Anatomy of the thorax

1. Thoracic wall
Dr.Mohamed Mahmoud Mosaed

2. Thoracic wall
The thoracic cage is the framework of the walls
of the thorax and is formed by;
• the vertebral column behind,
• the ribs and intercostal spaces on either side,
• the sternum and costal cartilages in front.
Functions of the thoracic cage
• It protects the lungs and heart.
• It affords attachment for the muscles of the
thorax, upper extremity, abdomen, and back

5. Structure of the Thoracic Wall
• The thoracic skeleton includes;
• The sternum
• 12 pairs of ribs and costal cartilages, The
ribs and their cartilages are separated by
intercostal spaces
• 12 thoracic vertebrae and intervertebral
discs.

6. Sternum
• Site: The sternum is a flat bone lies in the midline of
the anterior chest wall.
• Parts
Three parts: manubrium sterni, body of the
sternum, and xiphoid process.
• The manubrium sterni is the upper part of the
sternum. It articulates with the body of the sternum at
the manubriosternal joint.
• It also articulates with the clavicles and with the first
costal cartilage and the upper part of the second
costal cartilages on each side
• It lies opposite the third and fourth thoracic vertebrae.

8. • The body of the sternum articulates;
• Above with the manubrium at the
manubriosternal joint and
• Below with the xiphoid process at the
xiphisternal joint.
• On each side it articulates with the second to
the seventh costal cartilages
• The xiphoid process is a thin plate of cartilage
that becomes ossified at its proximal end during
adult life. No ribs or costal cartilages are
attached to it.

9. The sternal angle) angle of Louis), formed by
the articulation of the manubrium with the
body of the sternum, can be recognized by the
presence of a transverse ridge on the anterior
aspect of the sternum.
• The transverse ridge lies at the level of the
second costal cartilage, the point from which
all costal cartilages and ribs are counted.
• The sternal angle lies opposite the
intervertebral disc between the fourth and fifth
thoracic vertebrae.
The xiphisternal joint lies opposite the body of
the ninth thoracic vertebra

10. Ribs
• There are 12 pairs of ribs, all of which are attached
posteriorly to the thoracic vertebrae .
The ribs are divided into three categories:
• True ribs: The upper seven pairs are attached
anteriorly to the sternum by their costal cartilages.
• False ribs: The 8th
, 9th
, and 10th
pairs of ribs are
attached anteriorly to each other and to the 7th
rib by
means of their costal cartilages and small synovial
joints.
• Floating ribs: The 11th
and 12th
pairs have no anterior
attachment.

12. Typical Rib
• The ribs from the 3rd
to the 9th
have the same general
anatomical features so they are refereed to typical rib
• A typical rib is a long, twisted, flat bone
• It has a shaft, anterior and posterior ends.
The anterior (costal) end
• The anterior end of each rib is attached to the
corresponding costal cartilage .
The shaft
• The shaft is thin and flattened and twisted on its long axis.
It has superior and inferior borders.
• The superior border is rounded and smooth
• The inferior border is sharp and thin. It overhangs and
forms the costal groove, which accommodates the
intercostal vessels and nerve.
The angle is where the shaft of the rib bends sharply forward

13. • The posterior (vertebral) end
• It has a head, neck and tubercle:
• The head
• It has two facets. The lower and larger facet
articulates with the body of the corresponding
vertebra, the upper facet articulates with the vertebra
above.
• The neck
• It is a constricted portion situated between the head
and the tubercle
• The tubercle
• It is a prominence on the outer surface of the rib at the
junction of the neck with the shaft
• It has a facet for articulation with the transverse
process of the numerically corresponding vertebra

16. Atypical Rib
• First rib
• This rib is small and flattened from above downward.
• The head bears circular facet, to articulates with the body of
the first thoracic vertebra.
• The Shaft is flat and has superior and inferior surfaces, and
inner and outer borders;
• The first rib is important clinically because of its close
relationship to the lower nerves of the brachial plexus and the
subclavian artery and vein.
• The scalenus anterior muscle is attached to its upper surface
and inner border.
• Anterior to the scalenus anterior, the subclavian vein crosses
the rib; posterior to the muscle attachment,
• the subclavian artery and the lower trunk of the brachial plexus
cross the rib and lie in contact with the bone.

