"What are the respiratory organs of the human body?"
Unique visceral organs that facilitate external respiration and undergo disintegration. In other words, they limit the respiratory surface to a specific area and evolve as adaptive structures. Animals with simple systems or slow movements often rely on cutaneous and intestinal respiration, lacking distinctive vocal organs. Even if they possess disintegrated vocal organs, they often function in conjunction with cutaneous and intestinal respiration. Vocal organs such as the ctenidia in gastropods are specialized disintegrated visceral organs that also serve other physiological functions, like the lamellar gills in bivalves and the parapodia in polychaetes.
Mutual Characteristics:
(1) Possess thin walls and diverse blood supply.
(2) Occupy a significantly expanded area due to projections, folds, and branches, enhancing the efficiency of gas exchange between internal and external substances.
Vocal Organs in Animals
The origin of vocal organs varies among microorganisms, but their form, appearance, and function exhibit convergence. Aquatic respiratory animals are generally referred to as having gills (gill respiration), while air-breathing animals are known as having lungs (lung respiration), each with similar characteristics. However, terrestrial arthropods possess unusual air-breathing organs called bronchial systems, which are relatively well-developed.
Gills are mostly exposed externally, suitable for contact with the water's surface. In contrast, lungs and bronchial tubes are integrated into the body, allowing for the appropriate intake of air while preventing water loss through evaporation. Air-breathing organs require active respiratory movements, and gill respiration in animals often serves as an auxiliary function, facilitating gas diffusion in water with low diffusion rates.
From a systematic perspective, gills are more prevalent in annelids, mollusks, and arthropods, exerting significant influence among invertebrates. Compared to reproductive and digestive organs, the development of these vocal organs is relatively late. Vertebrates may have initially respired through skin and digestive tracts, with some still relying on cutaneous (e.g., frogs) and intestinal (e.g., loaches) respiration to varying degrees. The gills of fish and amphibian larvae, or the lungs of adult amphibians and amniotes, are located near the anterior end of the digestive tract, derived from the nasopharyngeal region. This ontogenetic connection sometimes leads to the digestive tract being referred to as the "gill gut."
