Coronary circulation

Source: Wikipedia, the free encyclopedia.
Coronary circulation
Blood vessels of the coronary circulation of the human heart viewed from the front and from behind
Identifiers
MeSHD003326
Anatomical terminology

Coronary circulation is the

arteries and veins that supply the heart muscle
(myocardium). Coronary arteries supply oxygenated blood to the heart muscle. Cardiac veins then drain away the blood after it has been deoxygenated. Because the rest of the body, and most especially the
level of consciousness
of the brain from moment to moment. Interruptions of coronary circulation quickly cause heart attacks (
oxygen starvation. Such interruptions are usually caused by coronary ischemia linked to coronary artery disease, and sometimes to embolism
from other causes like obstruction in blood flow through vessels.

Structure

Coronary arteries

Coronary arteries labeled in red text and other landmarks in blue text
Schematic view of the heart

right coronary arteries, respectively. The third sinus, the right posterior aortic sinus, typically does not give rise to a vessel. Coronary vessel branches that remain on the surface of the heart and follow the sulci of the heart are called epicardial coronary arteries.[1]

The left coronary artery distributes blood to the left side of the heart, the left atrium and ventricle, and the interventricular septum. The

coronary artery blockage often results in myocardial infarction causing death of the cells supplied by the particular vessel.[1]

The right coronary artery proceeds along the coronary sulcus and distributes blood to the right atrium, portions of both ventricles, and the

heart conduction system. Normally, one or more marginal arteries arise from the right coronary artery inferior to the right atrium. The marginal arteries supply blood to the superficial portions of the right ventricle. On the posterior surface of the heart, the right coronary artery gives rise to the posterior interventricular artery, also known as the posterior descending artery. It runs along the posterior portion of the interventricular sulcus toward the apex of the heart, giving rise to branches that supply the interventricular septum and portions of both ventricles.[1]

Cardiac veins

Base and diaphragmatic surface of heart showing some cardiac veins

The

left ventricle, and the oblique vein of Marshall. Heart veins that go directly to the right atrium: the anterior cardiac veins, the smallest cardiac veins (Thebesian veins).[2]

Anastomoses

Cast of coronary arteries (right = yellow, left = red)

There are some anastomoses between branches of the two coronary arteries. However the coronary arteries are functionally end arteries and so these meetings are referred to as potential

anastomoses, which lack function, as opposed to true anastomoses like that in the palm of the hand. This is because blockage of one coronary artery generally results in death of the heart tissue due to lack of sufficient blood supply from the other branch. When two arteries or their branches join, the area of the myocardium receives dual blood supply. These junctions are called anastomoses. If one coronary artery is obstructed by an atheroma, the second artery is still able to supply oxygenated blood to the myocardium. However, this can only occur if the atheroma progresses slowly, giving the anastomoses a chance to proliferate.[citation needed
]

Under the most common configuration of coronary arteries, there are three areas of anastomoses. Small branches of the LAD (left anterior descending/anterior interventricular) branch of the left coronary join with branches of the posterior interventricular branch of the right coronary in the interventricular sulcus (groove). More superiorly, there is an anastomosis between the circumflex artery (a branch of the left coronary artery) and the right coronary artery in the atrioventricular groove. There is also an anastomosis between the septal branches of the two coronary arteries in the interventricular septum. The photograph shows area of heart supplied by the right and the left coronary arteries.[citation needed]

Variation

The left and right coronary arteries occasionally arise by a common trunk, or their number may be increased to three; the additional branch being the posterior coronary artery (which is smaller in size). In rare cases, a person will have the third coronary artery run around the root of the aorta.[citation needed]

Occasionally, a coronary artery will exist as a double structure (i.e. there are two arteries, parallel to each other, where ordinarily there would be one).[citation needed]

Coronary artery dominance

The artery that supplies the posterior third of the interventricular septum – the posterior descending artery (PDA)[3] determines the coronary dominance.[4]

  • If the posterior descending artery is supplied by the right coronary artery (RCA), then the coronary circulation can be classified as "right-dominant."
  • If the posterior descending artery is supplied by the circumflex artery (CX), a branch of the left artery, then the coronary circulation can be classified as "left-dominant."
  • If the posterior descending artery is supplied by both the right coronary artery and the circumflex artery, then the coronary circulation can be classified as "co-dominant."

