Nasal Anatomy - Clinical Tree

More than 500 years ago, Leonardo Da Vinci illustrated the importance of facial proportions and beauty. In no area of the human body is that more important than the face. As an aesthetic surgeon it is imperative for one to understand the ideal facial proportions, and this is particularly important when considering the nose. Many say that rhinoplasty and nasal surgery is a procedure where mere millimeters can have a significant impact, both positively and negatively. It is therefore essential for the nasal surgeon to have a thorough understanding of the nasal anatomy to achieve a harmonious structure that is not only aesthetically pleasing, but also functional. This chapter will discuss the complex nasal anatomy, along with a brief discussion of nasal physiology.

Anatomy of the Nose

When discussing nasal anatomy, one must begin with terminology as this can be confusing to the novice surgeon. The standard terms of direction (superior, inferior, anterior, and posterior) are used far less often to describe the nasal anatomy than the terms cephalad, caudad, dorsal, and basal. Fig. 2.1 helps to identify these terms, which, while confusing, are a more specific way to describe nasal anatomy during a surgical procedure. After learning the terminology to describe the nasal directions, one can then begin to describe the complex nasal anatomy.

Fig. 2.1, Relative spatial relationships. When one anatomic part is described relative to another, the standard anatomic descriptors are used, including anterior, posterior, superior, and inferior. Specifically, when referring to nasal relationships, additional terms are used including dorsal, basal, caudal, and cephalic. This figure shows the direction indicated when describing one part as it relates to another.

Skin

During the assessment of nasal anatomy, it is important for the surgeon to develop a systematic way to evaluate all aspects of the nose, beginning at the top, the radix, and working your way down to the nasal tip and base. Yet one must begin by first assessing the skin. The nasal skin is an important structure which must be addressed preoperatively. The result of rhinoplasty can be dramatically affected or influenced by the texture, thickness, and sebaceous nature of the skin. Thicker skin will adapt more readily and be more forgiving of the changes below compared with thinner skin. Changes in the cartilaginous or bony framework will seem less obvious in a thick-skinned nose. Therefore, a greater change in the anatomy will be needed in order to change the external appearance of the nose in thick-skinned individuals. Thick skin may also hide any imperfection in the nasal skeleton that might otherwise be obvious in a thin-skinned nose. Fig. 2.2 shows the areas of thickest and thinnest skin.

Traditionally, the skin of the nose will differ in thickness depending on which area of the nose you are looking at, and this is of importance to note during your preoperative evaluation. At the region of the radix, the skin is fairly thick and immobile, whereas the skin at the rhinion (junction of the nasal bones and upper lateral cartilages) is the thinnest and typically quite mobile. The skin oftentimes becomes thickened and more adherent at the tip secondary to the increased sebaceous units. The thickened skin can sometimes mask the cartilages beneath it, thus making the tip very ill-defined or amorphous. These variations in an amorphous tip can be seen in Fig. 2.3 . It is important to identify all of this prior to surgery, as small changes of the nasal anatomy can have large impacts on facial aesthetics.

Fig. 2.3, Three examples of ill-defined or amorphous nasal tips. All lack tip-defining points or any specific tip definition. The nose in (A) has poor definition because of irregular nasal tip cartilage as well as thick skin. The patient in (B) has an amorphous nasal tip due to rhinophyma, which is overgrowth of sebaceous subcutaneous tissues, often secondary to rosacea. The female in (C) has such enlarged and bulbous lower lateral cartilages that specific tip definition is obscured.

Nasal Blood Supply

The nasal tissue is extremely vascular, and this healthy blood supply comes from several different sources, stemming from both the internal and external carotid arteries. This convergence of vessels from the carotid arteries creates a rich vascular plexus that supplies not only the external nose, but the nasal septum and internal structures as well. A branch from the anterior ethmoid, dorsal nasal artery, and branches from the facial artery, the angular and superior labial artery, converge to create an anastomotic network of vessels to supply the nasal tip and its underlying structures. Fig. 2.4 helps us to identify the robust blood supply to the external nose and nasal tip. Branches from the superior labial artery, sphenopalatine artery, and the anterior ethmoid arteries supply the nasal septum, as can be seen in Fig. 2.5 .

Fig. 2.4, The blood supply to the nose arises from both the internal and external carotid arteries. a ., Artery; m ., muscle.

Fig. 2.5, Blood supply to the lateral internal nasal wall is vigorous and helps prevent problems when grafting the nose or stretching nasal tissues. Multiple branches arise from both the internal and external carotid arteries.

This stout blood supply allows the nose to heal quite well with very minimal risk of infection or risk of skin necrosis. The venous and lymphatic systems that drain the nose parallel the arterial supply. The nose will drain to the pterygoid plexus, as well as the ophthalmic and facial veins.

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