Gross Anatomy of Gross Anatomy of Skeletal MovementSkeletal Movement

• The fleshy part of the muscle containing the muscle cells is the belly. 

• At either end of the belly are the attachments, which are usually tendons that hold the muscle to the bones or other organs. 

• Tendons (can be very long) allow the muscle to transmit force across a great distance. 

– Good example: wrists

– Most of the muscles that move the fingers are found above the wrist. 

– These muscles are isolated by long tendons away from the point of movement.  If all of our muscles were in our hands, our hands would be too large and movement would not be as effective nor could we handle things as delicately as we can. 

Tendons attach muscles to bone

Muscle contraction at the macroscopic level

• Muscles are attached at each end to the skeletal system

– Origin: the fixed (immovable) point of attachment.

– Insertion: attachment to the movable bone

• As a muscle shortens (contracts) the insertion moves toward the origin

Muscle contraction at the macroscopic level

• As a muscle shortens (contracts) the insertion moves toward the origin

• Muscles can only pull they cannot push

Direction of movement of radius towards scapula as biceps shortens

Pectoralis majorPectoralis major““big chest big chest muscle”muscle”

Latissimus dorsiLatissimus dorsi““big muscle on side of big muscle on side of back”back”

Pulls arm forward and Pulls arm forward and upup

Pulls arm back and Pulls arm back and down. Used by down. Used by swimmersswimmers

Antagonists oppose one another

Look at distance between scapula and radius when

the triceps are contracted

The pink shows the additional length when the triceps are relaxed. Notice when the triceps are contracted that the elbow is no longer flexed and that the angle of the elbow joint is ~180

Triceps contracted

Look at distance between scapula and radius when

the biceps are contracted

The pink shows the additional length when the biceps are relaxed. Notice when the biceps are relaxed that the elbow is no longer flexed and that the angle of the elbow joint is ~180

Biceps contracted

Look at distance between tibia and femur when the

quadraceps are contracted

Quadraceps are knee extensors and will straighten the knee when they shorten

Insertion

Look at distance between tibia and femur when the

hamstrings are contracted

Hamstrings are knee flexers and will bend the knee joint when they contract

Insertion

Insertion

• Muscle can only pull they cannot push

• Here the supraspinatus pulls on the greater tubercle of the humerus towards the posterior aspect of the scapula at the supraspinous fossa during abduction of the arm. It also helps to prevent the downward dislocation of the shoulder when carrying a heavy suitcase

Muscle contraction at the macroscopic level

RelaxeRelaxedd ContractContract

eded

Term Definition Example

Prime movers

Muscles that assume the major responsibility for producing a specific movement

Biceps brachii (elbow flexion)

Antagonists Muscles that oppose, or reverse, movement by a prime mover. When a prime mover is active, the antagonist muscle fibers are relaxed, yielding to the movement of the prime mover. Antagonists can also help to regulate the action of the prime mover by partially contracting to provide some resistance or to slow or stop the action

Triceps brachii (during flexion)

Synergists Muscles that reduce undesirable or unnecessary extra movements that might result as the prime mover contracts

Fixators Muscles that immobilize the origin of the prime mover so that the prime mover can act more efficiently.

Pectoralis minor, rhomboids, and trapezius muscles fix scapula when deltoid contracts

• Organize the muscles in your objectives by the joints that they move and learn them in groups.

• Organize the muscles for each joint by the direction the move the joint (i.e., flex, extend, abduct)

• Look at which bones and on what bone markings the muscles are attached.

• Determine which is the origin and which is the insertion.

Approaches for learning the muscles.

Bipedialism key to understanding limb movement

Bipedialism (walking upright) believed to have first taken place between 3 - 5 million years ago provided for a division of labor between the limbs.

