General review:

In dealing with the human body the whole is greater than the sum of the parts. The human skeleton combines two opposites: STABILITY - from the front the skeleton is balanced BI-symmetrically: ACTION - from the side balance is achieved by movement around a center of gravity.

The skeleton is the ARCHITECTURAL aspect of the body, the mechanical design. The individual parts can be separated from the rest without destroying the whole. The division between the parts is clearly defined. The proportions and actions of the figure are determined by the skeleton.

The muscles are the ORGANIC aspect of the body. They imbricate or lace together the bony structure. All joints but one (the iliac crest) are crossed by muscles. The muscular system cannot be taken apart as can the skeletal without damaging the integrity of the system.

The skeleton can be clearly seen in the living figure. Where bone is near the surface it is said to be SUBCUTANEOUS.

The single most important influence on the skeleton is the backbone. While the backbone is never seen in its entirety in the living body its influence is always felt.

The skeletal divisions of the trunk of the body are: the thorax (ribcage), the lumbar region (section between the ribcage and pelvis), and the pelvis.

GENERAL TERMS OF DESCRIPTION:

                anterior - front                                                posterior - back

                superior - upper, towards top                        inferior - lower, towards bottom

                internal - inside                                                external - outside

                medial - nearer mid line                                lateral - further from mid line

                supine - forearm and hand, turned                prone - forearm and hand, turned palm-side

                         palm-side upward                                                 downward

                dorsal - refers to back; also the back of the hand and top of the foot

TERMS OF DESCRIPTION: THE MUSCULAR SYSTEM

                origin - relatively fixed point of muscle attachment

                insertion - relatively moveable point of muscle attachment

PARTS:

                ligament - fibrous tissue binding bone together or lashing tendons or muscles in place body or belly of muscle - fleshy                                  part that contracts and changes form

                tendon - fibrous end of muscle that attaches to bone (tendons do not change form but do become more visible in action

                aponeurosis - expanded tendon for attachment of flat muscle

                fascia - fibrous envelope covering groups of muscles

TYPES:

                long - long body with cord-like tendons (arm and leges)

                broad - wide, thin body with aponeurotic tendons (trunk)

                short - sometimes without tend, making direct connection with bone (face, hands, feet)

SITUATION:

                superficial - principally on external form

                deep - fill depression of skeleton; lie under superficial muscles and influence form indirectly

MUSCLES ARE NAMED ACCORDING TO:

                region - as in pectoral (breast), temporalis (temporal region of skull)

                direction - as in external oblique (direction of fibers)

                dimension - as in supinator longus

                form or shape - as in trapezius, rhomboid

                structure - as in semitendinosus or number of heads - triceps, biceps

                function - as in erector spinae, extensor digitorium longus

                attachments - as in sternomastoid (sternocleidomastoid)

NAMES DESCRIBING ACTION:

                flexor - causes bending or angulation

                extensor - straightens

                levatator - raises

                abductor - draws away from mid line

                adductor - draws toward mid line

                tensor - draws tight

                rotator - causes to revolve

                supinator - turns palm of hand upward or forward

                pronator - turns palm of hand downward or backward

PECTORALIS MINOR: deep muscle - helps fill out side of chest

                origin: ribs 3, 4, 5

                insertion: corocoid process of scapula

                form: helps fill out armpit area

                function: helps pull scapula and clavicle down and lower the margin of the scapula medially

SERRATUS MAGNUS: greater part of the muscle is hidden by pectorals and lattisimus

                origin: upper 8 ribs - each segment wraps around a rib

                insertion: in back - medial border of scapula on interior surface

                form: can see lower 3 segments when arm is at the side; 4 when arm is raised - often mistaken for ribs

                function: pulls scapula tight against ribs

PECTORALIS MAJOR: entirely superficial

                origin: inner half or third of clavicle; entire length of sternum; upper six ribs

                insertion: bicipital groove

                form: fills in upper part of chest, creates anterior margin of armpit

                function: draws arm forward and inward; rotates arm inward (with teres major); lowers raised arm

EXTERNAL OBLIQUE:

                origin: extends from lower 8 ribs to anterior half of iliac crest; more a muscle of the side interdigitates with the serratus                              magnus; broad, flat aponerosis from base of pectoralis major to anterior superior iliac spines and pubic bone

                insertion: anterior third of iliac crest - thickest part just above the iliac crest

                form: fills space between base of ribcage and pelvic crest

                function: with fixed pelvis - draws ribcage downward; rotates torso side to side and pulls ribcage down in side bends; with                                  fixed ribcage - elevates the pelvis (os coxae)

