5Thoracic Cage- The thoracic cage consists of the sternum, the ribs, and the thoracic vertebrae. - It has a narrow inlet and a wide outlet. I. Thoracic inlet: (the upper opening of the thoracic cage) Boundaries: a. Anterior Supra-sternal notch of the manubrium sterni. b. On each side First rib. c. Posterior First thoracic vertebra.
6II. Thoracic outlet It is the lower opening of the thoracic cage. Boundaries:a. Anterior Xiphoid process.b. On each side Lower six costal cartilages + Last two ribs.c. Posterior Last thoracic vertebra.- It is closed by the diaphragm which separates it from the abdominal cavity.
7RibsClassification of ribs according to their attachments to the sternum: - There are twelve ribs on each side classified as: A: True ribs Upper seven ribs (their anterior end is attached to the sternum). B: False ribs Lower five ribs (they are not attached anteriorly to the sternum). - The lower two ribs are called the floating ribs because they are free anteriorly. Classification of ribs according to their structure: A: Typical rd - 9th ribs. B: Atypical st, 2nd, 10th, 11th, and 12th ribs. (first two and last 3) ribs)
9A: Posterior end, formed by: 1 A: Posterior end, formed by: 1. Head, contains: - Small upper demifacet for articulation with the small lower demifacet on the side of the vertebra above it. - Large lower demifacet for articulation with the large upper demifacet on the side of the vertebra of the same number. - Between both demifacets there is the crest of the head. 2. Neck - It is the flattened constriction next to the head. 3. Tubercle, formed by: - Articular part (medial part), which articulates with the circular facet on the tip of the transverse process of the vertebra of the same number. -Non articular part (lateral part), which is attached to the lateral costo-transverse ligament .
21Thoracic vertebrae Classification of thoracic vertebrae: - There are twelve thoracic vertebrae classified as:A: Typical nd – 8th vertebrae.B: Atypical st, 9th, 10th, 11th, and 12th vertebrae (first one and last 4 vertebrae).
22Characteristics of a typical thoracic vertebra 1. The body is characterized by:- Small in size and heart shaped.- Its side contains two demifacets:a. Large upper demifacet for articulation with the head of the rib of thecorresponding number.b. Small lower demifacet for articulation with the head of the rib below it. 2. The tip of the transverse process contains circular facet for articulation with thetubercle of the rib of the corresponding number. 3. The spine is long, tapering, and directed downwards and backwards.4. The vertebral foramen is circular and small. 5. The superior articular process faces backwards, while the inferior articular
24First thoracic vertebra 1. The body is small .2. The vertebral foramen is wide and triangular.3. The body carries complete circular articular facet for articulation with the head of the first rib.4. The spine is horizontal.