The costal margin, also known as the costal arch, is the lower edge of the

chest The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main di ...

(thorax) formed by the bottom edge of the

rib cage The rib cage or thoracic cage is an endoskeletal enclosure in the thorax of most vertebrates that comprises the ribs, vertebral column and sternum, which protect the vital organs of the thoracic cavity, such as the heart, lungs and great ve ...

Structure

The costal margin is the medial margin formed by the cartilages of the seventh to tenth ribs. It attaches to the body and

xiphoid process The xiphoid process (), also referred to as the ensiform process, xiphisternum, or metasternum, constitutes a small cartilaginous process (extension) located in the inferior segment of the sternum, typically ossified in adult humans. Both the Gr ...

of the

sternum The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major bl ...

. The

thoracic diaphragm The thoracic diaphragm, or simply the diaphragm (; ), is a sheet of internal Skeletal striated muscle, skeletal muscle in humans and other mammals that extends across the bottom of the thoracic cavity. The diaphragm is the most important Muscles ...

attaches to the costal margin. The costal angle is the

angle In Euclidean geometry, an angle can refer to a number of concepts relating to the intersection of two straight Line (geometry), lines at a Point (geometry), point. Formally, an angle is a figure lying in a Euclidean plane, plane formed by two R ...

between the left and right costal margins where they join the

Function

The costal margins somewhat protect the higher abdominal organs, such as the

liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...

Clinical significance

The costal margin may be used for tissue harvesting of cartilage for use elsewhere in the body, such as to treat

microtia Microtia is a congenital deformity where the auricle (external ear) is underdeveloped. A completely undeveloped auricle is referred to as anotia. Because microtia and anotia have the same origin, it can be referred to as microtia-anotia. Micro ...

. Different abdominal organs may be palpated just below the costal margin, such as the

on the right side of the body. Pain across the costal margin is most commonly caused by costochondritis. The costal paradox, also known as Hoover's sign and the costal margin paradox, is a sign where the costal angle decreases upon inspiration rather than increasing, indicating

chronic obstructive pulmonary disease Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by chronic respiratory symptoms and airflow limitation. GOLD defines COPD as a heterogeneous lung condition characterized by chronic respiratory s ...

References

External links

* —"Bony landmarks of the abdomen" * {{Authority control Bones of the thorax de:Arcus costalis