Reproduction: Uterine cycle, menstrual cycle, fertilization Flashcards
What are the 4 phases of the uterine cycle?
menstruation;
proliferative phase;
secretory phase;
premenstruation
when does the uterine cycle begin?
day 1 of menses => degeneration of corpus luteum
When does the proliferative phase begin?
after menses in latter portion of follicular phase of menstrual cycle and ending near ovulation
What is the hormone responsible for the proliferative phase?
estrogen
What does elevated estrogen provide in the proliferative phase?
proliferation of endometrial cells;
increase in length and number of endometrial glands;
increase blood flow to uterus
What is the interaction of estrogen and progesterone in proliferative phase?
estrogen stimulates progesterone receptor increase on the endometrium for fertilization preparation
What occurs in the uterus at the end of the proliferative phase and into the secretory phase?
edema in the uterus
Secretory phase and what menstrual cycle phase are the same?
luteul phase
What characterizes the secretory phase?
endometrial cell hypertrophy;
increased vascularity;
edema
What is the principle hormone of the secretory phase?
progesterone
What do elevated levels of progesterone lead to?
thick secretion of glycoproteins, sugars, amino acids;
increases cell proliferation;
increases vascularization;
depresses uterine contractility
Describe the premenstrual phase of the uterine cycle
artery constriction => ischemia, anoxia;
superficial layer of endometrium degenerates => blood and tissue in uterine lumen
what are 4 phases of menstrual cycle
menses;
follicular phase;
ovulation;
luteal phase
When does the variation occur in the menstrual cycle?
follicular phase has variation;
luteal phase is always 14 days
Menses marks day 1. What triggers this?
decrease in estrogen and progesterone
What does a decrease in estrogen and progesterone cause?
loss of endometrium support=> tissue necrosis, arterial rupture => sloughing of superficial layer and bleeding
What is the significance of the follicular phase’s decrease in progesterone and estrogen?
negative feedback is removed => increase in frequency of GnRH pulses => stimulates FSH secretion for follicular growth
What leads to the dominant follicle?
one secretes more estradiol to become dominant => atresia occurs to others
What leads to the FSH and LH secretion spike during the follicular phase leading to ovulation?
Estrogen rises until critical point where it is positive feedback on GnRH to pulsatile stimulation of LH and FSH
What causes ovulation?
LH surge and high estrogen levels trigger ovulation
What happens to the follicle during ovulation?
follicle ruptures 24-36 hours after LH surge => oocyte resumes meiosis and 1st polar body extruded
What occurs to the follicle during the luteal phase?
forms corpus luteum => secretes high levels of progesterone and low estrogen
What is the purpose of high progesterone during the luteal phase?
negative feedback to slow GnRH pulse => LH and FSH remain low
What happens to the corpus luteum if no fertilization occurs?
luteolysis causing progesterone and estrogen to decrease until hormonal suppor for endometrium declines and cells undergo apoptosis
What is the purpose of the semen associated with the sperm?
neutralize the acidic vaginal fluids to permit sperm survival
In preparation for fertilization, what hormone is released and what is its action?
estrogen is increased to thin the cervical mucus for easier transit of sperm to uterus
Define capacitation
uterine fluid solubilizes the glycoproteins coating the sperm
Purpose for capacitation
aids in fertilization by increasing energy metabolism, enhancing motility, allowing acrosome rxn at zona pellucida
What aids in sperm movement through the uterus?
contraction of the female reproductive tract => mostly the uterus
Name the path the oocyte must take to reach the uterus. What enables this process?
fimbria => infundibulum => ampulla => isthmus => uterus;
via peristaltic contractions
How long are sperm viable after ejaculation?
72 hours
What happens after sperm reaches the oocyte?
binds to zona pellucida to under acrosome reaction
Once the acrosome reaction takes place, what is the next step?
sperm and oocyte membranes fuse and sperm cell contents enter oocyte
What disease will limit the membrane fusion? Why?
Kartagener’s syndrome => poor sperm motility
Define cortical reaction
occurs when membranes fuse and zona pellucida hardens to prevent additional sperm from entering oocyte
Before male and female pronuclei fuse, what occurs to the oocyte?
undergoes 2nd meiotic division producing 2nd polar body and female pronucleus
What forms the embryo?
male pronucleus and female pronucleus
Why does an embryo remain in the ampulla for several days?
allows progesterone levels to decline =>uterine and fallopian tube musculature relaxes => easier pass into uterus
When does the embryo arrive in uterus and implant?
arrives 3 days after fertilization;
implants in uterus 3 days after arriving
Before implanting in the uterus, what must the embryo do?
develop a vasculature to aid in nutrient receiving
