attachment
site (tendon, aponeurosis, or raphe)
• Muscle fibers pull in different
directions, depending on stimulation
• e.g., pectoralis muscles
Pennate Muscles
Figure 11–1c, d, e
Pennate Muscles
• Unipennate:
– fibers on 1 side of tendon
– e.g., extensor digitorum
• Bipennate:
– fibers on both sides of tendon
– e.g., rectus femoris
• Multipennate:
– tendon branches within muscle
– e.g., deltoid
Pennate Muscles
• Form an angle with the tendon
• Do not move as far as parallel muscles
• Contain more myofibrils than parallel
muscles
• Develop more tension than parallel
muscles
Circular Muscles
Figure 11–1f
Circular Muscles
• Also called sphincters
• Open and close to guard entrances of
body
• e.g., obicularis oris
Skeletal Motion
• Skeletal muscles attach to skeleton,
produce motion
• Type of muscle attachment affects
power, range, and speed of muscle
movement
What are the classes of
levers, and how do they make
muscles more efficient?
Levers
• Mechanically, each bone is a lever (a
rigid, moving structure):
– and each joint a fulcrum (a fixed point)
• Muscles provide applied force (AF):
– required to overcome resistance (R)
Functions of a Lever
• To change:
– direction of an AF
– distance and speed of movement
produced by an AF
– effective strength of an AF
3 Classes of Levers
• Depend on the relationship between
applied force, fulcrum, and resistance:
– first class
– second class
– third class
PLAY
First, Second, and Third-Class Levers
First-Class Levers
Figure 11–2a
First-Class Levers
• Seesaw is an example
• Center fulcrum between applied force
and resistance
• Force and resistance are balanced
Second–Class Levers
Figure 11–2b
Second-Class Levers
• Wheelbarrow is an example
• Center resistance between applied
force and fulcrum
• A small force moves a large weight
Third-Class Levers
Figure 11–2c
Third-Class Levers
• Most common levers in the body
• Center applied force between
resistance and fulcrum
• Greater force moves smaller resistance
• Maximizes speed and distance traveled
KEY CONCEPT
• Skeletal muscles can shorten to 70% of
resting length
• Power, speed, and range of movement
• Depend on positions of muscle
attachment
• Relative to joints
How are actions of a muscle
based on the relative positions
of its origin and insertion?
Origins and Insertions
• Muscles have 1 fixed point of
attachment (origin) and 1 moving point
of attachment (insertion)
• Most muscles originate or insert on the
skeleton
• Origin is usually proximal to insertion
Actions
• Movements produced by muscle
contraction
• Body movements
– e.g., flexion, extension, adduction, etc.
• Described in terms of bone, joint, or
region
How do muscles interact to
produce or oppose movements?
Muscle Interactions
• Muscles work in groups to maximize
efficiency
• Smaller muscles reach maximum
tension first, followed by larger,
primary muscles
Muscle Terminology
Based on Function
• Agonist (prime mover):
– produces a particular movement
• Antagonist:
– opposes movement of a particular agonist
• Synergist:
– a smaller muscle that assists a larger agonist
– helps start motion or stabilize origin of agonist
(fixator)
Muscle Opposition
• Agonists and antagonists work in pairs:
– when 1 contracts, the other stretches
– i.e., flexors–extensors, abductors–
adductors, etc.
How does the name of a muscle
help identify its location,
appearance, or function?
Names of Skeletal Muscles
• Correct names of muscles include the
term muscle
• Exceptions:
– platysma
– diaphragm
Naming Skeletal Muscles
Table 11–1 (1 of 2)
Naming Skeletal Muscles
Table 11–1 (2 of 2)
Descriptive Names
for Skeletal Muscles
1. Location in the body-Identifies body
regions: e.g.- temporalis muscle
2. Origin and insertion- First part of name
indicates origin, Second part of name
indicates insertion: e.g. genioglossus
muscle
3. Fascicle organization-Describes fascicle
orientation within muscle:
–
i.e., rectus (straight), transversus, oblique
Descriptive Names
for Skeletal Muscles
4. Relative position- Externus (superficialis):
–
visible at body surface
• Internus (profundus):deep muscles
• Extrinsic:muscles outside an organ
• Intrinsic:muscles inside an organ
5. Structural characteristics- Number of tendons:
–
bi = 2, tri = 3
• Shape: trapezius, deltoid, rhomboid
• Size6. Action- Movements: e.g., flexor, extensor, retractor
• Occupations or habits: e.g., risor = laughter
Names for Muscle Size (1 of 2)
•
•
•
•
•
•
•
•
•
Longus = long
Longissimus = longest
Teres = long and round
Brevis = short
Magnus = large
Major = larger
Maximus = largest
Minor = small
Minimus = smallest
Axial and Appendicular Muscles
Figure 11–3a
Axial and Appendicular Muscles
Figure 11–3b
Divisions of the Muscular System
1. Axial muscles:
–
–
–
position head and spinal column
move rib cage
60% of skeletal muscles
2. Appendicular muscles:
–
–
–
support pectoral and pelvic girdles
support limbs
40% of skeletal muscles
What are the principle
axial muscles of the body,
their origins, insertions,
actions, and innervation?
