Thorax Part 1: Thoracic Wall

1st Semester | Prelims | Montezo, NJ. | DMD-2 Explorer

Overview articulates with the clavicles and with

the first costal cartilage and the upper
Chest or thorax (thora- Greek for "breastplate" part of the second costal cartilage on
"chest") each side.
- ls the region of the body between the Suprasternal (jugular) notch- ls the easily
neck and the abdomen. palpable, concave notch on the superior border
- It is flattened ln front and behind but of the manubrium.
rounded at the sides.
o Skin and muscles of the shoulder girdle Clavicular notch- an ovoid articular surface at
cover the exterior of the thoracic wall, each superolateral comer of the manubrium, on
whereas parietal pleura lines its inner each side of the jugular notch.
surface.
o Each holds the sternal end of a clavicle.
Thoracic cage- skeletal framework of the
thoracic walls.
2. Body- relatively long, middle part of the
- protects the lungs and heart and
sternum.
provides attachment for the muscles of
- It articulates above with the
the thorax. upper extremity, abdomen,
manubrium at the manubriosternal
and back.
- formed by the thoracic part of the
vertebral column posteriorly, the ribs
and intercostal spaces laterally on either
side, and the sternum and costal
cartilages anteriorly.
o Superiorly, the thorax communicates
with the neck, and Inferiorly, It is
separated from the abdomen by the
diaphragm.

Mediastinum- division of thoracic cavity, median

portion and the laterally placed pleurae and
lungs.

Visceral pleura- thin membrane that covers the

lungs and passes from each lung at its root.

Parietal pleura- inner surface of the chest wall.

Pleural cavities- two membranous sacs that

forms one on each side of the thorax, between
the lungs and the thoracic walls.

OSTEOLOGY:

o The thoracic skeleton forms an

osseocartilaginous, cagelike unit that
surrounds and protects the heart, lungs, joint and below with the xiphoid
and adnexa. process at the xiphisternal joint.
o It also covers all or parts of certain - It articulates with second to the
upper abdominal organs (e.g., liver, seventh costal cartilages on each
stomach, spleen, kidneys). side.
o The thoracic cage is a component of the
axial skeleton and Is formed by the Clinical notes
sternum, ribs, costal cartilages, and
Sternum and Marrow Biopsy:
thoracic vertebrae.
The sternum Is subcutaneous and readily
Sternum palpable along its entire length. Like the ribs, it
(stern) Greek for "breast"; "breast bone" consists largely of highly vascular cancellous

o the elongate, flat bone that lies in the bone enclosed by a thin shell of compact bone. It
midline of the anterior chest wall. possesses red hematopoietic marrow
throughout lite.
The adult sternum consists of three parts:
manubrium, body, and xiphoid process. Because of Its morphology and shallow depth In
the chest. the sternum can be punctured readily
1. Manubrium- manubri (latin for handle), In a needle biopsy procedure ("sternal puncture)
ls the upper part of the sternum. It for aspiration of red marrow. Under a local
articulates with the body of the sternum anesthetic, a wide-bore needle Is Inserted Into
at the manubriosternal joint, and it also the marrow cavity through the anterior surface

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Thorax Part 1: Thoracic Wall
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of the bone. The sternum may also be split In 3. xiphoid process- (xiph- Is Greek for "sword)
surgery to allow the surgeon to gain easy access ls the small, "pointed" (at its inferior end), most
to the heart, great vessels, and thymus. inferior part of the sternum.
Sternum, ribs, and costal cartilages forming - a thin plate of cartilage that becomes ossified at
the thoracic: skeleton. its proximal end during adult life.

- ls highly variable in size, shape, and degree of

ossification.

- No ribs or costal cartilages attach to it. However,

the seventh costal cartilage may have a shared
attachment with the xiphoid process and the body.

-The xiphistemal joint lies opposite the body of the

ninth thoracic vertebra.

-The inferior end of the xiphoid provides

attachment for the linea alba of the abdominal
wall.

Sternal angle (angle of louis)- articulation of the

manubrium with the body forms.

- can be recognized by the presence of a

transverse ridge on the anterior aspect of
the sternum.
- an important landmark for thoracic
Lateral view of the thorax showing the anatomy because it marks (1) the
relationship of the surface markings to the manubriosternal joint (a symphyseal
vertebral levels.
joint), (2) the attachment points of the
second costal cartilages (thus, these
attach to both manubrium and body), (3) a
horizontal line that typically projects
posteriorly onto the T4 intervertebral
disc, and (4) the plane of separation
between the superior and inferior
mediastina.

Ribs

(cost- is Latin for "ribs), elongate, flattened,

arched bones that form a large part of the
thoracic wall.

- consist largely of highly vascular

cancellous bone enclosed by a thin
shell of compact bone.
Embryology Notes True ribs (pairs 1-7)- are connected directly to
the sternum via individual costal cartilages.
Sternum development:
False ribs (pairs 8 to 10)- are connected the
The adult sternum consists of three parts:
sternum via Individual costal cartilages that join
manubrium, body, and xiphoid process.
together and attach collectively to the seventh
Prenatally, lt consists of six main parts. The first
costal cartilages.
and last parts remain distinguishable as the
manubrium and xiphoid process, respectively. Floating ribs (pairs 11 to 12) - do not attach to
The middle four parts (sternebrae) fuse to form the sternum.
the body. The three main parts were named after
the resemblance of the sternum to the short TYPICAL RIBS:
sword favored by Roman troops and gladiators-
- a long, twisted, flat bone having
thus, the manubrium (handle), the body (in older
rounded, smooth superior border
terminology = gladiolus = small sword), and the
and a sharp, thin inferior border.
xiphoid process (sword point).
- The anterior end of each rib is
attached to the corresponding costal
cartilage.

