Chapter 11:
The Muscular System
BIO 210 Lab
Instructor: Dr. Rebecca Clarke
Muscular System
 Includes all voluntary skeletal muscles
 Approximately 700 skeletal muscles
 “Newest” muscle
 Identified in 1996
 Sphenomandibularis muscle
 Assists with mastication
Functions of Skeletal Muscles
 Attach to skeleton, produce motion
 Support soft tissue
 Form slings or sheets between bony elements
 Guard an entrance/exit
 Completely encircle the opening
Skeletal Muscle Organization
 Muscle cells (fibers) are organized in bundles (fascicles)
 Muscle organization affects power, range, and speed of
muscle movement
 Arrangement of fascicles, shape and/or appearance provide
clues to primary function
Skeletal Muscles and the
Skeletal System
 Skeletal muscles have a direct or indirect association with the
skeletal system
 Attach to:
 Bony processes via tendons
 Aponeuroses (singl …sis) = broad, flat sheets of tendinous
connective tissue
Organization of
Skeletal Muscle Fibers
 4 patterns of fascicle organization:
 Parallel
 Convergent
 Pennate
 Circular
Parallel Muscles
 Fibers parallel to long axis of
muscle
  plump, spindle-shape
with:
 Central body
 Tendons at one or both ends
 When muscle contracts, gets
shorter, larger in diameter
 Most skeletal muscles are this
type
Figure 11–1a
Convergent Muscles
 Broad, fan-shaped area
converges on attachment
site
 Versatile because muscle
fibers pull in different
directions depending on
stimulation
Figure 11–1b
Pennate Muscles
 Unipennate: fibers on 1 side of tendon
 Bipennate: fibers on both sides
 Multipennate: tendon branches in muscle
Figure 11–1c, d, e
Circular Muscles
 Also called sphincters
 Fibers encircle opening
 Open and guard
entrances/exits of
external/internal
passageways, e.g., digestive,
urinary tracts
 contraction   diameter
of opening
Figure 11–1f
Origins and Insertions
 Muscles have
 1 stationary point of attachment (origin)
 1 moving point of attachment (insertion)
 Most muscles originate or insert on the skeleton
 Origin is usually proximal to insertion
Action
 Movement muscle produces when it contracts
 Body movements
 e.g., flexion, extension, adduction, etc.
 Described in terms of bone, joint, or region
How does the name of a muscle
help identify its location,
appearance, or function?
Names of Skeletal Muscles
 Correct name of muscle includes the term “muscle”
 Exceptions:
 Platysma
 Diaphragm
Descriptive Names
for Skeletal Muscles
•
•
•
•
•
•
Fascicle organization
Location in the body
Origin and insertion
Relative position
Structural characteristics
Action
Fascicle Organization
 Describes fascicle orientation within muscle:
 i.e., rectus (straight), oblique (diagonal), transversus
(transverse)
Location in the Body
 Identifies body regions:
 e.g., temporalis muscle
Origin and Insertion
 First part of name indicates origin
 Second part of name indicates insertion, e.g.,:
 coracobrachialis muscle,
 sternocleidomastoid
Relative Position
 External (superficialis):
 Visible at body surface
 Internal (profundus):
 Deep muscles
 Extrinsic:
 Muscles outside an organ
 Intrinsic:
 Muscles inside an organ
Structural Characteristics
 Number of tendons/head:
 bi = 2, tri = 3
 Biceps brachii
 Shape:
 Trapezius, deltoid, rhomboid
Names for Muscle Size (1 of 2)
 Longus = long
 Longissimus = longest
 Teres = long and round
 Brevis = short
 Magnus = large
Names for Muscle Size (2 of 2)
 Major = larger
 Maximus = largest
 Minor = small
 Minimus = smallest
Action
 Movements:
 e.g., flexor, extensor, levator
 Occupations or habits:
 e.g., risor = laughter  risorius
 e.g., sartor = tailor  sartorius
