The initial part of the respiratory tract is also the olfactory organ. It consists of external nose, nasal cavity and paranasal sinuses, and consists of nasal bone, nasal cartilage, nasal muscle and covered skin. The nasal cavity is divided into left and right cavities by the nasal septum, with the nostrils communicating with the outside world at the front and the nasopharynx at the back. In front of the nasal cavity is the nasal vestibule, which is covered with skin and has nasal hair, which plays a filtering role and is prone to boils.

The posterior part is the proper nasal cavity, lined with mucosa, which can be divided into olfactory part and respiratory part. Has the functions of smelling fragrance, moistening and purifying inhaled air. Sinus is located in the skull around the nasal cavity, which is a cavity containing gas and communicating with the nasal cavity, and its mucosa is connected with the nasal mucosa. When the nasal cavity is inflamed, it can spread to the sinuses and cause sinusitis. The paranasal sinuses are involved in moistening and heating the inhaled air, and play a role in pronunciation.

External nose: the external nose refers to the part protruding from the face, which is supported by bone and cartilage and covered with skin. The external nose is shaped like a triangular pyramid, protruding from the center of the face and vulnerable to trauma. The upper end is narrow, and the uppermost part is located between the eyes, which is called nasal root. The protruding part at the lower end is called the tip of the nose. The central bulge is called the bridge of the nose, and the sides of the bridge of the nose are the back of the nose. The protruding parts on both sides of the tip of the nose are called the alar. The skin at the tip of nose and alar is thick, rich in sebaceous glands and sweat glands, closely connected with deep subcutaneous tissue and perichondrium, and prone to furuncle. Therefore, when inflammation occurs, local swelling compresses nerve endings, which can cause severe pain.

Nasal bone: paired left and right, connected with the midline, connected with the nose end of the frontal bone to form a nasal frontal suture, the outer edge connected with the frontal process of the left and right maxilla, the nasal bone crest connected with the middle plate of the ethmoid bone behind, and the lower edge connected with the lateral nasal cartilage with soft tissue. The upper part is narrow and the lower part is thick, and the lower part is wide and thin, which is easy to fracture due to trauma and saddle nose. Because of the rich blood vessels, the fracture is easy to heal after reduction.

Blood vessels: the veins of the external nose mainly flow into the internal and external jugular veins through the internal canthus vein and facial vein. Because the inner canthus vein communicates with the intracranial cavernous sinus through the upper and lower ophthalmic veins, and the facial vein has no valve, the blood can move up and down. If the nose or upper lip (called the dangerous triangle) suffers from furuncle, it is likely to cause thrombophlebitis in the cavernous sinus.

Nasal cavity: it is a cavity between two lateral skulls, based on bony nasal cavity and cartilage, and its surface is lined with mucosa and skin. The nasal cavity is an irregular long and narrow cavity with a narrow upper part and a wide lower part, and the front and rear diameter is larger than the left and right sides. It begins in the anterior nostril and ends in the posterior nostril, leading to the nasopharynx. The nasal cavity is divided into left and right cavities by nasal septum, the front cavity communicates with the outside world through nostril, and the back cavity communicates with pharyngeal cavity through rear nostril. Each nasal cavity can be divided into nasal vestibule and inherent nasal cavity.

Nasal vestibule refers to the enlarged space surrounded by the alar, and its inner surface is lined with skin, which has the function of retaining and inhaling dust. In addition, the skin is tightly attached to the perichondrium, so when the furuncle is swollen, the pain is severe. The front of the nasal vestibule is equivalent to the inner corner of the tip of the nose, and there is a concave protruding outward, which is called the nasal vestibule recess, and it is often the place where boils and acne occur.