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.
If your baby isn't able to hold her head up steadily by the time she's about six months old and hasn't started learning to prop herself up on her arms, bring it up the next time you talk to your doctor.hile you can prop your baby in a sitting position almost from day one, true independent sitting doesn't begin until your baby has head control. Starting at about four months, your baby's neck and head muscles strengthen rapidly, and she'll learn to raise and hold her head up while she's lying on her stomach.