Thoracic Cavity

Examples of Thoracic Cavity in the following topics:

• Thoracic Cage: Ribs

  • The ribs are long curved bones which protect the lungs, heart, and other organs of the thoracic cavity.
  • The thoracic cage can expand and contract facilitating breathing in association with the diaphragm and also protects the lungs, heart and other organs of the thoracic cavity.
  • Finally, the shaft forms the majority of the length of the rib as it curves around the thoracic cavity forming the rib-cage.

• Body Cavities

  • The thoracic cavity is the anterior ventral body cavity found within the rib cage in the torso.
  • The thoracic cavity is lined by two types of mesothelium, a type of membrane tissue that lines the ventral cavity: the pleura lining of the lungs, and the pericadium lining of the heart.
  • The abdominoplevic cavity is the posterior ventral body cavity found beneath the thoracic cavity and diaphragm.
  • Humans have multiple body cavities, including the cranial cavity, the vertebral cavity, the thoracic cavity (containing the pericardial cavity and the pleural cavity), the abdominal cavity, and the pelvic cavity.
  • In mammals, the diaphragm separates the thoracic cavity from the abdominal cavity.

• Inspiration

  • Inspiration begins with the contraction of the diaphragm, which results in expansion of the thoracic cavity and the pleural cavity.
  • External intercostal muscles: muscles located in between the ribs that help the thoracic cavity (and thus pleural cavity) to expand during quiet and forced inspiration.
  • Trapezius muscle: muscles in the shoulders, which retracts the scapula and expands the upper part of the thoracic cavity.
  • The accessory muscles assist breathing by expanding the thoracic cavity in a similar way to the diaphragm.
  • However, they expand a much smaller part of the thoracic cavity compared to diaphragm.

• Thoracic Aorta

  • The thoracic aorta is the section of the aorta that travels through the thoracic cavity to carry blood to the head, neck, thorax and arms.
  • The thoracic aorta forms part of the descending aorta and is continuous with the aortic arch at its origin before becoming the abdominal aorta.
  • Contained within the posterior mediastinal cavity it begins at the lower border of the fourth thoracic vertebra where it is continuous with the aortic arch, and ends in front of the lower border of the twelfth thoracic vertebra at the aortic hiatus in the diaphragm.
  • The posterior intercostal arteries are branches that originate throughout the length of the posterior aspect of the thoracic aorta.
  • The aorta, highlighted in red, includes the thoracic aorta, the section of the aorta which runs from the lower border of the fourth thoracic vertebra to the diaphragm.

• Lungs

  • The lungs are found in the thoracic cavity, and extend laterally into right and left halves around the heart.
  • The ribcage is a structure of bones that surrounds and protects the thoracic cavity, with 12 ribs protecting each of the two lungs.
  • The outer layer of the lungs are the pleura, a type of mesothelium (membrane tissue) that surrounds the lung and attaches it to the thoracic cavity.
  • The pleura contain two layers, the outer parietal pleura (attached to the thoracic cavity), and the inner visceral pleura (covers the lungs).
  • This is a transverse view of the thoracic cavity, showing the pleural cavity and the major structures around the lungs.

• Pericardium

  • The pericardium is one of the mesothelium tissues of the thoracic cavity, along with the pleura which cover the lungs.
  • It prevents the heart from overfilling with blood and protects it from nearby infections by completely separating it from the rest of the thoracic cavity.
  • The space between the parietal and visceral layers is called the pericardial cavity.
  • The space between these two serous layers, the parietal and the visceral, is the pericardial cavity, which contains pericardial fluid.
  • The pleural and pericardial cavities are exaggerated since normally there is no space between parietal and visceral pleura and between pericardium and heart.

• Veins of the Thorax

  • It is joined just before entering the heart by the azygos vein which runs up the right side of the thoracic vertebral column, transporting blood from the external thoracic cavity.
  • The internal thoracic vein is a vessel that drains the chest wall and breasts.
  • Bilaterally, it arises from the superior epigastric vein, accompanies the internal thoracic artery along its course and terminates in the brachiocephalic vein.

• Intercostal Nerves

  • The anterior divisions of the thoracic spinal nerves (T1-T11) are called the intercostal nerves.
  • The anterior division of the first thoracic nerve divides into two branches:
  • The anterior divisions of the second, third, fourth, fifth, and sixth thoracic nerves, and the small branch from the first thoracic, are confined to the walls of the thorax and are named thoracic intercostal nerves.
  • Unlike the nerves from the autonomic nervous system that innervate the visceral pleura of the thoracic cavity, the intercostal nerves arise from the somatic nervous system.
  • This explains why damage to the internal wall of the thoracic cavity can be felt as a sharp pain localized in the injured region.

• Thoracic Cage: Sternum

  • Together with the anterior ribs it helps to protect the heart and lungs from damage facilitates expansion and contraction of the thoracic cavity during respiration.
  • Explain the structure and function of the sternum in the thoracic cage

• Abdominal Aorta

  • The abdominal aorta is the largest artery in the abdominal cavity and supplies blood to most of the abdominal organs.
  • The abdominal aorta is the largest artery in the abdominal cavity.
  • As part of the descending aorta, it is a direct continuation of the thoracic aorta.
  • The abdominal aorta supplies blood to much of the abdominal cavity through numerous branches becoming smaller in diameter as it descends.