The nose is a complex structure that serves as the entry point for air and contains the specialized receptors for the sense of smell. Its shape and function are determined by a precise arrangement of rigid bone, flexible cartilage, and specialized soft tissues. Understanding the nose’s composition reveals how it provides structural support and performs the specialized functions of filtering, warming, and moistening the air we breathe.
The Bony and Cartilaginous Framework
The distinct shape of the human nose is maintained by a skeleton composed of bone and cartilage, providing support and flexibility. The superior portion, often called the bridge or dorsum, contains the rigid components. This upper third is formed by the paired nasal bones, which connect to the frontal bone of the skull and parts of the maxilla, anchoring the structure.
The majority of the external nose, including the lower two-thirds, is shaped by a flexible framework of hyaline cartilage. This material allows the nose to withstand minor impacts and return to its original form. The major cartilages include the paired lateral cartilages, which support the sides of the middle portion of the nose.
Further down, the paired alar cartilages form the rounded shape of the nostrils, or nares. These are the most flexible parts of the external nose and are sometimes accompanied by smaller alar cartilages. This combination of fixed bone superiorly and movable cartilage inferiorly gives the nose its characteristic appearance and functional capacity.
The Internal Structure and Mucosal Lining
The structural framework is covered by skin, underlying fat, and small muscles necessary for minor movements like flaring the nostrils. The internal surfaces of the nasal cavity are lined with a specialized soft tissue called the nasal mucosa, which is a continuation of the respiratory tract’s mucous membrane.
The nasal mucosa’s primary function is to condition the inhaled air before it reaches the lungs. It is composed of ciliated columnar epithelial cells and interspersed goblet cells, which form an effective air-filtration system. The goblet cells secrete mucus, a sticky substance that traps airborne particles, dust, and pathogens.
The hair-like projections on the epithelial cells, known as cilia, rhythmically sweep the mucus layer toward the back of the throat. This process, called mucociliary clearance, continuously removes the trapped debris. The rich blood supply beneath the mucosa helps to warm the incoming air, while the mucus humidifies it, protecting the lower airways.
Understanding the Nasal Septum
The nasal septum is the vertical wall that divides the nasal cavity into two passages. It is a composite structure, formed by a combination of bone and cartilage fused together. This central divider is about two millimeters thick.
The anterior (front) portion of the septum is formed by the septal cartilage, also known as the quadrangular cartilage. This flexible part is often the site of injury and allows the nose to be repositioned after facial trauma. Behind and above this cartilage lies the perpendicular plate of the ethmoid bone, forming the superior bony part of the septum.
The lower and posterior (back) part of the septum is largely composed of the vomer bone, which joins with the ethmoid bone and the septal cartilage. The fusion of these three components creates the central wall separating the left and right sides of the nose. The bony crests of the maxilla and palatine bones also contribute to the septum’s base, adding stability.