A flat nose, or low nasal bridge, describes a common variation in human facial anatomy where the upper portion of the nose lacks significant outward projection. This feature is characterized by a profile that appears less defined and closer to the face than a nose with a high bridge. It is a natural aspect of human diversity and is largely the result of inherited genetic factors. The structural differences that create this appearance are a normal part of how the human face develops.
Defining the Structure and Features
The appearance of a flat nose is primarily determined by the bony and cartilaginous framework that makes up the nose’s structure. The nasal bridge, also called the dorsum, refers to the upper segment of the nose, which is supported by the paired nasal bones. A low nasal bridge is defined by a reduced height or protrusion of these nasal bones where the nose meets the forehead and eyes.
This reduced height creates a smoother, less angular transition from the forehead to the tip of the nose when viewed from the side. Below the bony segment, the cartilaginous framework also contributes to the overall shape. The lower part of a flat nose often features an increased width at the base and a less projected, or “button-like,” nasal tip.
The nasal bones themselves are shorter and flatter in this structure, which is in contrast to a high-bridged nose, where the bones are more pronounced and elevated. This structural difference means the nose appears broader across the face and sits closer to the facial plane, lacking the sharp definition of noses with a more prominent dorsal hump.
Genetic and Ethnic Variation
Genetic inheritance is the most significant factor determining an individual’s nasal shape, with the trait often running in families. The complex interaction of multiple genes dictates the size of the nasal bones, the shape of the cartilage, and the width of the nostrils. This genetic blueprint results in the wide range of nasal morphologies observed across the global population.
These variations are often linked to evolutionary adaptations to different climates, a concept known as the nasal index. This index is a scientific measurement that calculates the ratio of the nose’s width to its height. Noses are broadly categorized based on this ratio, with “platyrrhine” (wide) and “leptorrhine” (narrow) representing the two extremes.
Anthropological studies suggest that wider, flatter noses, which correspond to a higher nasal index, are more common in populations that historically developed in warm, humid environments. Conversely, narrower, more projected noses are frequently found in populations from cold, dry climates. The theory is that a narrower structure better conditions cold or dry air before it reaches the lungs, while a broader structure may prioritize efficient airflow.
Functional Considerations and Other Causes
In the vast majority of cases where a low nasal bridge is a natural, inherited feature, the structure does not impair normal respiratory function. The nasal passages and internal structures are generally well-formed and capable of handling airflow. However, any nose shape can sometimes be associated with structural issues that affect airflow, potentially leading to breathing difficulties or chronic nasal congestion.
A flat nose can also result from causes other than typical genetic variation. Traumatic injury, such as a severe blow, can cause the nasal bones and cartilage to collapse, resulting in a distinct shape known as a saddle nose deformity. This acquired condition can lead to both cosmetic concerns and functional issues, including nasal obstruction.
A flattened nasal bridge is also a characteristic feature of specific congenital conditions. Genetic syndromes like Down syndrome, Fetal Alcohol Syndrome, or Williams Syndrome often include a low or depressed nasal bridge as part of unique facial features. These medical causes are distinct from the normal range of human variation and are typically accompanied by other defining signs.