Sub-objectives and Clickers Flashcards
The principal energy source for ejaculated spermatozoa is:
Fructose in seminal vesicle fluid
Of the barriers to sperm survival and transport within the female reproductive tract, low pH is most important in the: A. Upper uterine tube B. Lower uterine tube C. Uterine Cavity D. Cervix E. Vagina
E. Vagina
During the menstrual cycle, a sharp spike in plasma levels of which of the following hormones just before ovulation is responsible for ovulation? A. FSH B. LH C. Estrogen D. Progesterone E. Estradiol
B. LH
Transcription of which of the following genes is required to permit cleavage to proceed to the 2 cell stage in mammalian embryos? A. Nanog B. 4-Oct C. Cdx-2 D. Sox-2
B. 4-Oct
Which of the following cells are responsible for the production of testosterone in the testes? A. Sertoli cells B. Leydig cells C. Granulosa Cells D. Spermatogonia
B. Leydig cells
The graffian follicle, in addition to participating in ovulation, also has endocrine function. What component of the graffian follicle forms the corpus luteum? A. Granulosa cells B. Thecal cells C. Corona radiata cells D. Both granulosa and thecal cells
D. Both granulosa and thecal cells
Where does fertilization typically occur?
Ampulla
In mammalian embryos, unlike non mammalian and invertebrate enbryos, most transcription via the embryonic genome, as opposed to the maternal genome, occurs as early as which of the following stages? A. Zygote B. 4-cell stage C. Blastula D. Gastrula
B. 4-Cell stage
In Drosophilia, from which of the following gene categories are mRNA derived from maternal genome rather than embryonic genome? A. Egg polarity genes B. Pair rule genes C. Homeotic genes D. Gap genes
A. Egg Polarity Genes
Which of the following is a transcription factor? A. FGF B. Pax C. TGF D. Notch E. Wnt
B. Pax
Zinc fingers or helix-loop-helix arrangements are characteristic of members of what class of molecules? A. Proto-oncogenes B. Signaling molecules C. Receptors D. Transcription Factors
D. Transcription Factors
Sonic Hedgehog is produced in which signaling center?
A. Notochord
B. Intestinal portals
C. Floor plate and neural tube
D. Zone of polarizing activity in the limb bud.
E. All of the Above
E. All of the above
Based on your knowledge of paralogous groups, which of the genes would be expressed most anteriorly in the embryo? A. Hoxa-13 B. Hoxc-9 C. Hoxd-13 D. Hoxb-1 E. Hoxb-6
???
The principal inductor in primary neural induction is the: A. Hypoblast B. Primitive streak C. Extraembryonic mesoderm D. Notochordal process E. Embryonic ectoderm
D. Notochordal process
Cells of which germ layer are not present in the oropharyngeal membrane? A. Ectoderm B. Mesoderm C. Endoderm D. All are present
B. Mesoderm
Brachyury, a deficiency in caudal tissues in the body, is caused by a mutation in what gene? A. Lim-1 B. Noggin C. T D. Sonic Hedgehog E. Activin
C. T
The hypoblast gives rise to which of the following tissue types? A. Extraembryonic only B. Embryonic only C. Embryonic and Extraembryonic D. Neither
A. Extraembryonic only
In meiosis, pairing of homologous chromosomes begins during which of the following stages of prophase I: A. Leptotine B. Zygotene C. Pachytene D. Diplotene
B. Zygotene
Which of the following descriptions best describes the oogonium and the ovary during the early fetal period? A. Diploid, no follicle B. Diploid, few follicle cells C. Haploid, no follicle D. Haploid, few follicle cells
A. Diploid, no follicle
Inhibin released by the granulosa cells during the mammary cycle inhibits secretions of gonadotropins, especially FSH. This results in:
Regression of the corpus luteum
Splitting of the blastocyst during early development results in two complete blastocyst enclosed within a single trophoblast is the most common mode of twinning. Assuming complete normal identical twins result, what developmental property is illustrated? A. Differentiation B. Determination C. Regulation D. Morphogenesis
C. Regulation
When do germ cells first appear in human embryogenesis and where?
