Thoracic cage

Bones forming thoracic cage and joints of thorax

1. THORACIC CAGE Dr. Aunum Iqbal

2. COMPONENTS OF THORACIC CAGE: Sternum Manubrium , Body (Gladiolus), Xiphoid process Ribs 7 True Ribs 5 False Ribs (including 2 floating ribs) Clavicle Pectoral Scapula girdle 12 Thoracic Vertebrae (T1 - T12)

3. Thoracic Cage It forms a conical enclosure for the lungs and heart and provides attachment for the pectoral girdle and upper limb. It has a broad base and a narrower superior apex; it is rhythmically expanded by the respiratory muscles to create a vacuum that draws air into the lungs. The inferior border of the thoracic cage is formed by a downward arc of the ribs called the costal margin. The ribs protect the thoracic organs and spleen, most of the liver, and to some extent the kidneys.

4. Sternum/Breast bone Flat bone, with 3 parts: Manubrium sterni Body/Gladiolus Xiphoid process

5. PARTS OF STERNUM: Manubrium sterni Jugular/ suprasternal notch Articulates with Clavicles and Ribs 1 and 2 Lies opposite to T3 and T4 vertebrae Manubriosternal joint inferiorly – called Sternal Angle/Angle of Louis – opposite articulation with 2 nd rib – at the level of intervertbral disc between T4 and T5 vertebrae (imp. for counting the ribs)

6. PARTS OF STERNUM: 2. Body/Gladiolus Articulates with Ribs 2-7 Xiphisternal joint inferiorly- opposite to T9 vertebra 3. Xiphoid process Cartilaginous - calcifies through time Allows attachment of muscles Tip of xiphoid – at level of T10

7. Clinical Anatomy Bone marrow biopsy (to take sample of bone marrow) Median sternotomy (Sternum is split in half, longitudinally to gain access to thoracic organs for surgery)

8. Sternocostal joints

9. Ribs Typical Ribs 2-7 Head Neck Tubercle Angle Shaft Subcostal groove At ypical Ribs 1, 8 -10 Rib 1 - short, flat and supports Subclavian vessels Ribs 1, 10-12 - articulate with only 1 vertebra Ribs 11 and 12 – “ floating ribs” – do not articulate with Transverse processes of Vertebrae or Sternum

10. Typical ribs:   1 – 7 pairs of ribs are attached anteriorly to the sternum by their costal cartilages. Atypical ribs:   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 . They are embedded in the abdominal muscles.

11. Typical Ribs (2 -7) Long, twisted, flat bone The anterior end of each rib is attached to the corresponding costal cartilage A rib has a  head, neck, tubercle, shaft , and  angle Head – located posteriorly - has 2 facets for articulation – one for the numerically corresponding vertebral body and the other for the vertebral body immediately above it. Neck  is a constricted portion - between the head and the tubercle. The  Tubercle  is a prominence on 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. The Shaft is thin, flat and twisted on its long axis. It has a rounded, smooth superior border and a sharp, thin inferior border which has   costal groove ( it accommodates the intercostal vessels and nerve (VAN ) The angle is where the shaft of the rib bends sharply forward.

12. Atypical Rib (1 st Rib) The first rib has a close relationship to the lower nerves of the Brachial plexus, Subclavian artery and vein This rib is small and flattened from above downward Scalenus anterior muscle is attached to its upper surface and inner border Anterior to the attachment of Scalenus anterior, the Subclavian vein crosses the rib Posterior to the attachment of Scalenus anterior, the Subclavian artery and the lower trunk of the Brachial plexus cross the rib and lie in contact with the bone

13. Clinical Anatomy Fracture of 1 st rib may cause: Injury to lower trunk of Brachial plexus: Klumpke’s paralysis Injury to Subclavian vessels: Hemorrhage/Ischemia Thoracic outlet syndrome: Compression of Subclavian vessels/Brachial plexus between 1 st Rib and Clavicle – Klumpke’s paralysis and ischemia.

14. JOINTS

15. JOINTS OF STERNUM 1. MANUBRIOSTERNAL JOINT: cartilaginous joint, symphysis between Manubrium and body of Sternum 2. XIPHISTERNAL JOINT cartilaginous joint between Xiphoid process and body of Sternum The Xiphoid process usually fuses with the body of the Sternum during middle age

16. JOINTS OF RIBS 1. COSTOVERTEBRAL JOINTS: 2 joints between heads of the Ribs and bodies of Vertebrae (corresponding and upper)- Synovial joints 1 st , 10 th , 11 th and 12 th rib has 1 synovial joint with the corresponding vertebra, the rest have 2 each; one for the corresponding vertebra and the other for the vertebra above it 1 joint between tubercle of Ribs and transverse process of Vertebra (corresponding) - Synovial joint (1 st -10 th Rib) Intra articular ligament connects head of Rib to the intervertebral disc

17. JOINTS OF RIBS 2. COSTOCHONDRAL JOINTS: Joints of the Ribs with costal cartilages Cartilaginous joints 3. STERNOCOSTAL JOINTS: Joints between Sternum and costal cartilages 1 st : Cartilaginous joint 2 nd – 10 th : Synovial joints= 2 nd -7 th costal cartilages with Sternum 8 th -10 th costal cartilages with each other (11 th and 12 th costal cartilages are embedded in muscles)

18. MOVEMENTS Cartilaginous joints are immobile (thus 1 st rib and all costochondral joints do not move during respiration) Synovial joints are slightly mobile (due to movements in both the joints between head, tubercle and vertebrae, necks of Ribs rotate along their axis, helping in raising and lowering of ribs during respiration)

19. Cervical Rib (Accessory Rib) Occurs in 0.5% population There is an extra pair of ribs just above the 1 st rib They arise from the transverse process of C7 vertebrae Anteriorly , they may be attached to 1 st Rib or may be free Clinical Anatomy: Cervical Rib may compress Brachial plexus/ Subclavian artery; causing Klumpke’s paralysis/Ischemia