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Thorax Part 1: Thoracic Wall
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Head- the posterior (vertebral) end of the rib and - In old age, the costal cartilages tend
has two facets for articulation with the to lose some of their flexibility as the
result of superficial calcification.
numerically corresponding vertebral body and
that of the vertebra immediately above.

Neck- the flattened, slightly constricted portion

situated between the head and the tubercle.

Tubercle- prominence on the outer posterior

surface of the rib at the junction of the neck with
the body. It has a facet for articulation with the
transverse process of the numerically
corresponding vertebra.

Body (shaft)- long, thin, flattened, and twisted

(on its long axis) part that extends from the
tubercle to the anterior (sternal) end.

Costal groove- elongate depression along the

inferior aspect of the internal surface of the shaft
of the rib. This holds the intercostal vessels and
nerve.

Angle- the point (usually slightly distal to the

tubercle) at which the body of the rib bends
sharply and turns from a lateral to a more
anteriorly directed orientation.

Anterior (sternal) end- flat and has a depression

for the costal cartilage.

FIRST RIB:

Important because of its close relationship to the

lower nerves of the brachial plexus and the main
vessels to the arm, namely, the subclavian artery
and vein

Fifth right rib, as seen from the posterior

aspect. Vertebrae

COSTAL CARTILAGES:
Costal facets (facet latin for little face)- are small
- bars of cartilage connecting the articular surfaces at approximately the
upper seven ribs to the lateral edge
posterolateral aspect of the body, at the junction
of the sternum and the 8th, 9th, and
of the body and the pedicle.
10th ribs to the cartilage immediately
above. o Typical thoracic vertebrae (2 to 8) have
- The cartilages of the 11th and 12th two on each side. One is located
ribs end In the abdominal superiorly (superior costal facet). One is
musculature located inferiorly (Inferior costal facet).
- Contribute to the elasticity and
- sites where the heads of the ribs
mobility of the thoracic walls.
articulate with the body.

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Thorax Part 1: Thoracic Wall
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o Adjacent typical thoracic vertebrae (2 to longitudinal incision Is then made through the
8) share the articulations of ribs. bed of the rib, which is the inner covering of the
- head of an individual rib articulates periosteum. After the operation, the rib
with both the superior costal facet of regenerates from the osteogenetic layer of the
the numerically corresponding periosteum.
vertebral body and the Inferior
costal facet of the vertebra
immediately above.

Demifacet (demi- French for half)- carries half of

rib articulation.

o The Tl vertebra has a full costal facet

(instead of a superior demifacet) for the
head of the first rib, plus an inferior
demifacet for the superior half of the
head of the second rib.
o The Tl 1 and T12 vertebrae each have full
costal facets (located mainly on the
pedicles) instead of demifacets because
the heads of ribs 11 and 12 articulate only
with their own Individual vertebrae.

Transverse costal facets- small articular

surfaces on the transverse processes.

- sites where the tubercle of each rib

articulates with the transverse
process.
Thoracic cage distortion:
- not present on the T11 and T12
vertebrae because ribs 11and12 do The shape of the thorax can be distorted by
not articulate with the transverse congenital anomalies of the vertebral column or
processes. by the ribs. Destructive disease of the vertebral
column that produces lateral flexion or
Clinical Notes scoliosis results in marked distortion of the
thoracic cage.
Cervical rib:
Traumatic injury to thorax:
The importance of a cervical rib is that it may
cause pressure on the lower trunk of the Common as a result of automobile accidents.
brachial plexus, causing pain down the medial Sternum fracture:
side of the forearm and hand and wasting of the
small muscles of the hand. It can also exert The sternum ls a resilient structure that ls held
pressure on the overlying subclavian artery and ln position by relatively pliable costal cartilages
Interfere with the circulation of the upper limb. and bendable ribs. For these reasons, fracture of
the sternum Is not common; however, it does
Rib excision: occur in high-speed motor vehicle accidents.
Remember that the heart lies posterior to the
- Perform by surgeons to gain
sternum and may be severely contused by the
entrance to the thoracic cavity. sternum on Impact.
A longitudinal incision ls made through the Rib fractures:
periosteum on the outer surface of the rib, and
a segment of the rib ls removed. A second Common chest injuries. In children, the ribs are
highly elastic, and fractures in this age group are

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Thorax Part 1: Thoracic Wall
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therefore rare. Unfortunately, the pliable chest Joints of Costal Cartilages

wall In the young can be easily compressed so with Sternum
that the underlying lungs and heart may be
Injured. With Increasing age, the rib cage o The first costal cartilages articulate with
becomes more rigid, owing to the deposit of the manubrium by cartilaginous joints
calcium in the costal cartilages, and the ribs that do not permit movement.
become brittle. The ribs then tend to break at o The second to seventh costal cartilages
their weakest part, their angles. articulate with the lateral border of the
sternum by synovial joints.
Ribs 5 through 10 are the most commonly o the 6th, 7th, 8th, 9th, and 10th costal
fractured ribs. The clavicle and pectoral muscles cartilages articulate with one another
protect the first four ribs anteriorly and the along their borders by small synovial
scapula and its associated muscles do so joints.
posteriorly. The 11th and 12th ribs float and move o The cartilages of the 11th and 12th ribs do
with the force of impact. not articulate with the sternum and are
Flail chest: embedded ln the abdominal
musculature.
a section of the chest wall is disconnected from
the rest of the thoracic wall. If the fractures Rib and Costal Cartilage
occur on either side of the sternum, the sternum Movements
may be flail. In either case, the stability of the
chest wall ls lost, and the flail segment ls sucked o The first ribs and their costal cartilages
in during lnspiration and driven out during are fixed to the manubrium and are
expiration, producing paradoxical and Ineffective immobile.
respiratory movements. o The raising and lowering of the ribs
during respiration are accompanied by
Sternal Joints movements in both the joints of the head
and the tubercle, permitting the neck of
Manubriosternal joint- a cartilaginous joint each rib to rotate around its own axis.
between the manubrium and the body of the
sternum. Thoracic Aperture
- A small amount of angular
movement is possible here during
respiration. superior thoracic aperture (thoracic outlet)

