In the
anatomy
Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its ...
of 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 t ...
, the smallest cardiac veins, also known as the Thebesian veins (for
Adam Christian Thebesius
Adam Christian Thebesius (January 12, 1686 – November 10, 1732) was a German anatomist who was a native of Sandenwalde, Silesia.
He studied medicine in Jena, Leipzig and Leiden, receiving his doctorate from the University of Leiden in 170 ...
), are small valveless
vein
Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated b ...
s in the walls of all four
heart chambers
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 ...
.
Structure
Course
The smallest cardiac veins are most abundant in the
right atrium
The atrium ( la, Ätrium, , entry hall) is one of two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular valves.
There are two at ...
and least in the
left ventricle
A ventricle is one of two large chambers toward the bottom of the heart that collect and expel blood towards the peripheral beds within the body and lungs. The blood pumped by a ventricle is supplied by an atrium, an adjacent chamber in the upper ...
. They drain the
myocardium
Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that ...
.
They run a perpendicular course to the endocardial surface, directly connecting the heart chambers to the medium-sized, and larger coronary veins. The smallest cardiac veins have been successfully identified by following the route of contrast flow - during catheterization procedures - from the subendocardium, through the smallest cardiac veins, into larger veins, and into the
coronary sinus
In anatomy, the coronary sinus () is a collection of veins joined together to form a large vessel that collects blood from the heart muscle ( myocardium). It delivers deoxygenated blood to the right atrium, as do the superior and inferior ven ...
. The
coronary sinus
In anatomy, the coronary sinus () is a collection of veins joined together to form a large vessel that collects blood from the heart muscle ( myocardium). It delivers deoxygenated blood to the right atrium, as do the superior and inferior ven ...
empties into the right atrium.
Openings
The ''openings of the smallest cardiac veins'' are located in the
endocardium
The endocardium is the innermost layer of tissue that lines the chambers of the heart. Its cells are embryologically and biologically similar to the endothelial cells that line blood vessels. The endocardium also provides protection to the v ...
. Here the smallest cardiac veins return
blood
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...
into the
heart chamber
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 ...
s from the
capillary bed in the muscular cardiac wall, enabling a form of collateral circulation unique to the heart. Not every endocardial opening connects to the smallest cardiac veins, as some connect to the vessels of Wearn, which are arteries. Therefore, the endocardial opening must be traced to a vein before it is definitely called an opening of the smallest cardiac veins.
Function
The small cardiac venous network is considered an alternative venous drainage of the
myocardium
Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that ...
. The smallest cardiac veins draining into the left heart, along with deoxygenated blood originating from the
bronchial veins
The bronchial veins are small vessels that return blood from the larger bronchi and structures at the roots of the lungs. The right side drains into the azygos vein, while the left side drains into the left superior intercostal vein or the accesso ...
draining into the
pulmonary veins
The pulmonary veins are the veins that transfer oxygenated blood from the lungs to the heart. The largest pulmonary veins are the four ''main pulmonary veins'', two from each lung that drain into the left atrium of the heart. The pulmonary vei ...
, contribute to normal physiologic
shunting of blood. As a consequence of the input of these vessels, blood in the left heart is less oxygenated than the blood found at the pulmonary capillary beds, usually to a very small degree.
History
Etymology
The smallest cardiac veins are also known as the Thebesian veins. They are named after the German
anatomist
Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its ...
Adam Christian Thebesius
Adam Christian Thebesius (January 12, 1686 – November 10, 1732) was a German anatomist who was a native of Sandenwalde, Silesia.
He studied medicine in Jena, Leipzig and Leiden, receiving his doctorate from the University of Leiden in 170 ...
, who described them in a 1708 treatise called ''Disputatio medica inauguralis de circulo sanguinis in corde''.
Mislabelling
The smallest cardiac veins are sometimes accurately referred to as vessels, but they are frequently confused with a distinct set of
artery
An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pul ...
connections, eponymously referred to as the "vessels of Wearn". In his 1928 publication, Wearn himself referred to the arterio-cameral connections (vessels of Wearn) as Thebesian, but later, after additional research, provided disambiguation and strictly used the term Thebesian for coronary vein-heart chamber connections.
References
External links
GPnotebook - "venae cordis minimae"
{{Authority control
Cardiac anatomy