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.
Boys. In boys, between the ages of about 12 and 15, the pituitary gland produces LH and FSH, which together stimulate the production of the sex hormones. The testes start to produce testosterone which begins the development of secondary sexual characteristics.he ovaries start to produce oestrogen and progesterone which begin the bodily changes that happen during puberty. The changes, known as secondary sexual characteristics, are: 1  The breasts develop. 2  The hips and thighs widen.