– Upper Limb

• Primarily structured for mobility and manipulation

• Lost adaptation to support weight ( weight bearing) and/ or locomotion

– Lower limb

• Primarily structured for locomotion and weight bearing (support)

• Slight ability to manipulate

Movement of Movement of Arm/Shoulder Arm/Shoulder

MusclesMuscles

Movements of the upper limb

The upper limb is used for a broad range of both powerful and subtle actions, ranging from climbing, grasping, and throwing to writing, playing musical instruments and manipulating small objects.

The major bones acted upon are:

– Scapula

– Humerus

– Radius

– Ulna

Arm movements

• Abduction

• Adduction

• Flexion

• Extension

• Lateral rotation

• Medial rotation

• Elevation

• Depression

• Retraction

• Protraction

• Pronation

• Supination

Arm muscles move against the joints of the pectoral girdle (shoulder), elbow and wrist

Sternoclavicular joint

Acromioclavicular joint

Coracovicular joint

Glenohumeral joint

Scapulothoracic joint

scapulscapulaa

clavicaclavicall

hum

eru

shum

eru

s

“shrugging of shoulders” (raise scapula)

Elevation Trapezius, levator scapulae

“unshrug shoulders” (lower scapula to inferior position)

Depression

Pectoralis minor, latissimus dorsi , trapezius

“squaring of shoulders” (scapula moves backward)

Retraction Trapezius, rhomboids

TrapeziusTrapezius

Levator Levator scapulaescapulae

Rhomboid Rhomboid major major

Rhomboid Rhomboid minor minor

Posterior Posterior muscles muscles that act on that act on the pectoral the pectoral girdle girdle

“upward swing” abduction of upper limb (i.e., arm overhead)

Superior Rotation

Trapezius, serratus anterior

“downward swing” adduction of upper limb (i.e. arms by side)

Inferior rotation

Levator scapulae, rhomboids, pectoralis minor

Anterior Anterior muscles muscles that act on that act on the pectoral the pectoral girdle girdle

TrapeziusTrapezius

Levator Levator scapulaescapulae

Rhomboid Rhomboid major major

Rhomboid Rhomboid minor minor

“hunching of shoulders” (i.e., scapula moves forward)

Protraction Pectoralis minor, serratus anterior

“pushing and punching” (i.e., forward movements of arm)

Lateral rotation Serratus anterior

“upward swing” abduction of upper limb (i.e., arm overhead)

Medial Rotation Serratus anterior

Anterior Anterior muscles that muscles that act on the act on the pectoral pectoral girdle girdle

Serratus Serratus anterioranterior

Pectoralis Pectoralis minorminor

Teres minor Supraspinitus Infraspinitus Sucapsularis

Latissimus dorsi

Pectoralis minor

Deltoid Coracobrachialis Teres major

2 axial2 axial3 scapular3 scapular

4 rotator cuff4 rotator cuff

Nine muscles act on humerusNine muscles act on humerus

Axial muscles acting on the humerus attach arm to trunk and are prime movers of shoulder

Pectoralis major

Flexes, abducts and medially rotates (as in climbing or hugging)

Latissimus dorsi

Extensor/adductor/medial rotatorExtends shoulder joint as in pulling on oars of a row boat; produces backward spring of arm when walking or bowling; with hands overhead pulls body forward and upward in climbingMore concerned with arm movement than movement of scapula

Rotator cuff muscles reinforce the joint capsule and hold humerus in the glenoid cavity

Supraspinatus Adductor

Infraspinatus Adductor, lateral rotator

Teres Minor Lateral rotator

Subscapularis Rotates medially

SupraspinatuSupraspinatuss

InfraspinitInfraspinitususTeres Teres minorminor

Supraspinitus assists in abduction of the arm.

