Thoracic wall basic anatomy 1 pdf - Thorax

Basic Anatomy

it. This is especially so in an era in which automobile accidents,

blunt or penetrating wounds can injure the soft organs beneath

them considerable protection. Although the chest wall is strong,

nal organs, such as the liver, stomach, and spleen, and offers

life-sustaining organs—lungs, heart, and major blood vessels. In

Contained within the protective thoracic cage are the important

■

An understanding of the structure of the chest wall and the

diaphragm is essential if one is to understand the normal move-

ments of the chest wall in the process of aeration of the lungs.

■

addition, the lower part of the cage overlaps the upper abdomi-

stab wounds, and gunshot wounds are commonplace.

■

Because of the clinical importance of the chest wall, examiners

tend to focus on this area. Questions concerning the ribs and

their movements; the diaphragm, its attachments, and its func-

tion; and the contents of an intercostal space have been asked

many times.

natomy

asic

The thorax (or chest) is the region of the body between the

ninth thoracic vertebra (see Fig. 2.2).

lies opposite the body of the

xiphisternal joint

The

the 4th and 5th thoracic vertebrae.

sternal angle lies opposite the intervertebral disc between

from which all costal cartilages and ribs are counted. The

ridge lies at the level of the 2nd costal cartilage, the point

the anterior aspect of the sternum (Fig. 2.2). The transverse

can be recognized by the presence of a transverse ridge on

ulation of the manubrium with the body of the sternum,

(angle of Louis), formed by the artic

sternal angle

The

life. No ribs or costal cartilages are attached to it.

tilage that becomes ossified at its proximal end during adult

(see Fig. 2.1) is a thin plate of car

xiphoid process

The

Fig. 2.1).

it articulates with the 2nd to the 7th costal cartilages (see

On each side,

xiphisternal joint.

the xiphoid process at the

and below with

manubriosternal joint

manubrium at the

articulates above with the

body of the sternum

The

and 4th thoracic vertebrae.

tilages on each side (see Fig. 2.1). It lies opposite the 3rd

1st costal cartilage and the upper part of the 2nd costal car

joint, and it also articulates with the clavicles and with the

ulates with the body of the sternum at the manubriosternal

is the upper part of the sternum. It artic

manubrium

The

brium sterni, body of the sternum, and xiphoid process.

It is a flat bone that can be divided into three parts: manu

The sternum lies in the midline of the anterior chest wall.

cavity from the abdominal cavity.

inferiorly by the diaphragm, which separates the thoracic

tal spaces; superiorly by the suprapleural membrane; and

costal cartilages (Fig. 2.1); laterally by the ribs and intercos

part of the vertebral column; anteriorly by the sternum and

The thoracic wall is formed posteriorly by the thoracic

lined with parietal pleura.

by muscles attaching the shoulder girdle to the trunk. It is

The thoracic wall is covered on the outside by skin and

Structure of the Thoracic Wall

walls.

each side of the thorax, between the lungs and the thoracic

are formed, one on

pleural cavities

branous sacs called the

In this manner, two mem

parietal pleura.

it is called the

vessels enter) to the inner surface of the chest wall, where

lung at its root (i.e., where the main air passages and blood

which passes from each

visceral pleura,

brane called the

pleurae and lungs. The lungs are covered by a thin mem

and the laterally placed

mediastinum,

partition, called the

The cavity of the thorax can be divided into a median

upper extremity, abdomen, and back.

heart and affords attachment for the muscles of the thorax,

the diaphragm. The thoracic cage protects the lungs and

neck, and inferiorly it is separated from the abdomen by

in front. Superiorly, the thorax communicates with the

spaces on either side, and the sternum and costal cartilages

by the vertebral column behind, the ribs and intercostal

is formed

thoracic cage,

thorax, which is referred to as the

but rounded at the sides. The framework of the walls of the

neck and the abdomen. It is flattened in front and behind

Sternum

the surgeon to gain easy access to the heart, great vessels,

bone. The sternum may also be split at operation to allow

into the marrow cavity through the anterior surface of the

Under a local anesthetic, a wide-bore needle is introduced

Since the sternum possesses red hematopoietic marrow

Sternum and Marrow Biopsy

throughout life, it is a common site for marrow biopsy.

and thymus.

