The central tendon of the diaphragm is a thin but strong aponeurosis situated slightly anterior to the vault formed by the muscle, resulting in longer posterior muscle fibers. It is inferior to the

fibrous pericardium The pericardium, also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. It has two layers, an outer layer made of strong connective tissue (fibrous pericardium), and an inner layer made of ...

, which fuses with the central tendon of the diaphragm via the pericardiacophrenic

ligament A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal li ...

. The

caval opening The thoracic diaphragm, or simply the diaphragm ( grc, διάφραγμα, diáphragma, partition), is a sheet of internal skeletal muscle in humans and other mammals that extends across the bottom of the thoracic cavity. The diaphragm is the ...

(at the level of the T8 vertebra) passes through the central tendon. This transmits the

inferior vena cava The inferior vena cava is a large vein that carries the deoxygenated blood from the lower and middle body into the right atrium of the heart. It is formed by the joining of the right and the left common iliac veins, usually at the level of the ...

and right phrenic nerve.

Structure

The central tendon is shaped somewhat like a

trefoil A trefoil () is a graphic form composed of the outline of three overlapping rings, used in architecture and Christian symbolism, among other areas. The term is also applied to other symbols with a threefold shape. A similar shape with four ring ...

leaf A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

, consisting of three divisions or leaflets separated from one another by slight indentations. The right leaflet is the largest, the middle (directed toward the

xiphoid process The xiphoid process , or xiphisternum or metasternum, is a small cartilaginous process (extension) of the inferior (lower) part of the sternum, which is usually ossified in the adult human. It may also be referred to as the ensiform process. Bo ...

) the next in size, and the left the smallest. The central tendon is composed of several planes of fibers, which intersect one another at various angles and unite into straight or curved bundles—an arrangement which gives it additional

strength Strength may refer to: Physical strength *Physical strength, as in people or animals * Hysterical strength, extreme strength occurring when people are in life-and-death situations *Superhuman strength, great physical strength far above human c ...

Action during respiration

During inspiration, the diaphragm contracts, causing the central tendon to be drawn inferiorly which partially flattens the domes bilaterally. The result is an increase in the

thoracic The thorax or chest is a part of the anatomy of humans, 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 divisions of the crea ...

volume and a reduction in intra-thoracic

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

. This reduction allows air to enter the lungs, enhancing venous return. During inspiration, the central tendon retains its shape due to its tendinous nature, and prevents constriction of the inferior vena cava.

Clinical significance

Rarely, a central tendon defect may be involved in a central

congenital diaphragmatic hernia Congenital diaphragmatic hernia (CDH) is a birth defect of the diaphragm. The most common type of CDH is a Bochdalek hernia; other types include Morgagni hernia, diaphragm eventration and central tendon defects of the diaphragm. Malformation of ...

. This may be repaired with thoracoscopic surgery.

References

{{Authority control Tendons Thoracic diaphragm