1. Osteology of anterior thoracic wall Beth

2. Learning Objectives  Identify the ribs, sternum, costal cartilages, manubrium, clavicle and thoracic vertebrae.  Examine the important features of the relevant bones of the thorax.  Identify important surface landmarks on the anterior thoracic wall and use the sternal angle (of Louis) to accurately number the ribs on a living subject.

3. Case Study  Luke was rushed to A&E, having been in a car crash.  He has chest pain and shortness of breath.  You notice part of his chest wall moves in on inspiration (meant to move out).  Chest X-Ray is ordered.

4. Bony Thoracic Wall  Anterior: Sternum  Lateral: 12 ribs  Posterior: Thoracic Vertebrae (T1-T12)  Protects the internal viscera (organs)

5. Sternum  Manubrium Articulates with the first rib, part of second rib, and clavicle (sternoclavicular joint). Superior depression is the Jugular Notch: T2/T3  Body Several cartilage lined depressions (articular facets)for the costal cartilages of ribs 3-6.  Xiphoid Process Xiphisternal joint T9. Demifacet for 7 th rib articulation.

6. Ribs  Articulate with vertebrae posteriorly and terminate in costal cartilages anteriorly.  Role in protection and breathing.  Ribs 1-6 are true, 7-10 false, and 11-12 floating (see costal cartilages).

7. Typical RibAtypical Rib 3-91, 2, 10, 11, 12. The head is wedge shaped, and has two articular facets, one for the numerically corresponding vertebrae, and the other for the vertebrae above. Rib 1 is shorter and wider than the other ribs. It only has one facet on its head for articulation with its corresponding vertebrae (there isn’t a thoracic vertebrae above it). The superior surface is marked by two grooves, which make way for the subclavian vessels. The neck simply connects the head with the body. A roughed tubercle, which articulates with the transverse process of the corresponding vertebrae. Rib 2 is thinner and longer than rib 1, and has two normal articular facets. It has a roughened area on its upper surface, where the serratus anterior muscle attaches. The body, or shaft of the rib is flat and curved. The internal surface has a groove protecting the neurovascular supply of the thorax. Rib 10 only has one facet – for articulation with its numerically corresponding vertebrae. Ribs 11 and 12 have no neck, and only one facet, which is for articulation with their corresponding vertebrae. No transverse process facets.

8. Costal Cartilages  Hyaline cartilage  Segments of cartilage connecting the sternum to the ribs.  Help to extend the ribs into a forward motion.  Contributes to elasticity within the walls of the thorax, allowing the chest to expand during respiration.

9. Clavicle (Collarbone)  S-shaped horizontal long bone.  Sternoclavicular and Acromioclavicular joints at medial and lateral end, respectively. Shaft is between.  Supports the should, transmits physical impacts and protects the neurovascular bundle supplying the upper limb.  CLINICAL Relevance: Mid-clavicular line is a useful landmark. Fractures of the clavicle are most common in the midshift/at the junction between the middle and lateral third.

10. Thoracic Vertebrae  Thoracic spine consists of 12 vertebrae.  Vertebral body is heart shaped.  Costal facets on the sides of each vertebral body and transverse processes, articulating with the head and tubercles of the ribs, respectively.  The spinous processes are long and slant inferiorly.

11. Angle of Louis and Counting Ribs  Angle of Louis = Sternal Angle.  Palpable junction between manubrium and sternal body.  T4/T5 Important landmark for structures.  Useful place to start counting ribs: The angle of Louis is continuous with Rib 2. Find the sternal notch, walk your fingers down the manubrium a few centimetres until you feel a distinct bony ridge (the sternal angle). Slide your finger down to localize the 2nd intercostal space, and go from there.

12. Case Study Revisited Car crash caused a Flail Chest, which occurs when a segment of the rib cage breaks under extreme stress and becomes detached from the rest of the chest wall. It requires multiple adjacent ribs being broken in multiple places, separating a segment, so a part of the chest wall moves independently: paradoxical breathing (due to pressure changes). This also explains the chest pain and difficulty breathing, as well as the movement expressed.

13.  Cervical ribs – accessory rib articulating with C7  Can compress some of the nerves running into the arm Clinical Relevance

14. Quiz!  The Sternum is composed of the Manubrium, the Body and the Zygapophyseal process. False! It’s the Manubrium, Body and Xiphoid Process.  The ninth rib is a false rib, because it’s costal cartilage joins to the cartilage of the ribs above. True!  The Thoracic vertebrae articulate with the ribs by the body with the head and transverse process with the neck tubercle. True!  The sternal angle is at T2/T3, and is continuous with the 2 nd Rib. False! The plane level for the sternal angle is T4/T5.

15. Take Home Messages  Bony thoracic cavity comprises of Sternum, 12 ribs and 12 thoracic vertebrae.  Sternum is made up of Manubrium (superior is Jugular Notch and articulates with the clavicles), Body and Xiphoid Process.  Ribs 1-10 articulates with the sternum, directly or indirectly, via the costal cartilages.  Ribs articulate twice with the thoracic vertebrae, to the body and to the transverse processes.  Sternal angle/Angle of Louis is at T4/T5, and is continuous with the second rib. Therefore, it can be used as a starting point for counting other ribs.

16. References  Gray’s Anatomy  Teach Me Anatomy Website  Radiopaedia  Google Images

17. Thanks For Listening! Questions?  mzybb1@nottingham.ac.uk