Xiphisternal joint- a cartilaginous joint between - A narrow opening of the root of the
the xiphoid process and the body of the sternum. neck
– The xiphoid process usually fuses with the body - Called outlet because important
of the sternum during middle age vessels and nerves emerge from the
thorax here to enter the neck and
Joints of Heads and Ribs upper limbs.

o The first rib and the 3 lowest ribs have a o The body of the first thoracic vertebra
single synovial joint with their forms the posterior boundary of the
corresponding vertebral body. thoracic outlet
o second to ninth ribs, the head articulates
by means of a synovial joint with the o the medial edges of the first ribs and
corresponding vertebral body and that of their costal cartilages mark the lateral
the vertebra above it. A strong intra- boundaries.
articular ligament connects the head to
the intervertebral disc. o superior margin of the manubrium sterni
forms the anterior border.
Joints of Tubercles of Ribs
o The outlet Is obliquely directed, facing
o The tubercle of a rib articulates by upward and forward, and conveys the
means of a synovial joint with the esophagus, trachea, and several vessels
transverse process of the corresponding and nerves.
vertebra. This joint is absent on the 11th
Inferior Thoracic Aperture- Large opening of the
and 12th ribs.
abdomen where the thoracic cavity
Joints of Ribs and Costal communicates.
Cartilages o The body of the 12th thoracic vertebra
forms the posterior boundary of this
o These joints are cartilaginous joints. No
opening.
movement ls possible here.
o curving costal margin marks its lateral
boundaries
o the xiphisternal joint forms the anterior
border.

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Thorax Part 1: Thoracic Wall
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o The diaphragm closes the inferior blood vessels may compromise the
aperture. circulation of the upper limb.

SUPREPLEURAL MEMBRANE: Intercostal Spaces

The thoracic outlet transmits structures that o Gaps between adjacent ribs.
pass between the thorax and the neck
(esophagus, trachea, blood vessels, etc.) and for A needle passing through the entire depth of an
the most part lie close to the midline. intercostal space must penetrate seven
structural layers. In superficial to deep
Suprapleural membrane- dense facial layer sequence, the layers are the ff:
which closes the thoracic outlet on either side of
these structures. 1. Skin

o tent-shaped fibrous sheet attaches 2. Superficial fascia

laterally to the medial border of the first
3. Deep fascia
rib and costal cartilage; medially to the
fascia investing the structures passing 4. Intercostal muscles
from the thorax into the neck; and, at its
apex, to the tip of the transverse process 5. Endothoracic fascia
of the seventh cervical vertebra. 6. Extrapleural fatty layer
o It protects the underlying cervical pleura
and resists the changes in intrathoracic 7. Parietal pleura
pressure occurring during respiratory
o serratus anterior, may cover the
movements.
intercostal muscle layer.
ENDOTHORACIC FASCIA: o The three intercostal musles all act as
muscles of respiration
o a thin layer of loose connective tissue o The innermost intercostal muscle is
that separates the parietal pleura from lined internally by the endothoracic
the thoracic wall. fascia, which is lined internally by a
o The suprapleural membrane is a highly variable extrapleural fatty layer
thickening of this fascia. and then the parietal pleura.

Intercoastal Muscles
Three intercostal muscles fill the lntercostal
spaces: external lntercostal, Internal lntercostal,
and Innermost intercostal.

1. External intercostal muscle- the most

superficial of the three muscle layers.
o Its fibers are directed downward and
forward from the inferior border of the
rib above to the superior border of the
rib below.
o The muscle extends forward to the
costal cartilage where it is replaced by
an aponeurosis, the anterior (external)
lntercostal membrane.

2. Internal intercostal muscle- forms the

intermediate layer.
o Its fibers are directed downward and
backward from the subcostal groove
ofthe rib above to the upper border of the
rib below.
Clinical Notes o The muscle extends backward from the
sternum in front to the angles of the ribs
Thoracic outlet syndrome: behind, where the muscle is replaced by
o Obstruction of the thoracic outlet may an aponeurosis, the posterior (Internal)
compress these neurovascular lntercostal membrane.
structures in this area.
o Symptoms are caused by pressure on 3. Innermost intercostal muscle- forms the
the lower trunk of the plexus, causing deepest layer and corresponds to the
pain down the medial side of the forearm transversus abdominis muscle In the
and hand and wasting of the small anterior abdominal wall.
muscles of the hand. Pressure on the

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o It is an incomplete muscle layer and NERVE SUPPLY:

crosses more than one intercostal
o The corresponding lntercostal nerves
space.
supply the intercostal muscles. The
o It is related. internally to the
lntercostal nerves and blood vessels
endothoracic fascia and parietal pleura
(the neurovascular bundle), as in the
and externally to the intercostal nerves
abdominal wall, run between the middle
and vessels.
and innermost layers of muscles.
Divided into three portions: ARRANGEMENT: Intercostal vein -
Intercostal artery - Intercostal nerve
1. Transversus thoracis- anterior
2. Innermost intercostal- lateral
3. Subcostalis- posterior

