Fertilization And Implantation Flashcards
During ovarian cycle, ___ releases GnRH which goes to the ___ and releases ___ which act on ___
Hypothalmus releases GnRH which goes to the pituitary gland which stimulates release for LH and FSH which act on the ovaries
- Function of FSH?
2. Function of LH?
- Stimulates the development of ovarian follicles and production of estrogen by follicular cells
- Triggers ovulation; stimulates follicular cells and corpus luteum to produce progesterone
When the corpus luteum is degenerated, it is called?
Corpus albicans
Beginning of ovarian cycle:
- What stimulates primary stage follicles to grow?
- What else does this hormone do that significant at this stage
- What does GDF-9 do?
- What two cells produce estrogen?
- FSH - and only one fully matures and only one oocyte is discharged
- Stimulates maturation of follicular (granulosa) cells
- Growth differentiation factor mediates proliferation of follicular cells
- Granulosa and thecal cells
Name 3 things estrogen does to the body
Thins cervical mucus, uterine endometrium to enter follicular/proliferative phase, and stimulate pituitary gland to secrete LH
During mid cycle, there is an LH surge. What does this cause?
Causes oocyte to complete meiosis I and initiate meiosis II, stimulates production of progesterone by follicular cells, and causes follicular rupture and ovulation
During ovulation, FSH and LH stimulate follicle to do what?
Release the egg
- What are the 4 phases of a follicle growth?
- What is FSH role in these phases?
- What happens in order to get from phase 3 to phase 4?
- Primodial, growing, vesicular (antral) and vesicular (graafian)
- Primordial develop into growing independent of FSH. As cycle proceeds, FSH secretion recruits growing follicles to develop into antral.
- Estrogen stimulates increased production of LH, causing the the follicle to enter graafian phase to complete meiosis I
Where is meiosis II arrested?
In metaphase ~3 hours before ovulation
- Corpus luteum will form after ovulation under the influence of?
- What does corpus luteum do?
- What do progesterone and estrogen cause?
- LH
- Secretes progesterone
- They cause endometrial layer to enter secretory phase (preparation for implantation)
- After how many days of no fertilization will the corpus luteum start to shrink?
- If fertilization does occur, what happens?
- When pregnant, when does corpus luteum disappear?
- On day 9 of ovulation (decrease progesterone= menstrual bleed)
- HCG will prevent degeneration of corpus luteum
- Around month 4 of pregnancy (also when it stop secreting progesterone)
How is oocyte transported?
When ovary releases the egg, fimbriae catches it and moves it towards uterine cavity via contraction of fallopian tubes/propulsion from cilia.
- Where does fertilization occur?
2. How long does sperm remain viable? Secondary oocyte?
- Ampullary region of uterine tube
2. Sperm= 48 hours; secondary oocyte= 24 hours
What two things must sperm go through in order to fertilize oocyte?
Capacitation and acrosome reaction
What happens in capacitation?
Functional changes cause the tails of sperm to beat vigorously; removal of glycoprotein from acrosomal head causes receptors to be made available
What happens in an acrosomal reaction?
Sperm releases acrosomal enzymes to penetrate the zona pellucida of the egg
Phase 1 of fertilization:
What is corona radiata? What can pass through?
Outer layer of follicular cells; only capacitated sperm can pass through
Phase 2 of fertilization:
- Penetration of?
- What happens during this penetration?
- Zona pellucida (inner membrane of oocyte)
- Sperm contacts plasma membrane of oocyte causing the plasma membrane to release lysosomal enzymes. These enzymes make ZP impermeable to other sperm
When does oocyte finish second meiotic division?
What is a polar body? Function?
After entry of sperms forming a mature oocyte and second polar body
A small cell that buds off from an oocyte that cannot be fertilized; they eliminate one half of the diploid cell (to make it haploid)
~SUMMARY SLIDE~
Brief run through of meiosis so far
1st meiotic division: primary oocyte/primordial follicle. Puberty- GnRH releases LH and FSH (completion of meiosis I the day before ovulation). In meiosis 1 a diploid becomes 2 haploids (secondary oocyte and first polar body).
Secondary oocyte commences meiosis II, which arrests at metaphase and will not continue without fertilization.
Fertilization- meiosis II completes, forming a second polar body
What is a pronucleus? When is it present?
Either pair of gametic nuclei. In the stage following meiosis but before their fusion leads to formation of zygote nucleus
~each pronucleus replicates its DNA
When do pronuclei become zygote?
Once this happens, what is initiated?
When the pronuclei fuse into a single diploid aggregation of chromosomes (23 paternal/23 maternal)
Cleavage; after zygote formation, chromosomes in zygote becomes arranged on cleavage spindle in preparation for normal mitotic division
What is cleavage?
Where in the body is this happening?
What does cleavage produce?
Short division/split (cell division)
Along the uterine tube on the way to the uterus
Blastomeres (the same cells produced as the divide and get smaller and smaller)
When cells are compacted what are they called?
Purpose of compaction?
Morula
Greater cell to cell interaction/ important for development of blastocyst
- Blastocyst is composed of two parts:
- What do these two parts become?
- When blastocyst is formed, why does zona pellucida disappear?
- Trophoblast= outer layer and embryoblast= inner cell mass
- Trophoblast= placenta; embryoblast= embryo
- Allows blastocyst to rapidly increase in size giving higher chance of implantation
Trophoblast differentiates into two layers:
When does it differentiate into these two layers?
Early phase of implantation happens on what day?
Cytotrophoblast (inner) and syncytiotrophoblast (outer)]
As it attaches to the endometrium (implantation)
Day 6
Endometrium goes through 3 phases
- What are they?
- What are these phases controlled by?
- Proliferative phase, secretory phase and menstruation
2. Physiological changes that are controlled by circulating levels of estrogen and progesterone
Implantation occurs during which phase of endometrium?
What is blastocyst function in implantation?
Secretory (starts after ovulation, influenced by progesterone)
Differentiate into secretory cells called decidual cells, which help the uterus prepare for implantation
Function of syncytiotrophoblasts (outer layer) during implantation (2)
Implants blastocyst into endometrium by forming chorionic villi (these grow outward until they come into contact with maternal blood supply); produces hCG
Most common location for ectopic pregnancy?
Second most common?
Ampullary region of the fallopian tube (between actual tube and fimbriae)
Fallopian tube
Clinical:
- Immune reaction to paternal cells will lead to?
- Placenta previa
- Placenta accreta
- Hydatidiform mole
- Tissue rejection
- Placenta covers the mothers cervical opening
- Placenta grows too deeply into uterine wall
- Noncancerous tumor that develops in uterus as a result of a nonviable pregnancy