C L I N I C A L N O T E S

Ribs

the sternum by their costal cartilages.

The upper seven pairs are attached anteriorly to

True ribs:

2.5). The ribs are divided into three categories:

riorly to the thoracic vertebrae (Figs. 2.1 and 2.3, 2.4, and

There are 12 pairs of ribs, all of which are attached poste-

C H A P T E R O B J E C T I V E S

The Thorax: Part I—The Thoracic Wall

facet for
seventh costal
cartilage

xiphoid process

body of sternum

costal
cartilages

suprasternal notch

facet forclavicle

facet for
first costal
cartilage

facet for
second costal
cartilage

facet for
third costal
cartilage

facet for
fourth costal
cartilage

facet for
fifth costal
cartilage

facet for
sixth costal

cartilage

manubrium

body of first thoracic
vertebra

ribs

xiphoid process

rib 12

floating ribs

body

sternal angle

manubrium

FIGURE 2.1

Sternum, ribs, and costal cartilages forming the thoracic skeleton.

Anterior view of the sternum.

left brachiocephalic vein

left common carotid artery

sternal angle

xiphisternal

joint

diaphragm

aorta

heart

suprasternal notch

FIGURE 2.2

Lateral view of the thorax showing the relation

tionship to the lower nerves of the brachial plexus and the

The 1st rib is important clinically because of its close rela

sharply forward.

tal groove. The angle is where the shaft of the rib bends

twisted on its long axis. Its inferior border has the cos

tebra (see Fig. 2.4). The shaft is thin and flattened and

transverse process of the numerically corresponding ver

with the shaft. It has a facet for articulation with the

the outer surface of the rib at the junction of the neck

is a prominence on

tubercle

head and the tubercle. The

is a constricted portion situated between the

neck

The

and that of the vertebra immediately above (see Fig. 2.4).

tion with the numerically corresponding vertebral body

has two facets for articula

head

Figs. 2.4 and 2.5). The

(see

angle

head, neck, tubercle, shaft,

A rib has a

attached to the corresponding costal cartilage (Fig. 2.4).

costal vessels and nerve. The anterior end of each rib is

which accommodates the inter

costal groove,

forms the

(see Figs. 2.4 and 2.5). The inferior border overhangs and

smooth superior border and a sharp, thin inferior border

A typical rib is a long, twisted, flat bone having a rounded,

Typical Rib

attachment.

The 11th and 12th pairs have no anterior

Floating ribs:

their costal cartilages and small synovial joints.

anteriorly to each other and to the 7th rib by means of

The 8th, 9th, and 10th pairs of ribs are attached

False ribs:

ship of the surface markings to the vertebral levels.

and

Atypical Rib

Basic Anatomy

lamina

pedicle

facet for rib tubercle

transverse process

spinous process

inferior articular process

inferior vertebral notch

demifacet for rib head

body of vertebra

demifacet for rib head

superior articular process

heart-shaped body

demifacet for rib head

superior articular process

facet for rib
tubercle

transverse
process

spinous process

FIGURE 2.3

Thoracic vertebra.

Lateral surface.

Superior surface.

FIGURE 2.4

Fifth right rib as it articulates with the vertebral column posteriorly and the sternum anteriorly. Note that the rib

ence of the costal groove along the inferior border of the rib.

head articulates with the vertebral body of its own number and that of the vertebra immediately above. Note also the pres-

facet for tubercle of rib

tubercle of rib

angle of rib

cross section of rib

costal groove

costal cartilage

sternum

neck of rib

head of rib

intervertebral disc

body of vertebra

demifacet for head of rib

fifth rib

Cervical Rib

incision is then made through the bed of the rib, which is the

rib, and a segment of the rib is removed. A second longitudinal

sion is made through the periosteum on the outer surface of the

Rib excision is commonly performed by thoracic surgeons wish

It can also exert pressure on the overlying subclavian artery and

forearm and hand and wasting of the small muscles of the hand.

in some patients, producing pain down the medial side of the

can cause pressure on the lower trunk of the brachial plexus

late with the 1st rib. The importance of a cervical rib is that it

0.5% of humans (Fig. 2.7). It may have a free anterior end, may

transverse process of the 7th cervical vertebra) occurs in about

A cervical rib (i.e., a rib arising from the anterior tubercle of the

be connected to the 1st rib by a fibrous band, or may articu-

interfere with the circulation of the upper limb.

