Variation archive

854 published articles

• Encyclopedia entry9 August 2026

  Internal Thoracic Artery

  The origins of this artery may vary as follows: a) It may arise from the subclavian, behind or in front of scalenus anterior; b) the right artery may arise from the ascending aorta; or c) it may arise in common with the inferior thyroid. The left internal thoracic artery has been shown by Robicsek, et al.(1967), to give rise to a anterior interventricular (descending) coronary artery, the usual supply being the left anterior descending coronary artery (LAD-CA).

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• Encyclopedia entry9 August 2026

  Suprascapular Artery

  In a study of 400 cadavers, the suprascapular artery arose from the thyrocervical trunk in about 92%, internal thoracic in 4.1%, and transverse cervical in 2.5%, independently from the subclavian in about 2%, and rarely from the axillary, costocervical trunk, or from the dorsal scapular artery. It may arise from the subclavian or axillary artery (reported as high as 10%), or from an accessory inferior thyroid, the subscapular, or the thoracoacromial artery. When it arises from the second or third part of the subclavian, it usually passes through, rather than over the brachial plexus.

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• Encyclopedia entry9 August 2026

  Inferior Thyroid Artery

  In a study of 200 cadavers, the inferior thyroid arose from the thyrocervical trunk in 90.5%, subclavian in 7.5%, and very rarely from the common carotid, aortic arch, brachiocephalic, internal thoracic, pericardiacophrenic, or vertebral, or arose as a common stem with the contralateral inferior thyroid. The inferior thyroid may also arise as a common trunk with the dorsal scapular and suprascapular arteries (thyroscapular trunk). It may course behind the common carotid.

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• Encyclopedia entry9 August 2026

  Umbilical Artery

  This artery may provide a vesicodeferential, middle rectal, vaginal, accessory inferior epigastric, or an inguinal branch. An umbilical artery may be absent.

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• Encyclopedia entry9 August 2026

  Inferior and Superior Epigastric Arteries

  The inferior epigastric artery was not well understood until Mall (1898; F.P. Mall, an Iowan by birth, Belle Plaine, medically trained in Germany was the first Professor of Anatomy at The Johns Hopkins Medical School) studied its development. This artery has received much attention in the literature because of its relation to femoral hernia. It was shown in 1813 by Beckers that when the artery originated beneath the inguinal ligament it passed medial to the inguinal ring.

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• Encyclopedia entry9 August 2026

  Bronchial and Esophageal Arteries

  The bronchial arteries are the nutrient arteries of the lung; they also supply bronchial glands, and in part the pericardium and esophagus. These vessels vary frequently in number and in their mode of origin. On the right side there is usually one bronchial artery, which arises from the first aortic intercostal artery or by a trunk with the upper left bronchial artery from the descending thoracic aorta.

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• Encyclopedia entry9 August 2026

  Inferior Mesenteric Artery

  According to Poynter, this artery has not been extensively studied (i.e., before 1922) and the literature is not very extensive. The artery would appear to be rather stable and not subject to much variation. Cavasse (1856) found an accessory hepatic as one of its branches and noted that it occasionally furnishes renal branches. Vicq D'Azyr reported the absence of a connection (anastomosis) between the the middle colic and the left colic arteries. Poynter observed a middle colic that arose as a large branch from the left colic near its origin. Duplication of this artery has been reported.

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• Encyclopedia entry9 August 2026

  Cystic Artery

  See also hepatic artery above for additional text and references. Anson studied the cystic artery in detail and the results of that study follow: "The primary source of the cystic arteries is still of the classical variety, that is to say, they arise from the closest possible source (the right ramus of the hepatic artery proper). This form is the most common. Other sources occur - to make a total of twelve types encountered in a study of 800 specimens. The twelve types fall conveniently into four categories: Group I.

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• Encyclopedia entry9 August 2026

  Abdominal Aorta

  Variations in the abdominal aorta are not common. According to Quain, in 10 out of every 13 (about 80%) subjects examined, the bifurcation of the aorta occurred within 1.2 cm (~0.5 in) above or below the level of the highest point of the iliac crest, more frequently below the crest than above it. The most common place for its bifurcation, which is opposite the lower border of the body of the fourth lumbar vertebra, but it may divide opposite the disc between L4 and L5 or rarely opposite the body of the fifth lumbar vertebra.

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• Encyclopedia entry9 August 2026

  Gonadal (Ovarian and Spermatic or Testicular) Arteries

  If one or both testicular arteries are missing, the testes are supplied by branches from the vesical or prostatic arteries passing under the arch of the pubis. One or both gonadal arteries may arise from the renal arteries; more rarely, they arise from the middle suprarenal or lumbar arteries. One may branch off higher than the other. They may arise from a common stem, and one or both may be doubled, tripled, or quadrupled throughout or in a particular part of their course. The right spermatic may run behind, instead of in front of, the inferior vena cava.

