Osteology of the Anterior Thoracic Wall Aranga

Objectives Identify the bones of the thorax Describe the features of the relevant bones Identify the important surface landmarks

Anterior Thoracic Wall Bones of the thoracic wall: Clavicle Ribs True False Floating Sternum Manubrium Body Xiphoid Process Superior Thoracic aperture- Inlet of the thorax that communicates with the head and neck. Inferior Thoracic aperture- Outlet of the thorax that communicates with the abdomen.

Clavicle Long ‘S’ Shaped bone that extends between the sternum and the scapula Two ends sternal and acromial The midclavicular line is an important anatomical plane Functions: Attach the upper limb to the trunk Protection the the underlying neurovascular structures Transmits forces from the limb to the axial skeleton Sternal end articulates with the manubrium forming the sternoclavicular joint Acromial end forms the acromioclavicular joint The trapezoid line is the attachment of the coracoclavicular ligament which suspends the weight of the upper limb from the clavicle

Fracture of the clavicle Common to occur on a fall on an outstretched arm Or to a direct blow to the shoulder

Sternum Manubrium (Level of T3-T4) Body (Level of T5-T9) Superior part of sternum Trapezoid shape Forms suprasternal notch at its superior border Its articulation with the body forms the Angle of Louis (T4) Body (Level of T5-T9) Articulating facets for the costal cartilages Xiphoid Process (Level of T10)

Ribs True Ribs (1-7) False Ribs (8-10) Floating (11&12) Attach directly to the sternum by their own costal cartilage False Ribs (8-10) The costal cartilage of a false rib joins the costal cartilage of the superior rib first before attaching to the sternum. Floating (11&12) Do not attach to the sternum

Typical Ribs (3-9) Head Two articulating facets split by the crest of the head Superior facet articulates with body of its superior vertebrae Inferior facet articulates with the body of its numerically corresponding vertebrae Tubercle Articulates with transverse process of corresponding vertebrae Head Crest of head Angle Neck Body

Atypical Ribs (1, 2, 10-12) Have features that are different to typical ribs Rib 1 Short and broad Only one articulating facet on its head Grooves for underlying structures such as the subclavian artery Rib 2 Has formations for the attachment of some thoracic muscles Ribs 10-12 Have only one articulating facet like the first rib 11 and 12 are short, have no necks and no tubercles

Counting Ribs Method 1) Palpate the suprasternal notch Sternal Angle Method 1) Palpate the suprasternal notch 2) Walk you fingers down a few centimetres until you can feel a bony ridge (Sternal angle) 3) Slide your fingers across to feel the 2nd costal cartilages of the 2nd rib 4) Move your fingers down to find the 2nd intercostal space 5) From here you can easily move downwards counting ribs (yay!)

Flail Chest Rib breaks under pressure in two places Medical emergency, this prevents proper ventilation and therefore oxygenation of blood Rib breaks under pressure in two places This causes it to detach from the chest wall During inhalation the broken rib will move inwards During expiration the broken rib will move outwards

Thoracic Vertebrae 12 Thoracic vertebrae Characteristics Facet for articulation with rib All articulate with a rib Heart shaped vertebral body Circular vertebral foramen

Summary Bones of the thorax- ribs, sternum, clavicle, thoracic vertebrae Sternum is split into 3 parts manubrium, body and xiphoid process The clavicle is a horizontal long bone that articulates with the sternum and the scapula There are 12 ribs that are typical/atypical and true/false/floating Important landmarks for counting ribs are the Sternal Angle at T4 and the Suprasternal notch

Quiz The acromial end of the clavicle articulates with the sternum False! Articulates with the scapula From superior to inferior the sternum is composed of the Body, Manubrium and Xiphoid process False! Manubrium, Body, Xiphoid Process The superior articulating facet, articulates with the body of the adjacent thoracic vertebra False! With the body of the superior vertebra The tubercle of the rib articulates with the transvers process of a thoracic vertebra True!

Thanks for listening! If you have any questions please email me at: mzyavb@nottingham.ac.uk References: Moore and Agur Grays Anatomy Teach me Anatomy