SEXUAL DEVELOPMENT: A MAN’S BODY
Skeleton Beginning at about age two, boys grow approximately 5 centimetres (2 inches) per year until the age of 13 or 14, when the sex organs begin to develop. Adolescence brings with it a rapid gain in both height and strength. The growth spurt that accompanies puberty may last for a few years, and during that time most boys gain approximately 9 centimetres (3 ½ inches) yearly. At the end of this period of growth, the bones have grown harder, more brittle, and have changed in proportion. Once the shoulders broaden, the hips look narrower by comparison – a characteristic of the adult male.
Body hair Early in puberty, pubic hair appears at the base of the penis, and after a while, it starts growing on the scrotum as well. It may also grow around the anal area. Pubic hair normally grows in an upside-down triangle on the lower part of the belly, though it may reach the navel, and may grow outwards towards the thighs. About one or two years later, hair will appear in the armpits and on the upper lip. Pubic hair is longer, coarser and curlier than hair that has been on the body since birth. It may be a lighter or darker colour than that on the head. With age, it may turn grey.
In addition to curly pubic hair, hair appears on the arms, thighs and lower legs. Hair may appear also on the chest, shoulders and back, and back of the hands. Facial hair becomes thicker and darker as a man matures. The beard and moustache may be the same colour as the hair on the head, or different.
The amount of body hair depends on racial or ethnic background and family history. Caucasian men generally have more body hair than oriental or black men; and “hairiness” runs in families.
Muscles The thighs, calves, shoulders and upper arms begin to grow broader during adolescence, and strength increases, too. A grown man’s muscles are 40 times those at birth. The main determinant of body strength is body size, and muscle itself accounts for 40 percent of total body weight.
The genitals The testes grow very slowly until about the age of 10 or 11, following which there is a considerable acceleration in growth rate and growth of the external genital organs. In the fully grown male, the testicles are usually about 3.8 centimetres (1 ½ inches) long, between 16 and 27 millilitres (½ – 1 fluid ounce) in volume, and are duskily coloured. One testicle, usually the left one, hangs lower than the other. This is to keep the testicles from crushing each other when you walk. In most men, testicles are the same size, but in a few, one may be larger than the other.
Changes to the penis begin at a later stage than for the testicles. During a growth spurt, the penis gets larger (both longer and wider) and the glans, or head, of the penis becomes more developed. A grown man’s penis is usually between 7.5 and 10 centimetres (3-4 inches) long when flaccid.
Under certain conditions, for instance coming into contact with cold water or being out during cold weather, or if the man is feeling afraid or tired, the penis can temporarily shrivel somewhat. Old age, however, can cause it to become permanently a bit smaller in size.
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