The proper development of the atrioventricular canal into its prospective components (The

heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to t ...

septum and associated

valves A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fitting ...

) to create a clear division between the four compartments of the heart and ensure proper blood movement through the heart, are essential for proper heart function. When this process does not happen correctly, a child will develop atrioventricular canal defect which occurs in 2 out of every 10,000 births. It also has a correlation with

Down syndrome Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual dis ...

because 20% of children with Down syndrome have atrioventricular canal disease as well. This is a very serious condition and surgery is necessary within the first six months of life for a child.Brown, David MD "Atrioventricular Canal Defect" Children's Hospital Boston 20120 http://www.childrenshospital.org/az/Site521/mainpageS521P0.html Half of the children who are untreated with this condition die during their first year due to heart failure or pneumonia. Atrioventricular canal defect is a combination of abnormalities of the heart and is present at birth. There is a problem when there are holes present in the walls that separate chambers (

septa The Southeastern Pennsylvania Transportation Authority (SEPTA) is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly 4 million people in five c ...

), as well as when valves are incorrectly constructed. There are other names for these heart abnormalities such as endocardial cushion defects or atrioventricular septal defectMayo Clinic September 12, 2012"Atrioventricular Canal Defect" http://www.mayoclinic.com/health/atrioventricular-canal-defect/DS00745

Development

In a normal

there are four

chambers Chambers may refer to: Places Canada: *Chambers Township, Ontario United States: *Chambers County, Alabama * Chambers, Arizona, an unincorporated community in Apache County * Chambers, Nebraska * Chambers, West Virginia * Chambers Township, Hol ...

. These are the right and left atria, and right and left ventricles. The right atrium and right ventricle function to pump blood to the lungs while the left atrium and left ventricle pump blood to the rest of the body. There are

heart valve A heart valve is a one-way valve that allows blood to flow in one direction through the chambers of the heart. Four valves are usually present in a mammalian heart and together they determine the pathway of blood flow through the heart. A heart ...

s in place that inhibit back-flow between these chambers.

Clinical relevance

Atrioventricular canal defect

An atrioventricular canal defect is developed because of the improper formation of the

endocardial cushions Endocardial cushions, or atrioventricular cushions, refer to a subset of cells in the development of the heart that play a vital role in the proper formation of the heart septa. They develop on the atrioventricular canal and conotruncal region of ...

, and their job is to separate the different parts of the heart during development when they fuse. It is strongly associated with

Down's syndrome Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual disa ...

. The structures that develop from the fusion of the endocardial cushions are: * The

interatrial septum The interatrial septum is the wall of tissue that separates the right and left atria of the heart. Structure The interatrial septum is a that lies between the left atrium and right atrium of the human heart. The interatrial septum lies at angl ...

divides the left and right atrium * The

interventricular septum The interventricular septum (IVS, or ventricular septum, or during development septum inferius) is the stout wall separating the ventricles, the lower chambers of the heart, from one another. The ventricular septum is directed obliquely backwar ...

divides the left and right ventricles. * The mitral valve and

tricuspid valve The tricuspid valve, or right atrioventricular valve, is on the right dorsal side of the mammalian heart, at the superior portion of the right ventricle. The function of the valve is to allow blood to flow from the right atrium to the right ven ...

are formed by the proper division of an early common valve being separated into two.Cincinnati Children's Hospital "Atrioventricular Septal Defect" April 2010 http://www.cincinnatichildrens.org/health/a/avsd/ Atrioventricular canal defect may be divided into ''partial'' or ''complete'' forms. In the partial form, openings between the left and right atria and improper formation of the mitral valve exist. In the complete form, there is free movement in all chambers because there is a large hole where the atria and ventricles meet, and instead of there being two valves there is one common valve. Surgery is usually conducted in-between the 3rd and 6th month of life, and with this condition the earlier the better. Usually, intracardiac repair involves closing the holes in the septum and the creation of two new atrioventricular valves from the underdeveloped common valve leaflet.

References

{{Reflist Embryology of cardiovascular system

Development

Clinical relevance

Atrioventricular canal defect

See also

References