reproduction - march 12th Flashcards
What is the broad ligament? What does it do?
- Folding of the peritoneum
(mesothelium and connective tissue). - Supports several anatomical
components of the reproductive tract - Houses vascular supply, lymphatics and nerves
- Provides protection and structural support
What do the ovaries do?
- Glandular organ that houses oocytes and ovarian follicles.
- Production of gametes (oogenesis)
- Follicle development
- Hormone production
What produces the hormones secreted by the ovaries?
- Granulosa cells
- Theca cells
- Corpus luteum
What are steps of oogenesis (formation and genotypic maturation of the female gametes), and what does each step entail?
- Oocytogenesis:
- Mitotic divisions resulting in more oogonia
- Occurs during embryonic development - Ootidogenesis:
- First meiotic division
- Results in secondary oocyte and
polar body
- Occurs after puberty, cyclically - Oogenesis
- Completes second meiotic division
- Results in a mature ovum and polar body
How does the embryo acquire nutrients?
the yolk (cytoplasm)
polar bodies are composed of what?
genetic information only (no cytoplasm)
At what phase of the cell cycle does the oocyte arrest in the follicular phase of oogenesis?
metaphase II
What are the functions of the fallopian tubes?
- Oocyte capture and transport
- Sperm storage and transport
- Early embryo transport
Where does fertilization occur?
The ampulla of the fallopian tube
What captures the CoC?
Fimbriae of the infundibulum
What is the role of the Isthmus?
sperm storage in females (for about 3 days in humans)
What are the functions of the uterus?
- Site of embryo implantaton and fetal development
- Mucus secreton for optmal environment (conceptus or sperm)
- Uterine glands produce prostaglandins to control CL
- Mediates sperm transportation
- Hormone responsive, mediates contractions
What are the functions of the cervix?
- Flushes foreign materials, protecting developing conceptus.
- Protects sperm from hostile vaginal environment.
- Filters defective, abnormal and immotile spermatozoa.
- Inhibits sperm migration during the menstrual cycle.
What are the functions of the vagina?
- Provides passageway for extrusion of blood and mucosal tissue during menses
- Copulatory organ (possesses multiple nerve endings, expansive, mucus producing epithelium for lubrication)
- Sperm storage
- Parturition (birth) canal
What is the role of FSH in the Follicular Phase?
- Stimulates the growth and proliferation of granulosa cells (GCs) in recruited primary ovarian follicles
- Stimulates production of FSH receptors on GCs (results in increased sensitivity to FSH / less FSH required to stimulate selected follicles)
- Stimulates aromatase production and increased enzymatic activity in the GCs (converts testosterone to estradiol)
What is the role of LH in the Follicular Phase?
- Stimulates production of LH receptors on outer GCs (results in lower cGMP production which signals oocyte to reduce cGMPs – results in oocyte meiosis resumption)
- Stimulates theca interna cells to produce testosterone (testosterone diffuses into GCs and gets converted to estradiol via aromatase
enzymes)
What happens during the follicular phase (specifically hormone activity)
- Hypothalamus releases GnRH, stimulating the anterior pituitary to secrete FSH and LH.
- FSH sImulates the recruitment and proliferation of a new follicles (↑ FSH receptors on GCs → ↑ sensitivity, ↑ aromatase activity)
- LH stimulates the follicles (↑ LH receptors in GCs → resumption of meiosis in oocyte, theca cells generate testosterone, diffuses to GCs → converted by aromatase to E2)
- E2 production → ↑FSH receptors in dominant follicle (follicle requires less FSH to be simulated, low levels of FSH and LH along secreted by pituitary)
- ↑E2 in dominant follicle → + feedback to hypothalamus
What induces ovulation?
Increased E2 (estradiol) in late follicular stage induces GnRH pulses, resulting in an LH surge, which causes the follicle to burst
What happens during the luteal phase?
- Luteinization by LH converts remaining granulosa and theca cells into the corpus luteum.
- Modified granulosa and theca cells from the corpus luteum generate progesterone and E2.
- These hormones stimulate endometrial gland secretions and the development of spiral arteries.
What aides in fertilization?
- Cervical and uterine fluids aid in sperm activation.
- The occurrence of capacitation primes sperm for fertilization.
