Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Pregnancy, Development, and Lactation

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Fertilization Copulation: (act of breeding) intromission, thrusting, and ejaculation Copulation: (act of breeding) intromission, thrusting, and ejaculation Copulation triggers oxytocin release from posterior pituitary gland of the female Copulation triggers oxytocin release from posterior pituitary gland of the female Oxytocin causes contraction of smooth muscle of the female reproductive organs Oxytocin causes contraction of smooth muscle of the female reproductive organs Semen is usually deposited in the upper portion of the vagina Semen is usually deposited in the upper portion of the vagina Spermatozoa transported by swimming, by contractions of uterus and oviducts, and by action of cilia in oviducts Spermatozoa transported by swimming, by contractions of uterus and oviducts, and by action of cilia in oviducts

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Fertilization Capacitation: series of changes spermatozoa undergo in the female reproductive tract to increase their chance of fertilization Capacitation: series of changes spermatozoa undergo in the female reproductive tract to increase their chance of fertilization 1. Change in ion movements (influx of Ca ++ ) through the cell membra 2. Increase in cells' metabolic rate 3. Increase in rate of sugar usage for energy 4. Release of digestive enzymes from acrosome Help spermatozoa penetrate layers Help spermatozoa penetrate layers around ovum to accomplish fertilization

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc.Fertilization Large number of spermatozoa locate and swarm around ovum in oviduct Large number of spermatozoa locate and swarm around ovum in oviduct Some begin tunneling through layers surrounding ovum Some begin tunneling through layers surrounding ovum Aided by digestive enzymes in acrosome Aided by digestive enzymes in acrosome Once a single spermatozoon penetrates cell membrane of ovum, the membrane blocks other sperm from entering Once a single spermatozoon penetrates cell membrane of ovum, the membrane blocks other sperm from entering

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc.Zygote Zygote — a newly fertilized ovum. Male and female pronuclei join together Zygote — a newly fertilized ovum. Male and female pronuclei join together Male pronucleus: nucleus of the fertilizing spermatozoon Male pronucleus: nucleus of the fertilizing spermatozoon Female pronucleus: nucleus of the fertilized ovum Female pronucleus: nucleus of the fertilized ovum Each pronucleus contains the haploid chromosome number Each pronucleus contains the haploid chromosome number Restores the diploid chromosome number Restores the diploid chromosome number

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Cleavage: Zygote to Blastocyst Rapid mitosis of zygote (~1 division/day) Rapid mitosis of zygote (~1 division/day) Overall size of zygote does not change Overall size of zygote does not change Morula: solid mass of cells; stage after zygote Morula: solid mass of cells; stage after zygote Blastocyst: hollow ball of cells with a mass of cells on one side (future embryo); stage after morula; will implant in uterus Blastocyst: hollow ball of cells with a mass of cells on one side (future embryo); stage after morula; will implant in uterus

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Implantation While cleavage is taking place, the zygote is slowly moving from the oviduct to the uterus While cleavage is taking place, the zygote is slowly moving from the oviduct to the uterus propelled by muscular contractions and cilia propelled by muscular contractions and cilia Enzymes produced by the blastocyst dissolve away a small pit in the endometrium, where the blastocyst will attach Enzymes produced by the blastocyst dissolve away a small pit in the endometrium, where the blastocyst will attach In multiparous species, the multiple blastocysts randomly space along the horns and body of the uterus In multiparous species, the multiple blastocysts randomly space along the horns and body of the uterus Placenta begins to form as soon as the blastocyst implants in the uterus Placenta begins to form as soon as the blastocyst implants in the uterus

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Placenta Multilayered, fluid-filled, membranous sac that surrounds the fetus and links it to the blood supply of the uterus Multilayered, fluid-filled, membranous sac that surrounds the fetus and links it to the blood supply of the uterus Outermost layer of placenta attaches to uterine lining Outermost layer of placenta attaches to uterine lining Fetal and maternal blood vessels are in close proximity to each other in this area Fetal and maternal blood vessels are in close proximity to each other in this area Site of exchange of blood, nutrients, and wastes Site of exchange of blood, nutrients, and wastes No direct contact between fetal and maternal blood occurs No direct contact between fetal and maternal blood occurs Connected to the fetus via the umbilical cord Connected to the fetus via the umbilical cord Umbilical vein: carries oxygen-rich blood to fetus Umbilical vein: carries oxygen-rich blood to fetus Umbilical arteries: carry deoxygenated blood back to the placenta Umbilical arteries: carry deoxygenated blood back to the placenta

