Humans do not have gills. Although human embryos go through a phase where they have gill-like structures, they eventually disappear, and humans develop lungs for breathing air. Therefore, it is not accurate to say that human gills “turn into” something else.
During the embryonic development of humans and other vertebrates, there is a period known as the pharyngula stage, where embryos have gill-like structures known as pharyngeal arches. These arches develop into different structures depending on the species. In fish, they become gill slits, which allow the fish to extract oxygen from water. In humans, the first two pharyngeal arches develop into structures in the head and neck region such as the jaw, inner ear, and throat. The third and fourth arches form structures in the neck region, such as the thymus and thyroid glands, while the fifth and sixth arches form structures in the chest region, such as the aorta and pulmonary arteries.
As the human embryo develops, the gill-like structures disappear, and the respiratory system begins to develop. The respiratory system consists of the lungs, which are responsible for extracting oxygen from the air and expelling carbon dioxide from the body. The lungs develop from a structure known as the lung bud, which forms from the foregut during embryonic development.
The lung bud grows and branches, eventually forming the bronchial tree, which is a network of air passages that lead to tiny air sacs called alveoli. The alveoli are responsible for gas exchange, where oxygen from the air is absorbed into the bloodstream and carbon dioxide is expelled from the body. The lungs continue to develop after birth, with alveoli increasing in number and size until early adulthood.
In addition to the respiratory system, humans also have a circulatory system, which is responsible for transporting oxygen, nutrients, and other substances throughout the body. The circulatory system includes the heart, blood vessels, and blood. Oxygenated blood from the lungs is transported to the body’s tissues through the circulatory system, where it is used for cellular respiration, a process that generates energy for the body’s functions.
In summary, human gills do not turn into anything else because humans do not have gills. During embryonic development, human embryos go through a phase where they have gill-like structures known as pharyngeal arches, but these eventually develop into different structures, including the respiratory and circulatory systems. The respiratory system consists of the lungs, which extract oxygen from the air and expel carbon dioxide from the body, while the circulatory system transports oxygenated blood throughout the body.