Artery

Lore & Background

The anatomy of arteries can be separated into gross anatomy and microanatomy. The arterial system is divided into systemic arteries, carrying blood from the heart to the whole body, and pulmonary arteries, carrying deoxygenated blood from the heart to the lungs. Large arteries such as the aorta are composed of endothelial, smooth muscle, fibroblast, and immune cells. The arterial wall consists of three layers: the tunica intima, tunica media, and tunica externa, from innermost to outermost. The hollow internal cavity in which blood flows is called the lumen.

Reader's Guide

Arteries form part of the circulatory system and carry oxygenated blood away from the heart to the tissues, except for pulmonary arteries. They have a blood pressure higher than other parts of the circulatory system, varying during the cardiac cycle. The combination of cardiac output and systemic vascular resistance are the principal determinants of arterial blood pressure. Systemic arteries can be subdivided into elastic and muscular types. Arterioles have the greatest collective influence on local blood flow and overall blood pressure. Over time, factors such as elevated blood sugar, cholesterol, high blood pressure, stress, and smoking can damage artery walls, resulting in atherosclerosis. Accidental intra-arterial injection can cause intense pain, paresthesia, and necrosis, often requiring amputation.

Did You Know?

• The word 'artery' comes from Greek ἀρτηρία (artēríā).
• Pulmonary arteries carry deoxygenated blood to the lungs, unlike most arteries.
• The hollow internal cavity of an artery is called the lumen.
• Arterioles are the primary 'adjustable nozzles' in the blood system.

Anatomical Origin and Pelvic Journey

The internal pudendal artery represents the final branch emerging from the anterior trunk of the internal iliac artery, making it a terminal vessel within that arterial system. Its course through the pelvis is remarkably circuitous. After arising from the anterior division of the internal iliac, the vessel courses along the lateral pelvic wall before making its way out of the pelvic cavity entirely. It passes through the greater sciatic foramen, specifically inferior to the piriformis muscle, which deposits it into the gluteal region. From there, it hooks around the sacrospinous ligament and re-enters the pelvis via the lesser sciatic foramen to reach the perineum. Once in the perineal space, it travels alongside the internal pudendal veins and the pudendal nerve within the pudendal canal. Notably, this artery is measurably smaller in females than in males, reflecting differences in the vascular demands of the external genitalia between the sexes.

Branching Pattern and Sexual Dimorphism

The internal pudendal artery fans out into several named branches that serve the external genitalia. In females, it gives rise to the deep artery of the clitoris, which supplies the clitoral crura, as well as the dorsal artery of the clitoris. The urethral artery presents a point of anatomical debate: some authorities classify it as a direct branch of the internal pudendal artery, while others assign it to the perineal artery instead. In males, the branching pattern includes the perforating arteries of the penis, which are unique to the male perineum. The overall caliber of the artery differs between the sexes, being smaller in females. This sexual dimorphism in size and branching reflects the distinct vascular architecture required by the male and female external genital structures, and it carries practical implications for surgical and obstetric procedures where these vessels must be identified and preserved.

Clinical Relevance in Obstetrics

The most significant clinical encounter with the internal pudendal artery occurs in the context of childbirth. During vaginal delivery, the mechanical stress and stretching of the perineal tissues can compromise this vessel in women, leading to vascular injury. The most common consequence is the formation of a haematoma, a collection of blood in the surrounding soft tissues. In the majority of cases, such a haematoma is self-limiting and resolves on its own without the need for surgical intervention or other treatment. However, in a subset of cases, the pooled blood can become a medium for bacterial growth, transforming the haematoma into an infected abscess that requires more aggressive management. This clinical scenario underscores the vulnerability of the pudendal vasculature during obstetric events and highlights the importance of monitoring postpartum patients for signs of perineal swelling, pain, or systemic infection that might indicate a complication arising from injury to the internal pudendal artery or its branches.

Anatomical Variation in Males

One of the most striking features of the internal pudendal artery is its considerable anatomical variability, particularly in men. Approximately seventy percent of males possess an accessory internal pudendal artery, a finding that makes this variation the norm rather than the exception in the male population. What distinguishes this accessory vessel is its atypical origin: rather than arising from the internal iliac artery as the standard internal pudendal artery does, the accessory branch typically originates from one of several alternative sources. These include the external iliac artery, the obturator artery, or the vesical arteries. This variation carries important implications for any surgical procedure in the pelvic or perineal region, as a surgeon who is unaware of the accessory vessel's presence and its non-standard origin risks inadvertent injury. The high prevalence of this variant also means that anatomical descriptions presenting only the single, standard internal pudendal artery offer an incomplete picture of the typical male pelvic vasculature.

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