24 days after fertilization
In the endodermal layer of the yolk sac
Migration route of Germ cells:
Yolk sac –> Hindgut epithelium
Through dorsal mesentery
Into developing gonads
Leptotene
Chromosomes are threadlike
Each chromosome consists of two chromatids
Chromosomes begin to coil
Zygotene
Homologous chromosomes pair (synapsis)
Synaptonemal complex forms
Pachytene
Max. coiling
Tetrads
Crossing-over begins
Diplotene
Crossing-over continues
Chiamata are well-defined
Diakinesis
Crossing-over is complete
Terminalization
Spindle apparatus is in place
Nuclear membrane is disrupted
Metaphase I
Tetrads line up along equatorial plate
Centromeres do not divide
Anaphase I
Homologous chromosomes move to opposite poles.
Each homologue consists of two chromatids
Chromatids are not genetically identical bc of crossing-over
Daughter cells will be haploid
Telophase I
Cytokinesis occurs (usually)
Nuclear membranes reform (maybe)
Spindle apparatus disassembles
Chromosomes may uncoil to varying degrees
Prophase II
Chromosomes again condense Nuclear membranes disappear Spindle apparatus reforms in each cell Each chromosome consists of 2 chromatids Each daughter cell has one complete set of chromosomes (haploid)
Metaphase II
Chromosomes line up on equatorial plate
Anaphase II
Centromeres divide
Chromosomes move to opposite poles
Each chromosome consists of a single chromatid
Telophase II
Chromosomes uncoil
Cytokinesis is complete
Nuclear membranes reform
End result is four genetically unique haploid daughter cells
Aneuploidy
Abnormal number of chromosomes
Monosomy, Trisomy
Euploidy
Changes in number of complete sets of chromosomes
Haploid, Diploid
Compare the total number of oocytes that are present early in embryonic development to the number present at birth and prior to puberty.
7 million - embryonic midterm
2 million - birth
400,000 - puberty
400 - ovulated
Fetal period follicular structure
Diploid, no follicle cells
1 chromatid/chromosome
Later fetal period through birth follicular structure
Diploid, few flattened follicle cells
2 chromatids/chromosome
Birth to puberty follicular structure
Diploid, single layer of cuboidal follicle cels
Oocyte and follicle cells are connected via microvilli and gap junctions
Zona pellucida separates primary oocyte from follicular cells.
2 chromatids/chromosome
After puberty follicular structure
Diploid, multiple layers of follicle cells and beginning antrum formation
Membrane granulosa surrounds outside of follicle cells
2 chromatids/chromosome
Haploid secondary oocyte + haploid polar body
Tertiary follicle, multiple layers of follicle cells, corona radiata, and large antrum
Ovulation follicular structure
Haploid, corona radiata and thecal cells + haploid polar body
2 chromatids/chromosome
What causes the cell to resume meiosis after ovulation?
Due to LH surge which shuts down gap junctions between granulosa cells and oocyte
Reduces transfer of cAMP and cGMP form cumulus cells to oocyte
cAMP concentration is reduced, allowing activation of MPF
Describe the roles of FSH and LH receptors, FSH and LH, testosterone, estrogen, 17B-estradiol, and aromatase.
Granulosa cells develop FSH and LH receptors
Circulating FSH stimulates granulosa cells to produce estrogen
Theca externa - produce angiogenesis factor
Theca interna - LH receptors; secrete testosterone
Mural granulosa cells - develop FSH receptors, synthesize aromatose in response to FSH, aromatase coverts testosterone into 17B-estradiol, estrogens stimulate formation of LH receptors on granulosa cells.
Describe the meiotic state of the oocyte at puberty and prior to ovulation.
Arrested at Diplotene stage until puberty.
Upon ovulation, meiosis resumes and is arrested again at metaphase II
Meiosis resumes upon fertilization
Factors leading to meiotic arrest at the diplotenes stage of meiosis:
High concentrations of cAMP from oocyte and follicular cells:
- inactivates MPF
- Leads to meitic arrest
cGMP from follicular cells that inactivate phosphodiesterase 3A in oocyte:
- Prevents conversion of cAMP to 5’AMP
- Maintains high concentration of cAMP
Stages of Spermatogenesis
Primordial germ cells (2N) Spermatogonia (2N) - type a and b; b leave mitotic cycle and enter meiotic cycle under influence of retinoic acid Primary Spermatocytes (2N) Secondary spermatocytes (N) x 2 cells Spermatids (N) x 4 cells
Where are cells of Leydig found and what is their function?
