The lumbrical muscles do not attach to the proximal phalanx directly, but rather connect the tendons of flexor digitorum profundus (below, ie volar) to the extensor tendons (above, ie dorsal) and produce flexion by pulling on the extensor tendons as they pass over the proximal phalanx.
By the time they are 12 months old, most babies can weigh three times what they weighed at birth and gain about an inch per month in length. The average infant at one year may be between 2630 inches long. Social and Emotional Development-Infants respond when you say their name. They begin to fear strangers.
Once your baby can hold her head up on her own (usually around three to four months), you can sit her in a supportive chair like a Bumbo seat. Just be sure to always watch your baby while in the Bumbo seat or something similar. You can also use pillows to support your baby and help her sit up. As Baby grows stronger, she will be able to sit for a few seconds when you place her in a sitting position.