PSL300H1 Study Guide - Midterm Guide: Fallopian Tube, Reproductive System, Oogonium
PSL300
Female Reproductive System
Female Reproduction
➢ ovary - female gonad – source of oocyte (egg)
o arose from the bipotential gonad in utero
➢ fallopian tube
➢ see structures are not attached
o fimbriae – finger projections
➢ egg ejected down the fallopian tube
o implantation occurs in the uterus
➢ uterus – has many tissue layers
o Endometrium – on the inside
▪ embryo will contact and implant against
o myometrium
▪ Muscle-like layer
▪ Can contract and expand during the development of the fetus
▪ Required for traction labour and delivery process
➢ Best example - Coordination of two distinct organs → ovary and uterus → in sync,
communication
o Through process of menstruation and if there is a successful implantation, pregnancy →
maintain
➢ Uterus → womb
o Implantation and fetal development
➢ Menstrual cycle – what we will be talking about today
Cell Division (reminder)
➢ Talked about spermatogenesis in males
➢ All gametes are haploid
o Only 23 chromosomes
➢ In contrast to mitosis – 1 round of duplication, 2 daughter cells are diploid
➢ Meiosis – 1 round of duplication and then 2 rounds of cell division → leads to 4 sets of gametes
Oogenesis
➢ Males – germ cells sit and wait until puberty to start producing gametes
➢ Germ cells differentiate into gametes
o Begins in utero
➢ Process to create oogonia to generate oogonium to generate daughter cells
o Go through one or more rounds of mitosis to generate daughter cells
o Undergo meiosis to generate oogonia which turn into primary oocytes
▪ Meiosis to initiate development into an egg
➢ During fetal life, oogonia (diploid) develop
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o Enter, but do not complete meiosis I
▪ It has eited the itosis le ad has oitted to eiosis ut does’t
complete it
➢ (Most females) Born with ~1-2 million primary oocytes (for entire life)
o Contrast with males who produce 200 million sperm per day
Oogenesis adult
➢ After puberty, one primary oocyte completes meiosis I (first meiotic division) and enters meiosis
II to become a secondary oocyte and a polar body
o Polar body contains the extra 23 chromosomes that came from that cell division
o Both are not maintained
▪ Most of the cytoplasmic mass is left behind one of the daughter cells and the
other one is much smaller → ASYMMETRIC CELL DIVISON
• The 2 ells that diide do’t look idetial aoe
➢ After puberty about 300 000 remain from 1-2 million
➢ The secondary oocyte released at ovulation
➢ The secondary oocyte completes meiosis II only if it is fertilized
o Essentially, it starts meiosis II and stalls out and waits for the fertilization process
➢ Contrast to the male germ cells that go through meiosis I and II and produces spermatids with
23 chromosomes
➢ The ovulated oocyte is sitting there with 46 chromosomes → waits to discard the other 23 and
prepares itself for fertilization
➢ Can be changes in the way that fertilization occurs
Contrast oogenesis and spermatogenesis
➢ Oogenesis – generation of the gametes of the female
o Asymmetric meiosis
▪ Only 1 secondary oocyte produced
• 1 daughter cell to give rise to the secondary oocyte
• Other → primary polar body → removed and degraded
o Limited duration → no constant stem cell population that is constantly self-renewing
and creating more oocytes → oocytes are established in utero and set for the life time
of the female
▪ Some people claim that it is possible to isolate stem cell populations from
female ovaries → do’t see to e futioal i io, ut oe eoed fo
the body, they can be tricked into dividing and generating more
▪ Some people → could be a root for fertility treatments or arresting the fertility
for women, good for women who have gone through chemotherapy that has
been destructive for ovaries → way for them to recover some of that
• Controversial research → does it exist?
▪ No oocyte production after menopause
• Average age 51
➢ Spermatogenesis
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o Symmetric meiosis – all of the gametes from the daughter cell are derived continue to
produce spermatids
▪ One germ cell can produce multiple sperm
o Continuous throughout the life span
Question:
➢ What is the difference between male and female germ cells that explains the limit capacity of
female and the unlimited capacity of male reproduction?
o Males have stem cells → maintain stem cell population that can continuously give rise
to new spermatids
➢ Why limit female fertility?
Female fertility
➢ Reduced rate of fertility (ability to get pregnant)
➢ Increased rate of poor pregnancy outcomes
o Still birth
o Spontaneous abortion
o Preeclampsia
o IUGR
▪ Growth restriction of fetus
o Chromosomal pathology – first clue
▪ Since female gametes develop very early on, in utero and are held in a
precarious way
➢ Up until the age of 30, rate of fertility is pretty much flat and then after the age of 30, the
pregnancy rate starts to decline
o See an increase in the rates of pregnancies that have an adverse outcome
▪ Starts to go wrong
▪ Senescence → menopause
Chromosomal segregation
➢ There are 2 cells → Cell 1 and Cell 2 → has lined up with the potential to divide
o Green – microtubules (tubes of protein) attached to chromosomes labeled in red
▪ Going to pull and tug and rip the chromosomes away from each other so you
will have an equal number of chromosomes sliding to each side of the egg, then
cytokinesis (the division of the cytoplasm) will take place and create the 2
daughter cells
o In normal, healthy oocytes, we see this arrangement of spindle tubes, polarized at either
side of the embryo and the chromosomes are lined up right down the middle,
symmetrically → very nicely arranged, spindle pole apparatus, ready to divide
o In oocytes from aged women who have donated ovaries or eggs for various reasons, we
see much more frequently, the following:
▪ The spindle poles are poorly arranged, chromosomes are scattered around the
spindle pole apparatus; difficult to tell where 1 daughter cell will arise and
where another one is and where the plane of division will be
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Ovary - female gonad source of oocyte (egg: arose from the bipotential gonad in utero. See structures are not attached fimbriae finger projections. Egg ejected down the fallopian tube implantation occurs in the uterus. Uterus has many tissue layers: endometrium on the inside, embryo will contact and implant against, myometrium, muscle-like layer, can contract and expand during the development of the fetus, required for traction labour and delivery process. Best example - coordination of two distinct organs ovary and uterus in sync, communication: through process of menstruation and if there is a successful implantation, pregnancy maintain. Menstrual cycle what we will be talking about today. All gametes are haploid: only 23 chromosomes. In contrast to mitosis 1 round of duplication, 2 daughter cells are diploid. Meiosis 1 round of duplication and then 2 rounds of cell division leads to 4 sets of gametes. Males germ cells sit and wait until puberty to start producing gametes.