Interstitial cells
Produce testosterone
Describe the relation of Sertoli cells to the blood-testis barrier.
Form an immunological barrier between the forming sperm cells and the rest of the body and spermatogonia
Describe the role of testosterone on Sertoli cells and secondary sex characteristics.
LH secreted by anterior pituitary binds to LH receptors on Leydig cells. Testosterone is released into the blood and is taken to the Sertoli cells and throughout the body, where it affects a variety of secondary sexual tissues, often after it has been locally converted to dihydrotestosterone.
Sertoli cells then convert testosterone to estrogens and also synthesize leydig cell stimulatory factor.
When does ovulation occur int he ovarian cycle and what roles do FSH and LH play in ovulation?
Day 14 of ovarian cycle
Stimulus for ovulation is a rise in FSH levels and a sharp rise is LH
What components of the Graafian follicle form the corpus luteum?
Residual theca and granulosa cells
What is the fate of the corpus leuteum in the absense of fertilization?
Corpus albacans
Corpus luteum regresses and levels of progesterone and estradiol decrease, resulting in the beginning of the next menstrual phase.
What role does inhibin play in the menstrual cycle?
Released by the granulosa cells
Inhibits secretion of gonadotropins, especially FSH, resulting in regression of the corpus luteum
What is the proliferation phase due to?
increase in levels of estradiol secreted by the granulosa cells of the developing ovarian follicle.
What controls the secretory phase?
Rising levels of progesterone, secreted by both the granulosa and thecal cells of the ovarian follicle.
Describe the Graafian follicle immediately prior to ovulation
Mature
Oocyte arrested in diplotene of prophase I
Compare the two systems of dating pregnancy:
Fertilization Date: dates age of embryo from time of fertilization
Menstrual Age: Dates age of embryo from start of mother’s last period; 2 weeks greater than fertilization age.
Name the hormone necessary for egg rapid transport through the isthmus
Progesterone
What contributions are made to semen by the seminal vesicles and prostate?
Seminal vesicles - fructose and prostaglandins
Prostate - citric acid, Zn, Mg, and phosphatase
What is the optimal pH for sperm motility and how does this compare to the pH of in the cervix and upper vagina?
Optimal = 6 - 6.5 (pH of cervix) Vagina = 4.5 (seminal fluid buffers acidity of vaginal fluids)
What is the purpose of capacitation?
Required for sperm to undergo acrosomal rxn
Were does it occur in the female tract?
Isthmus of uterine tube
Explain how the sperm penetrates the corona radiata and name the enzyme involved and its source.
Fusion of the outer acrosomal membrane with the sperm plasma mem creates portals throufht which the contents of the acrosome can be release.
Fragmentation of fused acrosomal membrane and plasmalemma of the sperm result in the relase of acrosomeal enzymes.
Hyaluronidase
What is the function of ZP3 in the acrosomal reaction?
Mediates attachment of sperm to ZP.
Stimulates acrosomal rxn in mammals. (acts through G proteins)
Acrosin
Most important enzyme involved in the penetration of the zona pellucida.
Not released form the acrosome but remains attached to the portion of the acrosomeal membrane that fuses to the remaining sperm plasmalemma and overlies the nucleus.
Fast Block
Rapid depolarization of egg plasmalemma
-70 mv to +10 mV
Fast block temporarily prevents polyspermy and allows time for the egg to establish the slow block
Slow block
Mostly characterized by release of polysaccharides from the cortical granules located just under the plasmalemma of the egg.
What role does phospholipase C zeta play in the metabolic activation of the egg following fertilization?
IN response to the introduction of phospholipase C zeta, calcium ion within the egg cytoplasm is released metabolically activating the egg
Trophoblast cells
Extraembryonic structures including placenta
Inner Cell Mass
Embryo proper plus some extraembryonic structures
Define genomic imprinting and explain how it is related to the methylation of DNA.
Differential gene expression depending on whether a chromosome is inherited from the male or the female parent.
Due to DNA methylation differences in sperm and egg.
What is a Barr body?
Inactive X chromosome
Example of dosage compensation
Regulation
Refers to the ability of embryo to compensate for removal of structures or for addition of structures.
Bateson’s Rule
When duplicated structures are joined during critical developmental stages, one structure is the mirror image of the other.
