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A neurovascular bundle is a structure that binds nerves and veins (and in some cases arteries and
lymphatics The lymphatic vessels (or lymph vessels or lymphatics) are thin-walled vessels (tubes), structured like blood vessels, that carry lymph. As part of the lymphatic system, lymph vessels are complementary to the cardiovascular system. Lymph vessel ...
) with
connective tissue Connective tissue is one of the four primary types of animal tissue, a group of cells that are similar in structure, along with epithelial tissue, muscle tissue, and nervous tissue. It develops mostly from the mesenchyme, derived from the mesod ...
so that they travel in tandem through the body.


Structure

There are two types of neurovascular bundles: superficial bundles and deep bundles. As
arteries An artery () is a blood vessel in humans and most other animals that takes oxygenated blood away from the heart in the systemic circulation to one or more parts of the body. Exceptions that carry deoxygenated blood are the pulmonary arteries in ...
do not travel within the
superficial fascia A fascia (; : fasciae or fascias; adjective fascial; ) is a generic term for macroscopic membranous bodily structures. Fasciae are classified as superficial, visceral or deep, and further designated according to their anatomical location. Th ...
, the
loose connective tissue Loose connective tissue, also known as areolar tissue, is a cellular connective tissue with thin and relatively sparse collagen fibers. They have a semi-fluid matrix with lesser proportions of fibers. Its ground substance occupies more vol ...
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 animal coverings, such as the arthropod exoskeleton, have different ...
, 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 A capillary is a small blood vessel, from 5 to 10 micrometres in diameter, and is part of the microcirculation system. Capillaries are microvessels and the smallest blood vessels in the body. They are composed of only the tunica intima (the in ...
and
nerves A nerve is an enclosed, cable-like bundle of nerve fibers (called axons). Nerves have historically been considered the basic units of the peripheral nervous system. A nerve provides a common pathway for the electrochemical nerve impulses called ...
. Because capillaries function as the sites for substance exchange between
interstitial fluid In cell biology, extracellular fluid (ECF) denotes all body fluid outside the Cell (biology), cells of any multicellular organism. Body water, Total body water in healthy adults is about 50–60% (range 45 to 75%) of total body weight; women ...
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 is com ...
, they tend to have large
surface area The surface area (symbol ''A'') 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 d ...
and short diffusion path. Normally, capillaries consist of a central lumen lined with an
endothelium The endothelium (: endothelia) 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 r ...
, a single layer of smooth
epithelial cells Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...
.


Deep bundles

Deep neurovascular bundles, which often include
arteries An artery () is a blood vessel in humans and most other animals that takes oxygenated blood away from the heart in the systemic circulation to one or more parts of the body. Exceptions that carry deoxygenated blood are the pulmonary arteries in ...
, have a more complicated structure than superficial neurovascular bundles. Since arteries have high intraluminal
blood pressure Blood pressure (BP) is the pressure of Circulatory system, 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 ...
relative to capillaries and veins, these bundles have
smooth muscle Smooth muscle is one of the three major types of vertebrate muscle tissue, the others being skeletal and cardiac muscle. It can also be found in invertebrates and is controlled by the autonomic nervous system. It is non- striated, so-called bec ...
and
connective tissue Connective tissue is one of the four primary types of animal tissue, a group of cells that are similar in structure, along with epithelial tissue, muscle tissue, and nervous tissue. It develops mostly from the mesenchyme, derived from the mesod ...
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 spelling differences) is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action pot ...
, ensuring a continuous supply of oxygenated blood to important nerves.


Clinical significance

Both
superficial and deep Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provi ...
neurovascular bundles are at risk during
surgical incisions 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 possible to ...
.


Leg surgery

In surgeries, the principle superficial neurovascular bundles at risk are, medially, the
great saphenous vein The great saphenous vein (GSV; ) or long saphenous vein is a large, subcutaneous, superficial vein of the human leg, leg. It is the longest vein in the body, running along the length of the lower limb, returning blood from the foot, human leg, le ...
and its accompanying nerve, and, laterally, the
superficial peroneal nerve The superficial fibular nerve (also known as superficial peroneal nerve) is a mixed (motor and sensory) nerve that provides motor innervation to the fibularis longus and fibularis brevis muscles, and sensory innervation to skin over the antero-la ...
. The superficial peroneal nerve originates from the
common peroneal nerve The common fibular nerve (also known as the common peroneal nerve, external popliteal nerve, or lateral popliteal nerve) is a nerve in the lower leg that provides sensation over the posterolateral part of the leg and the knee joint. It divides a ...
near the neck of the fibula and passes between the
peroneus longus In human anatomy, the fibularis longus (also known as peroneus longus) is a superficial muscle in the lateral compartment of the leg. It acts to tilt the sole of the foot away from the midline of the body ( eversion) and to extend the foot downwa ...
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 The posterior tibial artery of the lower limb is an artery that carries blood to the posterior compartment of the leg and plantar surface of the foot. It branches from the popliteal artery via the tibial-fibular trunk. Structure The posteri ...
. 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. Posterior tibial tendonitis Posterior tibial tendonitis i ...
and
flexor digitorum longus muscle The flexor digitorum longus muscle or flexor digitorum communis longus 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 medial to the belly of
flexor hallucis longus muscle The flexor hallucis longus muscle (FHL) attaches to the plantar surface of phalanx of the great toe and is responsible for flexing that toe. The FHL is one of the three deep muscles of the posterior compartment of the leg, the others being the ...
. 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 Prostatectomy (from the Ancient Greek language, Greek , "prostate" and , "excision") is the surgical removal of all or part of the prostate gland. This operation is done for benignity, benign conditions that cause urinary retention, as well as ...
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 Cardiovascular system anatomy Tissues (biology)