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Placenta Amnion: membranous layer immediately surrounding the fetus Amnion: membranous layer immediately surrounding the fetus Forms the amniotic sac Forms the amniotic sac Fetus floats in amniotic fluid inside the amniotic sac Fetus floats in amniotic fluid inside the amniotic sac Allantois: layer surrounding amniotic sac; forms the allantoic sac Allantois: layer surrounding amniotic sac; forms the allantoic sac Outside of allantoic sac is covered by the chorion Outside of allantoic sac is covered by the chorion Chorion: attaches to lining of uterus Chorion: attaches to lining of uterus Chorion is linked to fetus by the umbilical cord Chorion is linked to fetus by the umbilical cord Urachus: tube that connects the bladder to the allantoic sac Urachus: tube that connects the bladder to the allantoic sac

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Placental Attachments 1. Diffuse: spread over the whole surface of the placenta and uterine lining (pigs, horses) 1. Cotyledonary: many small, separate attachment sites (placentomes) (ruminants) Placentome: cotyledon on placental surface joins with caruncle in the uterine lining Placentome: cotyledon on placental surface joins with caruncle in the uterine lining 2. Zonary: belt-shaped attachment that encircles the placenta (dogs,cats) 3. Discoid: placenta and uterus attached at a single disk-shaped area (humans, primates, rabbits, rodents)

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Placental Attachments

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Gestation period: time from fertilization of ovum to delivery of newborn Gestation period: time from fertilization of ovum to delivery of newborn Time varies among species Time varies among species Divided into three segments/trimesters Divided into three segments/trimesters First trimester: embryonic period First trimester: embryonic period Placenta develops Placenta develops Second trimester: fetal period Second trimester: fetal period Body tissues, organs, and systems develop Body tissues, organs, and systems develop Third trimester: fetal growth period Third trimester: fetal growth period SpeciesGestation Cat2 mo Cat2 mo Dog2 mo Dog2 mo Cow9 mo Cow9 mo Elephant21 mo Elephant21 mo Ferret6 w Ferret6 w Goat, Sheep5 mo Goat, Sheep5 mo Hamster3 w Hamster3 w Horse11 mo Horse11 mo Human 9 mo Human 9 mo Pig3 mo, 3 w, 3 d Pig3 mo, 3 w, 3 d Rabbit1 mo Rabbit1 moGestationPeriods

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc.Parturition Birth process Birth process Factors influencing parturition Factors influencing parturition Size and weight of uterus and fetus Size and weight of uterus and fetus Hormonal changes Hormonal changes ↓Progesterone, ↑ fetal Cortisone causes mother’s estrogen level to rise and Prostaglandin F 2α to be released from the uterine wall ↓Progesterone, ↑ fetal Cortisone causes mother’s estrogen level to rise and Prostaglandin F 2α to be released from the uterine wall The estrogen and prostaglandin increase the uterus’ sensitivity to oxytocin, which is now being released by the posterior pituitary The estrogen and prostaglandin increase the uterus’ sensitivity to oxytocin, which is now being released by the posterior pituitary Myometrium in uterus begins to contract due to the oxytocin, beginning labor Myometrium in uterus begins to contract due to the oxytocin, beginning labor Fetal changes at birth: Fetal changes at birth: Lungs expand and begin to function Lungs expand and begin to function foramen ovale and ductus arteriosus close foramen ovale and ductus arteriosus close

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Stages of Labor First stage - uterine contractions First stage - uterine contractions Myometrium contracts and presses fetus down against cervix Myometrium contracts and presses fetus down against cervix Sustained contractions cause cervix to gradually dilate Sustained contractions cause cervix to gradually dilate Second stage - delivery of newborn Second stage - delivery of newborn Results from combination of strong uterine and abdominal muscle contractions Results from combination of strong uterine and abdominal muscle contractions Rupture of amniotic and allantoic sacs of placenta usually precedes actual delivery of newborn Rupture of amniotic and allantoic sacs of placenta usually precedes actual delivery of newborn Third stage - delivery of the placenta Third stage - delivery of the placenta Placenta separates from wall of uterus and is expelled by weaker uterine contractions Placenta separates from wall of uterus and is expelled by weaker uterine contractions

