Chapter 31 PATHO - C hapter 31 :ovum :spermatozoon(spermcell

Chapter 31  23 chromosome female gamete: ovum  23 chromosome male gamete: spermatozoon (sperm cell)  These unite to form a 46 chromosome zygote that is capable of developing into a new individual  Male produces sperm and delivers them to female reproductive tract  ® Female reproductive produces ovum and if fertilized** (by spermatozoon) it can nurture and protect it and propel it at birth **once fertilized, called the embryo and developing fetus  These functions determined by anatomic structures, and complex hormonal, neurologic and psychogenic factors DEVELOPMENT OF THE REPRODUCTIVE SYSTEM Structure and function of both male and female depends on steroid hormones called sex hormones  Hormonal effects begin during embryonic development and continue in varying degrees throughout life  Until the 8th week of gestation:  Male and female embryos are homologous (the same)  Have one pair of primary sex organs: gonads  Have two pairs of ducts: mesonephric ducts and paramesonephric ducts  Both pair of ducts empty into urogenital sinus  At about 7 to 8 weeks of gestation:  MALE ▫ Gonads of male begin to produce testosterone ⋅ Causes gonads to develop into two testes which produce sperm after puberty ▫ Paramesonephric ducts degenerate ▫ Mesonephric ducts develop into the vans deferens : the two tubes that carry sperm from testes to urethra  FEMALE ▫ Presence of estrogen and absence of testosterone causes the two female gonads to develop into ovaries ⋅ Ovaries will produce ova ▫ Mesonephric ducts deteriorate ▫ Lower ends of paramesonephric ducts develop into the fallopian(uterine) tubes  These ducts will carry ova from ovaries to uterus during reproductive years  External structures also develop ▫ Both male and female embryos develop genital tubercle  Testosterone necessary for genital tubercle in male, if not female geneitalia develop  At nine months of gestation  Internal and external genital structures all present and gonads (testes) have descended into scrotum NEGATIVE FEEDBACK MECHANISM:  Gonadostat  Aka gonadotropin releasing hormone pulse generator  Responds to high placental estrogens by releasing low levels of gonadotropin –releasing hormone (GnRH)  After birth, sex hormones drop; negative feedback action on sex hormones on hypothalamus and pituitary are removed, and gonadotropin is released  GnRH secretion is restrained by low levels of sex hormones PUBERTY:  Between ages of 8 and 12 years gonads begin to produce more of the sex hormones, this triggers puberty 