Caval opening
Encyclopedia
The caval opening is a hiatus in the diaphragm of humans through which passes the inferior vena cava
, the wall of which is adherent to the margins of the opening, and some branches of the right phrenic nerve
.
It is located approximately at the level of the eighth thoracic vertebra (T8), and passes through the diaphragm's central tendon. It is quadrilateral in form, and is placed at the junction of the right and middle leaflets of the central tendon, so that its margins are tendinous.
By being situated in the tendinous part of the diaphragm, it is stretched open every time inspiration
occurs. However there has been argument that caval opening actually constricts during inspiration.
Since thoracic pressure decreases upon inspiration and draws the caval blood upwards toward the right atrium
, increasing the size of the opening allows more blood to return to the heart, maximizing the efficacy of lowered thoracic pressure returning blood to the heart
.
Inferior vena cava
The inferior vena cava , also known as the posterior vena cava, is the large vein that carries de-oxygenated blood from the lower half of the body into the right atrium of the heart....
, the wall of which is adherent to the margins of the opening, and some branches of the right phrenic nerve
Phrenic nerve
The phrenic nerve originates mainly from the 4th cervical nerve, but also receives contributions from the 5th and 3rd cervical nerves in humans....
.
It is located approximately at the level of the eighth thoracic vertebra (T8), and passes through the diaphragm's central tendon. It is quadrilateral in form, and is placed at the junction of the right and middle leaflets of the central tendon, so that its margins are tendinous.
By being situated in the tendinous part of the diaphragm, it is stretched open every time inspiration
Inhalation
Inhalation is the movement of air from the external environment, through the air ways, and into the alveoli....
occurs. However there has been argument that caval opening actually constricts during inspiration.
Since thoracic pressure decreases upon inspiration and draws the caval blood upwards toward the right atrium
Right atrium
The right atrium is one of four chambers in the hearts of mammals and archosaurs...
, increasing the size of the opening allows more blood to return to the heart, maximizing the efficacy of lowered thoracic pressure returning blood to the heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
.