Approximately 70% of the general population are right-dominant, 20% are co-dominant, and 10% are left-dominant.[4] A precise anatomic definition of dominance would be the artery which gives off supply to the AV node i.e. the AV nodal artery. Most of the time this is the right coronary artery.[citation needed]

Function

Supply to papillary muscles

The

tricuspid insufficiency or tricuspid regurgitation.[citation needed
]

The anterolateral papillary muscle more frequently receives two blood supplies:

left circumflex artery (LCX).[5]
It is therefore more frequently resistant to coronary ischemia (insufficiency of oxygen-rich blood). On the other hand, the posteromedial papillary muscle is usually supplied only by the PDA.[5] This makes the posteromedial papillary muscle significantly more susceptible to ischemia. The clinical significance of this is that a myocardial infarction involving the PDA is more likely to cause mitral regurgitation.[citation needed]

Changes in diastole

During contraction of the

systole
), the subendocardial coronary vessels (the vessels that enter the myocardium) are compressed due to the high ventricular pressures. This compression results in momentary retrograde blood flow (i.e., blood flows backward toward the aorta) which further inhibits perfusion of myocardium during systole. However, the epicardial coronary vessels (the vessels that run along the outer surface of the heart) remain open. Because of this, blood flow in the subendocardium stops during ventricular contraction. As a result, most myocardial perfusion occurs during heart relaxation (diastole) when the subendocardial coronary vessels are open and under lower pressure. Flow never comes to zero in the right coronary artery, since the right ventricular pressure is less than the diastolic blood pressure.[6]

Changes in oxygen demand

The heart regulates the amount of vasodilation or vasoconstriction of the coronary arteries based upon the oxygen requirements of the heart. This contributes to the filling difficulties of the coronary arteries. Compression remains the same. Failure of oxygen delivery caused by a decrease in blood flow in front of increased oxygen demand of the heart results in tissue

angina. Severe ischemia can cause the heart muscle to die from hypoxia, such as during a myocardial infarction. Chronic moderate ischemia causes contraction of the heart to weaken, known as myocardial hibernation.[citation needed
]

In addition to metabolism, the coronary circulation possesses unique pharmacologic characteristics. Prominent among these is its reactivity to adrenergic stimulation.[citation needed]

Branches

The following are the named branches of the coronary circulation in a right-dominant heart:[citation needed]

Clinical significance

The

heart muscle
.

The relatively narrow coronary arteries are commonly affected by

angina or a heart attack. The coronary arteries are classified as "terminal circulation", since they represent the only source of blood supply to the myocardium; there is very little redundant blood supply, that is why blockage of these vessels can be so critical.[citation needed
]

Additional images

  • Anterior view of coronary circulation
    Anterior view of coronary circulation
  • Posterior view of coronary circulation
    Posterior view of coronary circulation
  • Illustration of coronary arteries
    Illustration of coronary arteries

See also

References

This article incorporates text from the

CC BY book: OpenStax College, Anatomy & Physiology. OpenStax CNX. 30 July 2014.

Wikimedia Commons has media related to Coronary circulation.
  1. ^
    ISBN 978-1938168130
    . Retrieved 11 August 2014.
  2. ^ www.radiopaedia.org/
  3. ^ 00460 at CHORUS
  4. ^
    ISBN 0-07-135694-0
    .
  5. ^
    PMID 7882478
    .
  6. PMID 19966048
    . Retrieved 26 May 2021.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Coronary_circulation&oldid=1187377449"