Thorax

A region of the body

between the neck and
abdomen
 Comprises the thoracic
wall and the thoracic
cavity
 Have truncated cone
shaped
 Narrowest superiorly
and wider inferiorly,
 Thorax…

 The thoracic skeleton takes the form of a domed

thoracic cage (rib cage)
 Thoracic cage formed by:
Ribs and costal cartilages
 Supported by:
Sternum and thoracic vertebrae
 The floor of the thoracic cavity (the diaphragm) is
deeply invaginated inferiorly ( pushed upward) by
viscera of the abdominal cavity
 The lower half of the thoracic wall surrounds and
protects abdominal viscera
 Thorax…
 The thorax includes the primary organs of the
 respiratory and cardiovascular systems
 The thoracic cavity is divided into three major
spaces:
1. Central compartment (mediastinum): houses the
conducting structures that make up the thoracic viscera
2. Lateral compartments(pulmonary cavities): houses the
lungs that lie on each side of the mediastinum
 Functions of thoracic cage…
 Protection:
 Protect vital thoracic and abdominal organs
 Breathing:
 Moving air into and out of the lungs
 Conduit :
o The esophagus, vagus nerves, thoracic duct, phrenic
nerves, trachea, thoracic aorta, and superior vena cava
 Provide support for the upper limbs
 Provide attachment of the muscles the upper limbs
abdomen, neck, back and respiration
 Constantly in motion,
 Hence ,one of the most dynamic regions of the body
 Thoracic wall
Skeleton of thorax
Joints of thoracic wall
Movements of thoracic wall
 Muscles of the thoracic wall
Nerves of the thoracic wall
Vasculature of the thoracic wall
 Skeleton of thorax

 Forms:
osteocartilaginous
thoracic cage
 Includes:
 12 pairs of ribs
and costal
cartilages
 12 thoracic
vertebrae and
intervertebral
discs
 Sternum

08/26/2025 Feredegn T. 7
 Ribs
 Ribs (L. costae) are curved, flat bones that form
most of the thoracic cage
 They are remarkably light in weight yet highly
resilient
 Each rib has a spongy interior containing bone
marrow (hematopoietic tissue), which forms blood
cells
 Three types of ribs based on its attachment
Ribs…
with sternum
1. True (vertebrosternal) ribs
 (1st–7th ribs):
 They attach directly to the sternum with
costal cartilages.
2. False (vertebrochondral) ribs
 8th, 9th, and 10th ribs
 Their cartilages are connected to the
cartilage of the rib above them
 Connection with the sternum is indirect.
3. Floating (vertebral, free) ribs
 11th, 12th
 No attachment with the sternum; instead
 They end in the posterior abdominal
musculature.
Ribs…
 Typical ribs (3rd - 9th )
 Head:
 Wedge -shaped with two facets, separated by the
crest of the head
 One facet for articulation with the numerically
corresponding vertebra and
 One facet for the vertebra superior to it
 Neck:
 Connects the head with the body at the level of the
tubercle
 Typical ribs (3 rd
-9 th
)…
Tubercle:
 At the junction of the neck and body
 Has:
 a smooth articular part - for articulating with the
process of the vertebra, and
 a rough non-articular part - for attachment of the
costotransverse ligament
 Typical ribs (3 rd
-9 th
)
Body (shaft):
 Thin, flat, and curved, at the costal angle where the
rib turns anterolaterally
 The concave internal surface of the body has a
costal groove paralleling the inferior border of the
rib, which provides some protection for the
intercostal nerve and vessels
 Atypical ribs (1st , 2nd , 10th & 12th )
 The 1st rib: is the broadest, shortest, and most
sharply curved of the seven true ribs
 It has a single facet on its head for articulation
with the T1 vertebra only
 Has two transversely grooves crossing its superior
surface for the subclavian vessels;
 Atypical ribs (1st , 2nd , 10th & 12th )

 2nd rib:
 its main atypical feature is a rough area on its upper
surface, the tuberosity for serratus anterior, from
which part of that muscle originates
 10th - 12th ribs:
 Have only one facet on their heads and articulate with a
single vertebra

 11th and 12th ribs:

 Short and have no neck or tubercle
 Costal cartilages
 Contribute to the elasticity
of the thoracic wall,
 Increase in length through
the first 7 ribs
 The first 7 attach directly
to the sternum
 The 8th , 9th , and 10th
articulate with the costal
cartilages by seventh
 The 11th and 12th
cartilages do not reach
any other bone or cartilage
 Thoracic Vertebrae

 Are classified as: typical and atypical

Features of typical thoracic vertebrae

 T2-T9 are typical ribs

 Bilateral costal facets (demifacets) on their
bodies:
Occurring in inferior and superior pairs, for
articulation with the heads of ribs
 Costal facets on their transverse processes:
For articulation with the tubercles of ribs,
 Long, inferiorly slanting spinous processes
Typical thoracic vertebrae
 Features of atypical thoracic vertebrae

 Bear whole costal facets in place of demifacets

 The superior costal facets of vertebra T1 are
complete and rib 1 articulates only with vertebra T1
 T10 has only one bilateral pair of (whole) costal
facets, located partly on its body and partly on its
pedicle
 T11 and T12 also have only a single pair of (whole)
costal facets, located on their pedicles
Atypical thoracic vertebrae
 Features of atypical thoracic vertebrae…

 The spinous processes typical thoracic vertebrae

are long and slope inferiorly
 They cover the intervals between the adjacent
vertebrae, thereby preventing sharp objects injuring
the spinal cord
 Sternum
 The sternum (G.
sternon, chest) is the
flat, elongated bone that
forms the middle of the
anterior part of the
thoracic cage
 The sternum consists of
three parts:
Manubrium
Body
Xiphoid process
 Manubrium
 The widest and thickest
 The easily palpated
superior border of the
manubrium is the
jugular/suprasternal notch
 At the junction of manubrium
and body of sternum forms
sternal angle (of louis)
 Body of the sternum
 Longer, narrower, and thinner than the manubrium
 Located at the level of the T5 - T9 vertebrae
Xiphoid process
 The smallest and most variable part of the sternum
 Thin and elongated
 Lies at the level of T10 vertebra
 Cartilaginous in young people but ossified in adults
older than age 40
 In elderly people, it may fuse with the sternal body
 Thoracic Apertures
 Thorax has two opening ; superiorly and inferiorly
 Superior opening
 Much smaller
 Passageway that allows communication with the neck
and upper limb
 Inferior opening
 larger
 Provides the ring-like origin of the diaphragm, which
completely occludes the opening
 Superior Thoracic Aperture
 kidney shaped
 Structures that pass between the thoracic cavity
and the neck through it include trachea,
esophagus, nerves, and vessels
 It measures 6.5 cm anteroposteriorly and 11
cm transversely
 Superior Thoracic Aperture…

