D. J. (Daniel John) Cunningham.

Cunningham's manual of practical anatomy (Volume 1) online

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epicondyles of the humerus (Figs, i, 2, 85).

Both are landmarks. Behind the medial epicondyle lies
the ulnar nerve ; it can be felt quite easily in the living body
if a finger is pressed against the back of the epicondyle and
is moved from side to side. If the pressure is sufficiently
strong it gives rise to a tingling sensation along the medial
part of the hand.

Anterior to the lateral epicondyle and somewhat to its
medial side another large nerve, the radial, breaks up into
its terminal branches ; it cannot, however, be felt.

The posterior border of the ulna is subcutaneous in the
whole of its length. It extends from the olecranon, which is
the prominence at the back of the elbow, to a small pointed
process called the styloid process of the ulna which lies at the
medial side of the back of the wrist (Figs, i, 2, 3, 97, 98, 99).
i la



4 THE SUPERIOR EXTREMITY

Just lateral to the styloid process and slightly proximal to
it there is a rounded piece of bone called the head of the ulna.
It is best seen and felt when the palm of the hand is turned
downwards.

The radius is more deeply buried than the ulna, but there
is no difficulty in locating its proximal and distal ends. The
proximal end, called the head of the radius, lies a short distance
distal to the lateral epicondyle of the humerus. Its position
is marked on the back of the forearm by a dimple of the
skin. If a finger is placed in the dimple the head of the
radius can be felt rotating when the palm of the hand is
turned alternately upwards and downwards.

The distal end of the radius is the quadrangular mass of
bone which can be felt at the lateral side and the back of the
wrist. It lies lateral to the head of the ulna and it terminates
on the lateral side in a pointed process, the styloid process of
the radius.

The eight carpal bones of the wrist lie in the interval
between the styloid processes of the radius and ulna, beyond
which they extend distally for a short distance (Figs. 3, 67, 77).

The^fod metacarpal bones of the hand, one for each digit,
extend from the carpus to the phalanges.

They are numbered one to five from the thumb to the
little finger side, and all are easily felt at the back of the
hand, where the heads or distal ends form the prominences
known as the "knuckles."

The fourteen phalanges are in the free parts of the digits:
two in the thumb, first or proximal and second or distal ;
three in each finger, proximal or first, middle or second, and
distal or third. The second phalanx of the thumb and the
third phalanges of the fingers are frequently called terminal
phalanges.

The structures connected and associated with all the
bones mentioned have to be examined by the dissector of
the superior extremity, and whilst waiting to commence the
dissection the dissector should verify all the points above
mentioned upon his own body with the aid of his fingers and
a looking-glass.

Since many students commence dissecting before they
have attended either lectures or demonstrations on Anatomy,
they are unacquainted with terms which must be used in the
instructions given regarding the dissections which are to be






PECTORAL REGION 5

made. Fortunately most of the terms used, like those already
mentioned, refer to things which can be seen and felt ; they,
therefore, are easily understood. There are, however, certain
terms, used when branches of spinal nerves are under con-
sideration, which are not self-explanatory, and it is necessary,
therefore, that the student should possess a knowledge of the
terms used in connection with spinal nerves and their branches
before the actual work of dissection is commenced. The
following points should be noted: (i) Every spinal nerve is
attached to the spinal medulla (spinal cord) by two roots, an
anterior root and a posterior root. The anterior root is non-
ganglionated &i\<\ the posterior root is ganglionated. (2) As the
roots are leaving the vertebral canal, through an intervertebral
foramen, they unite to form a trunk. (3) Immediately after
its exit from the intervertebral foramen the trunk divides into
a posterior ramus and an anterior ramus of which the anterior
ramus is, with few exceptions, much the larger. (4) Each
posterior ramus divides into a medial branch and a lateral
branch. (5) Each anterior ramus divides into a lateral branch
and an anterior branch (Fig. 4). 1

Every anterior root consists of nerve fibres which spring
from nerve cells in the spinal medulla and pass to the muscle
fibres of various muscles. They carry motor impulses to the
muscles. Each posterior root consists of nerve fibres passing
to and from the nerve cells of the ganglion of the posterior
root The posterior root fibres carry sensory impulses, such
as cold, heat, pain, etc. The sensory impulses pass through
the cells of the ganglion of the posterior root and then onwards
to the spinal medulla.

