The smooth 50th percentile male and female growth curves illustrated above are aggregate values from thousands of individuals sampled at ages from birth to age 20. In reality, a single individuals growth curve shows large upward and downward spikes, partly due to actual differences in growth velocity, and partly due to small measurement errors. For example, a typical measurement error of plus or minus 0.5 cm (0.20 in) may completely nullify 0.5  cm of actual growth resulting in either a "negative" 0.5  cm growth (due to overestimation in the previous visit combined with underestimation in the latter), up to a 1.5 cm (0.6 in) growth (the first visit underestimating and the second visit overestimating) in the same elapsed period between measurements. Note there is a discontinuity in the growth curves at age 2, which reflects the difference in recumbent length (with the child on his or her back), used in measuring infants and toddlers, and standing height typically measured from age 2 onwards. Height, like other phenotypic traits, is determined by a combination of genetics and environmental factors. A childs height based on parental heights is subject to regression toward the mean, therefore extremely tall or short parents will likely have correspondingly taller or shorter offspring, but their offspring will also likely be closer to average height than the parents themselves. Genetic potential and several hormones, minus illness, is a basic determinant for height. Other factors include the genetic response to external factors such as diet, exercise, environment, and life circumstances.
Necrotizing sialometaplasia (NS) is a benign, ulcerative lesion, usually located towards the back of the hard palate. It is thought to be caused by ischemic necrosis (death of tissue due to lack of blood supply) of minor salivary glands in response to trauma. Often painless, the condition is self-limiting and should heal in 6–10 weeks. Although entirely benign and requiring no treatment, due to its similar appearance to oral cancer, it is sometimes misdiagnosed as malignant. Therefore, it is considered an important condition, despite its rarity. Signs and symptoms
The condition most commonly is located at the junction of the hard and soft palate. However, the condition may arise anywhere minor salivary glands are located. It has also been occasionally reported to involve the major salivary glands. It may be present only on one side, or both sides. The lesion typically is 1–4 cm in diameter.Initially, the lesion is a tender, erythematous (red) swelling. Later, in the ulcerated stage, the overlying mucosa breaks down to leave a deep, well-circumscribed ulcer which is yellow-gray in color and has a lobular base.There is usually only minor pain, and the condition is often entirely painless. There may be prodromal symptoms similar to flu before the appearance of the lesion. Causes
The exact cause of the condition is unknown. There is most evidence to support vascular infarction and ischemic necrosis of salivary gland lobules as a mechanism for the condition.