ACTION:

o primary function of the intercostal

muscles during respiration appears to
be to stabilize the position of the ribs to
maintain the intercostal spaces.
o Their actions in elevation (external
intercostals) and depression (internal
lntercostals) of the ribs are most likely
to occur during forced respiration.
o

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o o The superior surface of the tendon is

o partially fused with the inferior surface
o of the fibrous pericardium.
o o Some of the muscle fibers of the right
o crus pass up to the left and surround the
o esophageal orifice In a slinglike loop.
o
Diaphragm Shape
o
o - As seen in the front, the diaphragm
o curves up into right and left domes (
o cupulae ).
o o the right dome reaches as high as the
o upper border of the fifth rib, and the left
o dome may reach the lower border of the
o fifth rib.
o The right dome lies at a higher level
because of the large size of the right lobe
Diaphragm of the liver.
o The domes support the right and left
o thin muscular and tendinous septum that lungs, whereas the central tendon
separates the chest cavity above from
supports the heart.
the abdominal cavity below.
o Most important muscle in respiration. Nerve Supply of Diaphragm
o It ls dome shaped and consists of a
o Motor nerve supply comes from the right
peripheral muscular part, which arises
and left phrenic nerves (C3, 4, 5).
from the margins of the thorax, and a
o Each phrenic nerve supplies
centrally placed tendon.
approximately half of the diaphragm.
The origin of the diaphragm can be divided into Thus, functionally, the diaphragm
three parts: operates as two hemidiaphragms.
o For sensory nerve supply, phrenic
1. Sternal part- arising from the posterior nerves supply the parietal pleura and
surface of the xiphoid process. peritoneum covering the central
2. Costal part- arising from the deep surfaces of the diaphragm.
surfaces of the lower six ribs and their
costal cartilages. Diaphragmatic action
3. Vertebral part- arising by vertical
o On contraction, the diaphragm pulls
columns (crura) and from the arcuate
down its central tendon and increases
ligaments.
the vertical diameter of the thorax.
Right crus- arises from the sides of the bodies of
Diaphragmatic function
the first three lumbar vertebrae and the
intervertebral discs. 1. Muscle of Inspiration- on contraction,
the diaphragm pulls its central tendon
Left crus- arises from the sides of the bodies of
down and increases the vertical
the first two lumbar vertebrae and the
diameter of the thorax. The diaphragm is
intervertebral disc.
the most important muscle used in
inspiration.
o Lateral to the crura, the diaphragm 2. Muscle of abdominal straining- the
arises from the medial and lateral contraction of the diaphragm assists the
arcuate ligaments. contraction of the muscles of the
anterolateral abdominal wall in raising
Medial arcuate ligament- extends from the side the intra-abdominal pressure for
of the body of the second lumbar vertebra to the micturition, defecation, and parturition.
tip of the transverse process of the first lumbar o Taking a deep breath and closing the
vertebra. glottis of the larynx further aids this
Lateral arcuate ligament- extends from the tip of mechanism.
the transverse process of the first lumbar o The diaphragm is unable to rise because
vertebra to the lower border of the 12th rib. of the air trapped in the respiratory tract.
Now and again, air is allowed to escape,
Median arcuate ligament- crosses over the producing a grunting sound.
anterior surface of the aorta, connects the 3. Weight-lifting muscle- taking a deep
medial borders of the two crura. breath, the diaphragm assists the
muscles of the anterolateral abdominal
Central tendon- where diaphragm is inserted,
wall in raising the intra-abdominal
shaped like three leaves.
pressure to such an extent that it helps

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support the vertebral column and Clinical Notes

prevent flexion.
o adequate sphincteric control of Hiccup:
the bladder and anal canal is
The involuntary spasmodic contraction of the
important under these
diaphragm, accompanied by the approximation of
circumstances.
the vocal folds and closure of the glottis of the
4. Thoracoabdominal Pump- the descent of larynx.
the diaphragm decreases the
intrathoracic pressure and at the same o Common condition that occurs after
time increases the intra-abdominal eating or drinking as a result of gastric
pressure. irritation of the vagus nerve endings.
o this pressure change o may be a symptom of disease such as
compresses the blood in the o pleurisy, peritonitis, pericarditis, or
inferior vena cava and forces it uremia
upward into the right atrium of
Diaphragm Paralysis:
the heart.
o Lymph within the abdominal A single dome of the diaphragm (a
lymph vessels is also hemidiaphragm) may be paralyzed by crushing
compressed, and the negative or sectioning of the phrenic nerve in the neck.
intrathoracic pressure aids its
passage upward within the o This may be necessary in the treatment
thoracic duct. of certain forms of lung tuberculosis,
o The presence of valves within when the physician wishes to rest the
the thoracic duct prevents lower lobe of the lung on one side.
backflow. o Accessory phrenic nerve- the fifth
cervical spinal nerve joins the phrenic
Diaphragm openings nerve late as a branch from the nerve to
the subclavius muscle.
The diaphragm has three main openings:
o Recognizing that a paralyzed
1. Aortic opening- lies anterior to the body hemidiaphragm assumes a
of the 12th thoracic vertebra and hyperelevated posture rather than a
between the crura. depressed (flattened) posture is
o It transmits the aorta, the important.
thoracic duct, and the azygos
Penetrating Injuries to Diaphragm:
vein.
o the aortic opening is not a Penetrating Injuries to the diaphragm can result
true opening within the from stab or bullet wounds to the chest or
diaphragm. Rather, it is a gap abdomen. Any penetrating wound to the chest
behind the posterior margin below the level of the nipples should be
of the diaphragm. suspected of causing damage to the diaphragm
2. Esophageal opening- lies at the level of until proved otherwise.
the 10th thoracic vertebra In a sling of
muscle fibers derived from the right Embryology Notes
crus.
Diaphragm Development:
- It transmits the
esophagus, the right and The diaphragm is formed from the ff:
left vagus nerves, the
esophageal branches of 1. Septum transversum- forms the muscle
the left gastric vessels, and central tendon.
and the lymphatics from o Is a mass of mesoderm that ls formed In
the lower third of the the neck by the fusion of the myotomes
esophagus. of the third, fourth, and filth cervical
3. Caval opening- lies at the level of the segments.
eighth thoracic vertebra, in the central o With the descent of the heart from the
tendon. It transmits the inferior vena neck to the thorax, the septum is pushed
cava and terminal branches of the right caudally, pulling its nerve supply with it.
phrenic nerve. Thus, cervical nerves C3 to 5 form the
phrenic nerve, which supplies the
In addition to these openings, the sympathetic diaphragm.
splanchnic nerves pierce the crura, the 2. 2 pleuroperitoneal membranes- largely
sympathetic trunks pass posterior to the medial responsible for the peripheral areas of
arcuate ligament on each side, and the superior the diaphragmatic pleura and
epigastric vessels pass between the sternal and peritoneum that cover its upper and
costal origins of the diaphragm on each side. lower surfaces.
o grow medially from the body wall on
each side until they fuse with the septum

