The spinal curves developing in children after they begin sitting and standing are the ____ curve and the _____ curve.

The development of spinal curves in children as they begin to sit and stand appropriately pertains to the cervical and lumbar curves. As an infant starts to lift its head and eventually sits up, the cervical curve becomes prominent. This curve helps to support the head's weight and aids in balance and movement as the child grows and develops motor skills.

Similarly, once infants start to stand and walk, the lumbar curve develops. This curve is significant as it allows for better weight distribution and balance when a person is upright. Both the cervical and lumbar curves are classified as lordotic curves, which are characterized by an inward curvature. These curves are essential for maintaining an upright posture and facilitating efficient movement, which are vital during the early stages of a child's physical development.

In contrast, the thoracic and sacral curves are present at birth and are less about the development associated with sitting and standing. The thoracic curve is kyphotic (outward curvature) and does not originate as a result of sitting. The sacral curve, being similar, is a continuous curve from the spine but is not influenced by the activities of sitting and standing in early childhood. Thus, recognizing the correct development of the cervical and lumbar curves is crucial for understanding the biomechanical evolution of a child's