RelaxedRelaxed ContracteContractedd

Three rotator cuffs muscles pull the greater tubercle of the humerus toward the scapula

Infraspinitus rotate humerus laterally and prevents humerus from sliding upwards

Teres minor rotates humerus laterally, prevents humerus from sliding upwards and modulates action of deltoid

DeltoidFlexor/extensor/adductor/medial and lateral rotator-swinging of arm during walking and adjustment of arm height

Cocoracobrachialis

Flexes and medially rotates arm

Teres majorExtends and medially rotates arem contributes to arm swinging

CoracobrachiCoracobrachialisalis

DeltoiDeltoidd

Teres major

Remaining shoulder muscles are scapular

Origins:

1. sternal end of clavicle

2. sternum, cartilage of ribs 1-6 or 7,

3. apponeurosis of external oblique muscle

Insertion: intertubercular groove of humerus

When the pectoralis major shortens insertion moves toward origin and the arm is pulled across the chest is a movement that adducts the arm and flexes the shoulder

Muscle of the shoulder: pectoralis major

When the deltoid shortens insertion moves toward origin

Origin Origin

InsertioInsertion n

Arm is pulled away from body (i.e., abducted)

Arm is horizontal when the deltoid is contracted fully

Deltoid (large, fleshy, triangular muscle that covers the shoulder and causes the bulge of the upper arm) runs from both the clavicle and the scapula to the humerus.

Latissimus dorsi is a wide, triangular muscle of the lower back. This muscle originates from the lower spine and sweeps upward to insert on the humerus. to extend and adduct the arm. This muscle is very important for swimming, rowing, and climbing a rope.

Origin: indirect attachment via lumbodorsal fascia into spines of lower 6 thoracic vert., lumbar vert.,lower 4 to 4 ribs and iliac crest

Insertion: spirals around teres major to insert into the intertubercular groove of humerus

Shoulder movement: latissimus dorsi

Muscles with Bellies in the Arm (Brachium)

Brachialis Elbow flexion

Biceps brachiiRapid and forceful supination, synergist in elbow flexion

Triceps brachiiExtend elbow aid in shoulder adduction

Biceps brachii is a muscle of the anterior upper arm that is familiar because it bulges when the forearm is flexed. It also supinates the hand when a doorknob is turned or a cap of a jar is unscrewed. The name of the muscle refers to its two heads that attach to the scapula, where it originates. The biceps brachii inserts on the radius.

Muscles of the shoulder/elbow: biceps brachii

Origin Origin

InsertioInsertion n

Origins: scapula (long head); posterior shaft of humerus (lateral head); posterior humeral shaft distal to radial groove (medial head)

Insertion: by common tendon into olecranon process of ulna

Muscles of the shoulder/elbow: triceps brachii

Triceps brachii is the only muscle of the posterior upper arm. It has three heads that attach to the scapula and humerus, and it inserts on the ulna. The triceps extends the forearm when something is pushed. It is sometimes called the boxer's muscle because it straightens the elbow when a punch is thrown.

Muscles of the shoulder/elbow: triceps brachii

Contraction Contraction of triceps of triceps straightens straightens arm and arm and pulls the pulls the elbow openelbow open

Muscles with Bellies in the forearm (Antebrachium)

Brachioradialis Flexes elbow

Aconeus Extend elbow

Supinator Supinates forearm

Pronator teres Pronation

Muscle of the Wrist

Flexor carpi radialis Flexor, abduction

Flexor digitorum flexor

Flexor carpi radialis muscle originates on the bones of the forearm and insert on the bones of the hand. They move the wrist and hand. Notice this muscle is on the anterior side of the arm

Muscles of the wrist: flexor carpi radialis

Origin: medial epicondyle of humerus

Insertion: base of second and third metacarpals

When the flexor carpi radialis shortens the insertion moves toward origin and the wrist flexes

Origin Origin

Insertion Insertion

The hand moves out of the plane of the image towards you-bending the wrist downwards to the forearm

Muscles of the wrist: flexor carpi radialis

The extensor digitorum muscle originates on the bones of the forearm and insert on the bones of the hand. They move the fingers.

