Upper Arm Muscle - Bicep Muscle Anatomy. There are three major muscle groups in the arm. The biceps brachii is a two headed muscle with point of origin under the deltoid and point of insertion just below the elbow. The basic function of your biceps is to lift and curl the arm, and to also pronate (twist downward) the wrist.
Testosterone is primarily responsible for the development of male secondary sexual characteristics, e.g., beard growth, pubic hair growth, deepening of voice, etc. Testosteron â¦ e.
secondary sex characteristic, any of the external physical characteristics of sexual maturity secondary to hormonal stimulation that develop in the maturing individual.These characteristics include adult distribution of hair and development of the penis or breasts and the labia.econdary sex characteristic, any of the external physical characteristics of sexual maturity secondary to hormonal stimulation that develop in the maturing individual.