Somatic Growth and Development in Adolescence
Reproductive Growth and Development in the Female Adolescent
Adolescence is a period of peak somatic as well as reproductive growth and development. The pattern of growth and functional maturation of various reproductive structures in females is described in this chapter. The stages of normal puberty are described in Chapter 533 and an overview of the hormonal influences that lead to these changes is in Chapter 513.
Breast development can be divided into four stages: a prepubertal period of quiescence; a pubertal period of rapid growth and lobular development; cyclic changes in stromal and epithelial elements during menstruation and pregnancy; and finally, involution of lobules, which starts after the age of 35. Breast buds may be appreciated in newborns due to the influence of maternal hormones. These buds typically regress within a few weeks of life, after which the mammary glands remain a rudimentary framework of glandular tissue and stroma through the rest of childhood. During puberty, estrogen is the predominant hormone responsible for an increase in adipose tissue, stromal growth, and ductal growth and branching in the developing breast tissue. Growth hormone and insulin-like growth factor 1 are also important in pubertal breast development. The role of progesterone is to promote the development of the lobules and alveoli—this being particularly important during pregnancy. Prolactin collaborates with progesterone to promote alveolar epithelial development as well as lactogenesis. Oxytocin, which is secreted by the supraoptic, paraventricular, and other accessory nuclei of the hypothalamus, causes contraction of myoepithelial cells and milk let-down in a lactating woman.
In the newborn, the vagina is typically approximately 4 cm in depth. The vagina elongates throughout childhood commensurate with the growth of the child. Hence, unlike the uterus and the breast, which have a pubertal spurt in size, a drastic change in growth velocity of the vagina is not required. By menarche, the vagina reaches a mature depth of 5 to 7.5 cm anteriorly and 10.5 to 11.5 cm posteriorly. The prepubertal length of the vaginal orifice is about 10 mm. In addition to the increase in depth, the introitus increases in length during puberty to approximately 23 mm in an adult woman.
The effect of estrogen during puberty leads to a change in the appearance of the vaginal mucosa. Histologically, the vaginal epithelium consists of 4 layers of squamous cells—basal, parabasal, intermediate, and superficial. In early childhood, the epithelium is 2 to 8 layers thick and contains predominantly monomorphic-appearing basal and parabasal cells. During puberty, there is a transition to a thicker epithelium with several layers of superficial cornified squamous cells. To the naked eye, the mucosa appears pink rather than red, it develops a thick cobblestoned appearance, and the hymen appears thick with fimbriations.
With the onset of cyclic ovarian ...