Lecture 19 - Puberty, Estrous, Pregnancy

When an animal reaches a level of physiological maturity that permits conception

• age (genetics and environment) - weight (genetics)

Females - first estrous and ovulation • LH, FSH, estrogen at high enough concentrations • follicular growth, oocyte maturation, ovulation Males - production of sperm capable of fertilizing an oocyte

Estrus Metestrus Diestrus Proestrus

Sexual receptivity High estrogen from the preovulatory follicle Behavioral estrus

Sexual receptivity Urinating, winking vulva, swollen vulva, interest in males, mounting of other females

Formation of the CL and increased progesterone production

Progesterone predominate from CL If pregnant - CL remains and functions until progesterone Not pregnant - PGF2a from the endometrium indices literal regression

Interval between regression of CL and next estrus LH increasing, growth of preovulatory follicles, increasing estrogen

Polyestrus Seasonally polyestrus Monestrus Induced or “reflex” ovulator

Cycle continuously Cows, pig, mice

Ovulate during certain times of the year • short day breeders (fall/winter) sheep, goats, deer • long day breeder (spring) horses

Cycle once yearly Dog

Copulation stimulates ovulation LH released with mounting and intromission Cat, llama, rabbit

Live birth, fetus develops in the uterus

Egg-laying

Pregnancy Begins with fertilization and ends in parturition

A 16 cell embryo

Outer trophoblast layer, inner cell mass, and fluid filled cavity

Signal to prevent CL regression Progesterone from the CL maintains pregnancy

Attachment of the placenta to the uterus which allows for exchanges between the maternal and fetal blood supplies