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transversum anterior to the esophagus and with comprise the Intermediate layer of muscles of
the dorsal mesentery posterior to the the back.
esophagus.
o The superior muscle passes downward
3. Dorsal mesentery of the esophagus- and laterally and inserts into the upper
which the crura develop. ribs.
o The motor nerve supply to the entire o The inferior muscle passes upward and
muscle of the diaphragm is the phrenic laterally. and inserts into the lower ribs.
nerve. o Both are supplied by adjacent intercostal
o The central pleura on the upper surface nerves.
of the diaphragm and the peritoneum on o Both have been describe as respiratory
the lower surface are also formed from muscles because of their alignments,
the septum transversum, which explains with the superior muscle denoted as
their sensory Innervation from the acting In inspiration to elevate the ribs
phrenic nerve and the Inferior muscle acting In
expiration to depress the ribs.
Congenital herniae- occur as the result of
incomplete fusion of the septum transversum,
the dorsal mesentery, and the pleuroperitoneal
membranes from the body wall.

The herniae occur in the ff sites:

1. The pleuroperitoneal canal (more

common on the left side; caused by
failure of fusion of the septum
transversum with the pleuroperitoneal
membrane).
2. The opening between the xiphoid and
costal origins of the diaphragm.
3. The esophageal hiatus.

Acquired herniae- occur in esophageal opening

ln the diaphragm. These herniae may be either
sliding (hiatal) or paraesophageal.

Nerves
asd
Intercostal Nerves- supply the entire thoracic
wall. These nerves are the anterior rami of the
first 11 thoracic spinal nerves.
dd
Subcostal Nerve- the anterior ramus of the 12th
thoracic nerve lies in the abdomen and runs
forward in the abdominal wall.

o Each intercostal nerve enters an

intercostal space between the parietal
pleura and the posterior intercostal
membrane.
o The first six nerves are distributed within
Levatores Costarum their intercostal spaces.
o The seventh to ninth intercostal nerves
- Comprises 12 pairs. leave the anterior ends of their
intercostal spaces by passing deep to
- Each is triangular in shape and Inserts Into the the costal cartilages, to enter the
rib below its origin. anterior abdominal wall.
- They elevate the ribs, but their role in o The 10th and 11th nerves pass directly
respiration ls questionable. They may serve as into the abdominal wall.
proprioceptive devices.

Serratus Posterior Muscles

The serratus posterior superior and serratus
posterior Inferior are thin, flat muscles that

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Branches
Rami Communicantes- connect the intercostal and inner surfaces of the abdominal wall,
nerve to a ganglion of the sympathetic trunk. respectively, plus the anterolateral abdominal
wall muscles (which include the external
- The gray and white rami are adjacent to one oblique, internal oblique, transversus abdominis,
another. and rectus abdominis muscles).
Collateral Branch- runs forward inferiorly to the
Vasculature
main nerve on the upper border of the rib below.

Lateral cutaneous Branch- reaches the skin on

The subclavian artery, axillary artery, and
the side of the chest. It divides into an anterior
thoracic aorta supply the thoracic walls.
and a posterior branch.
o The subclavian artery provides blood
Anterior cutaneous branch- terminal portion of
through Its Superior intercostal and
the main trunk. reaches the skin near the
Internal thoracic branches.
midline. It divides into a medial and a lateral
o The axillary artery supplies via its
branch.
Superior thoracic and lateral thoracic
Muscular Branches- run to the intercostal branches.
muscles. o The thoracic aorta gives off posterior
intercostal and subcostal branches.
Pleural sensory branches- go to the parietal
pleura. Internal Thoracic Artery
Peritoneal sensory branches- (7th to 11th - supplies the anterior wall of the body from the
intercostal nerves only) run to the parietal clavicle to the umbilicus.
peritoneum.
- It is a branch of the first part of the subclavian
First intercostal nerve- joins the brachial plexus artery in the neck.
by a large branch that ls equivalent to the lateral
- It descends vertically on the pleura behind the
cutaneous branch of typical intercostal nerves.
costal cartilages, a fingerbreadth lateral to the
o The remainder of the first intercostal sternum, and ends ln the sixth intercostal space
nerve is small, and an anterior by dividing into the superior epigastric and
cutaneous branch does not exist. musculophrenic arteries.

