chapter 7 repro notes and beginning of chapter 8
chapter 7 repro notes and beginning of chapter 8 AGSC 352
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This 6 page Class Notes was uploaded by nicole l brown on Saturday October 3, 2015. The Class Notes belongs to AGSC 352 at Truman State University taught by Dr. Kelly Walter in Summer 2015. Since its upload, it has received 16 views. For similar materials see Reproduction Physiology in Agricultural & Resource Econ at Truman State University.
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Repro Dr Walter Chapter 8 follicular phase 0 Follicular phase this contains the proestrus and estrus and it is the kick starter to the follicular phase is luteolysis This causes CL to become nonfunctional and it reduces progesterone by using the negative feedback on the hypothalamus The GnRH is then released at higher amplitude and frequency the FSH and LH are then released at higher concentration follicular development estradiol secretion 0 There are four event that take place in the follicular phase 0 Gonadotropin release for AF 0 It is the major secretion of follicular phase from the hypothalamus AP ovary o The hypothalamus then regulates cycle by production of the GnRH The tonic center is in charge of the basal secretions and that happens in small pulses the varying of the bursts and the how long it lasts and the quantity is called episodic profile The surge center is where the preovulatory release of GnRH to start the surge LH the positive stimulus for the surge this the is the threshold concentration of estradiol and this happens in the absence of progesterone o Follicular preparation for ovulation 0 Sexual receptivity or estrus 0 Ovulation 0 GnRH secretion it is before ovulation and this then the surge of GnRH is controlled by the high amount of estradiol and the low progesterone high estradiol is positive feedback while high progesterone is negative feedback The threshold for estradiol is reached due to production from the follicle The rest of the LH will surge is 10 times greater than tonic pulse 0 Follicular dynamics 0 Process of follicular growth and degeneration this occurs continuously throughout the cycle The antral follicles then develop is response to FSH and LH in the pig a small follicle is less than 3mm medium is btw 46mm large is greater than 6mm in the mare a small follicular is less than 10mm a medium is btw 1020 mm and a large one is bigger than 20mm 0 Antral follicles involves 4 processes 0 Recruitment emergence it is a group of small antral follicles that begins to grow and they secrete estradiol Most of the follicles in this stage well undergo atresia and the then they well degenerate and resorption before ovulation 0 Selection this is when the growing follicles that haven t gone through atresia are selected and they become dominant latter they could become atretic In monotocous species only one follicle is selected for example cow mare and woman Polytocous species more than one follicle is selected and they all well become dominant o Dominance These follicles well secrete increasing amounts of estradiol and inhibin this inhibits FSH from the AP Because of the follicle becoming dominant it well inhibit other follicles from growing because of the suppressed FSH it reduces the blood supply to nondominant follicles that well then go to the next stage 0 Atresia this involves more follicles than just the dominance one about 90 percent of follicles o This was first looked at in cows that us ultrasonography by examining ovaries on a regular basis that allows visualization of the changes in size and the number over time o FSH and LH This hormone has different effects on the follicles and secretion is controlled differently FSH is from the AP is released in small amounts and stimulates recruitment of the follicles the follicle well grow and secrete estrogen and inhibin and then FSH drops then a second rise in FSH might then occur in Diestrus if a second wave of recruitment occurs 0 LH its primary role is to promote the final growth and maturation of the dominant follicles and then it stimulates ovulation The frequency of the pulse changes the Metestrus and Diestrus are about 6 pulses per day this does not start the first wave in the follicle After luteolysis the progesterone then drops and the concentration of LH increases about 24 pulses per day 0 Regulation for FSH is controlled by estrogen and inhibin decreases and it is secreted by the growing follicle because of the negative feedback For LH controlled by the increase pulses of GnRH 0 Two cell two gonadotropin model this happens during the follicular development by the LH binds to the membrane receptors for LH receptors on cells of the theca interna this converts cholesterol to testosterone and then testosterone travels to the granulosa cells Then granulosa cells contains the FSH receptors when the FSH binds to the receptor it causes testosterone to convert to estradiol This process well continue until it reaches