A 200-lb man decides to add to his exercise routine by walking up three flights of stairs (45 ft) 20 times per day. He figures that the work required to increase his potential energy in this way will permit him to eat an extra order of French fries, at 245 Cal, without adding to his weight. Is he correct in this assumption?
Week 1: Embryological Differentiation General Understandings - Gender is not binary: not all people fall into completely female or male identities - Sex is not binary: Not all people fall into completely female or completely male biological categories 1. Embryological Sex Differentiation Biological Sex - sex is not determined by any single biological factor - biological sex differentiation occurs in stages as different parts of the embryo develop - each stage is independent of the other stages Bipotentiuality of Sex Differentiation - undifferentiated structures necessary in either the biologically female or the biologically male direction are typically available at all stages of development - the biological environment at the moment that a stages of differntiraioon os taking pace determines the path taken at the stage - the same path does not have to be taken at each stage Stage 1 - Chromosomal Sex - humans have 46 chromosomes (23 pairs) - 44 chromosomes are autosomes (not directly related to sex) - 2 chromosomes are sex chromosomes - male (XY) - female (XX) - Bipotentiuality - an egg (ovum has an X chromosomes) - sperm has either an X or a Y - chromosomal sex is determined by which sperm fertilizes the egg - Y bearing seem move faster - X move slower (bigger and live longer) - Many other sex chromosome complements naturally occur - 1 in 400 identiﬁed as at birth have a sex-chromosome complement other than XY - Some individuals only have one sex chromosomes, but that sex chromosome must be an X (XO sex chromosome complement) - The YO combination cannot survive - the X chromosome has more than 1000 genes while the Y only has 70 genes (not enough genetic information) - Some individuals have more than 2 sex chromosomes - the greater the number of sex chromosomes: - the less likely a combination will occur - the more likely that the individual also will have non-sex related chromosomal differences Turner Syndrome - individual with only 1 sex chromosome (XO) 1 in 3500 female birth - due to fertilization of the ovum by a sperm that has no sex chromosome - typically identiﬁed as female and raised as a girl - does not develop functional ovaries - infertile - at puberty she does not develop female secondary sex characteristics (no estrogen) - typically receives estrogen treatment to stimulate female-typical development Stage 2 - Gonadal Sex - Gonads are glands that produce the reproductive or germ cells (ova and sperm) - Typical male (2 testes) - typical female (2 ovaries) - raw material: the undifferentiated gonads - undifferentiated gonads have 2 parts (the cortex – outer rind – and the medulla – inner core) Primordial Germ Cells - form in yolk sac - must migrate to the undifferentiated gonads before sex differentiation of the ovaries can start - testes can develop without migration - the PGCs are the earliest form of all the ova a female will ever possess Development of Male Gonads - Testes Requires: - the presence of a functional Y - a functional Y has an SRY gene that stimulates an autosome (a non-sex chromosome) to produce H-Y antigen - H-Y antigen - H-Y antigen stimulates the medulla Development of Female Gonads - Ovaries Requires: - the absence of a functional Y (no SRY-gene and no H-Y antigen) - the presence of at least 2 functional X chromosomes - under these conditions: cortex develops into an ovary and medulla shrinks Development of Gonads - The presence of any functional Y chromosome/H-Y antigen results in development of tests regardless of how many Xs are present - With only 1 X chromosome the gnonads remain in the undifferentiated state - gonadal streak (Turner syndrome Stage 3 - Internal Genitalia - internal reproductive plumbing - male: seminal vesicles, epidymus, ejaculatory ducts and tubes - female: uterus, oviducts (Fallopian tubes) and vagina - raw materials = Wolfﬁan ducts and Mullein Ducts - both types of ducts are found in all developing individuals regardless of paths taken in stages 1 and 2 Development of Male Internal Genitalia - requires the production of and ability to respond to: - androgens - muller inhibiting factor - inductor substance - All 3 substances are produced by testes - stimulate the development of the Wolfﬁan ducts into male internal genitalia and the regression of the Mullein ducts Development of Female Internal Genitalia - Requires the absence of - 1. androgens - 2. mullein inhibiting factor - 3. inductor substance - in the absence of these, the mullein ducts develop into female internal genitalia and the wolfﬁan ducts regress Stage 4 - External Genitalia - Undifferentiated raw materials - genital tubercle - labio scrotal swelling - uro genital fold - Found in all developing individuals regardless of sex chromosomes, gonads, or internal genitalia Male External Genitalia - to develop in the male typical direction, the fetus msut - 1. have a source of androgens (testes) - 2. have receptors that recognize the androgens - If androgen are present - genital tubercle -> penis - labio scrotal swelling -> scrotal sac or scrotum - urogenital fold -> urethra Female External Genitalia - If androgens are not reduced: - genital tubercle -> clitoris - labio scrotal swelling -> labia majors - urogenital fold -> labia minora Androgen Insensitivity Syndrome (AIS) - lacks receptors that respond to andrgens - XY sex chromosomes complement - normal testes - internal genitalia ambiguous - external genitalia female - typically raised as female and have female gender identity Congenital Adrenal Hyperplasia (CAH) - produce excess endogen due to malfunction of adrenal gland - effects vary with when the increased androgen starts and how high the levels are - may result in ambiguous internal genitalia and male like external genitalia in an XX individual with ovaries