RECTUS ABDOMINIS:

                origin: pubic crest

                insertion: 5, 6, 7th ribs right above thoracic arch and below pectoralis major - divided into four groups

                form: converts thoracic arch from V-shape to a more rounded shape

                function: to flex trunk: NOTE: rectus folds at the base of the ribs and at the navel

SURFACE LANDMARKS OF THE TRUNK:

                above the clavicle - triangular hollow made by sterno-mastoid and trapezius: supra clavicular depression

                below the clavicle - smaller triangular hollow; infra clavicular depression - between the deltoid and the pectoralis major

ERECTOR SPINAE GROUP - partly superficial, partly deep - run on either side of the spine; common mass is inferior end of                                  backbone and spreads into 3 separate groups

                origin: dorsal surface of sacrum; spinous processes of all lumbar vertebrae and 2 or 3 lowest thoracic vertebrae

                insertion: inserts into ribs at angle of the ribs and to various points of the spine

                function: connects lower spine to upper - braces spine, keeps body upright (when standing erect muscles do little work                                  but come into play as body begins to bend forward, backward or sideways)

                form: helps create rounded forms on either side of backbone in lumbar region

SPLENIUS - another deep muscle - important in moving neck (sometimes considered part of the erector spinae group)

                origin: lower part of nuchal ligament down to 7th cervical; another part drops down to the about to about mid-thoracic                                  vertebra (6th)

                insertion: both mastoid processes

                function: strengthens neck - helps hold neck erect - helps pull head around (from back)

                form: helps fill out upper back of the neck

RHOMBOIDS

                origin: lower 6th and 7th cervical spinous processes and spinous process of thoracic vertebrae 1 through 4

                insertion: upper and lower vertical margins of scapulae

                function: to draw shoulder blades together

                form: great fullness in center of back becoming a bulge when shoulder blades are drawn together

ELEVATOR OF THE SCAPULA - thin set of muscles

                origin: upper transverse pines (3 or 4) of cervical vertebrae

                insertion: upper medial angle of the scapula

                function: helps raise shoulder blades

                form: helps fill out sides of neck at back

SUPERFICIAL MUSCLES (posterior)

                three sets of muscles connect upper humerus with scapula - all underneath spine of the scapula

INFRASPINATUS - larger and superior to teres minor

        and

TERES MINOR

                origin - entire posterior surface of scapula starting at medial margin

                insertion: back of head of humerus

                function: rotate arms outward - pulls against head of humerus

                form: region over scapula bulges when flexed - fills in region under the spine of the scapula - creates a depression                                  along the spine of the scapula

TERES MAJOR

                origin - inferior angle of scapula

                insertion - passes to front of humerus and inserts in bicipital groove

                function - rotates arm inward

                form - same as teres minor

The muscles of the scapula all rotate the arm.

LATISSIMUS DORSI - largest muscle in the body in terms of covering square inches - flat muscle

                origin - lower 6 thoracic vertebrae; all lumbar vertebrae; region of the sacral triangle; posterior third of the iliac crest. The                                  lower part of the latissimus is a diamond-shaped tendonous sheath which covers the erector spinae muscles

                insertion - extends upwards, curves around side of body and becomes much thinner (a strap) and inserts in the bicipital                                  groove of the humerus

                function - pulls arms down and back (called the "swimmer’s muscle")

                form - muscle thickest on lateral margin of the trunk - it shows most clearly here

TRAPEZIUS - fill upper back

                origin - extends from the occipital protuberance of skull down nuchal ligament and spinous processes of thoracic                                  vertebrae to #12

                insertion - outer half to third of the clavicle, all the way around to the acromion process to the upper margin of the spine of                                  the scapula and then to the inner margin of the scapula

                function - can raise shoulders, help turn head if one side is contracted and the other relaxed; can pull down the shoulders                                  from the lower fibers

                form - fills out shoulders, adds fullness to upper center back

DELTOID - like the trapezius it wraps from front to back of the trunk

                origin - directly below insertion of trapezius on outer third to half of the clavicle - seems to continue the mass of the                                  trapezius; continues around to the acromion process and the entire lower margin of the spine of the scapula

                insertion - on lateral side of humerus about half way down (the deltoid impression)

                function - to raise arms - not much leverage because the attachment is only halfway down the humerus

                form - rounds shoulder - thickest mass is about center of the upper half of the humerus NOT at the head of the humerus