Boundary:
 Posteriorly:
 T1 vertebrae
 Laterally:
 ribs 1 and its cartilage
 Anteriorly:
 superior border of the
manubrium
 Inferior Thoracic Aperture
 Much more spacious than the superior thoracic
aperture and is irregular in outline
 Its posterior thoracic wall is much longer than the
anterior wall
 Diaphragm separates the thoracic and abdominal
cavities
 Structures passing from or to the thorax from the
abdomen pass through openings that traverse the
diaphragm
 Inferior Thoracic Aperture
Boundary:
Posteriorly: by the 12th thoracic
vertebra
Posterolaterally: by the 11th
and 12th pairs of ribs
Anterolaterally: by the joined
costal cartilages of ribs 7 -10,
forming the costal margins
Anteriorly: by the xiphisternal
joint
 Movements of the Thoracic Wall
 Movements of the thoracic wall and diaphragm during inspiration
Produce increases in the intrathoracic volume and diameters of the
thorax
 During passive expiration:
o The diaphragm relax
o intercostal muscles, and
o other muscles,
 Decreasing intrathoracic volume
 Increasing the intrathoracic pressure
 The dimension the thoracic cavity increases during inspiration:
Contraction of the diaphragm
Descend down
 compressing the abdominal viscera
 Muscles of the Thoracic Wall
 Thoracoappendicular muscles
Attach to upper limb with the thoracic cage
Such as :
 Pectoralis major
Pectoralis minor
Subclavius,
Serratus anterior muscles
Latissimus dorsi muscles
 True muscles of the thoracic wall:
 Serratus posterior
 Levatores costarum
 Intercostal
 Subcostal
 Serratus posterior muscles
 Extend from the vertebrae to the ribs
 Have traditionally been described as inspiratory muscles
 Are two in number: serratus posterior superior and
serratus posterior inferior
 Intercostal muscles
 The intercostal muscles
occupy the intercostal
spaces
 The superficial layer is
formed by the external
intercostals, the inner layer
by the internal intercostals
 The deepest layers: lying
internal to the intercostal
vessels are the innermost
intercostals
Intercostal muscles…
 External intercostal muscles
 11 pairs occupy the intercostal spaces from the
tubercles of the ribs posteriorly to the
costochondral junctions anteriorly
 Anteriorly, the muscle fibers are replaced by the
external intercostal membranes
 Run inferoanteriorly from the rib above to the rib
below
 Are most active during inspiration
 External intercostal
Superior attachment:
Inferior border of ribs above
Inferior attachment:
Superior border of ribs below
Innervation:
Intercostal nerve
Main action:
Elevate ribs during forced inspiration
 Internal intercostal muscles
 11 pairs, run at right angles infero-posteriorly
 Attach to the bodies of the ribs and sternum and
Posteriorly to angles of the ribs
 Posteriorly, it replaced by the internal intercostal
membranes
 Continuous with the internal oblique muscles
 Weaker than the external intercostal muscles
 Active during expiration
 Internal intercostal
Superior attachment:
 Inferior border of ribs
Inferior attachment:
 Superior border of ribs below
Innervation:
 Intercostal nerve
Main action:
 Interosseous part: depresses ribs
 Interchondral part: elevates ribs
 Innermost intercostal muscles
 Similar to the internal intercostals and are
essentially their deeper parts
 Are separated from the internal intercostals by the
intercostal nerves and vessels
 Their actions are the similar to internal intercostal
muscles.
 Innermost intercostal
Superior attachment:
Inferior border of ribs
Inferior attachment:
Superior border of ribs below
Innervation:
Intercostal nerve
Main action:
Interosseous part: depresses ribs
Interchondral part: elevates ribs
 Subcostal muscles

