The pelvis is, in general, different between the human female and male skeleton. The female skeleton is generally less massive, smoother, and more delicate than the male its rib cage is more rounded and smaller, its lumbar curve greater, and a generally longer and smaller female waist results from the chest being more narrow at the base, and the pelvis generally not as high. Size, weight and body shape Ĭomparison between a male (left) and a female pelvis (right). X-chromosome inactivation is random in the somatic cells of the body as either the maternal or paternal X-chromosome can become inactivated in each cell. In humans, X-chromosome inactivation enables males and females to have an equal expression of the genes on the X-chromosome since females have two X-chromosomes while males have a single X and a Y chromosome. The X-chromosome carries a larger number of genes in comparison to the Y-chromosome. There are other variations of sex chromosomes that lead to a variety of different physical expressions. In some cases, for example, chromosomally female babies that have been exposed to high levels of androgens before birth can develop masculinized genitals by the time they are born. Chromosomes are not the final determinant of sex. There are rare exceptions to this rule in which, for example, XX individuals develop as males or XY individuals develop as females. If an egg fuses with sperm with an X chromosome, the resulting individual is female. If an egg fuses with sperm with a Y chromosome, the resulting individual is male. In sperm, about half the sperm have an X chromosome and half have a Y chromosome. The sex chromosome in a human egg is always an X chromosome since a female only has X sex chromosomes. When an egg and sperm fuse at fertilization, the two sets of chromosomes come together to form a unique diploid individual with 46 chromosomes. Sperm also have only one set of 23 chromosomes and are therefore haploid. Ī human egg contains only one set of chromosomes (23) and is a haploid. In humans and in almost all other mammals, females carry two X chromosomes, designated XX, and males carry one X and one Y, designated XY. There are two kinds of sex chromosomes– X and Y. Of these 23 pairs of chromosomes, 22 are autosomes, and one is a sex chromosome. One set of 23 comes from the mother and one set comes from the father.
The human genome consists of two copies of each of 23 chromosomes (a total of 46). See also: Sexual differentiation in humans The most obvious differences between males and females include all the features related to reproductive role, notably the endocrine (hormonal) systems and their physiological and behavioural effects, including gonadal differentiation, internal and external genital and breast differentiation, and differentiation of muscle mass, height, and hair distribution. For example, most males are taller than most females, but an individual female could be taller than an individual male. This may or may not preclude overlap in distributions. Often only the mean or mean difference between sexes is given.
normal) distribution which can be broadly described by the mean (peak distribution) and standard deviation (indicator of size of range). Most differing characteristics will conform to a bell-curve (i.e. Indirect sex differences are general differences as quantified by empirical data and statistical analysis. These include, most conspicuously, male (vs female) gonads. Therefore, direct sex differences are usually binary in expression (though complex biological processes result in variation within each sex). The complementary result for the X-chromosome follows, either a double or a single X. Through the process of meiosis and fertilization (with rare exceptions), each individual is created with zero or one Y-chromosome. Sexual dimorphism is a term for the phenotypic difference between males and females of the same species. Direct being the direct result of differences prescribed by the Y-chromosome, and indirect being a characteristic influenced indirectly (e.g. These can be of several types, including direct and indirect. Sex differences in human physiology are distinctions of physiological characteristics associated with either male or female humans. Example of male and female anatomy from front and back.
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