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Muscle Groups
Um…
Groups of muscles
Their names
‘N stuff
How muscles are named
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There are over 600 muscles in
the human body
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Together, these account for about
40% of the body’s weight
Most anatomical terms were
developed in the mid- to late1500s, when many anatomists
were beginning to perform
human body dissections

As a result, many of these have
Latin and Greek roots
How muscles are named
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Muscles are often named according to:
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direction in which their fibers run
size
location in the body
bones they attach to
what the muscle looks like
where it is in relation to certain bones
function within the body
Often, the names are combinations of
the above factors.
Direction of Muscle Fibers

If the fibers are running parallel
to the midline, the term rectus
(meaning “straight”) is often
used
• E.g. rectus femoris, rectus abdominis

If the fibers run at an angle to
the midline, they are often
termed oblique
• E.g. external oblique muscles of the
thorax
Size

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If a muscle is long, its name
often includes the term
longus, while if a muscle is
short, it often has the term
brevis in the name
Muscles that are large often
have the term maximus,
major, or vastus, while
small muscles contain terms
such as minimus or minor
Location

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Association with a particular
area of the body
Where would you expect to
find…?
 Biceps brachii
 Rectus femoris
 Adductor pollicis longus
 Obicularis oculi
 External intercostals
 Tibialis anterior
 Spinalis thoracis
 Peroneus longus
Attachment to bone

E.g. frontalis muscle covers the
frontal bone of the skull

Location of origin and insertion on bone
 For bones that are named based on
origins and insertions, the first part
of the muscle name indicates the
origin, while the second part
indicates the insertion
• E.g. the sternocleidomastoid
muscle has its
origin on the breast bone (sterno)
and clavicle (cleido), and inserts
on a “breast shaped” process of
the skull (mastoid)
How muscles are named

Muscles with multiple
origins

E.g. biceps brachii and
triceps brachii
• ceps refers to “head” ~
how many heads and
origins would the triceps
brachii have?
Position in relation to bone
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E.g. subscapularis
Shape of muscle
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Delt = triangle
Oid = like
Trapezius = Table
Serratus = Saw
Teres = Round
Orbi = Circle
Cul = Little
Lat = Broad/Wide
Simus = Likeness
Type of action produced

E.g. extensor
digitorum
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Note: these assume
that the body is
starting at the
anatomical position
Head and Neck Muscles

Facial muscles

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Frontalis - raises
eyebrows
Orbicularis oculi closes eyes, squints,
blinks, winks
Orbicularis oris closes mouth and
protrudes the lips
Buccinator flattens the cheek,
chews
Zygomaticus raises corners of the
mouth
Head and Neck Muscles
 Chewing
muscles
Masseter closes the jaw
and elevates
mandible
 Temporalis synergist of the
masseter, closes
jaw

Head and Neck Muscles
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Neck muscles
Platysma - pulls the
corners of the mouth
inferiorly
 Sternocleidomastoid
- flexes the neck,
rotates the head

Muscles of Trunk,
Shoulder, Arm

Anterior muscles
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Pectoralis major adducts and flexes the
humerus
Intercostal muscles
• External intercostals raise rib cage during
inhalation
• Internal intercostals depress the rib cage to
move air out of the
lungs when you exhale
forcibly
Muscles of Trunk,
Shoulder, Arm

Muscles of the abdominal
girdle
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Rectus abdominis - flexes
vertebral column and
compresses abdominal
contents (defecation,
childbirth, forced breathing)
External and internal
obliques - flex vertebral
column; rotate trunk and
bend it laterally
Transversus abdominis compresses abdominal
contents
Muscles of Trunk,
Shoulder, Arm
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Posterior muscles
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Trapezius - elevates,
depresses, adducts, and
stabilizes the scapula
Latissimus dorsi extends and adducts the
humerus
Erector spinae - back
extension
Quadratus lumborum flexes the spine laterally
Deltoid - arm abduction
Muscles of the Upper Limb
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Biceps brachii supinates forearm,
flexes elbow
Brachialis - elbow
flexion
Brachioradialis weak muscle
Triceps brachiielbow extension
(antagonist to
biceps brachii)
Muscles of the Lower Limb
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Gluteus maximus - hip
extension
Gluteus medius - hip
abduction, steadies pelvis
when walking
Iliopsoas - hip flexion,
keeps the upper body from
falling backward when
standing erect
Adductor muscles adduct the thighs
Muscles of the Lower Limb

Muscles causing
movement at the
knee joint

Hamstring group
- thigh extension
and knee flexion
• Biceps femoris
• Semimembranosus
• Semitendinosus
Muscles of the Lower Limb

Muscles causing
movement at the knee
joint
Sartorius - flexes the
thigh
 Quadriceps group extends the knee
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• Rectus femoris
• Vastus muscles (three)
Muscles of the Lower Limb
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Muscles causing movement
at ankle and foot
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Tibialis anterior dorsiflexion and foot
inversion
Extensor digitorum longus
- toe extension and
dorsiflexion of the foot
Fibularis muscles - plantar
flexion, everts the foot
Gastrocnemius - plantar
flexion, knee flexion
Soleus - plantar flexion
Calf Muscles