 Are variable in size and shape,

 Found only in the lower

thoracic wall
 Extend from the internal
surface of the angle of one rib
to the internal surface of the
2nd or 3rd rib inferior to it
 Crossing one or two intercostal
spaces
 Depress ribs
 Transverse thoracic
 Consist of four or five slips
 Attach posteriorly to the
xiphoid process, inferior part of
the body of the sternum, and
costal cartilages
 They pass superolaterally
 Attach to the 2nd - 6th costal
cartilages
 Continuous inferiorly with the
transverse abdominal muscles
 Have a weak expiratory
function
 Proprioceptive information.
 Fascia of the Thoracic Wall
 The thoracic cage is lined internally with
endothoracic fascia
 This thin fibro-areolar layer attaches the adjacent
portion of the costal parietal pleura to the thoracic
wall
 Nerves of the Thoracic Wall
 12 pairs of thoracic spinal nerves supply the
thoracic wall
 Divide into anterior and posterior primary rami
 The anterior rami of nerves T1- T11 intercostal
nerves run in intercostal spaces
 T12, coursing inferior to the 12th rib, is the
subcostal nerve
 The posterior rami of thoracic spinal nerves
pass posteriorly, supply the joints, muscles, and
skin of the back in the thoracic region
 Typical Intercostal Nerves
 The 3rd - 6th are typical intercostal nerves
 Running within the endothoracic fascia
 Between the parietal pleura and the intercostal
spaces
 Near the angles of the ribs, they pass between the
internal intercostal and the innermost intercostal
muscles
 Running inferior to the intercostal arteries and
intercostal veins
 Typical Intercostal Nerves
 The neurovascular bundles are
sheltered by the inferior margins
of the ribs
 The nerves continue anteriorly
between the internal and the
innermost intercostal muscles,
giving muscular branches and
giving rise to lateral cutaneous
branches in the MAL
 Anteriorly, the nerves appear on the
internal surface of the internal
intercostal muscle
 Near the sternum, the intercostal
nerves turn anteriorly, passing between
the costal cartilages to become anterior
cutaneous branches.
 Atypical Intercostal Nerves
 The anterior ramus of the 1 st
thoracic (T1) spinal
nerve first divides into:
 The superior part: joins the brachial plexus,
 The inferior part: becomes the 1st intercostal nerve
 The 1st intercostal nerve has no anterior cutaneous
branch and often no lateral cutaneous branch
 When there is a lateral cutaneous branch, it supplies
the skin of the axilla
 The 1st and 2nd intercostal nerves course on the
internal surface of the 1st and 2nd ribs
 Atypical Intercostal Nerves…
 The 2nd intercostal nerve gives rise lateral cutaneous
branch, the intercostobrachial nerve:
Supplies skin of the axilla ,the medial and posterior
surfaces of the arm
 The 7th- 11th intercostal nerves
o Giving rise to lateral cutaneous branches, cross the costal
margin posteriorly and continue on to supply abdominal
skin and muscles
o They become the thoracoabdominal nerves of the anterior
abdominal wall
o Their anterior cutaneous branches pierce the rectus
sheath, becoming cutaneous close to the median plane.
Atypical Intercostal Nerves…
Atypical Intercostal Nerves…
 Arteries of the Thoracic Wall
The arterial supply to the
thoracic wall derives from:
 Thoracic aorta: through
the posterior intercostal and
subcostal arteries
 Subclavian artery: through
the internal thoracic and
supreme intercostal arteries
 Axillary artery: through the
superior and lateral thoracic
arteries
Arteries of the Thoracic Wall…
 Arteries of the Thoracic Wall
• The intercostal arteries course through the thoracic
wall between the ribs
• With the exception of the 10th and 11th intercostal
spaces, each intercostal space is supplied by three
arteries:
• a large posterior intercostal artery and
- a small pair of anterior intercostal arteries
Arteries of the Thoracic Wall…
 Posterior intercostal arteries
The 1st and 2nd intercostal arteries arise
 From the supreme (superior) intercostal artery
 A branch of the costocervical trunk of the subclavian
artery
 The 3rd- 11th and the subcostal arteries arise from the
thoracic aorta
Supply the spinal cord, vertebral column, back muscles,
and skin
 They lie between the intercostal vein and nerve
 Internal thoracic arteries
 Arise in the root of the neck
 The first parts of the subclavian
arteries
 Terminate in the 6th intercostal
space
o Dividing into the superior epigastric
and musculophrenic arteries
 Give rise to the anterior intercostal
arteries
o supplying the superior six intercostal
space
 Of the 7th - 9th intercostal spaces
derive from the musculophrenic
arteries
 Are absent from the inferior two
intercostal spaces:
 These spaces are supplied only by
the posterior intercostal arteries
 Veins of the Thoracic Wall
 Intercostal veins accompany the intercostal arteries
and nerves
 11 posterior intercostal veins and one subcostal
vein
 As they approach the vertebral column, the
posterior intercostal veins receive a posterior
branch
 Which accompanies the posterior ramus of the
spinal nerve and an intervertebral vein
 Veins of the Thoracic Wall
 Anterior intercostal vein is the tributaries of internal thoracic
vein
 The posterior intercostal veins of the 1st enter directly into
brachiocephalic veins
 The posterior intercostal veins of the 2nd and 3rd intercostal
spaces unite to form a trunk, the superior intercostal vein
 The right superior intercostal vein
The tributary of the azygos vein, before it enters the SVC
 The left superior intercostal vein
Empties into the left brachiocephalic vein
 (4th -11th ) P. intercostal veins end in the
azygos/hemiazygos venous system, later to the SVC
Veins of the Thoracic Wall…
 Lymphatic drainage
 Lymphatic vessels of the
thoracic wall drain
associated with the internal
thoracic arteries into
parasternal nodes
 The heads and necks of ribs
drain in to intercostal nodes
 Lymph node along the
diaphragm drain in to the
diaphragmatic nodes
 Diaphragm
 A thin musculotendinous septum that separates the
thoracic cavity a from the abdominal cavity
 It is pierced by the structures that pass between the
chest and the abdomen
Important muscle of respiration
 Dome shaped and consists of a peripheral muscular
part, and a centrally tendon
Diaphragm…
 Diaphragm…
 Has three origins
 Sternal part
Arising from the posterior
surface of the xiphoid
process
 Costal part
Arising from the deep
surfaces of the lower six ribs
and their costal cartilages
 Vertebral part
Arising by vertical columns or
crura and from the arcuate
ligaments
Nerve Supply of the Diaphragm
Motor nerve supply :
The right and left phrenic nerves (C3 - C5)
Sensory nerve supply :
To the central surfaces of the diaphragm are from the
phrenic nerve
To the periphery of the diaphragm is from the lower six
intercostal nerves
 Openings in the Diaphragm

