The Sternum Study Notes

THE STERNUMDEFINATIONSternum is a short sword shaped flat bone,forming the anterior median part of the thoracicSkeleton The upper part corresponding to the handle, is called"Manubrium" The middle part, resembling the blade is called4 "Body" The lowest tapening part forming the point of thesword is or "Xiphoid process".ANATOMICAL POSITIONDisnwama. RAY(1) Sterum as a whole is directed downwands.(2) Incined slightly forward with its rough convex surfacefacing antinonly3 Its broad end is directed upwardsAneromy(4) Lower painted end is directed doconwards.CLINICAL CORRELATION(2) STERNAL PUNCTURE: The Stemum is a common site for bonemarrow biopsy because:-(a) It contains red hemato poietic marrow throughout life.(b) It is subcutemeous & has thin cortical bone thus easily puncturedby a wide pore needle under local anaesthesia2 STERNAL SPLITTING: The tharacic sterrum may be split longitudinally atto gain heart, great vessels and thymus glandMID- STERNOTOMY access to the operations to allow the surgeon(3) STERNAL FRACTURE: Sterum is often fractured, in automobilefractured fragments may damage aorta, heart or liveraccidents at the Sternal angle Backward displacement ofand cause severe bleeding which may prove faral.(4) PIGEON CHEST (PECTUS CARINATUM)from Abnormal side shape to side of and thoracic Sternum cage in projects which forward chest is and compresseddownward like a Keel of a boat. THE STERNUM2STERNUM : PARTSSternum has I parts - (A) MANUBRIUM (B) BODY (c) XIPHISTERNUMMANUBRIUM (EPISTER NUM)It is roughly quadrilateral shaped, thickest and strongestpart of Stemum, lies opposite to the 3rd and 4th Thoracicvertebrae It represents the-2 surfaces and 4 borders.Surfaces - Anterior and PosteriorBorders - Superior, Inferior, Lateral (right and left)ANTERIOR SURFACE: Convex from side to side and concave fromabove downwards.POSTERIOR SURFACE: Concave and forms anterior boundary ofSuperior mediastinum.SUPERIOR BURDER: Thick, rounded and concare. It is marked byClaricular notch on each side.jugular hotch in the median part and by theINFERIOR BORDER: Forms a secondary cartilaginous joint with thebody of Stemum.Human Anaromy For Exam.LATERAL BORDER: (EACH). Forms a primary cartilaginous joint with1st costal carrilage.Present of a demifacet for Synovial articulation with the upperpart the 2nd costal cartilageBODY OF STERNUM (MESOSTERNUM)Body is longer, narrow er and thinner than manubrium Widest closeto It its has lower -2 end surfaces opposite the 5th costal carbilage arriculationand 2 lateral borders and 2 ends.ANTERIOR SURFACE:- upwards. Nearly flat and directed forwards and slightlyPOSTERIOR SURFACE :- Slightly concave and is marked by lessdistinct transverse line. THE STERNUM3LATERAL BORDERS: Forms synovial joints with the lowerpart of the 2nd costal cartilage the 3rd to 6th costalcartilages and upper half of the 7th costal cartilageUPPER END: Forms a secondary cartilagenous joint withthe manubrium at Sternal angle.LOWER END:- Narrow and forms a primary carbilagenousjoint with the xiphisternum.XIPHOID PROCESS (METASTERNUM)Xiphoid process is the smallest part of the stenum and liesin the floor of epigastric fossa!DIPANKAR RAYIt varies greatly in shape and may be bifid or perforatedIt has - 2 Borders (Lateral), 2 Surfaces 2 EndsLateral Lateral. Anterior Posterior Upper LowerUPPER END :- Forms primary cartilagenous joint with the bodyof Sternum.LOWER END:- Affords attachment to linea alba.ATTACHMENTS AND RELATIONSHuman AnaromyFor ExamMANUBRIUMAnterior Surface :- ORIGIN (On either side)1Pectoralis major2Posterior Surface:- ORIGIN - (1) Sternohyoid. 2SHmocleidomastoidSuprasternal Notch:- (2) Gires attachment (C) Interclavicular ligament LowerStemotheroid(Sternal head)Claricular Notch (Margin) :- Capsule of the correspondingInvesting layer of cervical fascia (2) Subdivisions)fibe)Posterior Surface (Lower half): Related to Arch of Aurta.Stemoclaricular joint.Posterior Surface (Upper half): Related to Left -Brachiocephalic VeinBrachiocephalic Artery, Left Common Candold AneryPust Surface (Lateral Portions): Related to Corresponding Lung and PleuraLeft Subelavian Artery THE STERNUM4Manubrium makes a slight angle with the body, convex forwardscalled the Stemal angle of Louis . Events at the Sternal angle(1) Formation of Candiac plexus. (2) Upper limit of the Heart(3) Arch of airta Starts heres as continuation of Assending Aorta(4) Arch of aorta ends here to continue of Descending Thorasic Aurta(5) Trachea -Dirisin into 2 branches.BODY OF STERNUMDIPAHKARRAYAnterior Surface:- ORIGIN I. for eitherside to) :- Pectoralis major. M.Posterior Surface (Lower Part):- ORIGIN (on either side.) :- Sternocostalis M.Between the lateral the facets for articulation with the costal cartilages,borders provide attachment to-IExternal Invercostal Membrane2Posterior Surface (On right side of Median Plane)Internal Intercostal Muscles.Related to 4 Anterior border of right lung2PleuraPosterior Surface (On left side of Median Plane)UPPER 2 PIECES OF BODYRelated to -ILOWER 2 PIECES OF BODYRelated to - Pericardium.Left lung2 PleuraXIPHOD PROCESSHuman AnaromyPosteriar Surface (i) ORIGIN:- DIAPHRAGM ANDFor Exam(ii) It is related to Anterior Surface of liver.Anterior Surface: Insertion: 2 Rectus abdominis (Medial fibres)Lateral Borders :- Gives attachment Obligive to- musdes of abdomen.Aponeurosis of External and IniernalITransverse abdominis muscles.2Aponeurosis of Internal Oblique