The breath is the process by which living things get oxygen and expel carbon dioxide. This entry and exit is called gas exchange. The oxygen obtained during respiration is used throughout the body, and, in addition, carbon dioxide is discarded by all organs and tissues. The metabolism of the organism depends on respiration.
There are animals that breathe through the skin. In skin respiration , gaseous exchange is carried out through the skin. For this to be possible, it must be very thin, well irrigated internally and kept externally moist. Therefore, animals that have this capacity live in humid or aquatic environments.
The skin respiration is oxygen diffusion through the integument, to the superficial blood vessels. As for the elimination of gases, carbon dioxide is eliminated from the blood vessels through the tegument. The oxygen that is collected by the blood vessels is carried to all the organs of the body, where it comes in contact with the cells and crosses the cell membrane.
The annelids are a phylum of invertebrate, protothous, cylindrical animals with bilateral symmetry, without limbs and soft and elongated bodies. They are divided into:
- Marine polychaetes : the largest number of annelids are marine polychaetes.
- Oligochaetes terrestrial and freshwater : if they are aquatic, they absorb oxygen from the water, while if they are terrestrial they absorb it from the air, but they are always kept in humid earth.
- Hirudíneos : they can be marine, terrestrial, arboreal or, in their great majority, of fresh water.
Amphibians are a class of vertebrates amniotes, four legs (tetrapods). They regulate their temperature from the ambient temperature, that is, they are ectothermic.
They differ from other vertebrates, undergo a metamorphosis during their development. They usually combine skin breathing with bronchial breathing (when they are larvae) or pulmonary respiration (when they are adults).
The echinoderms are a phylum of deuteróstomos and benthic marine animals. They are called echinoderms because they have either a dermato esqueleto (the structure of their body is external), or in an internal skeleton, a series of plates (calcareous ossicles) that articulate with each other. They have a radial symmetry.
Examples of skin respiration
- Starfish (echinoderm): There are between 1,500 and 2,000 species of starfish (asteroids) in the world. They have arms (between 5 and 50) that arise from the center of the body, radially. They are found in all oceans, in both cold and tropical environments. They capture the oxygen of the water by diffusion.
- Frog : (amphibian) Along with the toads, they are part of the anurans. They differ from toads because they have smoother skin, are more agile and have a more stylized body. This is because their legs are longer and ready to make fast and precise jumps. They are always in or near the water. They move by jumps. Anurans have branchial respiration when they are tadpoles and lungs when they become adults. However, they combine this breathing with the cutaneous one.
- Sea urchin (echinoderm): There are approximately 950 species of this spiny-skinned animal with a flattened spherical shape. The calcareous plates form a shell, where movable spines are articulated, which allow them to move. They live on the bottom of the sea. Although most spices breathe through gills, some of them have skin respiration.
- Earthworm : (anélido oligochaeta): There are between 4,000 and 6,000 species of earthworms. Oxygen dissolves in the mucus that lines your skin, then diffuses through the thin tegument. The oxygen is captured by the capillaries and carried to the cells. From the cells comes the carbon dioxide that is also expelled through the capillaries.
- Mollusks : Mollusks have gills and a respiratory system. However, in some molluscs the gills are modified or do not exist, since the exchange of gases occurs on the surface of the body and the mantle.
- Leech : (anilido hirudíneo) It is a worm of 0.5 to 46 cm in length. Live in freshwater rivers. It feeds on the blood it extracts from mammals, including man. They were used for medicinal purposes throughout history, and even today they are used to eliminate swelling and during the correction of dislocations. The leeches do not have a different respiratory system, but gas exchange occurs through a thin cuticle that covers them.
- Toad : (amphibian) As we said, it is one of the anurans. They differ from frogs in being heavier and sturdier. They do not move by jumping but walking (although there are exceptions). Poisonous glands that defend them from predators are found on their skin. Like frogs, they combine skin breathing with skin breathing with the branchial (when they are tadpoles) and pulmonary (when they are adults).