Second intercostal nerve- joins the medial Branches

cutaneous nerve of the arm by a large branch
named the lntercostobrachial nerve. 1. Two anterior intercostal arteries- supply
the upper six intercostal spaces.
- which is equivalent to the 2. Perforating arteries- accompany the
lateral cutaneous branch of other nerves. terminal branches of the corresponding
intercostal nerves.
o The second intercostal nerve supplies
3. Pericardiacophrenic artery -
the skin of the armpit and the upper
accompanies the phrenic nerve and
medial side of the arm. In coronary
supplies the pericardium.
artery disease, pain is referred long this
4. Mediastinal arteries- supply the
nerve to the medial side of the arm.
contents of the anterior mediastinum.
o The 7th to 11th intercostal nerves supply
5. Superior epigastric artery- enters the
skin and the parietal peritoneum
covering the outer rectus sheath of the anterior abdominal

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wall and supplies the rectus muscle as o Anterior intercostal arteries of the first
far as the umbilicus. six spaces are branches of the Internal
6. Musculophrenic artery- runs around the thoracic artery, which arises from the
costal margin of the diaphragm and first part of the subclavian artery. The
supplies the lower Intercostal spaces anterior intercostal arteries of the lower
and the diaphragm. spaces are branches of the
musculophrenic artery, one of the
Clinical Notes terminal branches of the internal
thoracic artery.
Skin Innervation of chest wall
o The corresponding posterior lntercostal
and referred pain veins drain posteriorly into the azygos or
o The supraclavicular nerves (C3 and 4) hemiazygos veins.
provide the cutaneous innervation of the o The anterior lntercostal vein drain
anterior chest wall above the level of the anteriorly into the internal thoracic and
sternal angle. Below this level, the musculophrenic veins.
anterior and lateral cutaneous branches
of the intercostal nerves supply oblique
bands of skin in regular sequence.
o An intercostal nerve not only supplies
areas of skin but also supplies the ribs,
costal cartilages, intercostal muscles,
and parietal pleura lining the intercostal
space.
o 7th to 11th intercostal nerves leave the
thoracic wall and enter the anterior
abdominal wall to supply dermatomes
on the anterior abdominal wall, muscles
of the anterior abdominal wall, and
parietal peritoneum.

Herpes Zoster (shingles)

- a relatively common condition caused by the
reactivation of the latent varicella-zoster virus In
a patient who has previously had chickenpox.

- The lesion is seen as an inflammation and

degeneration of the sensory neurons in a cranial
or spinal nerve with the formation of vesicles and
Inflammation of the skin.

Pneumothorax- can occur if the e needlepoint

misses the subcostal groove and penetrates too
deeply through the parietal pleura.
Clinical Notes

Hemorrhage- caused by the puncture of the Internal thoracic artery in

intercostal blood vessels. This is a common coronary artery disease
complication, so aspiration should always be treatment
performed before Injecting the anesthetic. A
small hematoma may result. o In patients with occlusive coronary
disease caused by atherosclerosis, the
Internal thoracic vein diseased arterial segment can be
bypassed by inserting a graft. The graft
- accompanies the internal thoracic artery and most commonly used is the great
drains into the brachiocephalic vein on each side. saphenous vein of the leg
Intercostal arteries and veins Arterial Anastomoses
Each intercostal space contains a large single o The anterior intercostal arteries
posterior intercostal artery and two small (branches of the subclavian artery via
anterior intercostal arteries. the internal thoracic and
o Posterior intercostal arteries of the first musculophrenic arteries) and the lower
two spaces are branches from the nine posterior intercostal arteries
superior intercostal artery, a branch of (branches of the thoracic aorta) typically
the costocervical trunk of the subclavian anastomose with one another at
artery. The posterior intercostal arteries approximately the costochondral
of the lower nine spaces are branches of junctions.
the descending thoracic aorta.

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o These Important connections create - making an incision through the thoracic

collateral circulatory routes that wall into the pleural space.
potentially allow blood flow to bypass - This may be a lifesaving procedure in
obstructions in the thoracic aorta or the patients with penetrating chest wounds
proximal part of the subclavian artery. with uncontrolled intrathoracic
o These anastomoses are notably hemorrhage.
prominent in circumventing the
constriction present In postductal
coarctation of the aorta.

Thoracic wall lymph

drainage
o The lymph drainage of the skin of the
anterior chest wall passes to the
anterior axillary lymph nodes; that
from the posterior chest wall passes
to the posterior axillary nodes.
o The lymph drainage of the
intercostal spaces passes forward
to the Internal thoracic nodes,
situated along the Internal thoracic
artery, and posteriorly to the
posterior intercostal nodes and the
para-aortic node In the posterior
mediastinum
o
o
o
o
o
o
Anatomic and physiologic
o
o
Thoracic changes with aging
o Certain anatomic and physiologic changes take
o place in the thorax with advancing years:
o
o o The rib cage becomes more rigid and
o loses its elasticity as the result of
o calcification and even ossification of the
o costal cartilages. This also alters their
o usual radiographic appearance.
o o The stooped posture (kyphosis), so often
o seen in the old because of degeneration
o of the intervertebral discs and/ or
o bodies, decreases the chest capacity.
o Disuse atrophy of the thoracic and
Needle thoracostomy abdominal muscles can result In poor
respiratory movements.
- is creating and maintaining an opening
o Degeneration of the elastic tissue In the
into the thoracic cavity by using a needle.
lungs and bronchi results In impairment
- necessary in patients with tension
of the movement of expiration.
pneumothorax (air in the pleural cavity
under pressure) or to drain fluid (blood
or pus) away from the pleural cavity to
allow the lung to reexpand.