Rib Excision

ing to gain entrance to the thoracic cavity. A longitudinal inci-

inner covering of periosteum. After the operation, the rib regen-

erates from the osteogenetic layer of the periosteum.

C L I N I C A L N O T E S

9th, and 10th ribs to the cartilage immediately above. The

seven ribs to the lateral edge of the sternum and the 8th,

Costal cartilages are bars of cartilage connecting the upper

with the bone.

trunk of the brachial plexus cross the rib and lie in contact

the muscle attachment, the subclavian artery and the lower

anterior, the subclavian vein crosses the rib; posterior to

upper surface and inner border. Anterior to the scalenus

downward. The scalenus anterior muscle is attached to its

vein (Fig. 2.6). This rib is small and flattened from above

main vessels to the arm, namely, the subclavian artery and

The Thorax: Part I—The Thoracic Wall

Costal Cartilages

demifacet for

vertebral

body

demifacet for

vertebral body

articular part

of tubercle

sharp inferior

border

costal
groove

angle

rounded
superior
border

nonarticular part
of tubercle

neck

head

FIGURE 2.5

Fifth right rib, as seen from the posterior aspect.

insertion of scalenus medius

insertion of
scalenus anterior

first rib

scalenus medius

brachial plexus

cervical dome of pleura

scalenus anterior

lower trunk of plexus

subclavian artery and vein

FIGURE 2.6

Thoracic outlet showing the cervical dome of pleura on the left side of the body and its relationship to the inner

12th ribs.)

tebra (see Fig. 2.4). (This joint is absent on the 11th and

joint with the transverse process of the corresponding ver

The tubercle of a rib articulates by means of a synovial

Joints of the Tubercles of the Ribs

tebral disc.

that connects the head to the interver

articular ligament

intra-

the vertebra above it (see Fig. 2.4). There is a strong

joint with the corresponding vertebral body and that of

2nd to 9th ribs, the head articulates by means of a synovial

vial joint with their corresponding vertebral body. For the

The 1st rib and the three lowest ribs have a single syno

Joints of the Heads of the Ribs

Joints of the Ribs

of the sternum during middle age.

sternum. The xiphoid process usually fuses with the body

between the xiphoid process (cartilage) and the body of the

is a cartilaginous joint

xiphisternal joint

respiration. The

A small amount of angular movement is possible during

between the manubrium and the body of the sternum.

is a cartilaginous joint

manubriosternal joint

The

Joints of the Sternum

Joints of the Chest Wall

result of superficial calcification.

costal cartilages tend to lose some of their flexibility as the

ticity and mobility of the thoracic walls. In old age, the

The costal cartilages contribute significantly to the elas

musculature (see Fig. 2.1).

cartilages of the 11th and 12th ribs end in the abdominal

border of the 1st rib. Note also the presence of brachial plexus and subclavian vessels. (Anatomists often refer to the tho-

racic outlet as the thoracic inlet.)

Basic Anatomy

The 1st costal cartilages articulate with the manubrium, by

Joints of the Costal Cartilages with the Sternum

possible.

These joints are cartilaginous joints. No movement is

Joints of the Ribs and Costal Cartilages

cartilaginous joints that permit no movement (see Fig. 2.1).

nerves, all of which pierce the diaphragm.

phragm, pass the esophagus and many large vessels and

Through this large opening, which is closed by the dia

ing costal margin, and anteriorly by the xiphisternal joint.

riorly by the 12th thoracic vertebra, laterally by the curv

through a large opening. The opening is bounded poste

The thoracic cavity communicates with the abdomen

into the neck.

ing, the apices of the lung and pleurae project upward

vessels and nerves. Because of the obliquity of the open

opening pass the esophagus and trachea and many

placed facing upward and forward. Through this small

border of the manubrium sterni. The opening is obliquely

and their costal cartilages, and anteriorly by the superior

vertebra, laterally by the medial borders of the 1st ribs

The opening is bounded posteriorly by the 1st thoracic

from the thorax here to enter the neck and upper limbs.

because important vessels and nerves emerge

outlet

It is called

thoracic outlet.

through an opening called the

The chest cavity communicates with the root of the neck

Openings of the Thorax

neck of each rib to rotate around its own axis.

both the joints of the head and the tubercle, permitting the

ribs during respiration are accompanied by movements in

ubrium and are immobile. The raising and lowering of the

The 1st ribs and their costal cartilages are fixed to the man

Movements of the Ribs and Costal Cartilages

the abdominal musculature.

