Homework Clinic
Science Clinic => Health Science => Topic started by: mwit1967 on Apr 11, 2021
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Create a flow chart illustrating the development of bipotential reproductive structures in an XY individual and an XX individual, indicating the stimuli for development or regression of the structures. Add to this chart the changes that occur at puberty and their stimuli. Finally, show the points on the chart at which abnormalities associated with the following conditions occur:
A. testicular feminization or androgen insensitivity (XY genotype, permanent female external morphology with internal testes and androgen production but faulty androgen receptors);
B. male pseudohermaphrodites (XY genotype and external female morphology with internal testes, and masculinization occurring at puberty);
C. congenital adrenal hyperplasia (XX genotype with normal female internal organs, masculinized external organs observed at birth);
D. sexual development is similar in nonhuman mammals, but there are some interesting pathologies not seen in humans. A freemartin occurs in cattle twins, with one male and one female. The male is normal but the XX female is sterile, born masculinized, and has testicular tissue. Explain the most likely cause of this masculinized phenotype, and indicate on your chart the point or points at which something abnormal occurred.
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Chart of normal male development should resemble Figures 26.2 and 26.3 in the chapter, with a similar chart in parallel for female development. Appearance of secondary sexual characteristics in both biological sexes results from increases in gonadal steroids and adrenal androgens.
A-B. Both testicular feminization and male pseudohermaphroditism begin with lack of response of target tissues to androgens produced in fetal development; testicular feminization allows development of female secondary sexual characteristics, whereas pseudohermaphroditism allows masculinization at puberty.
C. Congenital adrenal hyperplasia allows normal development of female internal structures, but masculinizes external organs before birth as an effect of adrenal androgens. If untreated, puberty-related changes would also be masculine.
D. The freemartin cow must receive anti-Müllerian hormone through shared placental circulation; therefore testicular tissue develops and androgens are secreted to produce further masculinization, in the fetus and at puberty.