Skeleton of the Thorax

Thorax - Skeleton Sternum Sternum Is a flat bone and consists of the manubrium, the body, and the xiphoid process. Is relatively shorter and thinner in the female, and its body is more than twice as long as the manubrium in the male but is usually less in the female. Manubrium Has a superior margin, the jugular notch, which can be readily palpated at the root of the neck. Has a clavicular notch on each side for articulation with the clavicle. Also articulates with the cartilage of the first rib, the upper half of the second rib, and the body of the sternum at the manubriosternal joint, or sternal angle. Sternal angle (angle of Louis) Is the junction between the manubrium and the body of the sternum. Is located at the level where: The second ribs articulate with the sternum. The aortic arch begins and ends. The trachea bifurcates into the right and left bronchi at the carina. The inferior border of the superior mediastinum is demarcated. A transverse plane can pass through the intervertebral disk between T4 and T5. Body of the sternum Articulates with the second to seventh costal cartilages. Also articulates with the xiphoid process at the xiphisternal joint , which is level with the ninth thoracic vertebra. Xiphoid process Is a flat, cartilaginous process at birth that ossifies slowly from the central core and unites with the body of the sternum after middle age. Lies at the level of T10 vertebra, and the xiphisternal joint lies at the level of the T9 vertebral body, which marks the lower limit of the thoracic cavity in front, the upper surface of the liver, diaphragm, and lower border of the heart. Can be palpated in the epigastrium and is attached via its pointed caudal end to the linea alba. Ribs Ribs Consist of 12 pairs of bones that form the main part of the thoracic cage , extending from the vertebrae to or toward the sternum. Increase the anteroposterior and transverse diameters of the thorax by their movements. Structure Typical ribs are ribs 3 through 9, each of which has a head, neck, tubercle, and body (shaft). The head articulates with the corresponding vertebral bodies and intervertebral disks and supra-adjacent vertebral bodies. The body (shaft) is thin and flat and turns sharply anteriorly at the angle and has a costal groove that follows the inferior and internal surface of a rib and lodges the intercostal vessels and nerves. The tubercle articulates with the transverse processes of the corresponding vertebrae, with the exception of ribs 11 and 12. Classification True ribs Are the first seven ribs (ribs 1 to 7) , which are attached to the sternum by their costal cartilages. False ribs Are the lower five ribs (ribs 8 to 12); ribs 8 to 10 are connected to the costal cartilages immediately above them to form the anterior costal margin. Floating ribs Are the last two ribs (ribs 11 and 12) , which are connected only to the vertebrae. First rib Is the broadest and shortest of the true ribs. Has a single articular facet on its head, which articulates with the first thoracic vertebra. Has a scalene tubercle for the insertion of the anterior scalene muscle and two grooves for the subclavian artery and vein. Second rib Has two articular facets on its head, which articulate with the bodies of the first and second thoracic vertebrae. Is about twice as long as the first rib. Tenth rib Has a single articular facet on its head, which articulates with the tenth thoracic vertebra. Eleventh and twelfth ribs Have a single articular facet on their heads. Have no neck or tubercle. ◄.....Go back to the Gross Anatomy homepage