The Axial Muscles
• Divisions based on location and
function:
–
–
–
–
muscles of head and neck
muscles of vertebral column
oblique and rectus muscles
muscles of pelvic floor
6 Muscle Groups of
the Head and Neck
• Muscles of facial expression:
– originate on skull
• Extrinsic eye muscles:
– originate on surface of orbit
– control position of eye
PLAY
3D Peel-Away of Muscles
of the Head and Neck
6 Muscle Groups of
the Head and Neck
• Muscles of mastication:
– move the mandible
• Muscles of the tongue:
– names end in glossus
• Muscles of the pharynx:
– begin swallowing process
6 Muscle Groups of
the Head and Neck
• Anterior muscles of the neck:
– control position of larynx
– depress the mandible
– support tongue and pharynx
Muscles of Facial Expression
Figure 11–4a
Muscles of Facial Expression
Figure 11–4b
Muscles of Facial Expression
• Orbicularis oris:
– constricts the mouth opening
• Buccinator:
– moves food around the cheeks
• Muscles of the epicranium (scalp)
Muscles of the
Epicranium (Scalp)
• Temporoparietalis
• Occipitofrontalis:
– frontal and occipital bellies
– separated by epicranial aponeurosis
• Platysma:
– covers anterior surface of neck
Summary: Muscles of
Facial Expression
Table 11–2 (1 of 2)
Summary: Muscles of
Facial Expression
Table 11–2 (2 of 2)
Extrinsic Eye Muscles
• Also called extra-ocular muscles
Figure 11–5a, b
Extrinsic Eye Muscles
Inferior rectus
Medial rectus
Superior rectus
Lateral rectus
Inferior oblique
Superior oblique
Figure 11–5c
Summary: Extrinsic Eye Muscles
Table 11–3
Muscles of Mastication
Figure 11–6
3 Muscles of Mastication
• Masseter:
– the strongest jaw muscle
• Temporalis:
– helps lift the mandible
• Pterygoid muscles:
– position mandible for chewing
Summary: Muscles of Mastication
Table 11–4
Muscles of the Tongue
Figure 11–7
4 Muscles of the Tongue
• Palatoglossus:
– originates at palate
• Styloglossus:
– originates at styloid process
• Genioglossus:
– originates at chin
• Hypoglossus:
– originates at hyoid bone
Summary: Muscles of the Tongue
Table 11–5
Muscles of the Pharynx
Figure 11–8
3 Muscles of the Pharynx
• Pharyngeal constrictor muscles:
– move food into esophagus
• Laryngeal elevator muscles:
– elevate the larynx
• Palatal muscles:
– lift the soft palate
Summary:
Muscles of the Pharynx
Table 11–6
Anterior Muscles of the Neck
Figure 11–9
6 Anterior Muscles of the Neck
• Digastric:
– from chin to hyoid
– and hyoid to mastoid
• Mylohyoid:
– floor of the mouth
• Geniohyoid:
– between hyoid and chin
• Stylohyoid:
– between hyloid and styloid
• Sternocleidomastoid:
– from clavicle and sternum to mastoid
• Omohyoid:
– attaches scapula, clavicle, first rib, and hyoid
Summary:
Anterior Muscles of the Neck
Table 11–7
Muscles of the Vertebral Column
Figure 11–10a
Muscles of the Vertebral Column
• Spinal extensors or erector spinae
muscles (superficial and deep)
• Spinal flexors (transversospinalis)
Superficial Spinal Extensors
• Spinalis group
• Longissimus group
• Iliocostalis group
Deep Spinal Extensors
•
•
•
•
•
Semispinalis group
Multifidus muscle
Interspinalis muscles
Intertransversarii muscles
Rotatores muscles
Spinal Flexors
• Neck:
– longus capitis and longus colli
– rotate and flex the neck
• Lumbar:
– quadratus lumborum muscles
– flex spine and depress ribs
Summary: Muscles of the
Vertebral Column
Table 11–8 (1 of 2)
Summary: Muscles of the
Vertebral Column
Table 11–8 (2 of 2)
Oblique and Rectus Muscles
• Lie within the body wall
Figure 11–11a, b
Oblique and Rectus Muscles
Figure 11–11a, c
Oblique and Rectus Muscles
• Oblique muscles:
– compress underlying structures