threshold that then causes preovulatory LH surge Repro Dr Walter Reproductive cyclicity terminology and basic concepts Estrous cycle it is the physiologic events that occur btw periods of sexual receptivity after puberty This is predictable by watching for estrus heat and the start of subsequent estrus This process can only stop if the animal becomes pregnant lactation and some species the season of year this can also stop under inadequate nutritional conditions and stressful environmental conditions The behavioral events that happen during this phase are the sexual receptivity and copulation Estrus or heat or season is from the Greek word that means sting or frenzy Another word for this state is oestridae that comes from an insect that would bit cattle and the cattle would move their tails this is also a sign of sexual receptivity in mammalian females 0 Estrus heat is the noun use of the word It is the sexual receptivity and it is used to say that someone is in estrus 0 Estrous if the adjective use of the word It is when estrous cycle is period from one estrus to another So you can say the animal is in the estrous cycle 0 Estrual is the adjective that is used to id the condition that is related to estrus Types of estrous cycles based on frequency of occurrence throughout the year 0 Polyestrus these are animals that display estrous cycle the same and it is distributed throughout the year that is without marked seasonal in uence Cattle swine rodents 0 Seasonally polyestrus when female exhibit multiple estrous cycles that is during specific season of the year this happens in sheep goats mares deer elk 0 Monoestrus this is in animals that display only one period of sexual receptivity during a year this happens in dogs wolves foxes bears Phases of estrous cycle 0 It is divided into two distinct phases it is named after the dominant structure that is present ovary during each phase of the cycle 0 Follicular phase it is the period from regression of the CL to ovulation it is relatively short about 20 of the cycle The primary structure is large growing follicles that secrete estradiol 0 Luteal phase it is the period from ovulation to CL regression it is longer then about 80 of cycle The primary structure of this phase is the CL and the primary hormone is progesterone Stages of estrous cycle each is then divided into the follicular and luteal phase 0 Proestrus follicular phase it begins in the progesterone and it declines because of the luteolysis the tear down of the CL This stage stops on the onset of estrus it lasts 2 to 5 days and it can depend on species It is characterized by the major endocrine transition where the progesterone dominance to the estradiol dominance the FSH and LH are responsible for this dominance tug of war During this stage the antral follicle is ready to ovulate and the female tract then prepares for estrus and mating to enter the system Estrus follicular phase this stage takes a while to develop and the behavioral symptoms are visible increased locomotion increased vocalization nervousness mounting and standing to be mounted The next step from this first start of the stage are the standing estrus which is when the female is ready to mate with the male this can also be displayed by something called lordosis which it the mating posture How long this usually takes depends on species The hormone that is most used is estradiol and that induces profound behavioral alterations and this can cause major physiological changes in the repro tract Metestrus luteal phase this is the period btw ovulation and the formations of the CL These two hormones estradiol and progesterone are in low concentrations in early stages This ovulated follicle then undergoes cellular and structural changes that results in intraovarian in the endocrine gland that well then turn into the CL this process to transform is called Latinization The hormone progesterone is secreted in the late stages of this process it is about 2 to 5 days that are required after ovulation for CL to produce a lot of this hormone Diestrus luteal phase this is the longest stage in estrous about 10 to 14 days The CL is then fully functional and the dominant hormone progesterone is used by the uterus for the early embryonic develop And then not estrous behavior displayed This process ends when CL is destroyed this is down by the luteolysis Ovulation Menstrual cycle it is the physiological events that occur btw menstrual periods The shedding of the endometrium it has no defined period of sexual receptivity this cycle begins with menses and at the middle of the cycle ovulation begins How long this usually takes is about 28 days The follicular phase is only half of the cycle and during follicles develop it produce high level of estradiol and this causes LH to surge and this end product is ovulation about 14 days long The estrous cycle in the follicular phase is 20 of less Dog has differing stage sequence where anestrus lasts about 20 weeks proestrus this is the beginning