We can explain the Anatomical Alignment of Asanas in many ways. Let us first understand what anatomical position is. When we stand up straight with the palms, toes, head and pelvis facing forward, this is anatomical position.
In Hatha yoga we often begin in a seated, meditative like (crossed-legged) position. Here our hips externally rotate, feet invert, elbows flex slightly to bring hands to the knees (or lap) and head, neck and back are in a straight line. This simple crossed leg position is known as Sukhasana
or easy pose. Here the tendency is to collapse the abdomen, which rounds the thoracic and/or lumbar spine. Beginners can sit against a wall to learn what it feels like to align the spine against a wall, keeping it straight, against gravities nature of drawing us downward. The reason we sit in this position is to allow room for proper breathing. We can practice many methods for improving the breath. This is known as pranayama. The lungs and diaphragm require space to inflate and deflate during the respiratory process. When we keep our spine erect, the open space for our organs and respiratory muscles is vital in taking efficient breath. In easy pose we can further develop into more challenging seated poses, as in Padmasana(lotus).
Balancing Asana Alignment
We can perform balancing asanas in seated, standing, inverting, forward bending, back bending, and using just our upper body. There are so many contraindications when considering whether or not to perform a balancing pose. As we age, brain function decreases and the cerebellum (which controls motion) loses ability to function, in the process. Anyone with cerebellum issues should not practice these asana. The effect of practicing the balancing asana is improvement in posture, physical grace and coordination and reduces stress and anxiety.