introduction to gross anatomy of the muscular system

ANATOMY & PHYSIOLOGY

BIO 181

INSTRUCTOR: FRED WENDLER

INTRODUCTION TO GROSS ANATOMY

OF THE MUSCULAR SYSTEM BASED ON THE BOOKS: HUMAN ANATOMY & PHYSIOLOGY, NINTH EDITION

BY ELAINE N. MARIEB AND KATJA HOEHN; AND ANATOMY AND PHYSIOLOGY

FROM OPENSTAX COLLEGE, ISBN 1-938168-13-5

WITH ILLUSTRATIONS FROM HUMAN ANATOMY & PHYSIOLOGY, NINTH

EDITION BY ELAINE N. MARIEB AND KATJA HOEHN; AND ANATOMY AND

PHYSIOLOGY FROM OPENSTAX COLLEGE, ISBN 1-938168-13-5

Following are the characteristics used in

naming skeletal muscles.

Refer to Exercise 11, page 126, Classification

of Skeletal Muscles

Naming Skeletal Muscles

• Direction of muscle fibers or fascicles

• Relative size of the muscle

• Muscle location

• Number of origins

• Location of attachments

• Muscle action

• Muscle shape


• Direction of muscle fibers or fascicles

– Rectus – fibers run straight; rectus abdominis

– Transversus – fibers run at right angles;

transversus abdominis

– Oblique – fibers run at angles to imaginary defined

axis; external oblique; internal oblique

Figure 10.12a Muscles of the abdominal wall.

Linea alba

Tendinous intersection

Rectus abdominis

Inguinal ligament

(formed by free inferior

border of the external

oblique aponeurosis)

Aponeurosis

of the external

oblique

Transversus abdominis

Internal oblique

External oblique

Based on: Elaine N. Marieb and Katia Hoehn; HUMAN ANATOMY & PHYSIOLOGY, Ninth Edition; Pearson Education, Inc.; Boston, 2013.


• Relative Size of Muscle

– Maximus – largest; gluteus maximus

– Minimus – smallest; gluteus minimus

– Longus – longest; adductor longus

– Brevis – shortest; adductor brevis


• Muscle location

– bone or body region with which muscle

associated

– The temporalis lie over the temporal bone

Figure 10.8a Muscles promoting mastication and tongue movements.

Buccinator

Temporalis

Masseters



• Number of origins

– 2 origins – biceps; biceps brachii

– 3 origins – triceps; triceps brachii


• Location of attachments

– named according to point of origin and insertion

(origin named first)

– Example: sternocleidomastoid

• Sternum (sterno)

• Clavicle (cleido)

• Mastoid

Figure 10.10a Muscles of the neck and vertebral column that move the head

and trunk.

Sternocleido-mastoid

Mastoidprocess

Anterior



• Muscle action

– named for action they produce

• Flexion - flexor digitorum

• Extension – extensor digitorum


• Muscle shape

– deltoid muscle is shaped like a triangle

– trapezius is shaped like a trapezoid

**Several criteria can be combined, e.g.,

extensor carpi radialis longus

Muscle Shape and Arrangement of

Fascicles/Fiber Alignment

Most common patterns:

• Circular

• Convergent

• Parallel

• Fusiform

• Pennate

Muscle Shapes and Fiber Alignment• The skeletal muscles of the body typically

come in seven different general shapes.

Figure 11.3

Arrangement of Fascicles

• Circular

– Fascicles arranged in concentric rings (e.g.,

orbicularis oris)

• Convergent

– Broad origin; fascicles converge toward single

tendon insertion (e.g., pectoralis major)

Figure 10.2 Patterns of fascicle arrangement in muscles.

