The skeletal system works constantly with the muscular system, and the circulatory system, endocrine system and integumentary system also have interactions with it. The skeletal system provides vital support and protection for all the other systems of the human body.
The skeletal and muscular systems work together to produce movement and maintain posture. Muscles attach at various points on the bones and work to change the bones' orientation relative to one another at the joints. Stress placed on the skeletal system by the muscular system influences its growth and development. Exercise causes the skeletal system to become denser and stronger.
The marrow inside bones is critical to the circulatory system, and the cells in the marrow generate both red and white blood cells. The endocrine system produces hormones that affect the way the bones grow. The bone cells also produce hormones themselves; osteoclasts are bone cells that help regulate both blood sugar and fat deposition.
The bones are reliant on the integumentary system, or skin, for the production of vitamin D. Vitamin D is required for calcium absorption by the bones. Without vitamin D, bones can lose calcium until they become soft and brittle. The skin creates vitamin D during exposure to sunlight.