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.
She should be able to hold her head more or less in line with the rest of her body as you pull her up (Scott 2010, Sheridan 2008: 9, 58) . Five months to six months. By six months, your baby should be able to hold her head steady and upright. She'll tilt her head forward when you pull her up into a sitting position (Sheridan 2008: 58) . Once your baby has good head control, she can move on to sitting up, rolling over.