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
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- Spring '11
- Clark
- Nursing, progesterone, Testicle, sex hormones
-
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