Tube Thoracostomy
- The preferred insertion site for a tube
thoracostomy is the fourth or fifth
intercostal space at the anterior axillary
line.
- The tube Is Introduced through a small
Incision.

Thoracotomy

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length and can be easily palpated. It articulates

at Its lateral extremity with the acromion
process of the scapula.

Ribs
o The first rib lies deep to the clavicle and
cannot be palpated.
o The 12th rib can be used to identify a
particular rib by counting from below.

Surface Anatomy

Anterior Chest wall

Suprasternal notch- the superior margin of the
manubrium sterni and is easily felt between the
prominent medial ends of the clavicles in the
midline.

- It Iies opposite the lower border of the

body of the second thoracic vertebra.

Sternal angle (angle of louis)- angle made

between the manubrium and the body of the
sternum.

- It Iies opposite the intervertebral disc

between the fourth and fifth thoracic
vertebrae.

Xiphisternal Joints- the joint between the xiphoid

process of the sternum and the body of the
sternum.

- Lies opposite the body of the ninth

thoracic vertebra

Subcostal angle- situated at the inferior end of

the sternum, between the sternal attachments of
the seventh costal cartilages.

Costal margin- the lower boundary of the thorax

and is formed by the cartilages of the 7th, 8th,
9th, and 10th ribs and the ends of the 11th and 12th
cartilages.

- The lowest part of the costal margin is

formed by the 10th rib and lies at the
level of the third lumbar vertebra.

Clavicle- subcutaneous throughout Its entire

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o The lower portion of the left ventricle

forms the apex of the heart.
o The apex of the heart being thrust
forward against the thoracic wall as the
heart contracts causes the apex beat.
(The heart Is thrust forward with each
ventricular contraction because of the
ejection of blood from the left ventricle
Into the aorta; the force of the blood in
the aorta tends to cause the curved aorta
to straighten slightly, thus pushing the
heart forward.)
o The apex beat can usually be felt by
placing the Oat of the hand on the chest
wall over the heart.
o The apex beat is normally found In the
fifth left intercostal space, 3.5 In. (9 cm)
from the midline.

Axillary folds
Anterior axillary fold-forms the lower border of
the pectoralis major muscle.

Posterior axillary fold- forms the tendon of the

latissimus dorsi muscle as It passes around the
lower border of the teres major muscle.

Posterior chest wall

Spinous processes of the thoracic vertebrae can
be palpated In the posterior midline.

o The first spinous process to be felt is that

of the seventh cervical vertebrae
(vertebra prominens). - The overlapping
spines of the thoracic vertebrae are
below this level.

Ligamentum nuchae- a large ligament.

Covers the spines of the Cl to 6 vertebrae. It
should be noted that the tip of a spinous
process of a thoracic vertebra lies posterior
to the body of the next vertebra below.

Scapula (shoulder blade)- flat and triangular

Diaphragm
in shape and is located on the upper part of
o The central tendon of the diaphragm lies the posterior surface of the thorax.
directly behind the xiphlstemal joint.
o Superior angle lies opposite the spine of
o In the midrespiratory position, the
the second thoracic vertebra.
summit of the right dome of the
o Spine of the scapula is subcutaneous,
diaphragm arches upward as far as the
and the root of the spine lies on a level
upper border of the fifth rib In the
with the spine of the third thoracic
midclavicular line, but the left dome only
vertebra.
reaches as far as the lower border of the
o Inferior angles lies on a level with the
fifth rib.
spine of the seventh thoracic vertebra.
Nipple Clinical notes
o In the male, the nipple usually lies in the
As medical personnel, you will be examining the
fourth intercostal space about 4 in. (10
chest to detect evidence of disease. Your
cm) from the midline.
examination consists of Inspection, palpation,
o In the female, its position is not constant.
percussion, and auscultation.
However, the T4 dermatome always
crosses the nipple in both sexes 1. Inspection shows the configuration of
regardless of the form of the breast. the chest. the range of respiratory
movement, and any inequalities on the
Apex base of the heart two sides.

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2. Palpitation enables the clinician to Trachea

confirm the Impressions gained by
Inspection, especially of the respiratory - Extends from the lower border of the
movements of the chest wall. cricoid cartilage (opposite the body of
- Abnormal protuberances or recession the sixth cervical vertebra) In the neck to
of part of the chest wall ls noted. the level of the sternal angle In the
- Abnormal pulsations are felt and tender thorax.
areas detected. - It commences In the midline and ends
3. Percussions is a sharp tapping of the just to the right of the midline by dividing
chest wall with the fingers. This into the right and the left principal
produces vibrations that extend through bronchi.
the tissues of the thorax. - At the root of the neck, it may be palpated
4. Auscultation enables the clinician to in the midline in the suprasternal notch.
listen to the breath sounds as air enters
and leaves the respiratory passages.
- If the alveoli or bronchi are
diseased and filled with fluid, the
nature of the breath sounds will
be altered.
- The rate and rhythm of the heart
can be confirmed by
auscultation, and the various
sounds produced by the heart
and its valves during the
different phases of the cardiac
cycle can be heard.
- Detecting friction sounds
produced by the rubbing
together of diseased layers of
pleura or pericardium may be
possible.