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• Encyclopedia entry9 August 2026

  Celiac Trunk Arteries

  The typical three-branched celiac trunk occurred in 86% of 756 cases studied. The celiac trunk may be absent (0.4%, Poynter); the branches usually arising from it then arise from the aorta. In one case, the splenic gave rise to the left gastric, and the common hepatic originated from the superior mesenteric. The trunk may be shorter or longer than usual. In the latter case, the branches commonly arise separately from the trunk instead of radiating from a single point.

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• Encyclopedia entry9 August 2026

  Left Gastric Artery

  The left gastric may arise directly from the abdominal aorta (5%, Rossi; 6.7% Eaton), and may provide one or both of the inferior phrenics or a common trunk for the two. There may be two left gastric arteries instead of one. The left gastric sometimes provides an enlarged (accessory) branch (8-25% of individuals) or sometimes it replaces the left hepatic artery (11-12% of individuals). Poynter refers to the Vesalian view that the left gastric usually arises as a branch of the splenic; this was corrected by Winslow in 1832.

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• Encyclopedia entry9 August 2026

  Femoral Artery

  According to Poynter, it was Hochstetter (1890) who demonstrated that the primary artery of the thigh, in mammals, was the artery (ischiadic artery) accompanying the ischiadic (sciatic) nerve, and that the femoral artery later took on that function. Leboucq (1893) observed and described the ischiadic artery in the human embryo and DeVriese (1902) gave the first systematic account of the of the development of lower limb arteries in the human embryo.

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• Encyclopedia entry9 August 2026

  Coronary Arteries

  A TV star sued his cardiac surgeon because, in a by-pass operation, he negligently removed the healthy coronary artery leaving the defective one behind. The surgeon was an experienced cardiac surgeon. The attorney for the surgeon argued in court that the mix-up was a natural result of "abnormalities in the patient's heart". The lawyers put the patient's arteries on trial. Their defense was that the patient had "freakish anatomy". The case was settled out of court in favor of the patient. Information source: People (Weekly). 612/00.

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• Encyclopedia entry9 August 2026

  Superior Mesenteric Artery

  The superior mesenteric artery is considered developmentally as part of the celiac complex and it follows that variations in the superior mesenteric are related, in large measure, to the celiac trunk. The variations in this artery are very common and numerous. The artery may be doubled, arising from the aorta as two trunks. On occasion it provides accessory branches to the liver, stomach, pancreas, spleen and gallbladder.

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• Encyclopedia entry9 August 2026

  Brachial Artery

  Major variations are present in about 25% of subjects studied and Poynter states that the variations are all explainable on an embryological basis. Classification of Arm Arterial Variations (Müller, 1903, from Poynter). Double brachial, i.e., superficial and deep: Superficial brachial continues as the: Superficial brachial as the radial and superficial antibrachial. In Group I.A. , the brachial is doubled and consists of deep and superficial branches. It is the homologue of the superficial brachial described by Bayer (1893) for monkeys. Haller called it vasa aberrentia.

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• Encyclopedia entry9 August 2026

  External Carotid Artery

  Variations in the origin of this artery are discussed under Common Carotids. It may be absent unilaterally or bilaterally. When unilaterally absent, the branches usually derived from it arise from the upward continuation of the common trunk or from the contralateral vessel. The artery is sometimes located superficially, and runs lateral to the stylohyoid muscle or between the posterior belly of the digastric muscle and the stylohyoid. The branches of the external carotid may arise irregularly or be diminished or increased in number.

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• Encyclopedia entry9 August 2026

  Ascending Pharyngeal Artery

  When this artery is absent (infrequent), it may be replaced by a branch from the facial. It may be a branch of the occipital (livini, 13%; Quain, 14%; Poynter, 15%), internal carotid (Poynter,6%), or even the common carotid or its bifurcation. It is occasionally doubled or tripled. It may give rise to the ascending palatine or superior laryngeal. A palatine branch of this artery may be larger than usual and supplies the soft palate, taking the place of the inferior palatine branch of the facial, which in such cases is small.

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• Encyclopedia entry9 August 2026

  Common Interosseous Artery

  The palmar and dorsal (posterior) vessels may arise separately from the ulnar. A high origin of the common interosseous has been described as arising from the axillary artery. Palmar interosseous arteries may be so well-developed that they substitute for branches of the ulnar and/or radial arteries The common interosseous may be a branch of a high radial artery and it may provide the radial artery deep to pronator teres. A usual anterior interosseous may be absent and be replaced by branches of the radial artery.

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• Encyclopedia entry9 August 2026

  Hepatic Artery

  The hepatic blood supply is said to fit the standard textbook description in slightly more than one-half of individuals. This may be a generous estimate. The common hepatic artery usually arises from the celiac trunk (85% of cases), but may also arise directly from the aorta or from the left gastric, superior mesenteric (3% of cases), gastroduodenal, right renal or splenic artery. The occurrence of these alternate sources for the common hepatic can be accounted for developmentally.

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