Download Sternum lecture outline

STERNUM
Location of Sternum
 17cm in length (less in females)
 Lies in midline of anterior chest wall.
Shape of sternum
 Convex in front
 Concave behind
 Broadest at its upper border
 Narrow at sternal angle
Parts of Sternum.
 Flat bone divided into three parts:
1. Manubrium sterni.
2. Body (mesosternum)
3. Xiphoid process
MANUBRIUM
 Upper part of sternum.
 Has 2 surfaces and 4 borders
 Anterior surface
 Posterior surface
 Superior border (has a jugular notch, forms
sternoclavicular joint)
Inferior border (forms manubriosternal joint)
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2 lateral surfaces (facet for 1st costal cartilage
demifacet for 2nd costal cartilage)
Articulates with:
Body of sternum at manubriosternal joint.
Clavicles
First costal cartilage.
Upper part of second costal cartilages on each
side.
Forms the anterior boundary of superior
mediastinum
Extends from T3--T4
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(BODY) MESOSTERNUM
Longer than manubrium
The body of sternum consists of four segments or
sternebrae.
There are three transverse processes
on anterior surface of body which
indicate the site of union of four
sternebrae
Has 2 surfaces and 4 borders
Anterior surface (has 3 transverse ridges)
 Posterior surface (concave)
 Superior border (forms manubriosternal joint)
Inferior border (forms xiphisternal joint)
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2 lateral surfaces (Demifacet for 2nd costal
cartilage
Facets for 3rd, 4th, 5th, 6th
Demifacet for 7th costal cartilage)
Extends from T5—T9
XIPHOID PROCESS
 Smallest and variable
Forms xiphisternal joint with body
th
 Has a demifacet for 7
costal cartilage
superolaterally
Midline marker for:
 Superior level of liver
Central tendon of diaphragm
 Inferior border of heart
Xiphoid process is cartilaginous in youth
MUSCLE ATTACHMENTS
MANUBRIUM
 Anterior surface
 Pectoralis major
 Sternocleidomastoid
 Posterior surface
Sternohyoid (on upper aspect)
 Sternothyroid (on lower aspect)
 Jugular notch
 Interclavicular ligament
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MESOSTERNUM
 Anterior surface
 Articular capsules of sterno-costal joint
 Sternal origin of pectoralis major
Posterior surface
 Transversus thoracis
XIPHOID PROCESS
 Anterior surface
 Rectus abdominis
Aponeurosis of ext. and int. oblique
Lower end
Linea Alba
 Borders
 Aponeurosis of int. oblique
 Transversus thoracis
Posterior
Slips of diaphragm
RELATIONS
Manubrium
 Forms the anterior boundary of superior
mediastinum
 Posteriorly related to
 Left common carotid artery
Brachiocephalic trunk
Left subclavian vein
Arch of aorta
Laterally lungs and pleura
Mesosternum
Right to median plane
 Right lung and pleura
 Left side related to
Upper sternebrae = left lung and
pleura
Lower sternebrae = pericardiumAPPLIED
ANATOMY OF STERNUM
MEDIAN STERNOTOMY
To gain access to thoracic cavity for
surgeries e.g. heart surgery CABG
 STERNAL BIOPSY
Bone marrow needle biopsy because of
its subcutaneous position and breadth
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CONGENITAL ABNORMALITIES OF STERNUM
Pectus carinatum ,
Also called pigeon chest ,is a deformity of the
chest characterized by a protrusion of the sternum
and
ribs .
Pectus excavatmu(
A Latin term meaning hollowed chest
the most common congenital deformity of
the anterior wall of the chest, in which several ribs
and the sternum grow abnormally
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