The word “thoracic” is an anatomical term used in medicine and biology to describe anything relating to the thorax, or chest. The thorax is the upper part of the human trunk, situated between the neck and the abdomen. This area acts as a protective shell for the body’s internal organs.
Defining the Thorax and Its Boundaries
The thorax is defined by a three-dimensional skeletal and muscular boundary that forms the thoracic cavity. The bony structure, often called the rib cage, provides a semi-rigid enclosure for the internal contents. In the front, the central boundary is established by the sternum, or breastbone.
The sides of the thorax are formed by the twelve pairs of ribs, which wrap around to the back. Posteriorly, the enclosure is completed by the twelve thoracic vertebrae of the spine. The superior limit, known as the thoracic inlet, is a narrow opening at the base of the neck where the trachea and esophagus pass through.
Separating the thoracic cavity from the abdominal cavity below is the inferior boundary, a large, dome-shaped sheet of muscle called the diaphragm. This muscular partition is essential for respiration, as its contraction increases the volume of the chest cavity, drawing air into the lungs. The intercostal muscles situated between the ribs also contribute to the mobility of the thoracic wall.
Critical Contents of the Thoracic Cavity
The thoracic cavity is internally divided into three main compartments. The two pleural cavities house the right and left lungs, and the central compartment is called the mediastinum. This space extends from the sternum to the thoracic vertebrae.
Within the mediastinum lies the pericardial cavity, which contains the heart, positioned slightly to the left of the midline. The major blood vessels, including the superior and inferior vena cava and the aorta, also course through the mediastinum.
Other non-cardiovascular structures are located here, such as the trachea, or windpipe, which branches into the main bronchi to deliver air to the lungs. The esophagus, which transports food from the throat to the stomach, also descends through the mediastinum. Additionally, the thymus gland, various nerves like the vagus and phrenic, and the thoracic duct for lymphatic drainage are found within this central compartment.
Where the Term Thoracic Appears in Medicine
The term “thoracic” is frequently used in clinical settings, often extending beyond the chest cavity itself to describe the middle section of the spine. The thoracic spine consists of the twelve vertebrae labeled T1 through T12. This spinal segment is unique because each vertebra connects to a pair of ribs, providing stability and support for the rib cage.
Medical procedures involving this region are grouped under the term thoracic surgery, a specialty focused on treating conditions of the chest, such as lung disease, esophageal disorders, and trauma. Although the heart is in the thorax, its procedures are often separated into a distinct subspecialty known as cardiac surgery. Thoracic surgeons frequently address issues like pneumothorax (collapsed lung) or lung cancer. The spine in this region is also subject to specialized procedures for conditions like spinal deformities, herniated discs, or fractures, which are referred to as thoracic spine surgery.