The trunk of every spinal nerve, therefore, contains both
motor or efferent and sensory or afferent nerve fibres, and the
posterior and anterior rami into which it divides also contain
both sets of fibres. The branches of the rami may contain
either both sets of fibres or only one or the other set.
Eventually, however, the peripheral parts of the fibres con-
veying impulses from and those conveying impulses to the
spinal medulla separate from one another. The fibres which
convey impulses from the spinal medulla become the motor
nerves which end in the muscle fibres, whilst the fibres which

1 This division is not always obvious, and in certain situations the
lateral and anterior branches are called, respectively, posterior and
anterior branches,
i 16



6 THE SUPERIOR EXTREMITY

convey sensory impulses only are the sensory nerve fibres.
The sensory nerve fibres which convey sensory impulses from
the skin are termed cutaneous nerves.

The dissector of the upper extremity must begin work on

Medial cutaneous branch of medial division of posterior ramus
Lateral cutaneous branch of medial division of posterior ramus > Medial division of

Lateral division of posterior ramus dividing ^
into terminal muscular branches' N



Posterior ramus



Anterior ramus



Muscular branches x



Posterior cutaneous

branch of lateral

division of

anterior ramus



Lateral division of
anterior ramus



Anterior cutaneous

branch of lateral

division of

anterior ramus



\ Recurrent branch
S'ympathetic ganglion
Anterior division of anterior ramus




posterior ramus

, Posterior ganglionated

root

Posterior funiculus of
spinal medulla

Posterior grey column



Antero-lateral
funiculus
Anterior grey
column



Medial cutaneous branch of anterior
division of anterior ramus



Lateral cutaneous branch of anterior division of anterior ramus



FIG. 4. Diagram of a Spinal Nerve. Note that the medial divisions of
the posterior ramus is represented as distributed to skin, whilst the lateral
division terminates at a deeper level in muscle. In some situations the
reverse condition occurs, and the medial and lateral divisions of all
posterior rami supply muscles.



the fourth day after the subject has been placed in the
dissecting-room. He will find the body lying upon its back.
The thorax will be raised to a convenient height by means of
blocks, and a long board will be placed under the shoulders
for the purpose of supporting the arms when they are abducted
from the sides.



PECTORAL REGION 7

Until the dissection of the axilla is completed the dissectors of the arm
and of the head and neck will find it advantageous to arrange to work
at different hours. The dissector of the head and neck, at this stage, is
engaged on the posterior triangle of the neck, and the dissection of the
triangle cannot be well done unless the arm is placed close to the side
and the shoulder depressed. For the dissection of the axilla the arm should
be stretched out at right angles to the thorax. A compromise between
these two positions always results in discomfort to both dissectors.

Five days are allowed for the examination of the axilla
and the muscles which pass to the upper extremity from the
anterior portion of the thoracic region of the body. The
following table will be found useful in regulating the amount
of work which should be carried out on each day :

First Day. (a) Surface anatomy ; (b) reflection of the skin ; (c) cutane-
ous vessels and nerves of the anterior and lateral aspects of the thorax ;

(d) examination of the fascia of the pectoralis major and the axillary fascia ;

(e) the cleaning of the pectoralis major ; (/) the reflection of the pectoralis
major.

Second Day. (a) The examination of the costo-coracoid membrane and
the structures piercing it ; (b} the removal of the costo-coracoid membrane
and the examination of the structures posterior to it.

Third Day. (a) The cleaning of the pectoralis minor ; (b) the cleaning
of the contents of the axilla below the pectoralis minor.

Fourth Day. (a) The reflection of the pectoralis minor ; (6} the com-
pletion of the cleaning of the contents of the axilla ; (c) the cleaning of the
serratus anterior ; (d) the cleaning of the posterior wall of the axilla ; (e)
the reflection of the subclavius ; (/) the examination of the" sterno-
clavicular articulation and the disarticulation of the clavicle at the sterno-
clavicular joint.

Fifth Day. (a) The brachial plexus and a general review of the axilla
and its contents.

