Title: Sexual differentiation in humans
Content:  Sexual differentiation in humans is the process of development of sex differences in humans. It is defined as the development of phenotypic structures consequent to the action of hormones produced following gonadal determination. Sexual differentiation includes development of different genitalia and the internal genital tracts and body hair plays a role in sex identification. The development of sexual differences begins with the XY sex-determination system that is present in humans, and complex mechanisms are responsible for the development of the phenotypic differences between male and female humans from an undifferentiated zygote. Females typically have two X chromosomes, and males typically have a Y chromosome and an X chromosome. At an early stage in embryonic development, both sexes possess equivalent internal structures. These are the mesonephric ducts and paramesonephric ducts. The presence of the SRY gene on the Y chromosome causes the development of the testes in males, and the subsequent release of hormones which cause the paramesonephric ducts to regress. In females, the mesonephric ducts regress. Divergent sexual development, known as intersex, can be a result of genetic and hormonal factors.
Title: Sex differences in human physiology
Content:  differences are general differences as quantified by empirical data and statistical analysis. Most differing characteristics will conform to a bell-curve (i.e. normal) distribution which can be broadly described by the mean (peak distribution) and standard deviation (indicator of size of range). Often only the mean or mean difference between sexes is given. This may or may not preclude overlap in distributions. For example, most males are taller than most females, but an individual female could be taller than an individual male. 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.
Title: Sexual differentiation
Content:  Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. Sex determination is often distinct from sex differentiation, sex determination is the designation for the development stage towards either male or female while sex differentiation is the pathway towards the development of the phenotype. Appearance of Sertoli cells in males and granulosa cells in females can be thought of as the starting point for testicular or ovarian differentiation in many species. As male and female individuals develop from embryos into mature adults, sex differences at many levels develop, such as genes, chromosomes, gonads, hormones, anatomy, and psyche. Beginning with determination of sex by genetic and/or environmental factors, humans and other organisms proceed down different pathways of differentiation as they grow and develop. These processes are not fixed, and can change over one organism's lifetime or over many generations evolutionarily.
Title: Sexual differentiation in humans
Content:  By 7 weeks, a fetus has a genital tubercle, urogenital groove and sinus, and labioscrotal folds. In females, without excess androgens, these become the clitoris, urethra and vagina, and labia. Differentiation between the sexes of the sex organs occurs throughout embryological, fetal and later life. This includes both internal and external genital differentiation. In both males and females, the sex organs consist of three structures: the gonads, the internal genitalia, and the external genitalia. In males, the gonads are the testes and in females they are the ovaries. These are the organs that produce gametes (egg and sperm), the reproductive cells that will eventually meet 
Title: Sex differences in humans
Content:  empirical data and statistical analysis. Most differing characteristics will conform to a bell-curve (i.e., normal) distribution which can be broadly described by the mean (peak distribution) and standard deviation (indicator of size of range). Often only the mean or mean difference between sexes is given. This may or may not preclude overlap in distributions. The most obvious differences between males and females include all the features related to reproductive roles, notably the endocrine (hormonal) systems and their physiological and behavioral effects, including gonadal differentiation, internal and external genital and breast differentiation, and differentiation of muscle mass, height, and hair distribution. There are also differences in the structure of specific areas of the brain. For example, on average, the SDN (INAH3 in humans) has been repeatedly found to be considerably larger in males than in females.
Title: Man
Content:   A man is an adult male human. Prior to adulthood, a male human is referred to as a boy (a male child or adolescent). Like most other male mammals, a man's genome usually inherits an X chromosome from the mother and a Y chromosome from the father. Sex differentiation of the male fetus is governed by the SRY gene on the Y chromosome. During puberty, hormones which stimulate androgen production result in the development of secondary sexual characteristics, thus exhibiting greater differences between the sexes. These include greater muscle mass, the growth of facial hair and a lower body fat composition. Male anatomy is distinguished from female anatomy by the male reproductive system, which includes the penis, testicles, sperm duct, prostate gland and the epididymis, as well as secondary sex characteristics.
Title: Sexual differentiation in humans
Content:  The internal genitalia consist of two accessory ducts: mesonephric ducts (male) and paramesonephric ducts (female). The mesonephric system is the precursor to the male genitalia and the paramesonephric to the female reproductive system. As development proceeds, one of the pairs of ducts develops while the other regresses. This depends on the presence or absence of the sex determining region of the Y chromosome, also known as the SRY gene. In the presence of a functional SRY gene, the bipotential gonads develop into testes. Gonads are histologically distinguishable by 6–8 weeks of gestation. Subsequent development of one set and degeneration of the other depends 
Title: Sexual differentiation
Content:  identification. The development of sexual differences begins with the XY sex-determination system that is present in humans, and complex mechanisms are responsible for the development of the phenotypic differences between male and female humans from an undifferentiated zygote. Atypical sexual development, and ambiguous genitalia, can be a result of genetic and hormonal factors. The differentiation of other parts of the body than the sex organ creates the secondary sex characteristics. Sexual dimorphism of skeletal structure develops during childhood, and becomes more pronounced at adolescence. Sexual orientation has been demonstrated to correlate with skeletal characters that become dimorphic during early childhood (such as arm length to stature ratio) but not with characters that become dimorphic during puberty—such as shoulder width.
Title: Sexual differentiation in humans
Content:  the gonads, that is the testis or ovaries, depending on which genes are expressed. Phenotypic sex refers to the structures of the external and internal genitalia. 6 weeks elapse after fertilization before the first signs of sex differentiation can be observed in human embyros. The embryo and subsequent early fetus appear to be sexually indifferent, looking neither like a male or a female. Over the next several weeks, hormones are produced that cause undifferentiated tissue to transform into either male or female reproductive organs. This process is called sexual differentiation. The precursor of the internal female sex organs is called the Müllerian system.
Title: Sex
Content:  the evolution of physical differences between the sexes. The terms male and female typically do not apply in sexually undifferentiated species in which the individuals are isomorphic (look the same) and the gametes are isogamous (indistinguishable in size and shape), such as the green alga Ulva lactuca. If there are instead functional differences between gametes, such as in fungi, they may be referred to as mating types. Sex is genetically determined in most mammals by the XY sex-determination system, where male mammals carry an X and a Y chromosome (XY), whereas female mammals carry two X chromosomes (XX). Other chromosomal sex-determination systems in animals include the ZW system in birds, and the X0 system in insects. Various environmental systems include temperature-dependent sex determination in reptiles and crustaceans.

Question: which body system differentiates a male from a female?
Answer: the external genitalia.
the sex hormones.
reproductive.
the type of gonads.