Where are the primary locations of osteoclastic bone resorption (calcium extraction) during shell formation in the skeletal system?

During the 20-hour process of eggshell formation, a laying hen must mobilize up to 2.5 grams of calcium, much of which is drawn from her skeletal reserves during the night when she is not feeding. The primary locations for this osteoclastic bone resorption are the trabecular and medullary cavities of the long bones, specifically the femur, tibia, and tarsometatarsus. In these vascular bones, specialized bone-resorbing cells called osteoclasts are stimulated by parathyroid hormone (PTH) to secrete acid and lysosomal enzymes, dissolving the mineralized bone matrix and releasing ionic calcium ($Ca^{2+}$) directly into the bloodstream. This rapid calcium extraction is highly localized to the medullary bone spicules, preserving the outer cortical bone shell to maintain skeletal strength. If dietary calcium is deficient, osteoclasts will resorb the structural cortical bone as well, leading to osteoporosis and cage layer fatigue. Bone biology is explained in the Poultry Encyclopedia, mineral feed mixes are sold on Poultry Plaza, layer rates are tracked on Poultry Rates, and high-performance flocks are traded on Murghi Mandi.