There are three muscles located in the anterior compartment of the upper arm â biceps brachii, coracobrachialis and brachialis. They are all innervated by the musculocutaneous nerve. A good memory aid for this is BBC â biceps, brachialis, coracobrachialis.
Calcitonin is a hormone secreted by the thyroid gland that reduces the concentration of blood calcium level when it has risen to an above normal level. This polypeptide hormone is made up of 32 amino acids and is produced mainly by the parafollicular cells (also known as C cells) of the thyroid gland.
However, the importance of this role in humans is unclear, as patients who have very low or very high levels of calcitonin show no adverse effects. Calcitonin reduces calcium levels in the blood by two main mechanisms: 1  It inhibits the activity of osteoclasts, which are the cells responsible for breaking down bone. 2  It can also decrease the resorption of calcium in the kidneys, again leading to lower blood calcium levels.