18. Costal Cartilages
• Costal cartilages are bars of cartilage
connecting the upper seven ribs to the lateral
edge of the sternum and the 8th
, 9th
, and 10th
ribs to the cartilage immediately above. The
cartilages of the 11th
and 12th
ribs end in the
abdominal musculature
• The costal cartilages contribute significantly to
the elasticity and mobility of the thoracic walls.
In old age, the costal cartilages tend to lose
some of their flexibility as the result of
superficial calcification

19. Joints of the Chest Wall

20. Joints of the Sternum
• The manubriosternal joint is a cartilaginous
joint between the manubrium and the body of
the sternum. A small amount of angular
movement is possible during respiration.
• The xiphisternal joint is a cartilaginous joint
between the xiphoid process (cartilage) and
the body of the sternum. The xiphoid process
usually fuses with the body of the sternum
during middle age.

21. Joints of the Ribs
Joints of the Heads of the Ribs
• The first rib and the three lowest ribs (10th
,11th
,12th)
have a
single synovial joint with their corresponding vertebral body.
• For the second to the ninth ribs, the head articulates by 2
synovial joints with the corresponding vertebral body and that of
the vertebra above it. There is a strong intraarticular ligament
that connects the head to the intervertebral disc.
Joints of the Tubercles of the Ribs
• The tubercle of a rib articulates by a synovial joint with the
transverse process of the corresponding vertebra (This joint is
absent on the 11th
and 12th
ribs.)
Joints of the Ribs and Costal Cartilages
• These joints are cartilaginous joints. No movement is possible.

22. Joints of the Costal Cartilages with the Sternum
• The first costal cartilages articulate with the manubrium, by
cartilaginous joints that permit no movement.
• The 2nd
to the 7th
costal cartilages articulate with the lateral
border of the sternum by synovial joints.
• In addition, the 6th
, 7th
, 8th
, 9th
, and 10th
costal cartilages
articulate with one another along their borders by small
synovial joints. The cartilages of the 11th
and 12th
ribs are
embedded in the abdominal musculature.
Movements of the Ribs and Costal Cartilages
• The 1st ribs and their costal cartilages are fixed to the
manubrium and are immobile.
• The raising and lowering of the ribs during respiration are
accompanied by movements in both the joints of the head and
the tubercle, permitting the neck of each rib to rotate around its
own axis.

24. Openings of the Thorax
1. The superior thoracic aperture (the thoracic outlet)
The thoracic cavity communicates with the neck through the
superior thoracic aperture.
• Structures entering and leaving the thoracic cavity through this
aperture include the trachea, esophagus, vessels, and nerves.
• The opening is obliquely placed facing upward and forward.
Because of the obliquity of the opening, the apices of the lung
and pleurae project upward into the neck.
• The superior thoracic aperture is bounded:
• Posteriorly: by the first thoracic (T1) vertebra.
• Laterally: by medial border of the first ribs and their costal
cartilages.
• Anteriorly: by the superior border of the manubrium sterni.

25. 2. The inferior thoracic aperture
The thoracic cavity communicates with the abdomen
through the inferior thoracic aperture,
• The diaphragm separates the thoracic and abdominal
cavities.
• The inferior thoracic aperture is more large than the
superior thoracic aperture. Structures passing to or
from the thorax to the abdomen pass through
openings in the diaphragm.
• The opening is bounded posteriorly by the 12th
thoracic vertebra, laterally by the curving costal
margin, and anteriorly by the xiphisternal joint.

26. The structure of the Vertebra
• The vertebra consists of: Body and vertebral
arch with vertebral foramen in between
• The vertebral arch carries seven processes
• 2 transverse
• 1 spinous
• 4 articular (2 superior and 2 inferior articular
processes)
• The pedicles lies between the body and the
transverse process
• The lamina lies between the transverse
process and the spine

28. Thoracic vertebrae
There are twelve thoracic vertebrae, each of which is
characterized by articulations with ribs.
A typical thoracic vertebra
• typical thoracic vertebra has:
• A heart-shaped vertebral body, with roughly equal
dimensions in the transverse and anteroposterior
directions.
• The vertebral foramen is generally circular and the
laminae are broad.
• The superior articular processes are flat, with their
articular surfaces facing almost directly posteriorly.
• The inferior articular processes project from the
laminae and their articular facets face anteriorly.
• The spine is long and points sharply downward