Convergent(pectoralis major)

Circular

(orbicularis oris)

Fusiform(biceps brachii)

Parallel (sartorius)

Multipennate

(deltoid)

Bipennate(rectus femoris)

Unipennate(extensor digitorum longus)

(a)

(b)(c)

(d) (f)

(g)

(e)

Elaine N. Marieb and Katia Hoehn; HUMAN ANATOMY & PHYSIOLOGY, Ninth Edition; Pearson Education, Inc.; Boston, 2013.

Muscle Mechanics: Arrangement of

Fascicles

• Parallel

– Fascicles parallel to long axis of straplike

muscle (e.g., sartorius)

• Fusiform

– Spindle-shaped muscles with parallel fibers

(e.g., biceps brachii)



Circular

(orbicularis oris)



Multipennate

(deltoid)



(a)

(b)(c)

(d) (f)

(g)

(e)


Muscle Mechanics: Arrangement of

Fascicles

• Pennate

– Short fascicles attach obliquely to central

tendon running length of muscle

• Three forms

– Unipennate – fascicles attach only to one side of tendon

(e.g., extensor digitorum longus)

– Bipennate – fascicles insert from opposite sides of

tendon (e.g., rectus femoris)

– Multipennate –appears as feathers inserting into one

tendon (e.g., deltoid)



Circular

(orbicularis oris)



Multipennate

(deltoid)



(a)

(b)(c)

(d) (f)

(g)

(e)


Arrangement of Fascicles

• Determines muscle's range of motion

• Determines muscle’s power

Types of Skeletal Muscle

• Muscles can only pull; never push

• What one muscle group "does", another

"undoes"


• Functional Groups

– Prime mover (agonist)

• Major responsibility for producing specific

movement

– Antagonist

• Opposes or reverses particular movement

– Prime mover and antagonist on opposite

sides of joint across which they act


• Synergist helps prime movers

– Muscle whose contraction helps a prime mover in

an action

• Fixator

– A special synergist

– Muscle that immobilizes bone or muscle's origin

– Gives other muscles a stable base on which to act

so all the tension is exerted at the insertion

– Example: the muscles that fix the scapula during

arm movements are fixators

Figure 11.2

Prime Movers

and Synergists• The biceps brachii

flex the lower arm.

• The brachoradialis,

in the forearm, and

brachialis, located

deep to the biceps

in the upper arm,

are both synergists

that aid in this

motion.

Anatomy and Physiology from OpenStax College

Major Skeletal Muscles of the Body

Figure 10.5 Superficial muscles of the body: Anterior view.

Head

Neck

Epicranius, frontal bellyOrbicularis oculiZygomaticusOrbicularis orisTemporalis

MasseterPlatysmaSternohyoidSternocleidomastoid

ThoraxPectoralis minorPectoralis majorSerratus anteriorIntercostals

AbdomenRectus abdominisExternal obliqueInternal obliqueTransversus abdominis

ThighTensor fasciae lataeSartoriusAdductor longusGracilis

Leg

Fibularis longusExtensor digitorumlongus

Tibialis anterior

ThighRectus femoris

Vastus lateralis

Vastus medialis

Pelvis/thighIliopsoas

Pectineus

ForearmPronator teresBrachioradialisFlexor carpi radialisPalmaris longus

ArmTriceps brachiiBiceps brachiiBrachialis

Shoulder

Trapezius

Deltoid

Facial


Figure 10.6 Superficial muscles of the body: Posterior view.

NeckEpicranius, occipital bellySternocleidomastoidTrapezius

ShoulderDeltoidInfraspinatusTeres major

Rhomboid majorLatissimus dorsi

HipGluteus mediusGluteus maximus

Adductor magnus

Biceps femorisHamstrings:

SemitendinosusSemimembranosus

LegGastrocnemiusSoleus

Fibularis longusCalcaneal(Achilles) tendon

Iliotibial tract

ArmTriceps brachii

BrachialisForearmBrachioradialisExtensor carpi radialislongusFlexor carpi ulnaris

Extensor carpi ulnarisExtensor digitorum

Thigh


introduction to gross anatomy of the muscular system

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