Notice that this muscle is on the posterior side of the arm

Muscles of the wrist: extensor digitorum

Origin: Lateral epicondyle of humerus

Insertion: medial 4 digits

Muscles of the wrist: extensor digitorum

When the extensor digitorum shortens the insertion moves toward origin and the wrist flexes

Origin Origin

Insertion Insertion

The hand moves out of the plane of the image towards you bending the wrist backwards

Movement of Movement of Hip/Thigh/Leg Hip/Thigh/Leg

MusclesMuscles

Muscles of the thigh and lower limb tend to be large and heavy because they are used to move the entire weight of the body and resist the force of gravity. Therefore, they are important for movement and balance.

Muscles that Move the Thigh

Muscle that Move the Thigh

Iliopsoas Flexion

Sartorius Flexion and adduction

Adductors (magnus, longus, brevis)

Flexion, adduction, medial rotation, and extension by Adductor Magnus

Gracilis Flexion, adduction, medial rotation

Rectus femoris Flexion

Muscles that Move the Thigh

IliopsoasIliopsoas originates originates from the ilium and the from the ilium and the bodies of the lumbar bodies of the lumbar vertebrae, and inserts vertebrae, and inserts on the femur anteriorly. on the femur anteriorly. This muscle flexes the This muscle flexes the thigh and is important thigh and is important to the process of to the process of walking. It also helps walking. It also helps prevent the trunk from prevent the trunk from falling backward when a falling backward when a person is standing person is standing erect.erect.

Muscles that Move the Thigh

The Sartorius is a long, straplike muscle that begins at the iliac spine and then passes inward across the front of the thigh to descend over the medial side of the knee. It flexes the leg and is used to sit cross-legged, as tailors were accustomed to do in another era. Therefore, it is sometimes called the tailor's muscle, and, in fact, sartor means tailor in Latin.

Origin: anterior superior iliac spine

Insertion: winds around medial aspect of knee and inserts into medial aspect of proximal tibia

Sartiorus

Because the insertion Because the insertion is below the knee as is below the knee as the muscle shortens the muscle shortens the knee will bend the knee will bend (flexion)(flexion)

Because the origin is Because the origin is above the hip as the above the hip as the muscle shortens the muscle shortens the hip will bend (flexion)hip will bend (flexion)

Because the muscle crosses from Because the muscle crosses from the lateral to the medial side of the the lateral to the medial side of the leg, when the muscle shortens the leg, when the muscle shortens the leg will twist outward (laterally leg will twist outward (laterally rotate) as insertion moves to rotate) as insertion moves to origin. origin.

Muscles that Move the Thigh

Arrow indicate direction of femur movement when adductors contract

Adductor muscles are located on the inner thigh (medial aspect). They originate from the pubic bone and ischium, and insert on the femur. Adductor muscles adduct the thigh and press the thighs together. As the muscles shorten they will pull the medial femur toward the midline

Insertion: anterior medial tibial condyle

Origin: inferior ramus and body of pubisThe Gracillis muscles are located on the

medial parts of each thigh. They originate from the pubic bone and ischium, and insert on the femur. Adductor muscles adduct the thigh and press the thighs together.

The Gracilis assists the Sartorius in flexing the leg and rotating it inward; it is also an adductor of the thigh. If the lower extremities are fixed, these muscles maintain the body in an erect posture and if contracted can flex the pelvis forward upon the femur

Note: this is the back of the legNote: this is the back of the legMuscle that Move the Thigh

Muscles that Move the Lower Limb

The quadraceps is a powerful knee extensor used in climbing, jumping, running, and rising from a seated position. This muscle group arises from 4 heads that form the flesh of the front sides of the thigh (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius)

Muscles that Move the Thigh

Quadriceps femoris group includes muscles found in the front and on the sides of the thigh.

The rectus femoris, which originates from the ilium, lies in front of the vastus intermedius. The vastus muscles originate from the femur. They are primary extensors of the lower leg, such as when a ball is kicked.