Orientation lines Lungs

Apex of the lungs projects into the neck.
• Midsternal line- lies in the median plane
over the sternum. - It can be mapped out on the anterior
• Midclavicular line- runs vertically surface of the body by drawing a curved
downward from the midpoint of the line, convex upward, from the
clavicle. sternoclavicular joint to a point 1 in. (2.5
• Anterior axillary line- runs vertically cm) above the junction of the medial and
downward from the anterior axillary fold. intermediate thirds of the clavicle.
• Posterior axillary line- runs vertically
downward from the posterior axillary Anterior border of the right lung begins behind
fold. the sternoclavicular joint and runs downward,
• Midaxillary line-runs vertically almost reaching the midline behind the sternal
downward from a point situated midway angle. It then continues downward until it
between the anterior and posterior reaches the xiphisternal joint.
axillary folds.
Anterior border of the left lung has similar
• Scapular line- runs vertically downward
course, but at the level of the fourth costal
on the posterior wall of the thorax, cartilage, It deviates laterally and extends for a
passing through the Inferior angle of the variable distance beyond the lateral margin of
scapula (arms at the sides) the sternum to form the cardiac notch.

- The heart displacing the lung to the left

produces this notch.
- The anterior border then turns sharply
downward to the level of the xiphisternal
joint.

Lower border of the lung in midinspiration

follows a curving line, which crosses the sixth rib
in the midclavicular line and the eighth rib in the
midaxillary line, and reaches the 10th rib
adjacent to the vertebral column posteriorly.

- inferior border of the lung changes

during inspiration and expiration.

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Posterior border of the lung extends - A curved line may be drawn, convex
downward from the spinous process of the upward, from the sternoclavicular
seventh cervical vertebra to the level of the joint to a point 1 in. (2.S cm) above the
10th thoracic vertebra and lies about 1.5 In. (4 Junction of the medial and
cm) from the midline.
intermediate thirds of the clavicle.
Oblique fissure of the lung can be indicated
Anterior border of the right pleura runs down
on the surface by a line drawn from the root
behind the sternoclavicular joint, almost
of the spine of the scapula obliquely
reaching the midline behind the sternal angle. It
downward, laterally and anteriorly, following
then continues downward until It reaches the
the course of the sixth rib to the sixth
xiphisternal joint.
costochondral junction.
Anterior border of the left pleura has a similar
Horizontal fissure- an additional fissure in
course, but at the level of the fourth costal
the right lung only.
cartilage. it deviates laterally and extends to the
- This fissure may be represented by a line lateral margin of the sternum to form the cardiac
drawn horizontally along the fourth notch. (Note that the pleural cardiac notch is not
costal cartilage to meet the oblique as large as the cardiac notch of the lung.) It then
fissure in the midaxillary line. turns sharply downward to the xiphisternal joint.

Lower border of the pleura on both sides follows

a curved line, which crosses the eighth rib In the
midclavicular line and the 10th rib In the
midaxillary line, and reaches the 12th rib adjacent
to the vertebral column-that Is, at the lateral
border of the erector spinae muscle

Costodiaphragmatic recess- distance between

two borders.

Clinical notes
Cervical dome of the pleura and the apex of the
lungs extend up into the neck so that at their
highest point, they Iie about 1 in. (2.5 cm) above
the clavicle. Consequently, they are vulnerable to
stab wounds ln the root of the neck or to damage
by an anesthetist's needle during nerve block of
the lower trunk: of the brachial plexus.

Heart
- both have apex and four borders.

Apex- formed by the left ventricle, corresponds

to the apex beat and is found in the fifth left
intercostal space 3.5 in. (9 cm) from the midline.

Superior border- formed by the roots of the great

blood vessels, extends from a point on the
second left costal cartilage (remember the
sternal angle) 0.5 in. (1.3 cm) from the edge of the
sternum to a point on the third right costal
cartilage 0.5 in. (1.3 cm) from the edge of the
sternum.

Right border- formed by the right atrium,

Pleura extends from a point on the third right costal
cartilage 0.5 in. (I.3 cm) from the edge of the
The boundaries of the pleural sac can be sternum downward to a point on the sixth right
marked out as lines on the surface of the costal cartilage 0.5 in. (1.3 cm) from the edge of
the sternum.
body.
Left border- formed by the left ventricle, extends
Lines of pleural reflection- the lines, which
from a point on the second left costal cartilage
indicate the limits of the parietal pleura where it
0.5 in. (1.3 cm) from the edge of the sternum to
lies close to the body surface.
the apex beat of the heart.
Cervical pleura bulges upward into the neck
and has a surface marking identical to that
of the apex of the lung.

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lnferior border- formed by the right ventricle and

the apical part of the left ventricle, extends from
the sixth right costal cartilage 0.5 in. (1.3 cm)
from the sternum to the apex beat.

Thoracic blood vessels

o Arch of the aorta and the roots of the
brachiocephalic and left common carotid
arteries lie behind the manubrium
sterni.
o The superior vena cava and the terminal
parts of the right and left
brachiocephalic veins also lie behind the
manubrium sterni.
o Internal thoracic vessels run vertically
downward, posterior to the costal
cartilages, 0.5 in. (I.3 cm) lateral to the
edge of the sternum
o lntercostal vessel and nerve (“vein,
artery, nerve"-VAN-is the order from
above downward) are situated
immediately below their corresponding
ribs

Mamillary Gland
- lies in the superficial fascia covering the
anterior chest wall.
o It is rudimentary in children and in
men. It enlarges and assumes its
hemispherical shape in females
after puberty.

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