The dorsal interossei are spreaders, drawing away from the centre, and so are fastened to both sides of the middle finger and to the ou tside of the other joints. In the thumb and little fingers the muscles of this set are called abductors, and being in exposed positions, are larger. That of the first finger forms a prominent bulge between it and the thumb; that of the little finger forms a long fleshy mass reaching to the wrist.
It is slightly arched across the back. Somewhat more arched are the knuckles, concentric around the base of the thumb. The second knuckle is larger and higher than the rest; the first is lower on its thumb side, where it has an overhang, as has also the knuckle of the little finger, due to their exposed positions.
Belonging to the hand is the pyramidal mass of the first segment of the thumb, which joins on at an angle, never quite flat with the hand, and bending under it to more than a right angle with its flat surface.
The thumb may be drawn in until only its root bulges beyond the lateral line of the hand, and may be carried out to a great angle with it. In this latter position its first segment forms a triangle whose base is the side of the hand, equal to it in length; whose height is, on the palmar surface, equal to the width of the hand, and on the dorsal surface, almost as great. On the little finger side, the form is given by the abductor muscle and the overhang of the knuckle, by which the curve of that side is carried well up to the middle of the first segment of the finger.
The pad of the palm overlaps the wrist below and the knuckles above, reaching to the middle of the first segment of the fingers. On the back of the hand, nearly flat except in the clenched fist, the tendons of the long extensors are superficial, and may be raised sharply under the skin.
They represent two sets of tendons more or less blended, so are double and have connecting bands between them. Eight bones carpal bones in two rows make the arch of the wrist; in size they are like deformed dice. The two pillars of this arch are seen on the palmar side, prominent under the thumb and the little finger. The latter is the heel of the hand, but the arch is thicker and a bit higher on the thumb side.
Under it pass the long flexor tendons to the fingers and thumb. The dome of the arch is seen on the back, with an apex at the trapezium under the first finger. I t is crossed by the long extensor tendons of the fingers, which converge on its outer half.
It is narrower both ways where it joins the arm, giving an appearance of constriction. There is always a step-down from the back of the arm, over the wrist, to the hand.
Its movement is like that of a boat in water; easily tipping sideways flexion and extension with more difficulty tilting endways side-bending which in combination give some rotary movement, but having no twisting movement at all. This movement is accomplished by the forearm. The inset of this boat-shaped joint with the arm gives the appearance of constriction. The prow, under the thumb, is higher than the stern under the little finger.
When the wrist is fully flexed, it forms at the back a great curve over which the extensor tendons are drawn taut, so much so that the fingers can never be closed when the wrist is fully flexed. In this position the flexor tendons are raised prominently under the skin. When hand and arm lie extended along a flat surface, it is the heel of the hand that is in contact, the arm bones being lifted from the surface. To the four corners of the wrist are fastened muscles; two in front flexor carpi radialis and flexor carpi ulnaris and two behind extensor carpi radialis and extensor carpi ulnaris, the former being double.
By their contraction the wrist is moved in all directions, except twisting, which movement is produced not in the wrist but in the forearm. Only the tendons cross the wrist, the muscular bodies lying in the forearm. The side with the greatest angle is the action side, the opposite is the inaction or straight side.
With the hand turned down prone and drawn toward the body, the thumb side is the action side, the Ii ttle finger the inaction side. The inaction side is straight with the arm, while the thumb is almost at right angles with it. The inaction construction line runs straight down the arm to the base of the little finger. The action construction line runs down the arm to the base of the thumb at the wrist, from there out to the middle joint, at the widest part of the hand; thence to the knuckle of the first finger, then to that of the second finger, and then joins the inaction line at the little finger.
With the hand still prone, but drawn from the body, the thumb side is the inaction side, and is straight with the arm, while the little finger is at almost right angles wi th it. The inaction construction line now runs straight to the middle joint of the thumb, while the action line runs to the wrist on the little finger side, thence to the first joint, etc.
These construction lines, six in number, are the same with the palm turned up, according as it is drawn in or out. They place the fingers and indica te the action and proportions of the hand.
The fingers, gathered together, form a corona around its tip. Spread out, they radiate from a common centre at its base; and a line connecting their tips forms a curve whose cen tre is this same point. This is true of the rows of joints knuckles also. Bent, in any position, or closed as in clasping, the fingers form arches, each one concentric on this same basal joint of the thumb.
Clenched, each circle of knuckles forms an arch with the same common centre. The mass of the thumb dominates the hand. The design and movement of even the forearm is to give the freest sweep to the thumb; while, through the biceps muscle, its movement is seen to begin really at the shoulder.