Before commencing the dissection of the axillary region
draw your finger along the clavicle from its sternal to its
acromial end. Note that in the medial two-thirds of its
length the bone curves forwards to give room for the passage
of vessels and nerves from the neck to the axilla. The lateral
third is curved backwards. Place your finger in the delto-
pectoral triangle below the junction of the intermediate and
lateral thirds of the clavicle, and note that the great pectoral
muscle lies to its medial side and the deltoid muscle to its
lateral side; both muscles spring from the anterior aspect
of the clavicle (see Fig. 10). Push your finger upwards and
backwards in the triangle under the medial border of the
deltoid until the coracoid process is distinctly felt. Next
examine the articulations of the clavicle. Little or no
prominence is formed by the lateral extremity of the bone
its superior surface lies in the same plane as the superior
i lc



8 THE SUPERIOR EXTREMITY

surface of the acromion of the scapula. When the upper
limb is moved, however, the joint can easily be detected.
In strong contrast to the inconspicuous acromio-clavicular
joint is the sterno-clavicular joint, where the medial end of the
clavicle can be felt as a marked projection, although it is
masked, to the eye, by the sternal part of the sterno-cleido-
mastoid muscle which causes the ridge-like prominence at the
side of the neck as it extends from the sternum and clavicle to
the skull behind the ear. Place the index finger in \hzjugular
notch on the upper border of the manubrium sterni, between
the clavicles, and carry it downwards, along the middle of
the sternum, in the interval between the attachments of the
great pectoral muscles. The portion of the sternum un-
covered by the two greater pectoral muscles is narrow above,
but it widens out below, and as the finger passes along it a
prominent ridge will be felt. The ridge marks the junction
of the manubrium sterni with the body of the sternum, and
also the level at which the costal cartilages of the second
ribs join the sternum. It is easily felt and can often be seen.
It is, therefore, an excellent landmark, indicating the positions
of the second pair of ribs, from which the counting of the other
ribs should always commence. At the lower end of the body of
the sternum, the finger, as it is carried downwards, will sink
suddenly into a depression, between the cartilages of the
seventh pair of ribs, and rest against the xiphoid process of
the sternum. The depression is termed the infrasternal fossa,
or pit of the stomach. The costal arches, below the first,
are easily recognised, but the first rib lies deeply under the
clavicle, and can be felt only in front, at its junction with
the manubrium sterni. The arm should now be abducted
(i.e. carried laterally from the trunk), when the hollow of
the axilla and the two rounded folds, which bound it
in front and behind, will be brought into view. The
anterior fold of the axilla is formed by the lower border of
the pectoralis major, and to a small extent also by the lower
border of the pectoralis minor. The posterior fold, which is
formed by the latissimus dorsi as it winds round the teres
major muscle, is carried downwards to a lower level than the
anterior fold. This, as will be seen later, is an important
point in connection with the anatomy of the axilla. If the
finger is pushed upwards into the axilla the globular head of
the humerus will be felt, when the arm is rotated. One other



PECTORAL REGION 9

point demands the attention of the student before the dis-
section is commenced, and that is the position of the nipple.
As a rule it lies superficial to the interspace between the
fourth and fifth ribs, and it is situated rather more than four
inches from the median line.

The student should examine these various landmarks, not
only upon the dead body but also upon himself and his
friends, until he is perfectly familiar with them, both by touch
and sight, and can at once put his finger on any given point,
whatever the position of the limb may be.

Dissection. Reflection of the Skin. Incisions: (i) Along
the middle line of the body from the upper margin of the manu-
brium sterni to the tip of the xiphoid process. (2) Upwards
and laterally from the tip of the xiphoid process to the nipple.
At the nipple the incision must bifurcate, to encircle the dark
patch of skin around the nipple which is called the areola,
then it must be continued along the anterior fold of the axilla
to the arm. As soon as it reaches the arm it must be carried
downwards for about 63 mm. (two inches and a half), and then
transversely to the lateral border of the arm. (3) From the tip
of the xiphoid process transversely across the front and side of
the chest to the plane of the posterior fold of the axilla (Fig. 5).

To make a clean incision in the skin place the point of the
scalpel on one end of the line of incision, and, holding the scalpel
at right angles to the surface to be incised, force the point
through the skin till it enters the soft superficial fascia which
lies beneath. Then incline the blade to an angle of 45 to
the surface of the skin, and, pressing firmly on the back of the
blade with the forefinger, carry it steadily to the opposite end
of the line of incision, but as the end of the line is approached
bring the blade again to a right angle with the surface, and so
withdraw it from the incision.

