Functional vs True End Arteries

What are End Arteries

An end artery is also called terminal artery. End arteries are those vessels that are the only effective blood supply to any tissue (or part of tissue). Which means, that if an end artery is blocked or damaged, the blood supply to that tissue or organ is compromised as there is no effective collateral to provide blood through any other channel.

True End Arteries

True end artery is that artery which has no anatomical collateral or anastomosis with any other blood vessel in that region. In short, pre-capillary anastomosis does not exist. So if the true end artery is ligated, there is no overlap in the are of blood supply to the effected tissue area and it may die or develop necrosis.

For example, retinal artery: central artery of retina, is a true end artery. Branches of opthalmic artery are also true end arteries.

Functional End Arteries

Functional end artery may have anastomosis with any other vessel in that area, but that anastomosis is not effective. That means, if the functional end artery is compromised due to damage or thrombus, the collateral or anastomosis blood supply is not sufficient to keep the tissue viable and tissue damage occurs due to lack of blood, oxygen and nutrients.

In short, pre-capillary anastomosis does exist, but is ineffective.

Examples of functional end arteries include blood vessels that supply blood to brain, kidney, heart, lungs, spleen, liver and intestines.

Difference between True & functional End Arteries

So based on above discussion, the difference between functional and true end arteries can be summarized in this table:

Examples of True & functional end arteries

Note that both types of arteries are examples of “terminal artery” or “end artery”. Lets divide the examples into relevant category:

Examples of True End Arteries:

• Central Retinal Artery
• Branches of Opthalmic artery (reference: snell anatomy 9th edition)
  • Trochlear
  • Ciliary
  • Lacrimal
  • Muscular

Examples of Functional End Arteries include blood vessels supplying:

• Heart (reference: snell anatomy 9th edition)
• Brain
• Kidney
• Lungs
• Spleen
• Liver
• Intestines

What to do when asked about End Arteries only?

What to do when in exam, the question asks about end arteries only, without mentioning functional or true? Well in that case, choose the option that has true end artery mentioned in it.

For example, the examiner may ask which organs are supplied by end arteries? And the options might contain only one organ supplied by true end artery, while others supplied by functional end arteries, choose the one that’s supplied by true end artery.

Note that the examiner can also ask: which organs are supplied by terminal artery? The answer remains the same.

Why coronary arteries are called functional end arteries?

This question usually confuses the students. Coronary arteries are distinct and have their regions demarcated. However, they do anastomose. Even if the anastomosis is not efficient and occlusion of an artery will result in myocardial infarction, but it does exist. That’s why coronary arteries are categorised as functional end artery, not true.

Please let us know if there is any question or correction (with reference) to this post.