Its bones are heavier than those of the fingers, its joints more rugged. Its last segment has a nail and a heavy skin pad.
The middle segmen t has onl y tendons. The basal segment is a pyramidal mass of muscle reaching to the wrist, tile "line of life" of the palm, and the base of the first finger. The superficial muscles of this mass are a fat one, a broad one, and a thin one.
The fat muscle hugs the bone opponens , the broad one forms the bulk of the pyramid abductor and the thin one lies inside, toward the index finger flexor brevis. The ball faces to the front more than sideways. It reaches to the middle joint of the first finger.
The last segment bends sharply back, carrying the nail. Its skin pad, broad at the base, gives it an appearance not unlike a foot, expressing its pressure-bearing function.
The middle segment is square with rounded edges, smaller than the other two, with a small pad. The basal segmen t is rounded and bulged on all sides except where the one is superficial at the back. The heavy middle joint moves less freely, also limited to one plane. The joint of the base is a saddle joint, with movement like one in a saddle, that is, with easy bending sideways, less easy forward and back; which two in combination give some rotary movement, but giving a twisting movement only with difficulty and strain.
Extensor brevis pollicis. Each phalanx turns on the one above, leaving exposed the end of the higher bone. There are no muscles below the knuckles; but the fingers are traversed by tendons on the back, and are covered on the front by tendons and skin pads. The middle finger is the longest and largest, because in the clasped hand it is opposite the thumb and wi th it bears the chief burden.
The Ii ttle finger is the smallest and shortest and most freely movable for the opposite reason. It may move farther back than the other fingers, and is usually held so, for two reasons; one is that the hand often "sits" on the base of the little finger; the other is that being diagonally opposite the thumb it is twisted farther backward in any outward twisting movement, and so tends to assume that position.
The joints are square, the shafts smaller but square, with rounded edges; the tips are triangular. The middle joint of each finger is the largest. In the clenched fist it is the end of the bone of the hand metacarpal that is exposed to make the knuckle.
The finger bone first phalanx moves around it, and bulges beyond. The extensor tendon makes a ridge on the knuckle and connects it with the first phalanx; but on the middle and the last [ 58 ] joints the tendon makes a depression or groove in the centre of the joint. The masses of these segments are not placed end to end, as on a dead centre, either in profile or in back view. In the back view, the fingers as a whole arch toward the middle finger.
In the profile view, there is a step-down from each segment to the one beyond, bridged by a wedge. A series of wedges and squares thus marks the backs of the fingers. Into the square of the knuckles a blunt wedge is seen to enter from above. From it a long tapering wedge arises and enters the square of the middle joint, from which a blunt wedge also reaches backward.
Another tapering wedge arises here and moves half way down the segment. The whole finger tapers from the middle joint, to become embedded in a horseshoe form holding the nail. This form begins back of the root of the nail and bevels to below its end, at the tip of the finger. The whole last segment is a wedge. The palmar webbing opposite the knuckles, which reaches to about the middle of the first segment of the finger, in front, bevels backward and points to the top of the knuckle in the back.
The segments of individual fingers are of different lengths, those of the middle finger being longest. From tip to base, and on into the bones of the hand, the segments increase in length by definite proportions. The reason is immediately seen when the finger is viewed closed on itself. The creases are then seen to form a cross, the pads to meet in the common centre, filling in the four sides of a diamond.
In the first finger the creases are: short of the last joint; opposite the middle joint: half way between middle and basal joint, and opposite the basal knuckle above the joint proper, which is considerably beyond the point of the knuckle. In the second finger they are: opposite the last joint: beyond the middle joint: midway between middle and basal joint, and opposite the basal joint. I n the other fingers they vary in different individuals.
The creases are all transverse except that opposite the basal joint, which forms one long wavy crease on the palm: and those next beyond, on first and little fingers, which slope down on the outside, in the spread fingers making a curve around the base of the thumb. One is large at the wrist, forming two-thirds of the ioint : the other is large at the elbow, where it also forms two-thirds of the joint.
They are joined at tReir sides and move like a long piece of cardboard folded diagonally. The one that is large at the elbow is the ulna. It forms a hinge joint and moves in the bending of the elbow. The other slides as the hinge moves. This second hone is the radius. Diagonally opposite the thumb, on the ulna. Overlying them and reaching higher up on the arm are the pronator's and supinator's of the radius.