The cartilages of the 11th and 12th ribs are embedded in

one another along their borders by small synovial joints.

6th, 7th, 8th, 9th, and 10th costal cartilages articulate with

border of the sternum by synovial joints. In addition, the

The 2nd to 7th costal cartilages articulate with the lateral

-
-

ing of the small muscles of the hand. Pressure on the blood

caused by pressure on the lower trunk of the plexus producing

be compressed between the bones. Most of the symptoms are

(see Fig. 2.6). It is here that the nerves or blood vessels may

face of the 1st rib and the clavicle as they enter the upper limb

The brachial plexus of nerves (C5, 6, 7, and 8 and T1) and the

The Thoracic Outlet Syndrome

subclavian artery and vein are closely related to the upper sur-

pain down the medial side of the forearm and hand and wast-

vessels may compromise the circulation of the upper limb.

C L I N I C A L N O T E S

Intercostal Spaces

nerves and vessels. The innermost intercostal muscle can be

cia) and parietal pleura and externally to the intercostal

the ribs. It is related internally to fascia (endothoracic fas

layer and crosses more than one intercostal space within

in the anterior abdominal wall. It is an incomplete muscle

layer and corresponds to the transversus abdominis muscle

forms the deepest

innermost intercostal muscle

The

Fig. 2.9).

(see

posterior (internal) intercostal membrane

rosis, the

ribs behind, where the muscle is replaced by an aponeu

backward from the sternum in front to the angles of the

border of the rib below (see Fig. 2.8). The muscle extends

from the subcostal groove of the rib above to the upper

ate layer. Its fibers are directed downward and backward

forms the intermedi

internal intercostal muscle

The

(Fig. 2.9).

brane

anterior (external) intercostal mem

aponeurosis, the

forward to the costal cartilage where it is replaced by an

border of the rib below (see Fig. 2.8). The muscle extends

from the inferior border of the rib above to the superior

ficial layer. Its fibers are directed downward and forward

forms the most super

external intercostal muscle

The

intercostal artery, and intercostal nerve (i.e., VAN).

the following order from above downward: intercostal vein,

deepest layers of muscles (Fig. 2.8). They are arranged in

nerves and blood vessels run between the intermediate and

is lined internally by the parietal pleura. The intercostal

which

endothoracic fascia,

muscle is lined internally by the

the innermost intercostal muscle. The innermost intercostal

ration: the external intercostal, the internal intercostal, and

The spaces between the ribs contain three muscles of respi-

Intercostal Muscles

scalenus

medius

brachial

plexus

scalenus

subclavian

artery

cervical rib

lower trunk of plexus

fibrous
band

cervical
rib

FIGURE 2.7

Thoracic outlet as seen from above. Note the

the brachial plexus and may kink the subclavian artery.

that the cervical rib may exert pressure on the lower trunk of

fibrous band that is attached to the first costal cartilage. Note

thorax, the rib is rudimentary but is continued forward as a

articulates anteriorly with the 1st rib. On the left side of the

right side of the thorax, the rib is almost complete and

) on both sides. On the

black

presence of the cervical ribs (

intercostal nerves.

The intercostal muscles are supplied by the corresponding

Nerve Supply

page 74.

