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Western University Health Science 4320B Final Exam Study Guide (Weeks 1-4)
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This is a full study guide for UWO's Health Science 4320B Final Exam. This is part 1 of 3 and covers weeks 1-4.
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WEEK 1 REVIEW Meiosis: gametes that can fuse with someone else's 3. Microtubules to form flagellum of tailLecture 1 - Why Embryology? gametes to form of complement of DNA (sperm and egg) 4. Mitochondria proliferation at mid-piece (ATP
Periods of Development: Pairing (at a chiasma) and recombination of homologous energy for tail)
Early Development Period -fertilization to 2-week chromosomes from maternal and paternal contribution = 5. Slough off excess cytoplasm
conceptus; Differentiation of cells into what will be makes unique DNA; Ends with 23 single chromosomes (n) 6. Further maturation
placenta or embryo; Implantation of embryo into uterus -2 rounds of meiosis: 1 ends with 23 double-structured Mature Sperm = head (nucleus + acrosome), tail (neck,
Embryonic Period - 3-8-weeks; Foundational steps for chromosomes in each cell (separated homologous middle piece, principal piece, end piece)
organ system development chromosomes); 2 ends with 23 single chromosomes in
Fetal Period - 9-38 weeks; Maturation of organ systems each cell (separated sister chromatids)
Periods of Susceptibility:
Introduction of harmful factors may prevent proper
development; severity depends on when they were
introduced (ex. virus, trauma, toxins, genetics):
->Early Development Period = embryonic death
->Embryonic Period = birth defects; Time of significant
development; Embryo can usually survive this, but can
have consequences for proper development; Cells are still
plastic, but environment may cause reprogramming
->Fetal Period = environment less likely to have a severe
impact; Developmental issues are more likely due to Lecture 3 - Male Anatomy and Gametogenesis
mechanical/internal issues (ex. not enough space) Spermatogonium produced and housed in the testes -
Lecture 2 - Gametogenesis seminiferous tubules; As more are produced, pushed out
Gonad Development: into epididymis (Matures here for 12 days)
Primordial Germ Cells (PGC) - primitive ectoderm cells of During ejaculation, passes through ductus deferens/vas
the inner cell mass deferens; Receives secretions from accessory glands (ex. Lecture 4 - Female Anatomy and Gametogenesis
During the 4th week, migrate from umbilical vesicle nutrients, alkaline substances) Oogonia housed in the ovaries, made into oocytes
(extraembryonic) to coelomic epithelium of gonadal ridges -Seminal gland, prostate gland, bulbourethral gland (pH -ovulated out of the ovary, fimbriae of fallopian/uterine
Travel through gut tube, close to mesonephric kidney neutralizing agents) tube collect it
Proliferate (mitosis) to eventually make gametes = sperm -Allow sperm to travel through urethra (since Fertilization occurs in the ampulla of uterine tube (sperm
or egg (oocyte); integrate with somatic cells of coelomic urine also passes through - acidic), and be able must be able to travel up to this point)
epithelium to become gonads = testes or ovaries to fertilize an oocyte in the female tract (which -If no fertilization, oocyte still travels to uterus, but no
When they first arrive, PGC are considered "Indifferent is also very acidic) implantation and oocyte will degrade/pass from the body
Gonadal Primordium" (have not become gametes yet) Sperm passes through the ejaculatory duct (which is during menses
BUT the somatic cells are NOT involved in differentiation through the prostate), then the urethra in the penis Uterine Layers:
b/w spermatocytes and oocytes -for support; come from Spermatogenesis vs. Spermiogenesis: ~ 64 days + 12 days Myometrium - muscular, vascular (artery penetrates
cells in the urogenital area (in gonadal ridge) Spermatogenesis: occurs within the seminiferous tubules through endometrium
PGCs lose motility once they reach the ridge, continue to Spermatogonia undergo mitosis, differentiation into Endometrium - tissue that will interact with embryo and
undergo mitosis primary spermatocyte and another cell to replace parent sustain pregnancy (if fertilized)
cell -2 layers: basal layer (stable), functional layer (changes
-Primary spermatocyte -> Secondary through cycle); 2 layers of functional layer: spongy (gets
spermatocyte (MEIOSIS I - n) sloughed) and compact
-Secondary spermatocyte -> Spermatids Oogenesis: formation of female gametes (oocytes)
(MEIOSIS II - n) Females are born with all the reproductive cells (oogonia)
Spermiogenesis: occurs in the lumen of seminiferous they will ever have; Oogonia (2n) made during Fetal
Mitosis vs. Meiosis: tubules; Spermatids undergo maturation into sperm with a Period, start meiosis I but stop at dictyotene stage of
Mitosis: 2 genetically identical daughter cells resembling tail and acrosome prophase = primary oocytes
parent cell; Interphase, Prophase, Metaphase, Anaphase, 1. Golgi apparatus packages acrosomal enzymes During childhood, primary oocytes remain inactive
Telophase (Cytokinesis); Division of sister chromatids 2. Acrosome positioned at front end, centrioles at Puberty produces hormones FSH and LH
