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FEMALE DUCTS AND GLANDS

     The females of acoels and most other flatworms lack reproductive ducts, as do lancelets and jawless fish.  In coelomates (including lancelets and jawless fish), ova are released into the coelom.  In many of these species, gametes exit the body through the mouth.    (Hickman, Beklemishev, vol. 2; Weichert, p. 316).  Specific ducts have evolved in separate lineages to transport gametes including the female ducts in ctenophores and nemertine worms and the oviducts of polyclad worms (Fretter, Beklemishev, vol. 2; Hickman).  

 

OVIDUCTS

   In gnathostomes, oviducts form which possess a ciliated infundibulum to “catch” the ova which still (even in higher vertebrates) are released into the coelom (Romer, p. 426).  In cartilaginous fish and amphibians, oviducts form from part of the archinephric duct.  This occurs after the archinephric duct divides and the other portion functions in excretion.  This is considered the primitive condition and these oviducts may be homologous to those of higher vertebrates, which are derived from a tube which develops near the archinephric duct called the Mullerian duct (Weichert, p. 288).   Muellerian ducts persist in the males of some fish and amphibians, especially those which are bisexual (Weichert, p. 289).  In amniotes, males no longer retain Muellerian ducts after embryonic development; this pattern is also observed in some amphibians and lungfish (Romer, p. 427).   In amniotes, ova move in the oviducts through ciliary action and muscle contraction (Weichert, p. 294).  In some rodents, the oviduct forms a closed capsule around the ovary (Weichert, p. 299). 

 

UTERUS

     A great deal of variation in reproductive strategies occurs in ealy chordates.  Some ascidians release their gametes into ocean water, some incubate embryos in an atrial chamber, and a few species are vivparous which even nourish their embryos with secretions of glycogen (Burighel, from Harrison, 1997, p. 280).  In amphibians, uteri form as temporary storage structures for eggs.  In amniotes, portions of oviduct specialize to become the uterus and vagina (Romer, p. 429).   In monotremes, the uterus produces nutrients for developing embryos which are absorbed through the thin shells.  The embryos do develop inside the uterus to some degree (Weichert, p. 299).  In marsupials, two lateral vaginae open into the urogenital sinus, although they may fuse to form a cecum-like “third vagina” (Weichert, p. 299). 

SALAMANDER

SALAMANDER

SALAMANDER

FROG

FROG

OPOSSUM

OPOSSUM

GOAT

GOAT

PIG

UTERUS

FEMALE SYSTEM

CAT

CAT

CAT

MONKEY

MONKEY

MONKEY
MONKEY MONKEY
MONKEY BABOON AND CHIMP

  Most female placental mammals possess a bipartite or bicornuate uterus rather than the primitive uterus duplex (in which the two uteri are completely separate tubes) (Romer, p. 431).  In some bats and salamanders, copulation and fertilization may be separated by months, and the sperm live for a considerable time inside the female reproductive tract (Weichert, p. 315).  Gorillas, chimpanzees, and humans possess transverse rugae in the vagina (Gibbs, 2002).

    In most placental mammals, the cloaca is lost except for ventral portion retained in females as the vestibule (Romer, p. 439).  Primates possess labia minora.  Humans and some apes possess labia majora as well (Weichert, p. 302).   Female amniotes can possess a clitoris (Romer, p. 441

     In higher primates there is an increase in receptivity of female during estrus cycle, and some, such as Aotus trivirgatus, Anguinus oedipus, and Pongo pygmaeus, are receptive throughout the entire cycle.  Most apes have a menstrual cycle of about 30 days (gibbons 30; orangutans 31; gorillas 31; chimps 28-37, humans 28)(Stockey, 2002).    In some species of Old World monkeys, especially those with multiple male mating systems, the sexual skin of females swells considerably in estrus (Dixson, 1987).

OPOSSUM

OPOSSUM

MONKEY

MONKEY

MONKEY
 

HUMAN MODEL

HUMAN MODEL

HUMAN MODEL