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.
Â­From the outside, the male has two visible sex organs, the testes (or testicles) and penis. The testes are the primary male sexual organs in that they make sperm and produce testosterone. The sperm is the male sex cell, or gamete, and each testicle produces more than 4 million new sperm per hour [source: Angier ]. Testosterone is the hormone that causes male secondary sex characteristics such as facial and pubic hair, thickened vocal cords and developed muscles. The testes are housed outside of the main part of the male's body, in a sac called the scrotum. This location is important because in order for the sperm to develop properly, they must be kept at a temperature about two degrees cooler than normal body temperature.