Naming Skeletal Muscles
Table 11–1 (1 of 2)
Axial and Appendicular Muscles
Figure 11–3a
Axial and Appendicular Muscles
Figure 11–3b
Divisions of the Muscular System
Axial muscles:
•



Position head and spinal column
Move rib cage
60% of skeletal muscles
Appendicular muscles:
•



Support pectoral and pelvic girdles
Support limbs
40% of skeletal muscles
Muscles of the Head
 Epicranium (scalp)
 Epicranial aponeurosis
(galea aponeurotica)
 CT sheet between frontalis
and occipitalis
 Frontalis (frontal belly of
occipito-frontalis)
 Covers forehead; raises
eyebrows, wrinkles forehead
Figure 11–4b
Muscles of the Head
 Occipitalis (occipital belly
of occipito-frontalis)
 Covers inferior occipital area;
tenses and retracts scalp
 Temporoparietalis
 Tenses scalp, moves auricle of
ear
Figure 11–4a
Muscles of the Head
 Orbicularis oculi
 Surrounds eye (external)
 Closes eye (internal)
 Nasalis
 bridge of nose
  nose movements
Figure 11–4b
Muscles of the Head
 Orbicularis oris
 Surrounds mouth
 Compresses, purses lips
 Depressor anguli oris
 Pulls down corner of mouth
 From body of mandible to angle of
mouth
 Mentalis
 Medial on chin
 Protrudes lower lip
Figure 11–4b
Muscles of the Head
 Zygomaticus (minor and major)
 From zygomatic arch to mouth
 Buccinator
 Wide, horizontal muscle in cheek
 Chewing, sucking, compresses
cheeks
 Masseter
 Runs vertically over buccinator,
covers lateral side of ramus of
mandible
 Elevates mandible (closes jaw)
 Strongest jaw muscle
Figure 11–4a
Muscles of the Head
 Risorius
 From parotid salivary gland to angle of
mouth (crosses buccinator and masseter)
 Draws corner of mouth to side
(grimace)
 Temporalis
 Large, fan-shaped, in temporal area deep
to temporoparietalis
 Assists in elevating mandible
 Platysma
 Covers inferior mandible and anterior
surface of neck
 Visible inferior to risorius
 Tenses skin of neck; depresses mandible
(opens jaw)
Figure 11–4b
Muscles of the Neck
 Sternocleidomastoid
 Long muscle at lateral side of
neck (under platysma)
 Extends from clavicle and
sternum to mastoid region of
temporal bone
 Flexes neck down
Figure 11–4a
Muscles of the Neck
 Scalenes (Fig 11-10b)
 3 muscles on each side, from
transverse processes of
cervical vertebrae to 1st and
2nd ribs
 Flex neck laterally, assist in
breathing (elevate ribs)
Figure 11–10b, c
Muscles of the Neck and Back
 Trapezius
 Large kite-shaped muscles on
back and neck
 Extend neck, elevate
clavicle, move scapula
upward
 Splenius capitis
 Deep to trapezius at back of
neck; rotate head
Figure 11–13a
Muscles of the Neck and Back
 Levator scapulae
 Deep to trapezius at lateral
side of neck
 Lift scapulae
Figure 11–13a
Muscles of the Anterior Torso
 Pectoralis major
 Large fan-shaped chest muscle
 Shoulder movements
 Pectoralis minor
 Under p. major
 Shoulder and scapula movements
 Serratus anterior
 Inferior to pectoralis minor
 Shoulder and scapula movements
Figure 11–13b
Muscles of the Anterior Torso
 Intercostals
 In intercostal spaces (between
ribs)
 Respiration
 External intercostals
 Fibers run medially from superior
rib to inferior rib
 Elevate ribs
 (for external think: putting hands in
front pockets)
 Internal intercostals
 Fibers run laterally from superior
rib to inferior rib deep to external
intercostals
 Depress ribs
 (for internal think: putting hands in
back pockets)
Figure 11–14b
Muscles of the Anterior Torso
 Obliques
 External obliques
 Superficial, fibers run medially and
inferiorly
 Depresses ribs, compresses
abdomen, bends and rotates spine
 Internal obliques
 Deep to external oblique, fibers run
