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Questions and Answers
Which part of the body serves as a bony framework encased with muscles, fat, and cutaneous tissues?
What serves as the main muscle of respiration in the body?
In vertebrates, which major organs are housed in the thorax?
What separates the thoracic cavity from the abdomen?
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What happens to the vertical diameter of the thorax during the contraction of the diaphragm?
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Which muscle pulls its central tendon downward during contraction, creating negative pressure in the thoracic cavity?
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Study Notes
Thorax
Introduction
The thorax is part of an animal's body between its head and midsection. It serves as a bony framework encased with muscles, fat, and cutaneous tissues (skin). In vertebrates, it contains the chief organs of respiration and circulation, such as lungs, air passages, heart, and blood vessels. Below it is bounded by the diaphragm. In insects, the thorax is the middle of the three major divisions of the body and consists of three parts, each of which commonly bears a pair of legs and wings.
Structure and Function
Thoracic Cavity
The thoracic cavity is the space surrounded by the rib cage, sternum, spine, and diaphragm. It houses the heart and lungs, which play vital roles in respiration and circulatory systems.
Diaphragm
The diaphragm is a dome-shaped muscle and tendon that functions as the main muscle of respiration. It separates the thoracic cavity from the abdomen, serving an important anatomical landmark for chest to abdomen differentiation. The esophagus, phrenic, vagus nerves, descending aorta, and inferior vena cava pass through the diaphragm between the thoracic and abdominal cavities. The left side of the diaphragm may be partially inferiorly located because of the presence of the liver.
Muscle of Inspiration
During contraction, the diaphragm pulls its central tendon downward, which increases the vertical diameter of the thorax and creates negative pressure inside the thoracic cavity. This draws in air, making the diaphragm the most important muscle used in inspiration. During exhalation, the rib cage and chest wall sag, while the diaphragm relaxes and elevates, forcing air out of the body.
Muscle of Abdominal Straining
The contraction of the diaphragm assists in abdominal straining, such as lifting heavy objects or giving birth.
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Description
Test your knowledge on the anatomy and function of the thorax, the part of an animal's body containing vital organs like the heart, lungs, and diaphragm. Learn about the structure of the thoracic cavity, the role of the diaphragm in respiration, and the muscles involved in breathing and abdominal straining.
