Pregnancy Development and Lactation act of breeding intromission
Pregnancy, Development, and Lactation
________: (act of breeding) intromission, thrusting, and ejaculation Fertilization Copulation triggers _____ release from posterior pituitary gland of the female Oxytocin causes contraction of smooth muscle of the female reproductive organs Semen is usually deposited in the upper portion of the _____ Spermatozoa transported by swimming, by contractions of uterus and oviducts, and by action of cilia in oviducts
Series of changes spermatozoa undergo in the female reproductive tract to increase their chance of fertilization 1. 2. 3. 4. Change in ion movements (influx of Ca++) through the cell membrane Increase in cells' metabolic rate Increase in rate of sugar usage for energy Release of digestive enzymes from _______ Help spermatozoa penetrate layers around ovum to accomplish fertilization Capacitation
Fertilization Large number of spermatozoa locate and swarm around ovum in _______ Some begin tunneling through layers surrounding ovum Aided by digestive enzymes in acrosome Once a single spermatozoon penetrates cell membrane of ovum, the membrane blocks other sperm from entering
n ______— a newly fertilized ovum. Male and female ______ join together n n n Male pronucleus: nucleus of the fertilizing spermatozoon Female pronucleus: nucleus of the ovum Each pronucleus contains the haploid chromosome number n Fertilization restores the ______ chromosome number Zygote
Rapid division of zygote (~1 division/day) Overall size of zygote does not change _____: solid mass of cells; stage after zygote _____: hollow ball of cells with a mass of cells on one side (future embryo); stage after morula; will implant in uterus Cleavage: Zygote to Blastocyst
While cleavage is taking place, the zygote is slowly moving from the oviduct to the ______ propelled by muscular contractions and cilia Enzymes produced by the blastocyst dissolve away a small pit in the endometrium, where the blastocyst will attach In _______ species, the multiple blastocysts randomly space along the horns and body of the uterus ______ begins to form as soon as the blastocyst implants in the uterus Implantation
n Multilayered, fluid-filled, membranous sac that surrounds the fetus and links it to the blood supply of the uterus n Outermost layer of placenta attaches to _________ n Fetal and maternal blood vessels are in close proximity to each other in this area n Site of exchange of blood, nutrients, and wastes n No direct contact between fetal and maternal blood occurs n Connected to the fetus via the ______ Umbilical ____: carries oxygen-rich blood to fetus Umbilical ____: carry deoxygenated blood back to the placenta Placenta
• ____: membranous layer immediately surrounding the fetus Forms the amniotic sac Fetus floats in amniotic fluid inside the amniotic sac _____: layer surrounding amniotic sac; forms the allantoic sac Outside of allantoic sac is covered by the chorion _____: attaches to lining of uterus Chorion is linked to fetus by the umbilical cord _____: tube that connects the bladder to the allantoic sac Placenta
Placental Attachments • ______: spread over the whole surface of the placenta and uterine lining (pigs, horses) • ______: many small, separate attachment sites (ruminants) • ______: cotyledon on placental surface joins with caruncle in the uterine lining • ______: belt-shaped attachment that encircles the placenta (dogs, cats) • _____: placenta and uterus attached at a single disk-shaped area (humans, primates, rabbits, rodents)
Placental Attachments
_____ period: time from fertilization of ovum to delivery of newborn Time varies among species Divided into three segments/trimesters First trimester: ______ period Placenta develops Second trimester: _____ period Body tissues, organs, and systems develop Third trimester: fetal _____ period Species n Cat n Dog n Cow n Elephant n Ferret n Goat, Sheep n Hamster n Horse n Human n Pig n Rabbit Gestation 2 mo 9 mo 21 mo 6 w 5 mo 3 w 11 mo 9 mo 3 mo, 3 w, 3 d 1 mo Gestation Periods
_____ process Factors influencing parturition Parturition Size and weight of uterus and fetus Hormonal changes ↓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 Myometrium in uterus begins to contract due to the oxytocin, beginning labor Fetal changes at birth: _____ expand begin to function Foramen ovale and ductus arteriosus ______
q. First stage - uterine contractions n Myometrium contracts and presses fetus down against cervix n Sustained contractions cause cervix to gradually dilate q. Second stage - delivery of newborn n Results from combination of strong uterine and abdominal muscle contractions n Rupture of amniotic and allantoic sacs of placenta may precede actual delivery of newborn q. Third stage - delivery of the placenta n Placenta separates from wall of uterus and is expelled by weaker uterine contractions Stages of Labor http: //www. clemson. edu/cafls/departments/animal_vet_science/behavior_database/equine. html
Involution of the Uterus gradually returns to nonpregnant size Endometrium sloughs into lumen of uterus at sites of placental attachment 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
Mammary Glands Specialized skin glands that produce _____ and _______ Present in both male and female animals Males do not secrete proper amount of hormones to make them work Number and appearance of mammary glands differs among species
Udder of Cow Four mammary glands (_____) Quarters are completely separate units from each other Each quarter has its own milk-secreting system and ducts leading down to separate teats
n n Mammary _____: saclike arrangement of cells that secrete milk into alveolar duct Arranged like clusters of grapes around alveolar ducts Smaller alveolar _______ join to form larger ducts Largest ducts empty into _______ sinus located just dorsal to teat n Continuous with ______ sinus inside teat n Milk accumulates in sinuses Alveoli and Duct System
Milk Letdown 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 ______ causes contraction of ______ cells around alveoli and small ducts Moves milk down into large ducts and sinuses
Mammary Gland Development Mammary glands develop in response to hormones produced at ______ 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. TSH and ACTH can also promote mammary development
“First milk” Pre-milk secretion Imparts __________- transfer of preformed _____ from dam to newborn Supplies important nutrients to newborn proteins, lipids, amino acids, and vitamins _____ effect helps clear meconium from newborn's intestinal tract Colostrum
Lactation Physical stimulation of teat or nipple and regular removal of milk from gland stimulates pituitary to continue release of hormones that keep lactation going prolactin, oxytocin Lack of hormonal/physical stimulation combined with increased pressure in the mammary gland gradually causes lactation to cease
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