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Thorax

T3

The thorax is the upper part of the trunk in the human body. It connects with the neck and upper limbs superiorly, and is separated by the diaphragm from the abdominal cavity inferiorly. The thoracic dimensions, proportions and capacity vary depending on each individual. This is also linked to age, sex and race. A study of the cross-sectional anatomy of this area allows a visual medium that facilitates the understanding of its structural organization. This will permit a unique representation of the positions, sizes, shapes, and relationships of the thoracic structures.

General anatomy

The bony framework of the thorax consists of twelve thoracic vertebrae (T1-T12) together with their intervertebral discs, twelve pairs of ribs and their costal cartilages, and the sternum. The sternum is comprised of three parts: the manubrium, body and xiphoid process. The clavicle, scapula and head of humerus can also be considered as part of the thoracic skeleton.

The muscles that make up the thoracic cage include the intercostalis group between the ribs, which consists of three layers: external, internal and innermost muscles; and the subcostalis, transversus thoracis and levatores costarum. Muscles that attach to the thoracic wall are the pectoralis major, pectoralis minor, serratus anterior, serratus posterior, scalenus anterior and scalenus posterior.

Other muscles in the thoracic region include the subscapularis, teres major, teres minor, infraspinatus, supraspinatus, rhomboid major, trapezius, erector spinae, latissimus dorsi, rectus abdominis, semispinalis capitis, splenius cervicis, splenius capitis, longus colli, semispinalis thoracis, multifidus, sternocleidomastoid, sternohyoid, sternothyroid, omohyoid muscle, levator scapulae, subclavius and deltoid muscles. Moreover, the musculotendinous diaphragm can also be considered as one of the most important muscles of thorax.

The major organs found in a thoracic cut-section are the heart and right, and left lungs. Other organs situated in this area are the thyroid gland, thymus, trachea, esophagus, bronchi, glandular breast tissue, nipples, a portion of the liver and the spinal cord.

Neurovasculature

The arteries of the thorax are mainly branches of the pulmonary trunk, brachiocephalic trunk and aorta. The veins, on the other hand, are those belonging to the brachiocephalic venous trunk, azygos system and vertebral venous system, together with all of their tributaries. The nerves present in the thoracic region are those that belong to the autonomic nervous system, and they originate from the sympathetic trunk and vagus nerve (CN X). The right and left phrenic nerves can also be found in this area. They innervate the diaphragm.

Clinical Note

Computed tomography (CT) and magnetic resonance imaging (MRI) are both tools of choice for evaluating conditions involving the thoracic region. Both of these modalities depend on the cross-sectional analysis of complex anatomic structures in this area. The scanned structures can be reformatted in multiple planes and generated into three dimensional images. This plays a vital role in clinical practice and aids in the diagnosis and evaluation of various diseases in the thorax like: blood vessel abnormalities, aortic aneurysms, fluid buildup, pleural effusions, pulmonary edema, bronchiectasis, swellings, pneumonia, tumors, heart failure, congenital anomalies and other heart conditions.

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