Schematic drawing of an avian oviduct. After ovulation, the oocyte is incorporated
into the infundibulum part of the oviduct, and the sperm ascending the oviduct
fertilizes the oocyte within 15 min of ovulation. After fertilization, the surface of
the zygote is enveloped by several egg envelopes (i.e., albumen, shell membrane, egg
shell and cuticle) through the passage of the oviduct, and is oviposited outside of the
body. The position of the utero-vaginal junction is indicated by an arrow. The
approximate time of zygote residency within each part of the oviduct is also
indicated.