Final answer:
The nasal cavity, paranasal sinuses, and pharynx make up the upper respiratory system. The nasal cavity is the primary opening and first section of the respiratory tract, connected to the external environment through the nostrils. The paranasal sinuses are air-filled cavities in the skull that communicate with the nasal cavity.
Step-by-step explanation:
The nasal cavity, paranasal sinuses, and pharynx make up the upper respiratory system. The nasal cavity is the primary opening and first section of the respiratory tract, connecting to the external environment through the nostrils or nares. It is lined with hairs and a mucous membrane to trap particles and produce mucus.
The paranasal sinuses are small air-filled cavities in the skull that communicate with the nasal cavity. They serve to warm and humidify incoming air and lighten the weight of the skull.
The pharynx, also known as the throat, is divided into three sections: the nasopharynx, oropharynx, and laryngopharynx. It connects the nasal cavity and the oral cavity to the trachea and esophagus.