Origin: anterior inferior iliac spine and superior margin of acetabulum

Insertion: patella and tibial tuberosity via patellar ligament

Origin: anterior inferior iliac spine and superior margin of acetabulum

Insertion: patella and tibial tuberosity via patellar ligament

Because muscle attaches to the anterior iliac spine (origin) and inserts into the patella and the tibial tuberosity (both on the anterior leg), the contraction of the rectus femoris is going to pull the knee closer to the hip. To achieve this the hip bends (flexion) and the knee is straightened (extension). When the knee is flexed the proximal tibia is actually farther away from the anterior pelvis than when the leg is straight.

Note: this is the front of the legNote: this is the front of the leg

Muscles that Move the Thigh

Muscles that Move the ThighGluteus maximus is the largest muscle in the body and covers a large part of the buttock. It originates at the ilium and sacrum, and inserts on the femur. The gluteus maximus acts to straighten the leg at the hip when a person is walking, climbing stairs, or jumping from a crouched position.

Gluteus medius lies party behind the gluteus maximus, runs between the ilium and the femur, and abducts the thigh. When it contracts the femur is pulled laterally and turned slightly inward

Gluteus minimus is the smallest and deepest of the gluteal muscles and has the same function as the gluteus medius. When contracted it pulls the femur out of the plane of this image and rotated slightly outward

Hamstring muscles: posterior thigh

Biceps femoris

Hamstrings are muscles in the back of the thigh that have origins on the ischium and insert on the tibia and flex the knee and extend the hip. Their strong tendons are felt behind the knee.

Semitendinosus

Semimembranosus

Note: images are posterior Note: images are posterior viewview

Long head origin: ischial tuberosity

Long head insertion: fibular head

Muscles that Move the Thigh and Leg

When the long head of the biceps femoris muscle shortens it is going to shorten the distance between the pelvis and the tibia. The only way this can happen is if the knee bends and the hip straightens

Muscles the Move the Leg

Short head origin: linea aspera

Short head insertion: Tibial condyle

When the short head of the biceps femoris muscle shortens it is going to shorten the distance between the femur and the tibia. The only way this can happen is if the knee bends

Moves backwards when muscle shortens

Origin: ischial tuberosity

Insertion: medial condyle of tibia and lateral condyle of femur

Note: this is the back of the legNote: this is the back of the leg

Semimembranousus: because the ischial tuberosity is on the posterior pelvis and both the medial condyle of the tibia and the lateral condyle are on the posterior femur, the contraction of the semimembranosus is (1) pulls the back of the femur (just above the knee joint) backwards toward the bottom (opening up or straightening out the hip; extension) and (2) pulling the proximal tibia towards the hip flexing the knee.

Muscles the Move the Leg

Origin: medial femoral condyle; femoral lateral condyle

Insertion: achilles tendon; calcaneal surface

Gastrocnemius is located on the back of the leg, where it forms a large part of the calf. It arises from the femur; distally, the muscle joins the strong Achilles tendon, which attaches behind the calcaneus bone (heel). The gastrocnemius is a powerful plantar flexor of the foot

Muscles that Move the Ankle and Foot

that aids in pushing the body forward during walking or running. It is sometimes called the toe dancer's muscle because it allows a person to stand on tiptoe.

Muscles that Move the Ankle and Foot

Origin: lateral condyle and upper 2/3 of tibial shaft

Insertion: by tendon into first metatarsal bone

Tibialis anterior is a long, spindle-shaped muscle located on the front of the lower leg. It arises from the surface of the tibia and attaches to the bones of the ankle and foot.

Contraction of this muscle causes dorisflexion and inversion of the foot.

As the muscle contracts this point is going to be drawn up and laterally rotated (turned out towards the knee)

Muscles that Move the Ankle and Foot

Flexor and extensor digitorum longus muscles are found on the lateral and posterior portion of the leg. They arise mostly from the tibia and insert on the toes. They flex and extend the toes, and assist in other movements of the feet.

Note: this is the back of the leg