Mechanics of Respiration

action of these muscles, see

intrathoracic pressure. For further details concerning the

ing in or the blowing out of the tissues with changes in

sues of the intercostal spaces, thus preventing the suck

different phases of respiration serves to strengthen the tis

addition, the tone of the intercostal muscles during the

contraction of the intercostal muscles, as in expiration. In

abdomen, the 1st to the 11th ribs will be lowered by the

ratus lumborum muscle and the oblique muscles of the

ration. If, conversely, the 12th rib is fixed by the quad

the 2nd to the 12th ribs toward the 1st rib, as in inspi

namely, the scaleni muscles, the intercostal muscles raise

by the contraction of the muscles in the root of the neck,

pull the ribs nearer to one another. If the 1st rib is fixed

When the intercostal muscles contract, they all tend to

Action

less separate from one another.

divided into three portions (see Fig. 2.9), which are more or

The Thorax: Part I—The Thoracic Wall

-
-

skin superficial

fascia

serratus

pleural

cavity (space)

lung

intercostal vein
intercostal artery
intercostal nerve

visceral pleura

parietal pleura

innermost

intercostal

internal

intercostal

external

intercostal

skin

superficial

fascia

serratus

syringe

external

intercostal

lung
visceral pleura
pleural cavity (space)

parietal pleura and

endothoracic fascia
innermost intercostal

internal intercostal

FIGURE 2.8

to pleural cavity. Depending on the site of penetration, the pectoral muscles will be pierced in addition to the serratus ante

Structures penetrated by a needle when it passes from skin surface

Section through an intercostal space.

rior muscle.

lateral

cutaneous branch

posterior ramus

spinal nerve

intercostal nerve

muscular branch

branches to

parietal pleura

anterior cutaneous branch

perforating branch

internal thoracic artery

anterior intercostal artery

lateral cutaneous

branch

innermost intercostal

internal intercostal

external intercostal

posterior intercostal

artery

thoracic aorta

posterior intercostal membrane

parietal pleura

anterior intercostal

membrane

FIGURE 2.9

ve and a posterior and an anterior

Cross section of the thorax showing distribution of a typical intercostal ner

intercostal artery.

Basic Anatomy

neous branch.

first intercostal nerve is small, and there is no anterior cuta

branch of typical intercostal nerves. The remainder of the

by a large branch that is equivalent to the lateral cutaneous

is joined to the brachial plexus

first intercostal nerve

The

nerves only) run to the parietal peritoneum.

(7th to 11th intercostal

Peritoneal sensory branches

go to the parietal pleura.

Pleural sensory branches

run to the intercostal muscles.

Muscular branches

midline. It divides into a medial and a lateral branch.

portion of the main trunk, reaches the skin near the

which is the terminal

anterior cutaneous branch,

The

rior branch.

side of the chest. It divides into an anterior and a poste

reaches the skin on the

lateral cutaneous branch

The

main nerve on the upper border of the rib below.

runs forward inferiorly to the

collateral branch

The

the white ramus leaves it.

gray ramus joins the nerve medial at the point at which

a ganglion of the sympathetic trunk (see Fig. 1.26). The

connect the intercostal nerve to

Rami communicantes

See Figures 2.9 and 2.12.

Branches

abdominal wall.

the corresponding ribs are floating, pass directly into the

anterior abdominal wall. The 10th and 11th nerves, since

spaces by passing deep to the costal cartilages, to enter the

intercostal nerves leave the anterior ends of their intercostal

distributed within their intercostal spaces. The 7th to 9th

tal and internal intercostal muscle. The first six nerves are

of the corresponding rib, between the innermost intercos

inferiorly to the intercostal vessels in the subcostal groove

membrane (see Figs. 2.8 and 2.9). It then runs forward

between the parietal pleura and the posterior intercostal

Each intercostal nerve enters an intercostal space

subcostal nerve.

ward in the abdominal wall as the

the 12th thoracic nerve lies in the abdomen and runs for

11 thoracic spinal nerves (Fig. 2.12). The anterior ramus of

The intercostal nerves are the anterior rami of the first

into the internal thoracic and the musculophrenic veins.

drain forward

anterior intercostal veins

and 2.11), and the

backward into the azygos or hemiazygos veins (Figs. 2.10

drain

posterior intercostal veins

The corresponding

ticularly large.

female, the branches to the superficial structures are par

skin, and parietal pleura. In the region of the breast in the

Each intercostal artery gives off branches to the muscles,

thoracic artery.

artery, one of the terminal branches of the internal

the lower spaces are branches of the musculophrenic

subclavian artery. The anterior intercostal arteries of

2.9 and 2.10), which arises from the first part of the

are branches of the internal thoracic artery (see Figs.

of the first six spaces

anterior intercostal arteries

The

aorta (Figs. 2.9 and 2.10).

nine spaces are branches of the descending thoracic

artery. The posterior intercostal arteries of the lower

branch of the costocervical trunk of the subclavian

are branches from the superior intercostal artery, a

of the first two spaces

posterior intercostal arteries

The

intercostal artery and two small anterior intercostal arteries.

