Arms can also refer to weapons or heraldic displays.
Upper arm -- Elbow -- Forearm -- Wrist -- Hand -- Finger -- Thumb
Running downward and outward from the inner
half of the clavicle, where that bone is convex forward, is
the clavicular part of the pectoralis major, while from the
outer third of the bone, where it is concave forward, is the
clavicular part of the deltoid; between these two muscles is
an elongated triangular gap with its base at the clavicle,
and here the skin is somewhat depressed, while the cephalic
vein sinks between the two muscles to join the axillary
vein. The tip of the coracoid process is situated just under
cover of the inner edge of the deltoid, one inch below the
junction between the outer and middle thirds of the clavicle.
The deltoid muscle forms the prominence of the shoulder, and its convex outline is due to the presence of the head of the humerus deep to it; when this is dislocated the shoulder becomes flattened. The pectoralis major forms the anterior fold of the axilla or armpit, the posterior being
formed by the latissimus dorsi and teres major muscles. The
skin of the floor of this space is covered with hair in the
adult, and contains many large sweat glands. The axillary
vessels and brachial plexus of nerves lie in the outer wall,
while on the inner wall are the serrations of the serratus
magnus muscle, the outlines of some of which are seen on the
side of the thorax, through the skin, when the arm is raised. Below the edge of the pectoralis major, the swelling of the biceps begins to be visible,
and this can easily be traced into its tendon of insertion,
which reaches below the level of the elbow joint. On each side
of the biceps is the external and internal bicipital furrow,
in the latter of which the brachial artery may be felt and
compressed. The median nerve is here in close relation to the
artery. At the bend of the elbow the two condyles of the
humerus may be felt; the inner one projects beneath the
skin, but the outer one is obscured by the rounded outline
of the brachio-radialis muscle. The superficial veins at
the bend of the elbow are very conspicuous; they vary a good
deal, but the typical arrangement is an M, of which the radial
and ulnar veins form the uprights, while the outer oblique
bar is the median cephalic and the inner oblique the median
basilic vein. At the divergence of these two the median
vein comes up from the front of the forearm, while the two
vertical limbs are continued up the arm as the cephalic and
basilic, the former on the outer side, the latter on the
inner. On the back of the arm the three heads of the triceps
are distinguishable, the external forming a marked oblique
swelling when the forearm is forcibly extended and internally
rotated. In the upper part of the front of
the forearm the antecubital fossa or triangle is seen;
its outer boundary is the brachio-radialis, its inner the
pronator radii teres, and where these two join below is the
apex. In this space are three vertical structures--externally
the tendon of the biceps, just internal to this the
brachial artery, and still more internally the median
nerve. Coming from the inner side of the biceps tendon the
semi-lunar fascia may be felt; it passes deep to the median
basilic vein and superficial to the brachial artery, and
in former days was a valuable protection to the artery when
unskillful operators were bleeding from the median basilic
vein. About the middle of the forearm the fleshy parts of
the superficial flexor muscles cease, and only the tendons
remain, so that the limb narrows rapidly. In front of the
wrist there is a superficial plexus of veins, while deep to
this two tendons can usually be made to start up if the wrist
be forcibly flexed; the outer of these is the flexor carpi
radialis, which is the physician's guide to the radial artery
where the pulse is felt. If the finger is slipped to the
outer side of this tendon, the artery, which here is very
superficial, can be felt beating. The inner of the two tendons
is the palmaris longus, though it is not always present. On
cutting down between these two the median nerve is reached.
The wrist joint may be marked out by feeling the styloid process
of the radius on the outer side, and the styloid process of the
ulna on the inner side behind, and joining these two by a line
convex upward. The superficial appearance of the palm of the
hand is described in the article on Palmistry; with regard
to anatomical landmarks the superficial palmar arterial arch
is situated in the line of the abducted thumb, while the deep
arch is an inch nearer the wrist. The digital nerves correspond
to lines drawn from the clefts of the fingers toward the
wrist. On the back of the forearm the olecranon process of
the ulna is quite subcutaneous, and during extension of the
elbow is in a line with the two condyles, while between it and
the inner condyle lies the ulnar nerve, here known popularly
as the "funny bone." From the olecranon process the finger
may be run down the posterior border of the ulna, which
is subcutaneous as far as the styloid process at the lower
end. On the dorsum of the hand is a plexus of veins, deep
to which the extensor tendons are seen on extending the
fingers. When the thumb is extended, two tendons stand out
very prominently, and enclose a triangular space between them
which is sometimes known as the "anatomical snuff box";
the outer of these is the tendon of the extensor brevis,
the inner of the extensor longus pollicis. Situated deeply
in the space is the radial artery, covered by the radial
vein. On the dorsum of the hand there is a plexus of
veins, and deep to these the tendons of the extensor longus
digitorum stand out when the wrist and fingers are extended.Anatomy of the (human) arm