– rotate vertebral column
• Rectus muscles:
– flex vertebral column
– oppose erector spinae
Oblique Muscles
Cervical region:
– scalene muscles
– flex the neck
Thoracic region:
– intercostal muscles (external and internal
intercostals):
• respiratory movements of ribs
– transversus thoracis:
• cross inner surface of ribs
Oblique Muscles
• Abdominopelvic region (same pattern
as thoracic):
– external oblique muscles
– internal oblique muscles
• Transversus abdominis
Rectus Group
• Rectus abdominis:
– between xiphoid process and pubic
symphysis
– divided longitudinally by linea alba
– divided transversely by tendinous
inscriptions
• Diaphragmatic muscle or diaphragm:
– divides thoracic and abdominal cavities
– performs respiration
Summary: Oblique and
Rectus Muscles
Table 11–9 (1 of 2)
Summary: Oblique and
Rectus Muscles
Table 11–9 (2 of 2)
Muscles of the Pelvic Floor
Figure 11–12a
Muscles of the Pelvic Floor
Figure 11–12b
Functions of Pelvic Floor Muscles
1. Support organs of pelvic cavity
2. Flex sacrum and coccyx
3. Control movement of materials
through urethra and anus
Perineum
• Muscular sheet forming the pelvic
floor, divided into:
– anterior urogenital triangle
– posterior anal triangle
Pelvic Diaphragm
– Deep muscular layer extending to pubis:
– supports anal triangle
Urogenital Diaphragm
• Deep muscular layer between pubic
bones:
– supports the pelvic floor
– and muscles of the urethra
• Superficial muscles of the urogenital
triangle:
– support external genitalia
Summary:
Muscles of the Pelvic Floor
Table 11-10 (1 of 2)
Summary:
Muscles of the Pelvic Floor
Table 11-10 (2 of 2)
What are the principal
appendicular muscles of
the body and their origins,
insertions, actions, and
innervations?
The Appendicular Muscles
Figure 11–13a
The Appendicular Muscles
Figure 11–13b
The Appendicular Muscles
• Position and stabilize pectoral and
pelvic girdles
• Move upper and lower limbs
Divisions of
Appendicular Muscles
1) Muscles of the shoulders and upper limbs:
• Position the pectoral girdle
• Move the arm
• Move the forearm and hand
• Move the hand and fingers
2) Muscles of the pelvis and lower limbs
Muscles that Position
the Pectoral Girdle
PLAY
3D Peel-Away of Muscles
of the Pectoral Girdle
Figure 11–14a
Muscles that Position
the Pectoral Girdle
Figure 11–14b
6 Muscles that Position the
Pectoral Girdle
• Trapezius:
– superficial
– covers back and neck to base of skull
– inserts on clavicles and scapular spines
• Rhomboid and levator scapulae:
– deep to trapezius
– attach to cervical and thoracic vertebrae
– insert on scapular border
6 Muscles that Position the
Pectoral Girdle
• Serratus anterior:
– on the chest
– originates along ribs
– inserts on anterior scapular margin
• Subclavius:
– originates on ribs
– inserts on clavicle
• Pectoralis minor:
– attaches to scapula
Summary: Muscles that
Position the Pectoral Girdle
Tables 11–11
Muscles that Move the Arm
Figure 11–15a
Muscles that Move the Arm
Figure 11–15b
9 Muscles that Move the Arm
(1 of 3)
• Deltoid:
– the major abductor
• Supraspinatus:
– assists deltoid
• Subscapularis and teres major:
– produce medial rotation at shoulder
PLAY
3D Rotation: Muscles of the Arm
9 Muscles that Move the Arm
(2 of 3)
• Infraspinatus and teres minor:
– produce lateral rotation at shoulder
• Coracobrachialis:
– attaches to scapula
– produces flexion and adduction at
shoulder
9 Muscles that Move the Arm
(3 of 3)
• Pectoralis major:
– between anterior chest and greater
tubercle of humerus
– produces flexion at shoulder joint
• Latissimus dorsi:
– between thoracic vertebrae and humerus
