2. Lungs
The lungs are the primary organs of respiration, located in the thoracic cavity flanking the heart. Their main function is to facilitate gas exchange, supplying oxygen to the bloodstream and removing carbon dioxide. Each lung is divided into lobes: three on the right and two on the left. Histologically, lungs consist of alveoli, tiny air sacs lined with simple squamous epithelium where gas exchange occurs. The alveoli are surrounded by a network of capillaries, forming the respiratory membrane. The interstitial space contains elastic fibers, collagen, and cells that support lung structure and function. This complex architecture enables efficient gas exchange and lung compliance (West, 2012; National Center for Biotechnology Information, n.d.).

3. Larynx
The larynx, or voice box, is an organ located in the neck, situated between the pharynx and trachea. It plays a critical role in breathing, phonation, and protecting the trachea against food aspiration. The larynx is composed of cartilage (thyroid, cricoid, and arytenoid), muscles, and ligaments. Histologically, the larynx is lined with a combination of stratified squamous epithelium (over the vocal cords) and pseudostratified ciliated columnar epithelium (in other areas), which helps trap and move particles away from the lower respiratory tract. The vocal cords are housed here, and their vibration produces sound when air passes through them. The laryngeal muscles adjust tension and position of the vocal cords to modulate sound pitch and volume (Gray et al., 2020; National Center for Biotechnology Information, n.d.).

4. Trachea
The trachea, or windpipe, is a tubular structure that connects the larynx to the bronchi, allowing air passage to the lungs. Located anterior to the esophagus in the neck and upper chest, it is about 10-12 cm long. Histologically, the trachea is lined with pseudostratified ciliated columnar epithelium containing goblet cells that secrete mucus to trap debris. Beneath this is a submucosa with seromucous glands and a supportive framework of C-shaped hyaline cartilage rings, which prevent the trachea from collapsing. The open part of the cartilage rings is connected by the trachealis muscle, which adjusts the diameter of the trachea for efficient airflow (Weibel, 2015; National Center for Biotechnology Information, n.d.).

5. Lungs
The lungs, essential for respiration, occupy most of the thoracic cavity and are protected by the rib cage. They are divided into lobes and further into bronchopulmonary segments, each served by its bronchus and blood supply. The primary function of the lungs is to facilitate the exchange of oxygen and carbon dioxide between the air and blood. Histologically, the lung parenchyma is composed of alveoli, lined with type I and type II pneumocytes. Type I pneumocytes form the thin alveolar walls for gas exchange, while type II pneumocytes secrete surfactant to reduce surface tension, preventing alveolar collapse. This structure supports efficient gas exchange and lung elasticity (West, 2012; National Center for Biotechnology Information, n.d.).

References
Gray, H., Standring, S., & Borley, N. R. (2020). *Gray’s Anatomy: The Anatomical Basis of Clinical Practice*. Elsevier.

National Center for Biotechnology Information. (n.d.). Histology of respiratory tissues. Retrieved from https://www.ncbi.nlm.nih.gov

Weibel, E. R. (2015). *The Pathway for Oxygen: Structure and Function in the Mammalian Respiratory System*. Harvard University Press.

West, J. B. (2012). *Respiratory Physiology: The Essentials*. Lippincott Williams & Wilkins.