- Mild secretions of progesterone secreted by the CoC work as a
chemoattractant.
When sperm reach the CoC in the
ampulla, they _______ the cumulus
cloud (granulosa cells)
degrade
how do sprm degrade the cumulus
cloud (granulosa cells)? (2)
- Hyaluronidase (on surface of capacitated sperm, and conatins a hydrolytic enzyme which disintegrates GCs)
- Sperm motility (physically disrupts cloud)
What prevents more than 1 sperm from fertilizing the egg? (2)
Fast block:
- Rapid depolarization of the vitelline membrane
- Triggered by influx of Na+ ions from NaK+ pumps
- Results in electrical barrier to sperm entry
Later oocyte response:
- Intracellular pH increases due to influx of Na+ ions
- Triggers efflux of H+ ions
- Together, pH increase and Ca2+ ion increase stimulate protein and DNA synthesis
What trigger the oocyte to continue meiosis after arresting in metaphase II?
Ca2+ wave
Describe the process of zygote formation
- Completion of meiosis results in a female pronucleus.
- Sperm nucleus decondenses to form the male pronucleus.
- Sperm centriole forms microtubules that integrate with ovum microtubules, drawing the pronuclei closer.
- Fusion of the two pronuclei
Describe the blastocyte structure
Inner cell mass:
- Embryoblast
- Gap junctions form
- Becomes the embryo proper
Outer cell mass:
- Trophoblast
- Tight junctions form
- Becomes fetal placental contribution
- Forms other extraembryonic membranes
What are the steps of implantation?
Apposition and Adherence:
- Embryonic pole adjacent to the uterine endometrium
- Adherence via cell adhesion molecules
- LIF involvement, L-selectin, trophinin
Penetration:
- Syncytiotrophoblast, differentiated multinucleated trophoblast cells
- Invasive: secrete digestive enzymes, works its way into uterine tissue
- Establishes contact with maternal blood vessels
Decidual reaction:
- Uterine tissue responds to invasion by setting up immunological barrier (the decidua)
- Becomes the chorionic portion of placenta
What is the Chorion membrane do?
Provides fetal oxygen and nourishment from the mother
What is the Amnion membrane do?
- Encloses the embryo
- Filled with amniotic fluid
- Provides physical protection from impact
What is the Amnion membrane do?
- Encloses the embryo
- Filled with amniotic fluid
- Provides physical protection from impact
What is the Yolk Sac membrane do?
- Initial site of blood cell production (hematopoiesis)
- Synthesizes a variety of proteins
- Involved in maternal-fetal transport
What is the Allantois membrane do?
Functions in independent storage waste and respiration (non-mammals)
What causes dichorionic/diamniotic twins?
cleavage of mordula (on days 1-3)
What causes monochorionic/diamniotic twins?
cleavage of blastocyte (on days 4-8)
What causes monochorionic/monoamniotic twins?
cleavage of implanted blastocyte (on days 8-13)
What causes conjoined twins?
cleavage of formed embryonic disc (on days 13-15)
What’s an ectopic pregnancy?
implantation occurs somewhere other than the uterus.
How does the Corpus luteum maintain pregnancy?
Synthesizes…
- Progesterone to keep the endometrium intact
- Progesterone, estrogen, inhibin: feedback suppression to pituitary
How does the placenta maintain pregnancy?
Synthesizes…
- hCG*
- Estriol (uterine myometrium regulation, oxytocin receptors, development breast ducts)
- Progesterone (suppresses uterine contractions, cervical plug, milk glands)
- PTHrP / parathyroid hormone-related peptide (mobilizes mother’s bone calcium)
- CRH / corticotropin-releasing hormone (fetal lung maturation)
What positive feedback occurs to trigger parturition?
- Fetal adrenal gland secretes dehydroepiandrosterone sulfate
(DHEAS) and cortisol upon stimulation by CRH (corticotropin
releasing hormone) and ACTH (adrenocorticotropic hormone). - Cortisol stimulates the placenta to secrete CRH, producing a
positive feedback loop. - DHEAS is converted by the placenta into estriol, which together
with prostaglandins and oxytocin, stimulate the myometrium of the
mother’s uterus to undergo changes leading to labor.