– produces extension at shoulder joint
The Rotator Cuff
• Muscles involved in shoulder rotation
– supraspinatus, subscapularis,
infraspinatus, teres minor,and their
tendons
Summary:
Muscles that Move the Arm
Table 11–12
Muscles that Move
the Forearm and Hand
Figure 11–16a
Muscles that Move
the Forearm and Hand
Figure 11–16b
Muscles that Move
the Forearm and Hand
• Originate on humerus and insert on
forearm
• Exceptions:
– the major flexor (biceps brachii)
– the major extensor (triceps brachii)
PLAY
3D Rotation: Muscles of the
Forearm and Hand
Extensors and Flexors
• Extensors:
– mainly on posterior and lateral surfaces of
arm
• Flexors:
– mainly on anterior and medial surfaces
13 Muscles that Move
the Forearm and Hand
• Biceps brachii:
– flexes elbow
– stabilizes shoulder joint
• Triceps brachii:
– extends elbow
– originates on scapula
– inserts on olecranon
• Brachialis and brachioradialis:
– flex elbow
– originates on scapula
– inserts on radial tuberosity
13 Muscles that Move
the Forearm and Hand
• Anconeus:
– opposes brachialis
• Palmaris longus:
– superficial
– flexes wrist
• Flexor carpi ulnaris:
– superficial
– flexes wrist
– adducts wrist
13 Muscles that Move
the Forearm and Hand
• Flexor carpi radialis:
– superficial
– flexes wrist
– abducts wrist
• Extensor carpi radialis:
– superficial
– extends wrist
– abducts wrist
• Extensor carpi ulnaris:
– superficial
– extends wrist
– adducts wrist
13 Muscles that Move
the Forearm and Hand (8 of 8)
• Pronator teres and supinator:
– originate on humerus and ulna
– rotate radius
• Pronator quadratus:
– originates on ulna
– assists pronator teres
Summary: Muscles that
Move the Forearm and Hand
Table 11–13 (1 of 2)
Summary: Muscles that
Move the Forearm and Hand
Table 11–13 (2 of 2)
Muscles that Move
the Hand and Fingers
Figure 11–17a, b
Muscles that Move
the Hand and Fingers
Figure 11–17c, d
Muscles that Move
the Hand and Fingers
• Also called extrinsic muscles of the
hand
• Lie entirely within forearm
• Only tendons cross wrist (in synovial
tendon sheaths)
Tendon Sheaths
• Extensor retinaculum:
– wide band of connective tissue
– posterior surface of wrist
– stabilizes tendons of extensor muscles
• Flexor retinaculum:
– anterior surface of wrist
– stabilizes tendons of flexor muscles
Summary: Muscles that
Move the Hand and Fingers
Table 11–14
The Intrinsic Muscles of the Hand
Figure 11–18a
The Intrinsic Muscles of the Hand
Figure 11–18b
Summary: The Intrinsic
Muscles of the Hand
Table 11–15 (1of 2)
Summary: The Intrinsic
Muscles of the Hand
Table 11–15 (2of 2)
Muscles of the Pelvis
and Lower Limbs
• Pelvic girdle is tightly bound to axial
skeleton:
–
–
permits little movement
has few muscles
Muscles that Position the Lower Limbs
1. Muscles that move the thigh
2. Muscles that move the leg
3. Muscles that move the foot and toes
Muscles that Move the Thigh
Figure 11–19a, b
Muscles that Move the Thigh
Figure 11–19c, d
Muscles that Move the Thigh
•
•
•
•
Gluteal muscles
Lateral rotators
Adductors
Iliopsoas
PLAY
3D Peel-Away of Muscles of the Thigh
PLAY
3D Peel-Away of Rectus Muscle
Gluteal Muscles (1 of 2)
• Cover lateral surfaces of ilia
• Gluteus maximus:
– largest, most posterior gluteal muscle
– produces extension and lateral rotation at
hip
Gluteal Muscles (2 of 2)
• Tensor fasciae latae:
– works with gluteus maximus
– stabilizes iliotibial tract
• Gluteus medius and gluteus minimus:
– originate anterior to gluteus maximus
– insert on trochanter
Lateral Rotators
• Group of 6 muscles, including:
– piriformis
– obturator
Adductors
• Adductor magnus:
– produces adduction, extension, and
