Bone matrices store these slightly soluble calcium salts so that they can be released into the bloodstream in times of low blood calcium levels. As a result, these salts are an example of how the skeletal system provides mineral storage for the body.

Movement and bone cell production are also primary functions of the skeletal system, but are not linked to calcium salts. Energy storage is linked to the fats stored in the yellow marrow of the bone.

When it comes to the strength and resilience of bone, both collagen and calcium play important roles. Collagen provides bones with great tensile strength, and calcium (usually in the form of hydroxyapatite) provides bones with great compressive strength. In the event of a calcium deficiency, weight placed on bones would cause them to bend irregularly, resulting in the characteristic bending of bones found with rickets.

A deficiency in collagen would cause damage to the bone during extension or stretching forces. Bone marrow does not play an important structural role, and is more important for bone function.

Bone consists of calcium-phosphate crystals, known as hydroxyapatite, in a collagen matrix. The molecular formula for hydroxyapatite is . Collagen's structure depends on hydroxylysine and hydroxyproline for stability. Potassium is not required in bone.

While these specific formulas are not generally tested knowledge, it is important to know what molecules may influence bone composition and growth.

Vitamin D aids in calcium absorption in the small intestine. In the absence of vitamin D, inadequate absorption causes a deficiency of calcium in the body. Without calcium, the bones will not have adequate tensile strength, which can cause a bowing effect in bones that support weight, such as the femurs. Collagen in the bones is associated with resistance to compression, rather than tensile strength, and is not linked to vitamin D.

Ligaments connect a bone to another bone, while tendons attach a muscle to a bone. Since two bones are being connected by the fibrous band of tissue in question, we can confirm that it is a ligament.

Muscle does not actually form a functional connection; rather, muscle will transition to a tendon, which will connect to a bone. Joints are comprised of several different structures and tissues, and are the articulations between two bones.

Skiers and American football players are prone to medial collateral ligament (MCL) injuries. The MCL is a major ligament of the knee that resides on the inner (medial) side of the knee. The MCL is connected to the tibia and femur, as well as the meniscus and anterior cruciate ligament, making compound injuries common.

The anterior cruciate ligament resides at the front (anterior) side of the knee, while the posterior cruciate ligament resides to the back (posterior) of the knee. The medial meniscus is a fibrocollagen band that is fused with the MCL.

The skeleton plays a role in musclular contraction in that it serves as an anchor and provides leverage against which muscles can exert force. It also serves as protection and support for soft tissues. Bones also maintain certain ion concentrations. The correct answer choice is the regulation of pH through hydration, which is not a function of the skeletal system.

There are organic (collagen) and inorganic (hydroxyapatite) components of the bone that contribute to its characteristic hardness. The key here is knowing the composition of hydroxypatite, which is primarily constructed of calcium and phosphorus.

Collagen is a protein that allows the bone to be somewhat flexible, so "removal of proteins" is the only correct answer. Other answer choices involve inorganic bone material, which add to hardness of the skeleton, but not to its flexibility.

Compact and spongy bone have similar chemical and structural compositions and are both hard and resistant to compression; however, due to the fact that compact bone is denser, nutrients are delievered through canals called Haversian systems in compact bone; spongy bone is less dense and lacks these specialized canals.