medially and superiorly from iliac
crest
 Same action as above
Figure 11–13b
Muscles of the Anterior Torso
 Rectus abdominis
 Deep to internal oblique, runs vertically near
midline
 Depresses ribs, flexes spine
 Divided by linea alba
 Linea alba
 Aponeurosis at midline (from xiphoid process to
symphysis pubis)
 Longitudinally divides rectus abdominis
 Rectus sheath
 A sheath formed by the aponeuroses of other
abdominal muscles, within which the rectus
abdominis moves
 Tendinous intersections
 separate parts of muscle
Figure 11–3a
Muscles of the Ventral Cavities
 Subcostal
 Oblique, on deep side of posterior thoracic wall; form straps
between ribs
Muscles of the Ventral Cavities
 Transversus abdominis
 Deepest, fibers run transversally
 Tightens abdominopelvic wall; protects viscera
Figure 11–11a, c
Muscles of the Vertebral Column
 Quadratus lumborum
 Posterior and lateral to psoas
major
 Attaches to last rib and lumbar
vertebrae
 Both sides together, depresses ribs;
alone, each side laterally flexes
vertebral column
Figure 11–10a
Muscles that Move the Thigh
 Psoas – originate on lumbar vertebrae
 Major – medial to quadratus lumborum
 Minor – medial and anterior to p. major
Figure 11–19c, d
Muscles that Move the Thigh
 Iliacus – triangular sheet across iliac fossa
 Iliopsoas – iliacus + psoas major
Figure 11–19c, d
Diaphragm
 Dome-shaped, muscular partition
 Divides thoracic and abdominopelvic cavities
 Central tendon, inferior vena caval hiatus, esophageal hiatus,
aortic hiatus
 Major role in respiration
Figure 11–11a, b
Perineum
 Muscular sheet that forms the pelvic floor
Muscles of the Pelvic Floor
Figure 11–12a
Muscles of the Pelvic Floor
Figure 11–12b
Functions of the Perineum
•
•
•
Supports organs of pelvic cavity
Flexes sacrum and coccyx
Controls movement of materials through urethra and anus
Muscles of the Posterior Torso
 Trapezius, splenius capitis, levator scapulae (see previous
description)
 Latissimus dorsi – inferior to trapezius; broadest muscle
of back; moves humerus
Figure 11–13a
Muscles of the Posterior Torso
 Rhomboid(eus) – deep to trapezius between scapula and
spine; move scapula
 Rhomboid minor and major
Figure 11–14a
Muscles of the Posterior Torso
 Supraspinatus – in supraspinous fossa of scapula;
abduction at shoulder
 Infraspinatus – in infraspinous fossa of scapula; lateral
shoulder rotation
Figure 11–15b
Muscles of the Posterior Torso
 Subscapularis – in subscapular fossa; medial shoulder rotation
Figure 11–15a
Muscles of the Posterior Torso
 Teres major – runs horizontally inferior to infraspinatus,
from scapula to humerus
 Teres minor – runs horizontally superior to teres major and
inferior to infraspinatus; from scapula to humerus
Figure 11–15b
Muscles of the Posterior Torso
 Serratus posterior – forms jagged edge, from vertebrae
to ribs
 Internal oblique (see description above)
Figure 11–13a
Muscles of the Upper Extremities
Muscles of the Upper Extremities:
Brachium
 Deltoid - large, triangular muscle at top of shoulder;
moves humerus
 Biceps brachii – anterior/lateral side of arm, 2 heads;
flexes elbow and shoulder, supination
Figure 11-15a
Muscles of the Upper Extremities:
Brachium
 Brachialis - inferior to
deltoid on lateral side of
arm between biceps and
triceps brachii; flexes
elbow
 Biceps brachii –
anterior/lateral side of
arm, 2 heads; flexes elbow
and shoulder, supination
Figure 11–16b
Muscles of the Upper Extremities:
Brachium
 Triceps brachii (Fig 11-15b) –
posterior side of arm, 3 heads;
extends elbow
 Coracobrachialis (Fig 11-16) –
superior lateral side of arm,
