Placental mammals use which organ for respiration?

Placental mammals use which organ for respiration?

• A. Gills
• B. Lungs
• C. Skin
• D. Tracheae

Answer: (B)

Placental mammals rely on lungs for gas exchange. While a fetus develops, oxygen is provided via the placenta and umbilical vessels, so the lungs aren’t the site of respiration before birth. After birth, breathing switches to the lungs: air is inhaled through the nose or mouth, travels down the trachea into the bronchi and bronchioles, and reaches tiny air sacs called alveoli where oxygen moves into the blood and carbon dioxide is released. The lungs provide a large, moist surface area and are protected inside the chest, well-suited for life on land. Gills are specialized for extracting oxygen from water, so they’re not used by placental mammals. The skin can contribute to gas exchange in some animals, but in adult placental mammals it isn’t the primary respiratory surface. Tracheae are part of insects’ breathing systems, not mammals’, which is why they aren’t used for respiration in placental mammals.

Placental mammals rely on lungs for gas exchange. While a fetus develops, oxygen is provided via the placenta and umbilical vessels, so the lungs aren’t the site of respiration before birth. After birth, breathing switches to the lungs: air is inhaled through the nose or mouth, travels down the trachea into the bronchi and bronchioles, and reaches tiny air sacs called alveoli where oxygen moves into the blood and carbon dioxide is released. The lungs provide a large, moist surface area and are protected inside the chest, well-suited for life on land. Gills are specialized for extracting oxygen from water, so they’re not used by placental mammals. The skin can contribute to gas exchange in some animals, but in adult placental mammals it isn’t the primary respiratory surface. Tracheae are part of insects’ breathing systems, not mammals’, which is why they aren’t used for respiration in placental mammals.