A neurovascular bundle is a structure that binds nerves and veins (and in some cases arteries and lymphatics) with

connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...

so that they travel in tandem through the body.

Structure

There are two types of neurovascular bundles: superficial bundles and deep bundles. As arteries do not travel within the superficial

fascia A fascia (; plural fasciae or fascias; adjective fascial; from Latin: "band") is a band or sheet of connective tissue, primarily collagen, beneath the skin that attaches to, stabilizes, encloses, and separates muscles and other internal organs. ...

( loose connective tissue under the

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...

), superficial neurovascular bundles differ from deep neurovascular bundles in both composition and function.

Superficial bundles

Superficial neurovascular bundles do not include arteries, and consist primarily of capillaries and nerves. Because capillaries function as the sites for substance exchange between interstitial fluid and

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...

, they tend to have large

surface area The surface area of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc ...

and short diffusion path. Normally, capillaries consist of a central lumen lined with an

endothelium The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...

, a single layer of smooth

epithelial cells Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellula ...

Deep bundles

Deep neurovascular bundles, which often include arteries, have a more complicated structure than superficial neurovascular bundles. Since arteries have high intraluminal

blood pressure Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" r ...

relative to capillaries and veins, these bundles have

smooth muscle Smooth muscle is an involuntary non-striated muscle, so-called because it has no sarcomeres and therefore no striations (''bands'' or ''stripes''). It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit mus ...

and

structures outside the endothelium. This structure allows arteries to contract, relax and remain flexible and transfer blood when under pressure.

Function

Neurovascular bundles are useful for

axons An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see American and British English spelling differences#-re, -er, spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, th ...

, ensuring a continuous supply of oxygenated blood to important nerves.

Clinical significance

Both superficial and deep neurovascular bundles are at risk during

surgical incisions In surgery, a surgical incision is a cut made through the skin and soft tissue to facilitate an operation or procedure. Often, multiple incisions are possible for an operation. In general, a surgical incision is made as small and unobtrusive as p ...

Leg surgery

In surgeries, the principle superficial neurovascular bundles at risk are, medially, the

great saphenous vein The great saphenous vein (GSV, alternately "long saphenous vein"; ) is a large, subcutaneous, superficial vein of the leg. It is the longest vein in the body, running along the length of the lower limb, returning blood from the foot, leg and thig ...

and its accompanying nerve, and, laterally, the

superficial peroneal nerve The superficial fibular nerve (also known as superficial peroneal nerve) innervates the fibularis longus and fibularis brevis muscles and the skin over the antero-lateral aspect of the leg along with the greater part of the dorsum of the foot (wit ...

. The superficial peroneal nerve originates from the common peroneal nerve near the neck of the fibula and passes between the peroneus longus and brevis muscles, supplying motor branches to these muscles. The superficial branch then continues onto the dorsum of the foot to supply sensory fibers to the skin there. The main deep neurovascular bundle at risk is the posterior tibial artery. It lies on the posterior aspect of the

tibialis posterior The tibialis posterior muscle is the most central of all the leg muscles, and is located in the deep posterior compartment of the leg. It is the key stabilizing muscle of the lower leg. Structure The tibialis posterior muscle originates on the i ...

and

flexor digitorum longus muscle The flexor digitorum longus muscle is situated on the tibial side of the leg. At its origin it is thin and pointed, but it gradually increases in size as it descends. It serves to flex the second, third, fourth, and fifth toes. Structure The fle ...

, and medial to the belly of

flexor hallucis longus muscle The flexor hallucis longus muscle (FHL) is one of the three deep muscles of the posterior compartment of the leg that attaches to the plantar surface of the distal phalanx of the great toe. The other deep muscles are the flexor digitorum longus an ...

. It also gives rise to

medial plantar artery The medial plantar artery (internal plantar artery), much smaller than the lateral plantar artery, passes forward along the medial side of the foot. It is at first situated above the abductor hallucis, and then between it and the flexor digitorum ...

and

lateral plantar artery The lateral plantar artery (external plantar artery), much larger than the medial, passes obliquely lateralward and forward to the base of the fifth metatarsal bone. It then turns medialward to the interval between the bases of the first and secon ...

. During surgery, these neurovascular bundles, both superficial and deep, should be protected in order to prevent neurological damage. A common anatomically informed, surgical technique to avoid damaging neurovascular bundles is to undermine anteriorly to the posterior tibial margin after reaching the fascia, in order to avoid the saphenous vein and nerve. The deep posterior compartment here is superficial and readily accessible. The fascia of the deep posterior compartment is carefully opened distally and proximally, under the belly of the soleus muscle, paying special attention to the posterior tibial neurovascular bundle. Through the same incision, the fascia of the superficial posterior compartment is opened widely, two centimeters posterior and parallel to the incision in the fascia of the deep compartment.

Prostate surgery

The preservation of both neurovascular bundles during nerve-sparing (NS) radical prostatectomy improves urinary continence and erectile function. Consequently, NS is recommended in elderly men and those with pre-existing erectile dysfunction, whom many surgeons would previously have only offered non-NS surgery. It was also found that during surgeries in which neurovascular bundles are preserved, the frequency of positive margins were only 5.8 percent.

References

* Gray's Anatomy: The Anatomical Basis of Clinical Practice, Expert Consult, 40e. By Susan Standring, PhD, DSc, Emeritus Professor of Anatomy, Head of Anatomy and Human Sciences, King's College London, London, UK. 9780443066849 {{Reflist Tissues (biology)