Section 1: Ovulation to Parturition Flashcards
when does the zona pellucida surround the oocyte?
secondary follicle
is the primary follicle or primordial follicle more developed?
primary follicle more developed
female is born with a lifetime supply of ____________________________
primordial and primary follicles
what makes a follicle an antral follicle or a tertiary follicle?
has cavity filled with follicular fluid
what are the three distinct layers of antral follicles?
theca externa
theca interna
granulosa cell layer
how does a corpus hemorrhagicum form?
following ovulation of dominant antral follicle: antrum collapses and fills with blood
what cells in the corpus luteum produce progesterone?
granulosa cells/large luteal cells
theca interna cells/small luteal cells
what is the corpus albicans?
remnant of lysed corpus luteum
what is the neural control center for reproductive hormones?
hypothalamus
what does the tonic center in the hypothalamus secrete?
gonadotropin releasing hormone (GnRH)
small pulses over a prolonged period of time
what is the surge center of the hypothalamus responsible for?
preovulatory release of gonadotropin releasing hormone
what does the paraventricular nucleus of the hypothalamus produce?
oxytocin
what does the anterior pituitary (adenohypophysis) release in response to gonadotropin releasing hormone?
follicle stimulating hormone
luteinizing hormone
prolactin
where does the paraventricular nucleus release oxytocin?
posterior pituitary (neurohypophysis): no portal system
how does the corpus luteum form?
luteinization
a cohort of small, antral follicles grow and produce estradiol and _________ in response to tonic levels of ______________
inhibin
FSH and LH
what is the point of deviation?
one or several (polyovulatory species) follicles become dominant of wave
rest of cohort undergoes atresia
what hormones are important in luteolysis?
PGF2alpha and oxytocin
in males, __________________________ is released from the hypothalamus every several hours in short, intermittent bursts
gonadotropin releasing hormone
what stimulates leydig cells to produce testosterone?
luteinizing hormone release
what organ is needed for luteolysis?
uterus
in whom may diestral ovulations in the face of high progesterone occur?
mare
what leads to the preovulatory surge of luteinizing hormone?
progesterone levels fall
estradiol reaches threshold level
surge of gonadotropin releasing hormone from surge center of hypothalamus
what ensures that a high proportion of PGF2alpha produced by the endometrium will be transported directly to the ovary and corpus luteum without being diluted in the systemic circulation?
vascular countercurrent exchange mechanism
what does luteolysis mark?
end of luteal phase
abrupt cessation of progesterone production and structural regression of the corpus luteum to form corpus albicans
what are the stages of spermatogenesis?
spermatocytogenesis
meiosis
spermiogenesis
spermiation
what happens in spermatocytogenesis?
spermatogonia undergo a series of mitotic divisions to become primary spermatocytes
what is produced in the meiosis step of spermatogenesis?
spermatids
what happens during spermiogenesis?
spermatids are transformed into spermatozoa
how long does spermatogenesis require?
5 to 9 weeks
true/false: spermatogenesis occurs in waves so that sperm is being continuously produced
true
when does maturation of the sperm occur?
as they travel the length of the convoluted tubule
once ovulated, how long do oocytes remain viable?
12 hours to a day or so
where does fertilization take place?
ampulla of the oviduct
how long does the fertilized oocyte remain in the oviduct before descending into the uterus?
days: 3-6
how many sperm are ejaculated into the tract and how many reach the oviduct?
millions to billions
small percent: tens to hundreds
what is the life span of sperm in the female tract?