 The diaphragm has

three main openings
through which
structures pass:
 Caval opening
 Esophageal hiatus and
 Aortic hiatus
Openings in the Diaphragm…
The caval opening:
Lies at the level of the 8th thoracic vertebra in
the central tendon
 It transmits
o inferior vena cava

o terminal branches of the right phrenic nerve

Diaphragm…
 Openings in the Diaphragm
Esophageal opening :
Lies at the level of the 10 th
TV
It transmits:
 esophagus
the right and left vagus nerves
the esophageal branches of the left gastric vessels
Diaphragm…
 Openings in the Diaphragm…

The aortic opening :

 Lies anterior to the body of the 12th TV between the
crura
It transmits
Aorta
Thoracic duct, and
Azygos vein
Diaphragm…
 Surface Anatomy of Thoracic Wall
 Sternum
 Lies subcutaneously
 In the anterior median line and
palpable
 Jugular notch
 Lies at the level of the inferior border
of the body of T2 vertebra
 Between the 1st and 2nd thoracic
spinous processes.
 Manubrium
 4 cm long
 Lies at the level of the bodies of T3
and T4 vertebrae
 Sternal angle
 Lies at the level of the T4–T5 IV disc
 between the 3rd and 4th thoracic
spinous processes.
 Surface Anatomy of Thoracic Wall…
 The sternal angle marks the level of the 2nd pair of costal
cartilages.
 The left side of the manubrium is anterior to the arch of the aorta,
 Its right side directly overlies the brachiocephalic veins to form
superior vena cava (SVC)
 Because it is common clinical practice to insert catheters into the
SVC for intravenous feeding
 It is essential to know the surface anatomy of this large vein.
 SVC:
 Passes inferiorly deep to the manubrium and manubriosternal
junction , projects as a fingerbreadth to the right margin of the
manubrium.
 Enters the right atrium of the heart opposite the right 3rd costal
cartilage
Surface Anatomy of Thoracic Wall…

 The body of the sternum

10 cm long
lies anterior to the right border of the heart and vertebrae T5–
T9
 The xiphoid process
Lies in a slight depression, the epigastric fossa.
Used as a guide in cardiopulmonary resuscitation (CPR) to
properly position the hand on the inferior part of the sternum.
 The xiphisternal joint is palpable at the level of the
inferior border of T9 vertebra.
Surface Anatomy of Thoracic Wall…
Surface Anatomy of Thoracic Wall…
 The ribs and intercostal spaces provide a basis for
locating the position of structures or sites of trauma in
the thoracic wall.
 Because the 1st rib is not palpable, rib counting in
physical examinations starts with the 2nd rib
 To count the ribs and intercostal spaces anteriorly, slide
the fingers laterally from the sternal angle onto the 2nd
costal cartilage
 The 1st intercostal space is that superior to the 2nd
costal cartilage
Surface Anatomy of Thoracic Wall…

 Anterior median
(midsternal) line (AML)
Indicates the
intersection of the
median plane with the
anterior thoracic wall
 Mid clavicular line
(MCL)
Passes through the
midpoint of the clavicle,
parallel to the AML.
Surface Anatomy of Thoracic Wall…

 Anterior axillary line (AAL)

 Runs vertically along the anterior
axillary fold
 Formed by the inferolateral
border of the pectoralis major
 Midaxillary line (MAL)
 Runs from the apex of the
axillary parallel to the AAL.
 Posterior axillary line (PAL
 Parallel to the AAL
 Drawn vertically along the
posterior axillary fold
 Formed by the latissimus dorsi
and teres major
Surface Anatomy of Thoracic Wall…

 Posterior median
(midvertebral) line
(PML)
A vertical line along the
tips of the spinous
processes of the
vertebrae
 Scapular lines (SLs)
Parallel to the posterior
median line
Intersect the inferior
angles of the scapula
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