The flexors and pronators flexor. Between them at the elbow lies the cubital fossa. Both of these masses arise fr the condyles of the humerus, or ann hone. These are the tips of the flattened lower end of that hone. From the inner condyle. This is a fat softly bulging mass which tapers to the wrist. The outer condyle is hidden by its muscular mass when the hand is turned out.
This mass is the extensor-supinator group, which bulges higher up, and becomes tendinous half way down. It is dominated by the supinator longus, which rises a third of the way up the arm, widens as far as the elbow, tapers beyond, and loses itself half way down the forearm. In turning, this wedge follows the direction of the thumb, and overlies the condyle when the arm is straight with the forearm.
From the back view, the elbow is seen to have three knohs of hone: the two condyles above referred to, and between them the upper end of the ulna. The latter is higher when the ann is straight and lower when it is flexed. The overlyinz muscular masses meet oyer half way down. The Arm.
The part facing the shoulder is rounded and enlarged to form the head, where it joins the shoulder blade. The lower end is flattened out sideways to give [69 ] attachment to the ulna and radius, forming the condyles. The shaft itself is straight and nearly round, and is entirely covered with muscles except at the condyles. On the flat front side of the condyles, reaching half way up the arm, is placed the broad, flat and short brachialis anticus muscle; and on top of that the thin, high and long biceps, reaching to the shoulder; its upper end flattened as it begins to divide in to its two heads.
One head passes to the inside of the bone and fastens to the coracoid process, under the shoulder; the other passes outside, grooving the head of the humerus, and attaching to the shoulder blade above the shoulder joint, under the deltoid or shoulder hood.
On the back, behind the flat surface made by the two condyles, arising from the central knob or olecranon, is the triceps three-headed muscle. Its outer head begins near the condyle, and occupies the outer and upper part of the back surface of the humerus. The inner head begins near the inner cond yle and occupies the inner and lower portion of the bone.
The middle head reaches diagonally in and up to the back of the shoulder blade. These all converge on the broad flat tendon from the olecranon, forming a wedge surrounded by two wings of muscle. The triceps also is overlaid by the deltoid above. Between biceps and triceps are grooves. The inner condyle sinks into the inner groove below, and it is filled out above by the coraco-brachialis muscle, entering the armpit.
The outer condyle sinks into the outer groove below, while midway of the arm the apex of the deltoid muscle sinks into it, overlying the upper ends of both biceps and triceps. Coraco-hrachialis: From coracoid process, to humerus, inner side, half way down.
Action: Draws forward, rotates outward, humerus. Biceps: Long head fr glenoid cavity under acromion through gToo"e in head of humerus; short head from coracoid process: to radius. Action: Depresses shoulder blade: Hexes forearm; rotates radius outward.
Supinator Longus: From external condyloid ridge to end of radius. Action: Supinates forearm. Pronator Radii Teres: From internal condyle and ulna to radius, outer side, half way down. Action: Pronates hand and flexes forearm. Brachialis Anticus: From front of humerus, lower half, to ulna. Action: Flexes forearm. Extensor Carpi Radialis Longior: From external condyloid ridge to base of index finger. Action: Extends wrist.
Anconeus: From back of external condyle to olecranon process and shaft of ulna. Action: Extends forearm. Audio Software icon An illustration of a 3. Software Images icon An illustration of two photographs. Images Donate icon An illustration of a heart shape Donate Ellipses icon An illustration of text ellipses.
Constructive Anatomy Item Preview. EMBED for wordpress. Want more? Advanced embedding details, examples, and help! The most valuable, detailed anatomical studies which are also beautifully drawn of all parts of the figure. Countless artists and students since the s have used this and other books by George B. Bridgman for nearly 50 years a teacher at the Art Students League in New York for a solid foundation and understanding of human anatomy.
They have found, and continue to find, that his unique way of discovering the vitalizing forces in the human form and realizing them in drawing carries the student pleasantly over one of art's most severe hurdles.
Bridgman's superb anatomical sketches, of which there are nearly in the book, also bring clearly to fruition his lucid theories of how to draw the human body in its structure and its complex movements.
Constructive Anatomy, an anatomical reference guide for the working artist, sculptor, and student, graphically shows important parts of the human body, both in motion and in repose — hand, wrist, thumb, fingers, forearm, arm, armpit, shoulder, neck, head, eye, nose, ear, mouth, chin, trunk front, side, and back , pelvis, hip, thigh, leg, knee, ankle, foot, and toes.
Drawings of bone and muscle structure of the working of the joints and the interrelation of the various parts of the body are mainly concerned with movement of all sorts — movements that are described in detail as well as illustrated.
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