48 hours
sperm must undergo _____________ before they can fertilize the oocyte
capacitation
what does capacitation involve?
loss of proteins from sperm plasma membrane that inhibit acrosome reaction
when does capacitation occur?
within a few hours of contact with female tract
what initiates the acrosome reaction in the sperm?
binding to zona pellucida
what releases the acrosomal enzymes allowing the sperm to digest its way through the zona pellucida?
external plasma membrane of the sperm fuses with the outer acrosomal membrane
what is the final step of fertilization?
fusion of male and female pronuclei and resulting zygote begins embryogenesis
how do the ewe and cow prevent luteolysis and the initiation of a new cycle after fertilization?
blastocyst produces specific proteins in the interferon class
what specific proteins does the blastocyst in the ewe and cow produce to prevent luteolysis after fertilization?
ovine trophoblastic protein 1: now ovine interferon tau
bovine trophoblastic protein 1: now bovine interferon tau
what is produced in the sow to signal for maternal recognition of pregancy?
estradiol
how does estradiol serve as the signal for maternal recognition of pregnancy in the sow?
reroutes PGF2alpha secretion away from the submucosal capillaries and toward the uterine lumen: little access to circulation
how many stages of parturition are there?
three
after the point of deviation, why does the rest of the cohort undergo atresia?
lack LH receptors and require FSH to grow
decreasing FSH concentrations
how do high progesterone levels impact the preovulatory surge?
inhibit it: if during luteal phase
how long does it take from initiation of spermatogenesis until those sperm appear in the ejaculate?
average of two months
there must be at least ___________________ present in each horn of the uterus in the sow for pregnancy to be maintained
two conceptuses
why is “attachment” the preferred term for placentation in domestic species?
chorion of fetal membranes attach to endometrium, do not implant
what do chorionic villi do?
interdigitate with maternal endometrium to form placenta
the trophoblast of the conceptus differentiates to form the chorion, which later fuses with the allantois to form the ____________________
chorioallantois
what does it mean for a placenta to be epitheliochorial?
maternal endometrial epithelium intact and in contact with chorionic villi
what does it mean for a placenta to be endotheliochorial?
maternal endometrial epithelium is completely eroded to the maternal capillaries are in direct contact with the chorionic villi
what does it mean for a placenta to be hemochorial?
maternal endothelium is eroded and the chorionic villi are bathed directly in maternal pools of blood
who has binucleate giant cells in their placenta?
ruminants
what type of placenta do ruminants have?
synepitheliochorial
what produces pregnancy associated glycoproteins in ruminants?
binucleate giant cells
what is the “progesterone block”?
inhibits myometrial contractions
which species require corpus luteum progesterone production for the entire gestational period (CL-dependent species)?
cow
sow
doe
bitch
llama/alpaca
what are some hormones of placental origin found in some species, but not others?
placental lactogen
relaxin
what triggers the onset of parturition?
fetus: ACTH released from fetal anterior pituitary
what does ACTH from the fetal anterior pituitary cause?
cortisol release from fetal adrenal gland
what lyses the corpus luteum of pregnancy?
PGF2alpha
what is stage 1 of parturition?
initiation of myometrial contractions
positioning of fetus for birth
ends with dilation of cervix
what is stage 2 of parturition?
expulsion of fetus from birth canal
hallmark is abdominal press presence
what is stage 3 of parturition?
expulsion of placenta
what will happen to a primary follicle?
develop into secondary follicle or degenerate
what is the graffian follicle?
when tertiary follicle becomes dominant follicle
what is the theca interna?
loose connective tissue surrounding the follicle
what protrudes into the pituitary stalk region known as the median eminence?
axons of neurons in the tonic and surge centers
what happens in proestrus?
formation of ovulatory follicles
estrogen secretion
what does the preovulatory LH surge coincide closely with?
onset of behavioral estrus due to high estrogen/low progesterone levels
how long after the preovulatory LH surge does ovulation occur in most species?
24-36 hours
what are the four stages of spermatogenesis (names of sperm precursors) that occur in the testes?
spermatogonia
spermatocytes
spermatids
spermatozoa
how does pregnancy recognition work?
interferes with action of PGF2alpha on corpus luteum lysis
what are the functions of progesterone?
stimulates secretion by endometrial glands
inhibits myometrial contractions
stimulates closure of cervix
helps maintain immunologically favored environment of fetus
associated with changes in blood flow and metabolism