To reflect the skin take hold of one of the angles of the flap
marked out by the incisions with the forceps ; in the case of
the upper flap (i, Fig. 5), which should be dealt with first, the
superior medial angle on the right side and the inferior medial
angle on the left side, and with the edge of the scalpel detach it
from the soft fat beneath.

As soon as the angle selected is sufficiently detached discard
the forceps, and, holding the detached angle of skin between
the thumb and forefinger of the left hand, keep it tense and
draw the edge of the scalpel across the skin at its junction with
the fat from one edge of the flap to the other, always keeping
the edge of the knife against the skin. Be careful not to take
any fat away with the skin. Continue the reflection until the
lateral border of the shoulder region is reached. Leave the
flap hanging along that border and turn to flap 2, Fig. 5. Com-
mence at the medial angle, proceed as with flap i, and con-
tinue the reflection until the posterior fold of the axilla is reached.

As the skin flaps are reflected towards the arm and the side
of the chest the small patch around the nipple must be left
untouched.



10



THE SUPERIOR EXTREMITY



As that reflection proceeds note that the connection between
the superficial fascia and the skin is stronger in some places
than in others. In the female definite fibrous strands will be



Sternal end of clavicle .^,,

Acromial end of clavicle ^
Head of burner us i-i



Nipple JU -JpN
Lower end of body of sternum _



Lateral epicondyle -ft

Medial epicondyle ;
/ 3

Ant. sup. spine of ilium J_ ^

Greater trochanter

Styloid process of radius
Styloid process of ulna



Junction of manubriuin
witb body of sternum




Medial condyle of femur I
Lateral condyle of femur V, "f



Lateral condyle of tibia
Head of fibula



\- Symphysis

of pubis
" Distal end of
: radius



Lateral malleol



Medial malleolus
- Lateral malleolus



p IG> ^ Surface view showing Incisions and Bony Points.



PECTORAL REGION n

found passing from the substance of the mammary gland to
the skin ; they are called the ligaments of Cooper.

When the reflection of the flaps is completed the superficial
fascia is exposed.

Superficial Fascia (Panniculus Adiposus). The superficial
fascia is found not only in the region now under considera-
tion but over the whole of the body. Its structure is
slightly different in different areas. In all parts, with the
exception of the region of the scrotum, it contains yellowish
fat, the amount of fat varying with the regions and with the
obesity of the subject. In some regions muscle fibres of
reddish tint are found in the deeper part of the superficial
fascia ; in the anterior part of the neck and the adjacent
portion of the upper part of the chest they form, on each
side, a definite sheet of muscle called \\\e platysma and in the
region of the scrotum they entirely replace the fat.

In the superficial fascia lie the cutaneous vessels and
nerves, and the deeper portions of the hairs and the sweat
glands. In some regions the deeper parts of the sebaceous
glands of the skin penetrate into it, and in the thoracic region,
the mammary glands, which are modified subaceous glands,
are developed in its substance. It contains also the super-
ficial lymph glands.

Under cover of the superficial fascia and intervening
between it and the muscles there is a more membranous
layer of fibrous tissue called deep fascia.

The superficial fascia, therefore, intervenes between the
skin and the deep fascia, and it is attached to both by fibrous
strands which pass through the fat. As it lies between the
skin and the deep fascia it forms a soft elastic cushion upon
which the skin rests, and which, by its elasticity, allows the
skin to be moved over the deeper parts. It rounds off the
angularities of the body and it forms the bed in which the
cutaneous vessels and nerves ramify before they enter the skin.

In the region at present exposed, the fat is not usually
very plentiful except in female bodies, where it is abundant
in the region of the mamma. In the neighbourhood of the
clavicle a reddish striation due to the lower part of the
platysma is usually visible, and if it is not seen the fibres of
the muscle can be exposed quite easily by the removal of the
thin layer of fat which lies superficial to them.

After the general characters of the superficial fascia have



12 THE SUPERIOR EXTREMITY

been noted the nerves and vessels which pass through it to
the skin must be sought for. They are :

Nervi Cutanei.

Supraclavicular, from the cervical plexus.

Anterior cutaneous) from the anterior (intercostal) rami of the thoracic
Lateral cutaneous / nerves.
Arterize Cutanese.

Cutaneous twigs from the branches of the thoraco-acromial artery :

From the clavicular branch.

