The Muscular System

Five Golden Rules of Skeletal Muscle Activity

Table 6.2

Muscles and Body MovementsMovement is attained due to a muscle

moving an attached boneMuscles are attached to at least two points

OriginAttachment to a moveable bone

InsertionAttachment to an immovable bone

Muscles and Body Movements

Figure 6.12

Types of Ordinary Body MovementsFlexion

Decreases the angle of the jointBrings two bones closer togetherTypical of hinge joints like knee and elbow

ExtensionOpposite of flexionIncreases angle between two bones

Types of Ordinary Body Movements

Types of Ordinary Body Movements

Figure 6.13b

Types of Ordinary Body MovementsRotation

Movement of a bone around its longitudinal axis

Common in ball-and-socket jointsExample is when you move atlas around the

dens of axis (shake your head “no”)

Types of Ordinary Body Movements

Figure 6.13c

Types of Ordinary Body MovementsAbduction

Movement of a limb away from the midlineAdduction

Opposite of abductionMovement of a limb toward the midline

Types of Ordinary Body Movements

Figure 6.13d

Types of Ordinary Body MovementsCircumduction

Combination of flexion, extension, abduction, and adduction

Common in ball-and-socket joints

Types of Ordinary Body Movements

Figure 6.13d

Special MovementsDorsiflexion

Lifting the foot so that the superior surface approaches the shin

Plantar flexionDepressing the foot (pointing the toes)

Special Movements

Figure 6.13e

Special MovementsInversion

Turn sole of foot mediallyEversion

Turn sole of foot laterally

Special Movements

Figure 6.13f

Special MovementsSupination

Forearm rotates laterally so palm faces anteriorly

PronationForearm rotates medially so palm faces

posteriorly

Special Movements

Figure 6.13g

Special MovementsOpposition

Move thumb to touch the tips of other fingers on the same hand

Special Movements

Figure 6.13h

Types of MusclesPrime mover—muscle with the major

responsibility for a certain movementAntagonist—muscle that opposes or

reverses a prime moverSynergist—muscle that aids a prime mover

in a movement and helps prevent rotationFixator—stabilizes the origin of a prime

mover

Naming Skeletal MusclesBy direction of muscle fibers

Example: Rectus (straight)By relative size of the muscle

Example: Maximus (largest)

Naming Skeletal MusclesBy location of the muscle

Example: Temporalis (temporal bone)By number of origins

Example: Triceps (three heads)

Naming Skeletal MusclesBy location of the muscle’s origin and

insertionExample: Sterno (on the sternum)

By shape of the muscleExample: Deltoid (triangular)

By action of the muscleExample: Flexor and extensor (flexes or

extends a bone)

Arrangement of Fascicles

Figure 6.14

Head and Neck MusclesFacial muscles

Frontalis—raises eyebrowsOrbicularis oculi—closes eyes, squints, blinks,

winksOrbicularis oris—closes mouth and protrudes

the lipsBuccinator—flattens the cheek, chewsZygomaticus—raises corners of the mouth

Chewing musclesMasseter—closes the jaw and elevates

mandibleTemporalis—synergist of the masseter,

closes jaw

Head and Neck MusclesNeck muscles

Platysma—pulls the corners of the mouth inferiorly

Sternocleidomastoid—flexes the neck, rotates the head

Head and Neck Muscles

Figure 6.15

Muscles of Trunk, Shoulder, ArmAnterior muscles

Pectoralis major—adducts and flexes the humerus

Intercostal muscles External intercostals—raise rib cage during

inhalationInternal intercostals—depress the rib cage to move

air out of the lungs when you exhale forcibly

Anterior Muscles of Trunk, Shoulder, Arm

Figure 6.16a

Muscles of Trunk, Shoulder, ArmMuscles of the abdominal girdle

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

Anterior Muscles of Trunk, Shoulder, Arm

Figure 6.16b

Muscles of Trunk, Shoulder, ArmPosterior muscles

Trapezius—elevates, depresses, adducts, and stabilizes the scapula

Latissimus dorsi—extends and adducts the humerus

Erector spinae—back extensionQuadratus lumborum—flexes the spine

laterallyDeltoid—arm abduction

Muscles of Posterior Neck, Trunk, Arm

Figure 6.17a

Muscles of Posterior Neck, Trunk, Arm

Figure 6.17b

Muscles of the Upper LimbBiceps brachii—supinates forearm, flexes

elbowBrachialis—elbow flexionBrachioradialis—weak muscleTriceps brachii—elbow extension

(antagonist to biceps brachii)

Anterior Muscles of Trunk, Shoulder, Arm

Figure 6.16a

Muscles of Posterior Neck, Trunk, Arm

Figure 6.17a

Muscles of the Lower LimbGluteus maximus—hip extensionGluteus medius—hip abduction, steadies

pelvis when walkingIliopsoas—hip flexion, keeps the upper

body from falling backward when standing erect

Adductor muscles—adduct the thighs

Muscles of the Pelvis, Hip, Thigh

Figure 6.19a

Muscles of the Pelvis, Hip, Thigh

Figure 6.19c

Muscles of the Lower LimbMuscles causing movement at the knee

jointHamstring group—thigh extension and knee

flexionBiceps femorisSemimembranosusSemitendinosus

Muscles of the Pelvis, Hip, Thigh

Figure 6.19a

Muscles of the Lower LimbMuscles causing movement at the knee

jointSartorius—flexes the thighQuadriceps group—extends the knee

Rectus femorisVastus muscles (three)

Muscles of the Pelvis, Hip, Thigh

Figure 6.19c

Muscles of the Lower LimbMuscles causing movement at ankle and

footTibialis anterior—dorsiflexion and foot

inversionExtensor digitorum longus—toe extension

and dorsiflexion of the footFibularis muscles—plantar flexion, everts the

footSoleus—plantar flexion

Muscles of the Lower Leg

Figure 6.20a

Muscles of the Lower Leg

Figure 6.20b

Superficial Muscles: Anterior

Figure 6.21

Superficial Muscles: Posterior

Figure 6.22

Superficial Anterior Muscles of the Body

Table 6.3 (1 of 3)

Superficial Anterior Muscles of the Body

Table 6.3 (2 of 3)

Superficial Anterior Muscles of the Body

Table 6.3 (3 of 3)

Superficial Posterior Muscles of the Body

Table 6.4 (1 of 3)

Superficial Posterior Muscles of the Body

Table 6.4 (2 of 3)

Superficial Posterior Muscles of the Body

Table 6.4 (3 of 3)