Variation archive

508 published articles

• Encyclopedia entry9 August 2026

  Middle Rectal Artery

  This artery may be absent. It may arise from the internal iliac with the inferior vesical artery. It has also been reported as arising with or from the internal pudendal, or inferior gluteal arteries. Unusual branches of the middle rectal include: the vaginal, seminal vesical, prostatic, and inferior lateral sacral arteries. In their report to the anatomical society of Great Britian and Ireland, Parsons and Keith, provided the following data. They had 45 observations.

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• Encyclopedia entry9 August 2026

  Middle Meningeal Artery

  The middle meningeal artery may be absent. In 99% of cases however, it enters the foramen spinosum. When this foramen is absent, the artery enters the foramen ovale , which is typically the foramen for the mandibular division of the trigeminal nerve. The middle meningeal gives rise, in about 50% of cases, to an accessory meningeal artery, which also enters the skull via the foramen ovale, or the emissary sphenoidal foramen (20% of cases). It may also supply a palatine branch.

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• Encyclopedia entry9 August 2026

  Middle Sacral Artery (Median Sacral)

  The middle sacral artery may deviated from the midline. It may arise in common with one or both of the fifth pair of lumbar arteries, or from the bifurcation of the aorta, or from one of the iliac arteries, more frequently from the left. It often provides, from each side, a large branch (the lowest lumbar artery), which courses backwards onto the fifth lumbar vertebra (see illustration from Tiedemann). The middle sacral artery may also provide an "accessory" renal or, a middle rectal artery. The middle sacral artery may also provide a renal artery in cases of pelvic kidney.

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• Encyclopedia entry9 August 2026

  Lumbar Arteries

  One or more pairs of the lumbar arteries may arise as a common stem from the back of the aorta. The first lumbar may be joined at its origin with the lowest intercostal artery; the third and fourth lumbar, or less often the second and third lumbars, may arise from the aorta as a common stem. The fifth pair is sometimes absent. One or both of the last pair of lumbar arteries may arise in common with the middle sacral.

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• Encyclopedia entry9 August 2026

  Lateral Thoracic Artery

  This artery may arise from the thoracoacromial (12% of individuals, Poynter). The lateral thoracic may be replaced by or it may replace the thoracodorsal. On rare occasions it gives rise to the ulnar artery, and itself may be a branch of the subscapular (8%, Poynter). In about 24% of individuals the lateral thoracic is doubled. Poynter found the distribution to the intercostal spaces to be irregular; the second space received no supply in 15% and the axillary sent another branch to supply this intercostal space in 17%.

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• Encyclopedia entry9 August 2026

  Medial and Lateral Femoral Circumflex Arteries

  Variations of the medial femoral circumflex artery include the following. It may arise from the profunda femoris before the lateral circumflex; from the femoral artery, external iliac (2%) or one of its branches, or superficial epigastric; or from the the inferior epigastric artery or it may be the source of the inferior epigastric. The artery of ligamentum teres femoris arises from the medial femoral circumflex in about 15% of cases, from the obturator and medial circumflex via an anastomotic connection in about 24%, and from both arteries independently in about 7%.

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• Encyclopedia entry9 August 2026

  Ulnar Artery

  The ulnar artery may arise from the brachial above the usual point of division or from the axillary, in which case it usually passes over the flexor muscles, but beneath the fascia, to reach its usual position in the forearm. In circumstances such as this, the artery may terminate in the proximal forearm with a persistent median artery supplying the superficial arch The recurrent arteries and the common interosseous are usually derived from the trunk vessel from which the ulnar arises.

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• Encyclopedia entry9 August 2026

  Lateral Internal Thoracic Artery

  The internal thoracic may give rise to a lateral internal thoracic as it enters the thorax. The lateral internal thoracic runs about midway between the spine and the sternum or somewhat forward, spans up to six intercostal spaces, and anastomoses with the intercostal arteries of those spaces. A lateral internal thoracic artery may arise from the costocervical trunk, thyrocervical trunk, or ascending cervical. The possible existence of this vessel must be remembered when paracentesis is performed.

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• Encyclopedia entry9 August 2026

  Variations in the Branches of the Subclavian Artery

  There is considerable variation in the branching of the subclavian artery, and the branches may be arranged differently on the two sides of the body. The usual branching order on the right side is for the vertebral, thyrocervical trunk (common trunk for the inferior thyroid, transverse cervical, and suprascapular arteries, in 50% of cases), and the internal thoracic (internal mammary) to arise from the first part of the right subclavian.

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• 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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