of the estrous cycle because of the drop of FSH that is then caused by negative feedback from inhibin this is secreted from the develop Follicle estrus and Diestrus This species doesn t develop Luteal tissue that happens after ovulation during estrus The decrease of estradiol and the increase of progesterone are showed by the receptivity to the male The surge center releases LH and ovulation occurs 23 days this is when fertilization is about 4872 hours after ovulation This allows for superfecundation more than one ovulation is produced then more one oocyte is produced when single estrus happens This means that one liter from one female can have babies from multiply dads The Metestrus is not as defined in this species the initial development t of luteal tissue that happens during estrus right after ovulation Cat there stages of estrous cycle proestrus estrus postestrus Diestrus anestrus This species needs mating to occur to kick start ovulation If a female doesn t get prego she well go back to postestrus for a few days and then she returns to estrus The time frame that estrus lasts in the female 9 days every 17 days Gestation of the fetus last about 60 days Anestrus this is when females that do not exhibit estrous cycle and the ovaries don t work so no follicle or CL present This is caused by an lesser amount of GnRH True anestrus it is caused by not enough hormonal stimuli this can be caused by poor nutrition stress lactation season pathology Apparent anestrus it is the failure to detect and or recognize female is pregnant This improves the pregnancy detection method and the estrus detection Gestational anestrus it is the lack of cyclicity and that equals to major clue that the female is pregnant The increases levels of progesterone from the CL and or the placenta the hypothalamus has a negative feedback and the result is no follicle maturation and the expression of estrus and then the surge of LH The levels of progesterone decreases before parturition and the estradiol increases Different species have differences in postpartum cyclicity Seasonal anestrus it evolved to be able to prevent pregnancy during the seasons when survival of the fetus would be last on the priority list In the spring is the most popular time for birth of an animal because of the abundance of nutritional conditions This process is controlled by photoperiod and the first ovulations after this anestrus is silent ovulation Seasonal cyclicity it is the reduction in frequency of GnRH secretion and this happens before breeding and it needs sufficient GnRH amount to cause SP to respond Long day breeder for example mare Because of the increase day length in spring causes cycling and the increased light can cause stimulation of kiss neurons So the more amount of light the mare is exposed to the less melatonin and the kiss neurons are started and then more GnRH is made The length of gestation for this species is 11 month Short day breeder is in the species of sheep goats elk and deer This happens in the fall and the length of gestation is about 5 months because of the decreased light the kiss neurons are stimulated So the less light more melatonin and kiss neurons get started and more GnRH Lactational anestrus this happens in females that nurse their young The exceptions to the rule are the mare and alpaca is displayed in cow and it is caused by the degree of sucking and the cyclicity can return is sucking two times a day or more happens This cycle does not happen in the sow the causes for this anestrus is visual encounter with offspring olfactory encounter with baby auditory encounter with baby But this is not started by the stimulation of teat as previously though To kick start cyclicity you can replace the calf with someone else s baby but this doesn t really happen in the dairy cow they take the calf right after birth Nutritional anestrus this is caused by negative energy balance because of the low intake of energy or protein The pulses of GnRH are not present in this anestrus because the amount of secretion of gonadotropins is not enough to cause a change so the ovaries don t work This process is common in primiparous females which means they gave birth for the first time These females are normally young and they are still growing the energy that is needed for growth and lactation It is difficult to manage If enough nutrition is increased to a normal level then the estrous cycles well start back up Amenorrhea is the anestrus for humans it is caused by menopause poor nitration lactation The menopause is caused be the regression or the follicles within the ovary because the estradiol contraction decreases then progesterone secretion is no longer happens this normally follows ovulation The energy status can cause the lack of cyclicity when the body is using all its energy to maintain its necessary systems it doesn t need to reproduce Lactational is caused by high prolactin and nutritional strain and the average time that this can take place is 6 months past partum