Thorax Anatomy: Structure and Function

• The thorax lies between the neck and abdomen.
• It houses major vessels, the heart, and the lungs.
• The thorax serves as a conduit for head and neck structures passing to the abdomen, pelvis, and lower extremities.

Thorax Functions

• Protection
• Support
• Conduit
• Segmentation
• Breathing
• Pumping blood

Learning Outcomes

• Describe the surface of the Thorax.
• Identify organs in the thoracic cavity.
• Describe the blood supply to the thorax.
• Identify the muscles of the thorax.
• List the nerves innervating the thorax.
• Be familiar with some clinical cases related to the topics above.

Mediastinum Subdivision

• The superior mediastinum extends from the thoracic inlet to the T4 transverse plane.
• The posterior mediastinum lies below the plane and behind the heart.
• The anterior mediastinum lies below the plane and anterior to the heart.
• The middle mediastinum contains the pericardium, heart, and main bronchi.

Thoracic Cage

• The thoracic cage is part of the axial skeleton.
• Components include the thoracic vertebrae, midline sternum, 12 pairs of ribs, and costal cartilages.

Thoracic Cage Joints

• Joints exist between the ribs and thoracic vertebrae.
• Joints exist between the ribs and sternum.
• There is an articulation between the clavicle with the manubrium of the sternum and the first rib.

Anterior Thoracic Wall Muscles

• Pectoralis major
• Pectoralis minor
• Serratus anterior

Intercostal Neurovascular Bundles

• Veins and arteries lie inferior to each rib.
• The intercostal neurovascular bundles run in the costal groove deep to the internal intercostal muscles.
• The intercostal nerves are the anterior rami of the first 11 thoracic spinal nerves.

Anterior Thoracic Wall Muscles Chart

• External intercostal: Originates on the inferior border of the rib above, attaches to the superior border of the rib below, is innervated by intercostal nerves, and elevates the ribs and supports the intercostal space.
• Internal intercostal: Originates on the inferior border of the rib above, attaches to the superior border of the rib below, has intercostal nerve innervation, and elevates ribs (upper four and five); others depress ribs.
• Innermost intercostal: Originates on the inferior border of the rib above, attaches to the superior border of the rib below, has intercostal nerve innervation, and works with internal intercostals.
• Transversus thoracis: Originates on the posterior surface of the lower sternum, attaches to the internal surface of costal cartilages 2-6, receives intercostal nerve innervation, and depresses ribs.
• Subcostal: Originates on the internal surface of the lower rib near their angles, attaches to the superior borders of the second or third ribs below, is innervated by the intercostal nerves, and depresses the ribs.
• Levator costarum: Originates on the transverse processes of C7 and T1-T11, attaches to subjacent ribs between tubercle and angle and is supplied by posterior rami of C8-T11, and elevates ribs and costal cartilages.

Female Breast

• The female breast is a modified sweat gland.
• Location: Extends from approximately the 2nd rib to the 6th rib and from the midaxillary line laterally to the sternum medially.
• Tissue Tubuloacinar glands organized into about 15 to 20 lobes, supported and separated by Cooper's suspensory ligaments and fat, with each lobe divided in lobules of secretory acini and their ducts.
• Includes: Breast, Areola, Nipple, Axillary tail, and Lymphatic system
• Arterial supply includes: anterior intercostal branches of internal mammary A, lateral mammary branches of lateral thoracic A, and thoracoacromial A. (all from axillary A).
• Venous drainage: parallels arterial supply, finally draining into internal thoracic, axillary, and adjacent intercostal veins.

Explore the anatomy of the thorax, its major organs, and its functions like protection, support, and breathing. Learn about the mediastinum's subdivisions and the components of the thoracic cage. Discover the blood supply, muscles, and nerves of the thorax, along with clinical cases.