either of two large organs lying within the chest cavity on either side of the heart; they supply the blood with oxygen inhaled from the outside air and dispose of waste carbon dioxide in the exhaled air, as a part of the process known as respiration.
Most babies first pull themselves up to a standing position between about eight months and 10 months. At this stage your baby will need to hang on to you or a solid piece of furniture. By 11 months she may be able to stand on her own.
By about 6 months, babies can usually sit alone for around 30 seconds, says Maribeth Gorman, a senior occupational therapist at Children's Memorial Hospital in Chicago. By 7 months, they are pretty steady and can begin using their hands to play in front of them while they sit..