Week 6 Thorax Anatomy 2024 PDF

Week 5: 10/7/2024: Thorax – Part I Travis McCann MSN, APRN, AGACNP-BC Bones of the Thorax / Thoracic Cage Thorax Part of the body between the neck and abdomen. Includes the primary organs of the respiratory and cardiovascular systems. The thoracic cavity is divided into three co...

Week 5: 10/7/2024: Thorax – Part I Travis McCann MSN, APRN, AGACNP-BC Bones of the Thorax / Thoracic Cage Thorax Part of the body between the neck and abdomen. Includes the primary organs of the respiratory and cardiovascular systems. The thoracic cavity is divided into three compartments: the central mediastinum occupied by the heart and structures transporting air, blood, and food right and left Pleural cavities occupied by the lungs. 3 Thoracic Cage Provides remarkable rigidity, given the light weight of its components, enabling it to perform the following functions: Protect vital thoracic and abdominal organs (most air or fluid filled) from external forces. Resist the negative (subatmospheric) internal pressures generated by the elastic recoil of the lungs and inspiratory movements. Provide attachment for and support the weight of the upper limbs. Provide the anchoring attachment (origin) of many of the muscles that move and maintain the position of the upper limbs Provide the attachments for muscles of the abdomen, neck, back, and respiration.  Skeleton of the Thoracic Wall: Ribs Ribs: Curved, flat bones that form most of the thoracic cage Remarkably light in weight yet highly resilient. Each rib has a spongy interior containing bone marrow (hematopoietic tissue), which forms blood cells.  Ribs: Three types of ribs that can be classified as typical or atypical 1. True (vertebrosternal) ribs (1st–7th ribs): They attach directly to the sternum through their own costal cartilages. 2. False (vertebrochondral) ribs (8th, 9th, and usually 10th ribs): Their cartilages are connected to the cartilage of the rib above them; thus, their connection with the sternum is indirect. 3. Floating (vertebral, free) ribs (11th, 12th, and sometimes 10th ribs): The rudimentary cartilages of these ribs do not connect even indirectly with the sternum; instead, they end in the posterior abdominal musculature. Costal Cartilages Contribute to the elasticity of the thoracic wall Increase in length through the first 7 and then gradually decrease. The first 7 costal cartilages attach directly and independently to the sternum The 8th, 9th, and 10th articulate with the costal cartilages just superior to them, forming a continuous, articulated, cartilaginous costal margin The 11th and 12th costal cartilages form caps on the anterior ends of the corresponding ribs and do not reach or attach to any other bone or cartilage.  Intercostal Spaces Separate the ribs and their costal cartilages from one another Spaces are named according to the rib forming the superior border of the space—for example, the 4th intercostal space lies between ribs 4 and 5. There are 11 intercostal spaces and 11 intercostal nerves. Intercostal spaces are occupied by: Intercostal muscles and membranes Two sets (main and collateral) of intercostal blood vessels and nerves The space below the 12th rib does not lie between ribs and thus is referred to as the subcostal space The spaces widen further with inspiration  Thoracic Vertebrae Composed of 12 stacked vertebrae Provide attachment points for ribs The Superior articular facets interlock with the inferior articular facets of the vertebra above. Thoracic spine provides ROM in all directions but provides more spinal rotation than other sections but less flex/ext than other sections. Thoracic Vertebrae Anatomy Continued Superior Articular Processes – for Pedicle – project vertebrae Vertebral Foramen – for articulation with inferior articular posteriorly allowing space for passage of spinal cord process of the vertebra above vertebral foramen Lamina – attachment sites for Inferior Articular Processes – for deep back muscles articulation with superior articular process of the vertebra below Thoracic Vertebrae Anatomy Continued In between vertebrae lie intervertebral discs. Made of fibrocartilage. Provide cushion and shock absorption Superior/Inferior Costal Facets Occur as bilaterally paired, on the superior and inferior posterolateral margins of the bodies of typical thoracic vertebrae (T2–T9). Facets are arranged in pairs on adjacent vertebrae an inferior (demi)facet of the superior vertebra and a superior (demi)facet of the inferior vertebra. Together they form a single socket to receive the head of the rib of the same identifying number as the inferior vertebra (Example: head of rib 6 with the superior costal facet of vertebra T6) Thoracic Vertebrae Anatomy Continued 5th thoracic vertebrae 6th Rib Lateral view showing articulation of Posterolateral view head of 6th rib with inferior costal showing articulation of facet of 5th thoracic vertebral body transverse costal facet and superior costal facet of 6th with tubercle of rib thoracic vertebral body Atypical Thoracic Vertebrae Atypical thoracic vertebrae bear whole costal facets in place of demifacets: The superior costal facets of vertebra T1 are not demifacets because there are no demifacets on the C7 vertebra above, and rib 1 articulates only with vertebra T1. T1 has a typical inferior costal (demi)facet. Rib 1 articulates completely with T1 only T1 T1 has an inferior costal demifacet to articulate with head of rib 2 Atypical Thoracic Vertebrae Continued T10 has only one bilateral pair of (whole) costal facets, located partly on its body and partly on its pedicle. T11 and T12 also have only a single pair of (whole) costal facets, located on their pedicles. T11 T10 T12 Spinous Processes projecting from the vertebral arches of typical thoracic vertebrae long and slope inferiorly usually overlap the vertebra below They cover the intervals between the laminae of adjacent vertebrae, thereby providing protection to the spinal canal  The Sternum (AKA: Breastbone) flat, elongated bone that forms the middle of the anterior part of the thoracic cage It directly overlies and affords protection for mediastinal viscera (mostly the heart) The sternum consists of three parts: manubrium body xiphoid process. Note: In adolescents and young adults, the three parts are connected together by cartilaginous joints (synchondroses) that ossify during middle to late adulthood  Manubrium of Sternum trapezoidal bone. The easily palpated concave center of the superior border of the manubrium is the jugular notch (suprasternal notch). Costal cartilage of the 1st rib is tightly attached to the lateral border of the manubrium—the synchondrosis of the first rib The manubriosternal joint forms the sternal angle (angle of Louis).