Muscle
Structure
and Function
Chapter 9 – Part 2
Muscles of the Arm, Leg,
Face, Torso, and Neck
Muscle Attachment
Does NOT move when
muscle contracts
Classification of Muscle Group Actions
• Agonist (Prime Mover)
▫ Muscle most responsible for movement
• Antagonist
▫ Opposes prime mover
▫ Provides precision and control during prime mover
contraction
▫ Relaxes when prime mover contracts
• Synergist
▫ Aid prime mover
▫ Contract at same time as prime mover
Limb muscles
Muscles of the limb function in:
• Movement, grasping, balance
• Deltoid: muscle forming the rounded contour of the shoulder;
moves upper arm
• Pectoralis major: thick, fan-shaped muscle, situated at the chest
(anterior) of the human body; moves upper arm
• Biceps brachii: two-headed muscle that lies on the upper arm
between the shoulder and the elbow; flexes arm
• Brachialis: muscle in the upper arm that flexes the elbow joint
• Brachioradialis: muscle of the forearm that flexes the forearm at
the elbow; capable of both pronation and supination
• Palmaris longus: muscle starts up near the elbow and runs
across the middle of the forearm; flexes hand
• Flexor carpi ulnaris: muscle of the human forearm that acts to
flex and adduct the hand
• Flexor carpi radialis: muscle of the human forearm that acts to
flex and abduct the hand
Color Key
•Purple: Muscles that move the
upper arm
•Orange: Muscles that move the
forearm
•Brown: Muscles that flex the
hand
Anterior
superficial
muscles of
the shoulder
and arm
Posterior Arm Muscles
• Triceps brachii: muscle (3 heads) on the back of the upper
arm; moves forearm
• Anconeus: small triangular elbow muscle connecting the
medial side of the ulna to the lateral side of the humerus;
extends forearm
• Extensor carpi radialis longus: found on the lateral side of
the humerus, and attaching to the base of metacarpal 2
(pointer finger)
• Extensor carpi radialis brevis: found on the lateral side of
the humerus, running alongside the radius; extends/abduct
the wrist
• Extensor digitorium: extends the medial four digits
(phalanges) of the hand
• Extensor digiti minimi: muscle of the forearm that extends
phalanx 5 (pinky finger!)
• Extensor carpi ulnaris: extend and adduct at the wrist
Color Key
•Orange: Muscles that move the
forearm
•Brown: Muscles that extend
the hand
Flexor Carpi Ulnaris
Posterior
superficial
muscles of
the arm
Anconeus
14
Extensor digiti
minimi
Find the muscles on your body.
Anterior Upper Leg Muscles
• Quadriceps: 4-headed muscle made up of the vastus
lateralis, vastus intermedius, vastus medialis, and rectus
femoris; moves lower leg
• Sartorius: assists in flexing, weak abduction and lateral
rotation of the hip, and flexion of knee
• Gracilis: originates at the ischiopubic ramus and
extends down to the tibia; responsible for hip adduction
and assists knee flexion
• Adductor Longus: main function is to adduct the thigh
Upper Leg
(Anterior)
psoas major
iliacus
quadriceps
rectus femoris
vastus intermedius
(under rectus femoris)
vastus medials
vastus lateralis
Upper Leg
(Anterior)
tensor fascia latae
sartorius
quadriceps tendon
patellar ligament
Posterior Upper Leg
• Gluteus Maximus: located in the buttocks and is
regarded as one of the strongest muscles in the human
body; responsible for movement of the hip and thigh
• Illotibial band: works to extend, abduct, and laterally
rotate the hip; knee stabilization
• Biceps femoris: Both heads of the biceps
femoris perform knee flexion. Since the long head
originates in the pelvis it is also involved in hip
extension; hamstrings
• Semimembranosus: enabling the leg to flex and rotate,
and serving as a thigh extensor; hamstrings
• Semitendinosis: long, superficial muscle in the back of
the thigh; hamstrings
gluteus medius
hamstring group
biceps femoris
gluteus maximus
iliotibial band
semitendinosus
semimembranosus
Upper Leg
(Posterior)
Muscles of the Lower Leg
• Gastrocnemius: Along with the soleus muscle, it
forms half of the calf muscle; function in plantar
flexion of the foot and flexing the leg at the knee joint
• Soleus: plantar flexion of the foot; powerful
musclevital in walking, running, and dancing
• Achilles tendon: largest and strongest tendon in the
human body; connects the calcaneus to the muscles at
the back of the calf
• Extensor digitorum: wing-shaped muscle works to
extend the foot at the ankle, along with phalanx 2-5
• Tibialis anterior: dorsiflexion and inversion of the
ankle
• Fibularis longus: also known as the peroneus
longus; muscle inside the outer area of the human leg,
which everts (bends in an outward direction) and
flexes the ankle.
adductor longus
gracilis
adductor magnus
gastrocnemius
sartorius
Medial Leg
Muscles
soleus
calcaneal (Achilles)
tendon
Lower
Lateral Leg
tibialis anterior
extensor digitorum
fibularis
(peroneus)
longus
retinaculum
Knee Muscles/Connections
• Patellar ligament: connects to two different
bones, the patella and the tibia.
• Quadriceps tendon: attaches patella to the
quadriceps muscles by the
• Meniscus: lateral and medial
▫ Two vital functions:
 Transfer the load from the upper leg to the lower leg
 Stabilize the knee during flexion, extension and during
circular movements.
▫ The menisci move during the backward flexion and
the forward extension of the knee in order to
balance the change of the articular surfaces.
anterior
cruciate
ligament
medial meniscus
posterior
cruciate
ligament
patella
patellar
ligament
lateral
meniscus
quadriceps
tendon
Knee
Joint
fibular (lateral)
collateral
ligament
tibial (medial)
collateral
ligament
Anterior
(with tendon & ligament removed)
Posterior
Head and Neck Muscles
There are 4 basic functions of
head and neck muscles:
o swallowing and chewing
(mastication)
o making facial expressions
o moving your neck
o supporting your head
Muscles of the Head and Neck
Posterior neck muscles
The muscles in the neck help to support the head. How much do you
think an average adult head weighs?
(over 11 pounds)
Superficial Back Muscles
Large, fan-shaped muscles provide force in a wide range of body positions
-EX: leaning back to straight vertical and all points in between.
Trapezius
Levator Scapulae
Supraspinitus
Deltoid
Infraspinitus
Teres Major
Latissimus Dorsi
Rhomboid Major
Trunk Muscles - Thorax
Elevate ribs
Depress
Ribs
Trunk Muscles
Abdomen
Flexes trunk
Compresses
abdomen
Stabilizes
Lower back
Strains vs. Sprains
• A strain is when you "pull" a muscle and a
sprain is when you damage a ligament.
• Classification of Strains and Sprains:
▫ First degree: a few fibers of the ligament/
muscle are torn and loss of function is mild
▫ Second degree: roughly half of the fibers of
the ligament/ muscle are torn loss of
function is moderate to severe
▫ Third degree: all or most of the fibers of the
ligament/ muscleare torn and loss of
function is severe
• RICE:
▫
▫
▫
▫
Rest
Ice
Compression
Elevation