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.
MOST HELPFUL POSTS. Each baby is different. My baby girl has been holding her head up since the day she was born. She has always had a very strong neck. She's 11 weeks old now and when she is laying on her back, she always is pulling her head/back up, trying to get into a sit-up position.