From the acromial branch.

From the deltoid branch.

Perforating branches of the internal mammary artery.
Branches form the lateral thoracic artery.
Branches form the transverse scapular artery.

Dissection. Cut through the superficial fascia to the deep
fascia along the lateral margin of the sternum. The level of
the deep fascia will be recognised by the increased resistance
offered to the knife, and by its bluish-white colour when it is
exposed. As regards the difference of resistance the dissector
must educate his fingers to recognise the different " feel " of the
various structures. As the edge of the knife touches them,
superficial fascia, deep fascia, nerves, vessels, muscles, they all
cause a different sensation, recognisable by the educated touch,
which can only be acquired by attention and practice.

As soon as the level of the deep fascia is reached raise the
cut margin of the superficial fascia with the forceps or fingers
and, with the edge of the scalpel, sever the strands which attach
the deep surface of the superficial fascia to the deep fascia,
cutting against the deep fascia and removing the whole of the
superficial fascia. As the separation proceeds pull the detached
superficial fascia away from the sternum, and as soon as the
anterior ends of the intercostal spaces are reached look for the
anterior cutaneous nerves and the perforating branches of the
internal mammary artery, which pierce the deep fascia near the
margin of the sternum. If the arteries are well injected one
should be found in each of the upper six intercostal spaces. It
is not probable that a nerve will be found in the first space, but
one should be found in each of the other five spaces. The
arteries will be recognised by the red injection which they
contain ; each is accompanied by a small vein. The nerves
are whitish threads, not unlike thin white thread. They are
much firmer to the touch, and much stronger than the blood-
vessels.

Trace both the vessels and nerves as far laterally as possible.
When the anterior cutaneous nerves and the accompanying
vessels have been secured look for the supraclavicular nerves;
to find them cut through the fibres of the platysma along the
upper border of the clavicle from the sternum to the shoulder,
and turn the lower part of the severed muscle and fascia down-
wards, detaching it from the fascia beneath with the edge of
the scalpel. As this is done look for the nerves which appear
as whitish strands running downwards across the clavicle and
passing from the deeper into the more superficial layer. Two
or three should be found about the middle of the clavicle, one



PECTORAL REGION



near its sternal end, and one near its acromial end descending in
the fascia over the anterior part of the deltoid muscle. Follow
the nerves downwards through the superficial fascia as far as
possible ; they descend to the level of the second or third rib,
and are sometimes accompanied by small branches of the trans-
verse scapular artery which pierce the deep fascia above the
clavicle. Near the sternal end of the clavicle small twigs of
the clavicular branch of the thoraco - acromial artery may be
seen. Near the acromion twigs of the acromial branch of the
same artery may be found ; and in the delto -pectoral triangle
twigs of the deltoid branch are occasionally visible.

After the supraclavicular nerves have been found and
followed to their terminations cut through the superficial fascia
along the line of the anterior fold of the axilla and the lower
margin of the pectoralis major. As soon as the level of the
deep fascia is reached turn the anterior part of the superficial
fascia towards the median plane, and look for the anterior
branches of the lateral cutaneous nerves, as they turn round the
border of the pectoralis major, pierce the deep fascia, and run
medially in the superficial fascia.



Accessory nerve.-

' Levator scapulae,^

Middle supraclavicula

nerve-
Posterior supraclavicular
nerve

Scalenus niediu



Nervus cutaneus
colli




FIG. 6. The Supraclavicular Branches of the Cervical Plexus.

Nervi supraclaviculares. The supraclavicular nerves arise
in the neck, from the third and fourth cervical nerves. They
spread out as they descend, pierce the deep fascia of the neck,
and they cross the clavicle under cover of the platysma.
They are classified, according to their positions, into the
anterior, the middle, and the posterior branches (Fig. 6). The
anterior are the smallest of the series ; they cross the medial
part of the clavicle to end in the skin immediately below.
The middle branches pass over the middle of the clavicle and
extend downwards, in the superficial fascia over the pectoralis
major, as far as the third rib. The posterior cross the lateral



i 4 THE SUPERIOR EXTREMITY

third of the clavicle, and will be afterwards followed to the
skin of the shoulder. They are frequently accompanied by



Online LibraryD. J. (Daniel John) CunninghamCunningham's manual of practical anatomy (Volume 1) → online text (page 3 of 44)