Each intercostal space contains a large single posterior

Intercostal Arteries and Veins

costal vein, intercostal artery, and intercostal nerve (i.e., VAN).

arranged in the following order from above downward: inter

innermost layers of muscles (see Figs. 2.8 and 2.9). They are

bundle), as in the abdominal wall, run between the middle and

The intercostal nerves and blood vessels (the neurovascular

■

Intercostal Nerves

■

Skin Innervation of the Chest Wall and

with inflammation of the skin. In the thorax, the first symptom

in a patient who has previously had chickenpox. The lesion is

the abdominal musculature. The abdominal pain in these

give rise to abdominal pain and tenderness and rigidity of

nia with pleurisy involving the costal parietal pleura could

across the costal margin into the anterior abdominal wall.

wall may be revealed as pain in a dermatome that extends

importance because it means that disease in the thoracic

and parietal peritoneum. This latter fact is of great clinical

abdominal wall, muscles of the anterior abdominal wall,

that they, in addition, supply dermatomes on the anterior

thoracic wall and enter the anterior abdominal wall so

Furthermore, the 7th to 11th intercostal nerves leave the

muscles, and parietal pleura lining the intercostal space.

but also supplies the ribs, costal cartilages, intercostal

An intercostal nerve not only supplies areas of skin,

Referred Pain

Above the level of the sternal angle, the cutaneous innerva-

tion of the anterior chest wall is derived from the supracla-
vicular nerves (C3 and 4). Below this level, the anterior and

lateral cutaneous branches of the intercostal nerves supply

oblique bands of skin in regular sequence. The skin on the

posterior surface of the chest wall is supplied by the posterior

rami of the spinal nerves. The arrangement of the dermatomes

is shown in Figures 1.23 and 1.24.

For example, a pulmonary thromboembolism or a pneumo-

instances is called referred pain.

Herpes Zoster

Herpes zoster, or shingles, is a relatively common condition

caused by the reactivation of the latent varicella-zoster virus

seen as an inflammation and degeneration of the sensory neu-

ron in a cranial or spinal nerve with the formation of vesicles

is a band of dermatomal pain in the distribution of the sensory

neuron in a thoracic spinal nerve, followed in a few days by a

skin eruption. The condition occurs most frequently in patients

older than 50 years.

C L I N I C A L N O T E S

The Thorax: Part I—The Thoracic Wall

azygos vein

about to enter

superior vena

cava

azygos vein

right subcostal

vein

left superior
intercostal vein

superior hemiazygos
vein

posterior
intercostal veins

inferior hemiazygos
vein

left ascending lumbar
vein

FIGURE 2.11

The common arrangement of the azygos vein,

the inferior hemiazygos (hemiazygos) vein.

the superior hemiazygos (accessory hemiazygos) vein, and

superior

hemiazygos

vein

descending

thoracic

aorta

innermost
intercostal
muscle

internal
intercostal
muscle

intercostal
nerve

posterior
intercostal artery

posterior
intercostal vein

superior
epigastric
vessels

internal
thoracic
vessels

FIGURE 2.10

Anterior view of the chest showing the courses of the internal thoracic vessels. These vessels

been removed for clarity.

Internal view of the posterior end of two typical intercostal spaces; the posterior intercostal membrane has

descend about one fingerbreadth from the lateral margin of the sternum.

anterior ramus

posterior

ramus

second thoracic
spinal nerve

anterior
cutaneous
branch

lateral

cutaneous

branch

intercostobrachial

nerve

intercostal nerve

FIGURE 2.12

The distribution of two intercostal nerves

skin and the parietal peritoneum covering the outer and

In addition, the 7th to 11th intercostal nerves supply the

and the levatores costarum and serratus posterior muscles.

tively, and the intercostal muscles of each intercostal space

outer and inner surfaces of each intercostal space, respec

therefore supply the skin and the parietal pleura covering the

With the exceptions noted, the 1st six intercostal nerves

is referred along this nerve to the medial side of the arm.

coronary artery disease,

medial side of the arm. In

therefore supplies the skin of the armpit and the upper

neous branch of other nerves. The 2nd intercostal nerve

which is equivalent to the lateral cuta

costobrachial nerve,

inter

cutaneous nerve of the arm by a branch called the

is joined to the medial

second intercostal nerve

The

relative to the rib cage.