(separate at centromere); 46 chromosomes (2n) the back end
, Only some oocytes activated each month; only 1 oocyte Female Reproductive Cycle: If fertilization occurs after 24 hours, embryo is low quality
moves on FSH slightly higher levels in beginning of cycle, stimulates and pregnancy may be lost
Primary oocyte -> secondary oocyte + first polar body follicle to recruit and mature an oogonia into an oocyte Spermatozoa: Can survive in the female reproductive tract
(completion of meiosis I) that's ready for ovulation for about 48 hours
Secondary oocyte (if dominant follicle) begins meiosis II Follicular cells (ex. granulosum) produce estrogen Abnormal Gametes:
before being ovulated, does NOT complete until Increasing estrogen levels trigger an LH surge Oocytes: Can have an ovarian follicle containing 2-3
fertilization Follicle is grown and matured enough for the oocyte to be oocytes, or multiple nuclei; rare and degenerated before
If fertilization occurs, meiosis II completed and oocyte released (ovulation) reaching maturity (also less likely to become the dominant
splits into ovum and second polar body After ovulation, extra follicular cells (now the corpus follicle)
Nuclei of sperm and egg unite = SYNGAMY (diploid zygote - luteum) stop producing as much estrogen and start Spermatozoa: Abnormal spermatozoa are very common
2n) producing progesterone (promotes fertilization and (up to 10%); Can have issues with head or tail (too many,
SUMMARY: pause on meiosis I until puberty, pause on maintains uterine lining) too big or small), unlikely to fertilize because of motility
meiosis II until fertilization (ensures correct DNA number) If fertilization occurs, corpus luteum continues to produce issues
Timeframe of Oogonia: progesterone; If no fertilization, corpus luteum degrades, Assisted Reproductive Technologies: can be used if there
Phase A (6th-8th week) - PGCs grow, proliferate, and progesterone levels decrease, uterine lining cannot be are issues with the gametes
become sheathed with coelomic epithelial cells maintained so it sheds IUI (Intrauterine Insemination) - sperm directly deposited
Phase B (9th-22nd week) - growth spurt, cellular clones of into uterus; may be used if issues with sperm
oogonia motility/cervix conditions
Phase C - oogonia become primary oocytes, enter Oocyte Retrieval - hormone therapy and over-ovulation,
prophase of meiosis I oocyte is directly taken from the ovary; may be used if
Phase D (16th-29th week) - primary oocytes paused at issues with ovulation; Follicles assessed for quality, then
dictyotene stage of prophase; engendered primordial can be fertilized
follicles (X and X chromosomes separate into each IVF (in-vitro fertilization) - oocyte retrieval and exposing it
oogonia) to many sperm; possible chance of polyspermy (inviable
Phase E (around 14th week) - drop in number germ cells embryo)
and follicular atresia ICSI (intracytoplasmic sperm injection) - oocyte and sperm
Number of available oogonia declines with age, very low are retrieved, sperm is manually injected into the oocyte
numbers at around 40-50 years (if pregnancy were to (better results than IVF)
occur, high risk of birth defects, chromosomal anomalies, Embryo Transfer/Surrogate Mother - sperm and oocyte
complications) retrieved, embryo made outside of body, then
transplanted into female (could be mother or surrogate)
Phases of the Uterine Lining: Needs to be timed based on the woman's ovulation (need
Proliferative Phase - up to ovulation, uterine lining builds thick uterine lining to support the pregnancy)
up to support a pregnancy (around day 5-14) Oocyte Cryopreservation - oocyte retrieval, dehydrate it
Luteal Phase - after ovulation, uterine lining maintained by with saline so its small enough to "freeze" with liquid
progesterone (around day 14-27) nitrogen; when needed, it is rehydrated and could be
Ischemic Phase - if NO fertilization, stop building lining, fertilized with ICSI
less progesterone Use of Cryopreservation in Cancer - if young female
Follicular Atresia: regression of follicles at various stages in Menstrual Phase - uterine lining not maintained, lining diagnosed with cancer, and treatment would eliminate her
a woman's life; these follicles do NOT ovulate sheds in menses (around day 1-5) available oocytes, can do this if she plans on having
Most intense atresia occurs at: fetal period, early The Menstrual Cycle: cyclic changes in endometrium, children later
postnatal, and beginning of menarche (period) based on estrogen and progesterone levels Embryo Cryopreservation - for people trying to have
Average cycle = 28 days (range is 23-25 for 90% of women) children currently; few embryos are made, implant a
Most variation in proliferative phase couple at a time (so need to preserve others in meantime)
Lecture 5 - Gametogenesis Clinical Correlates - embryos are smaller, so easier to preserve versus oocytes
Viability of Gametes: Viable for many years; if unused can be "adopted" by
Oocytes: To make a viable embryo, oocytes usually need to other couples
be fertilized within 12 hours of ovulation, but NOT more
than 24 hours after ovulation
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