between 2 brachii
Figure 11–15a
Muscles of the Upper Extremities:
Antebrachium - Anterior
 Brachioradialis – inferior to
brachialis on lateral side of
forearm; flexes elbow
 Pronator teres – antecubital
region of forearm, diagonal
orientation; pronates forearm
 Flexor carpi radialis – medial to
brachioradialis, inferior to
pronator teres; flexes wrist,
abducts hand
Figure 11–16b
Muscles of the Upper Extremities:
Antebrachium - Anterior
 Palmaris longus – medial to
above; flexes wrist
 Flexor carpi ulnaris – medial to
above and adjacent to ulna;
flexes, adducts wrist
Figure 11–16b
Muscles of the Upper Extremities:
Antebrachium - Posterior
 Extensor carpi ulnaris –
adjacent to ulna, lateral to
flexor carpi ulnaris; extends
and abducts wrist
 Extensor digitorum – lateral
to above; extends fingers IIV
 Extensor carpi radialis brevis
– along upper lateral side of
above
Figure 11–16a
Muscles of the Upper Extremities:
Antebrachium - Posterior
 Extensor carpi radialis
longus – along medial side of
brachioradialis; extends and
abducts wrist
 FYI [Supinator – antecubital region of forearm
deep to brachioradialis;
supinates forearm]
Figure 11–16a
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)
Muscles that Move
the Hand and Fingers
Figure 11–17a, b
Intrinsic Muscles of the Hand
Figure 11–18a
Muscles of the Lower Extremities
Muscles of the Pelvis and Upper Leg
 Iliotibial tract – dense CT sheet on lateral
thigh
 Gluteus - covers lateral surfaces of ilia
 Gluteus
 Maximus
 Medius
 Minimus
 Tensor fasciae latae -
small tensor muscle of
fascia, stabilizes
iliotibial tract, laterally
supports knee
Figure 11–19a, b
Muscles of the Pelvis and Upper Leg –
Anterior, Extensors
 Quadriceps femoris – anterior thigh area,
strongest muscle group in body; extends knee;
made of 4 muscles
 Vastus lateralis – anterior to iliotibial tract, lateral to
rectus femoris
 Rectus femoris – runs “straight” vertically along
anterior thigh; superior portion between tensor
fasciae latae and sartorius
 Vastus medialis – medial to rectus femoris
 FYI [Vastus intermedius – deep, hidden by
rectus femoris]
 Sartorius – long, slender, oblique; longest muscle
in body; tailor’s muscle
Figure 11–20b
Muscles of the Pelvis and Upper Leg –
Medial, Adductors
 Pectineus – inferior and medial to
iliopsoas
 Adductor longus – inferior to pectineus
and medial to sartorius
 Gracilis – vertical along medial side of
thigh and medial to adductor longus
 Adductor magnus (Fig 11-20a) –
superior portion posterior to gracilis
Figure 11–20b
Muscles of the Pelvis and Upper Leg –
Posterior, Flexors (Hamstrings)
 Adductor magnus (see previous slide)
 Semimembranosus – lateral to
adductor magnus (superior) and
gracilis (inferior), medial and deep to
semitendinosus
 Semitendinosus – superficial, lateral
to semimembranosus
 Biceps femoris – lateral to
semitendinosus, posterior to iliotibial
tract
Figure 11–20a
Muscles of the Lower Leg - Flexor
 Tibialis anterior – along anterior, lateral side of tibia
Figure 11–21a, b
Muscles of the Lower Leg - Extensors
 Fibularis (peroneus) longus – along lateral side of fibula
 Fibularis (peroneus) brevis – inferior and deep to fibularis longus
Figure 11–21a, b
Muscles of the Lower Leg - Extensors
 Extensor digitorum longus – lateral to tibialis anterior; extends
toes II-V
 Gastrocnemius – calf muscle (2 heads)
 Soleus – deep (lateral and medial) to gastrocnemius
Figure 11–21a, b
Muscles of the Lower Leg
 Calcaneal (Achilles) tendon – large tendon from gastrocnemius
and soleus to calcaneus
Figure 11–21a, b
Intrinsic Muscles of the Foot
Figure 11–22a