Anatomy and physiology of sternum In this slide you have brief detail on sternum anatomy and its clinical importance.

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2. STERNUM

3. Introduction
 The sternum, commonly known as the breastbone,
is a long, narrow flat bone that serves as the
keystone of the rib cage and stabilizes the thoracic
skeleton. Several muscles that move the arms,
head, and neck have their origins on the sternum.
 It also protects several vital organs of the chest,
such as the heart, aorta, vena cava, and thymus
gland that are located just deep to the sternum.
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4. The sternum is located along the body’s midline in the anterior thoracic
region just deep to the skin. It is a flat bone about six inches in length,
around an inch wide, and only a fraction of an inch thick.

5. Parts of Sternum
The sternum develops as three distinct parts
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6. Division of Sternum
The sternum develops as three distinct parts: the manubrium, the
body of the sternum (sometimes called the gladiolus), and the xiphoid
process.

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The shape of the sternum looks somewhat like a sword pointing
downwards, with the manubrium forming the handle, the body
forming the blade, and the xiphoid process forming the tip. In fact,
the name manubrium means “handle,” gladiolus means “sword,”
and xiphoid means “sword-shaped.”
BLOOD SUPPLY:
The sternum is supplied both by the sternal and perforating branches. After
mobilization of the internal thoracic artery, the collateral blood supply may reach
the sternum by means of the anterior intercostal artery.
NERVE SUPPLY:
The sternum and manubrium are innervated by the intercostal nerves which are
part of the somatic nervous system. These nerves arise from the anterior rami of
spinal nerves from segments T1-T11. ... These nerves play a role in the
contraction of the intercostal muscles as well as providing sensation to the skin.

8. ManubriumThe manubrium is a large quadrangular shaped bone that
lies above the body of the sternum.
 The manubrium is a large quadrangular shaped bone
that lies above the body of the sternum.
 The manubrium is a large quadrangular shaped bone
that lies above the body of the sternum At the superior
border of the bone is the jugular notch or suprasternal
notch, fibres of interclavicular ligaments are attached
here. The clavicular notches for the articulation of
clavicles are projected upward and laterally on both
sides of jugular notch.

9. Manubrium
The costal cartilages of the first rib and part of the second rib also articulate
with the manubrium, and they fit into facets on its lateral border.
The sternal fibers of pectoralis major and sternocleidomastoid are attached
to the anterior surface. Posterior surface gives attachment
to sternohyoid and sternothyroid muscles. The superior sternopericardial
ligament connects the pericardium (that lies in the superior part of the
middle mediastinum) to the manubrium.
The lower border of the manubrium articulates with the body of the sternum
at the sternal angle (of louis), it is where the second pair of costal cartilage
attaches to the sternum and at the level of the inferior border of T4, is also
clinically known as the Angle of Louis.

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Body
The body of the sternum is the longest region of
the sternum and is roughly rectangular in shape.

11. 11Body of the sternum:
The body of the bone (also known as the gladiolus) is a long flat structure,
with a convex anterior surface, and a concave posterior surface. It has
facets on its each lateral border for articulation with the costal cartilage of
the 3rd to 7th ribs along with the part of second costal cartilage.
The sternocostal head of the pectoralis major muscle attaches the
sternum, on the lateral sides of its anterior surface. The posterior
surface of the body gives rise to the transversus thoracic
muscle (innervated by intercostal nerves). The lower part of the bone
is narrower and articulates with the xiphoid process.

12. Xiphoid
The xiphoid process is a small projection of bone which is usually
pointed. It possesses demi facets for part of seventh costal cartilage at
its super lateral angle. The fibers of rectus abdominis and aponeurosis
of internal and external oblique's are attached to its anterior surface.
Posterior surface gives rise to the inferior stern pericardial ligament. It
also is the site of insertion of part of the thoracic diaphragm. Blood
supply to the sternum arises from the internal thoracic artery.

13. Ligaments of Sternum
 Acromioclavicular ligament
 Sternoclavicular ligament
 Interclavicle ligament

14. Clinical Relevance
 Sternal fractures are associated with severe blunt trauma
to the chest, such as in a vehicular accident. They are
relatively uncommon.
 Typically, the sternum will break into several pieces – this
type of fracture is classified as a comminuted fracture.
The most common site of fracture is the manubriosternal
joint – where the manubrium meets the body of the
sternum. Despite the degree of damage to the sternum,
the fragments are not usually displaced due to the
attachment of the pectoralis muscles.
 .

15. Clinical Relevance
Sternal fracture:
 This is a rare fracture and most commonly results from a motor
vehicle accident, or high impact direct trauma of another cause.
The manubrium is the most commonly injured part of the bone.
Due to their direct connection and proximity, the ribs are also
commonly fractured in the process. The vital organs can be
compromised.

16.  Costochondritis:
 Costochondritis is the most common cause of sternum pain and
occurs when the cartilage between the sternum and ribs becomes
inflamed and irritated.
 Costochondritis can sometimes occur as the result of osteoarthritis
but may also happen for no apparent reason.
 The symptoms of costochondritis include:
 sharp pain on the side of the sternum area
 pain that worsens with a deep breath or a cough
 discomfort in the ribs

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Sternoclavicular joint injury
The sternoclavicular joint connects the top of the
sternum to the collarbone. Injuries to this joint
generally cause pain and discomfort at the top of
the sternum in the upper chest area.
People experiencing sternum pain due to a
sternoclavicular joint injury will often experience
the following:
•mild pain or swelling in the upper chest area
•difficulty or pain when moving the shoulder
•popping or clicking around the joint

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