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Involution of the Uterus Uterus gradually returns to nonpregnant size Uterus gradually returns to nonpregnant size Endometrium sloughs into lumen of uterus at sites of placental attachment Endometrium sloughs into lumen of uterus at sites of placental attachment Myometrium continues mild contractions to move remaining uterine contents out through birth canal Myometrium continues mild contractions to move remaining uterine contents out through birth canal May take from a few weeks to a month or more for involution to be complete May take from a few weeks to a month or more for involution to be complete

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Mammary Glands Specialized skin glands that produce colostrum and milk Specialized skin glands that produce colostrum and milk Present in both male and female animals Present in both male and female animals Males do not secrete proper blend of hormones to make them work Males do not secrete proper blend of hormones to make them work Number and appearance of mammary glands differs among species Number and appearance of mammary glands differs among species

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Udder of Cow Four mammary glands (quarters) Four mammary glands (quarters) Quarters are completely separate units from each other Quarters are completely separate units from each other Each quarter has its own milk-secreting system and ducts leading down to separate teats Each quarter has its own milk-secreting system and ducts leading down to separate teats

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Mammary alveoli: saclike arrangement of cells that secrete milk into alveolar duct Mammary alveoli: saclike arrangement of cells that secrete milk into alveolar duct Arranged like clusters of grapes around alveolar ducts Arranged like clusters of grapes around alveolar ducts Smaller alveolar ducts join to form larger ducts Smaller alveolar ducts join to form larger ducts Largest ducts empty into gland sinus Largest ducts empty into gland sinus located just dorsal to teat Continuous with teat sinus inside teat Continuous with teat sinus inside teat Milk accumulates in sinuses Milk accumulates in sinuses Alveoli and Duct System

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Milk Letdown Milk accumulates high up in mammary gland in alveoli and small ducts Milk accumulates high up in mammary gland in alveoli and small ducts Physical stimulation of nipple or teat sends sensory impulses that cause release of oxytocin from post. pituitary Physical stimulation of nipple or teat sends sensory impulses that cause release of oxytocin from post. pituitary Oxytocin causes contraction of myoepithelial cells around alveoli and small ducts Oxytocin causes contraction of myoepithelial cells around alveoli and small ducts Moves milk down into large ducts and sinuses Moves milk down into large ducts and sinuses

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Mammary Gland Development Mammary glands develop in response to hormones produced at puberty Mammary glands develop in response to hormones produced at puberty Prolactin and GH directly encourage mammary gland development Prolactin and GH directly encourage mammary gland development Estrogen and progesterone produced by the ovaries during the estrous cycle encourage mammary alveoli and duct systems to develop. Estrogen and progesterone produced by the ovaries during the estrous cycle encourage mammary alveoli and duct systems to develop. TSH and ACTH can also promote mammary development TSH and ACTH can also promote mammary development

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. Colostrum “ First milk ” “ First milk ” Pre-milk secretion Pre-milk secretion Imparts passive immunity - transfer of preformed antibodies from dam to newborn Imparts passive immunity - transfer of preformed antibodies from dam to newborn Supplies important nutrients to newborn Supplies important nutrients to newborn proteins, lipids, amino acids, and vitamins proteins, lipids, amino acids, and vitamins Laxative effect helps clear meconium from newborn's intestinal tract Laxative effect helps clear meconium from newborn's intestinal tract

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc.Lactation Physical stimulation of teat or nipple and regular removal of milk from gland stimulates ant. pituitary to continue production of hormones that keep lactation going Physical stimulation of teat or nipple and regular removal of milk from gland stimulates ant. pituitary to continue production of hormones that keep lactation going prolactin, oxytocin prolactin, oxytocin Lack of hormonal stimulation combined with increased pressure in the mammary gland gradually causes lactation to cease Lack of hormonal stimulation combined with increased pressure in the mammary gland gradually causes lactation to cease