-
-

pain

Basic Anatomy

Intercostal Nerve Block

The skin and the parietal pleura cover the outer and inner sur

Area of Anesthesia

faces of each intercostal space, respectively; the 7th to 11th

intercostal nerves supply the skin and the parietal peritoneum

covering the outer and inner surfaces of the abdominal wall,

respectively. Therefore, an intercostal nerve block will also

anesthetize these areas. In addition, the periosteum of the adja-

cent ribs is anesthetized.

Indications
Intercostal nerve block is indicated for repair of lacerations of

the thoracic and abdominal walls, for relief of pain in rib frac-

tures, and to allow pain-free respiratory movements.

Procedure
To produce analgesia of the anterior and lateral thoracic and

abdominal walls, the intercostal nerve should be blocked before

the lateral cutaneous branch arises at the midaxillary line. The

ribs may be identified by counting down from the 2nd (opposite

sternal angle) or up from the 12th. The needle is directed toward

the rib near the lower border (see Fig. 2.8), and the tip comes

to rest near the subcostal groove, where the local anesthetic is

infiltrated around the nerve. Remember that the order of struc-

tures lying in the neurovascular bundle from above downward

is intercostal vein, artery, and nerve and that these structures

are situated between the posterior intercostal membrane of the

internal intercostal muscle and the parietal pleura. Furthermore,

laterally, the nerve lies between the internal intercostal muscle

and the innermost intercostal muscle.

Anatomy of Complications
Complications include pneumothorax and hemorrhage.

Pneumothorax can occur if the needle point misses the subcos-

tal groove and penetrates too deeply through the parietal pleura.

Hemorrhage is caused by the puncture of the intercostal

blood vessels. This is a common complication, so aspiration

should always be performed before injecting the anesthetic.

A small hematoma may result.

C L I N I C A L N O T E S

inner surfaces of the abdominal wall, respectively, and the

movements.

in intrathoracic pressure occurring during respiratory

tects the underlying cervical pleura and resists the changes

structures passing from the thorax into the neck. It pro

cervical vertebra and medially to the fascia investing the

its apex to the tip of the transverse process of the seventh

border of the 1st rib and costal cartilage. It is attached at

tent-shaped fibrous sheet is attached laterally to the medial

(Fig. 2.13). This

suprapleural membrane

layer called the

of these structures, the outlet is closed by a dense fascial

for the most part lie close to the midline. On either side

and the neck (esophagus, trachea, blood vessels, etc.) and

outlet transmits structures that pass between the thorax

(see page 39). The

thoracic outlet

a narrow aperture, the

Superiorly, the thorax opens into the root of the neck by

tus abdominis muscles.

oblique, internal oblique, transversus abdominis, and rec

anterior abdominal muscles, which include the external

Suprapleural Membrane

The shape of the thorax can be distorted by congenital anom

Thoracic Cage Distortion

alies of the vertebral column or by the ribs. Destructive dis-

ease of the vertebral column that produces lateral flexion or

scoliosis results in marked distortion of the thoracic cage.

C L I N I C A L N O T E S

Endothoracic Fascia

The suprapleural membrane is a thickening of this fascia.

sue that separates the parietal pleura from the thoracic wall.

The endothoracic fascia is a thin layer of loose connective tis-

location of

apex of lung

first rib

transverse process of
seventh cervical vertebra
suprapleural membrane

parietal pleura

visceral pleura

clavicle

FIGURE 2.13

Lateral view of the upper opening of the

of the endothoracic fascia.

tected by the suprapleural membrane, which is a thickening

covered with visceral and parietal layers of pleura and is pro

superiorly into the root of the neck. The apex of the lung is

thoracic cage showing how the apex of the lung projects