flexion
• Adductor brevis:
– hip flexion and adduction
• Adductor longus:
– hip flexion and adduction
• Pectineus:
– hip flexion and adduction
• Gracilis:
– hip flexion and adduction
Iliopsoas
• 2 hip flexors insert on the same
tendon:
• psoas major
• iliacus
Summary: Muscles that
Move the Thigh
Table 11–16 (1 of 2)
Summary: Muscles that
Move the Thigh
Table 11–16 (2 of 2)
Muscles that Move the Leg
Figure 11–20a
Muscles that Move the Leg
Figure 11–20b, c
Muscles that Move the Leg
• Flexors of the knee:
– originate on the pelvic girdle
• Extensors of the knee:
– originate on the femoral surface
– insert on the patella
Flexors of the Knee
•
•
•
•
Biceps femoris- Hamstrings
Semimembranosus- “
Semitendinosus“
Sartorius:
– originates superior to the acetabulum
• Popliteus:
– rotates the tibia to unlock the knee
Extensors of the Knee
• 4 muscles of the quadriceps femoris:
– 3 vastus muscles
– rectus femoris muscle
Summary: Muscles that
Move the Leg
Table 11–17 (1 of 2)
Summary: Muscles that
Move the Leg
Table 11–17 (2 of 2)
Muscles that Move
the Foot and Toes
Figure 11–21a, b
Muscles that Move
the Foot and Toes
Figure 11–21c, d
Muscles that Move
the Foot and Toes
• Extrinsic muscles that move the foot
and toes include:
– muscles
ankle
– muscles
– muscles
toes
– muscles
that produce extension at the
that produce flexion at the ankle
that produce extension at the
that produce flexion at the toes
4 Muscles that Produce Extension
at the Ankle
• Gastrocnemius
• Soleus
• Fibularis
• Tibialis posterior
+ The Achilles TendonThe calcaneal tendon (Achilles
tendon):
– shared by the gastrocnemius and soleus
Muscles that Produce
Flexion at the Ankle
• Tibialis anterior:
– opposes the gastrocnemius
Muscles that Produce Flexion at the Toes
• Flexor digitorum longum
• Flexor hallucis longus:
– oppose the extensors
Muscles that Produce
Extension at the Toes
• Extensor digitorum longum
• Extensor hallucis longus
• Extensor retinacula:
– fibrous sheaths hold tendons of toes as
they cross the ankle
Summary: Muscles that
Move the Foot and Toes
Table 11–18
The Intrinsic Muscles of the Foot
Figure 11–22a
The Intrinsic Muscles of the Foot
Figure 11–22b, c
Summary: The Intrinsic
Muscles of the Foot
Table 11–19
Effects of Aging
on the Muscular System
1. Skeletal muscle fibers become
smaller in diameter
2. Skeletal muscles become less elastic:
–
develop increasing amounts of fibrous
tissue (fibrosis)
3. Decreased tolerance for exercise
4. Decreased ability to recover from
muscular injuries
Integration with Other Systems
Figure 11–24
Integration with
Other Systems
• Cardiovascular system:
– delivers oxygen and fuel
– removes carbon dioxide and wastes
• Respiratory system:
– responds to oxygen demand of muscles
• Integumentary system:
– disperses heat from muscle activity
• Nervous and endocrine systems:
– direct responses of all systems
SUMMARY
• Effects of muscle structure on function
• Organization of skeletal muscle fibers:
– parallel, convergent, pennate, circular
• Relationships between levers and
movement
• Actions of first, second, and third class
levers
• Origins and insertions of skeletal muscles
• Actions of skeletal muscles:
– agonist, antagonist, synergist
• How skeletal muscles are named
SUMMARY
• Structures and functions of axial muscles:
–
–
–
–
muscles of head and neck
muscle of vertebral column
oblique and rectus muscles
muscles of pelvic floor
• Structures and functions of the appendicular
muscles:
– muscles of shoulders and upper limbs
– muscles of pelvis and lower limbs
• Effects of aging on the muscular system