Embryology Test 1 Flashcards
During spermatozoa maturation protamines replace histones to facilitate chromatin condensation. When or where are sperm DNA protamines removed and replaced by histones?
In the oocyte after fertilization
When does the zona pellucida “hatching” occur?
Blastocyst stage
The amniotic cavity is formed when?
A cavity forms in the epiblast
The chorionic cavity or extraembryonic coelom forms between which two layers?
Splanchnic extraembryonic mesoderm and somatic extraembryonic mesoderm.
Where does the intraembryonic coelom form during the week 3 of embryonic development?
Lateral plate mesoderm
When does tetras formation and crossing over occur?
Prophase 1 of meiosis 1
How many chromosomes and how many copies of the DNA (n) would be present in a human primary oocyte?
46 and 4N
How many chromosomes and how many copies of DNA (n) would be present in a human secondary oocyte?
23 and 2N
How long does the embryonic period last?
8 weeks
Which sequence best reflects the sperm pathway through the male reproductive system?
Seminiferous tubules, rete testis, efferent ductules, epididymis, ductus deferens, ejaculatory duct, prostatic urethra, membranous urethra, penile urethra
Approximately 60% of seminal fluid derives from a yellowish, alkaline, viscous fluid produced by which source?
Seminal vesicles
Which structure would not be included in or related to the female vestibule?
Mons pubis
When during the cell cycle does centriole replication occur?
S phase
Sister chromatid separation due to kinetochore microtubule shortening occurs during which phase of mitosis?
Anaphase
Meiosis occurs during which phase of spermatogenesis?
Spermatocyte phase
During spermiogenesis the spermatid actually reorients so the flagellum will extend into the seminiferous tubule lumen. What event initiates this reorientation?
Acrosomal sac formation
The lining of the body of the uterus is referred to as the?
Endometrium
Which area of the female reproductive tract is characterized by by large glands that shift their secretion around the time of ovulation?
Endocervical canal
Which area of the female reproductive tract has a lining epithelium described as a nonkeratinized stratified squamous epithelium and there are no glands?
Vagina
How would you classify an ovarian follicle made up of multiple layers of Granulosa cells with several small fluid filled spaces?
Secondary follicle
When does zona pellucida formation begin?
Early primary follicle
Identify this collection of cells. (Large oocyte surrounded by one layer of follicle cells, with a small zona pellucida in between, and surrounded by stroma cells
Early primary follicle
Which cells or structures would not be present in a mature Graafian immediately prior to ovulation?
Primary oocyte
Circulating levels of which hormone produced by the ovary will reach their peak level during the follicular stage?
Estrogen
The circulating levels of which hormone produced by the anterior pituitary will be highest immediately prior to ovulation?
Lutenizing hormone (LH)
The circulating levels of which hormone produced by the ovary will reach their peak levels during the lute all phase?
Progesterone
Which hormone is essential to final thickening of the functional endometrium during the secretory phase?
Progesterone
Where does capacitation occur?
Oviduct isthmus
Which major organelle is contributed to the zygote by the sperm during cell fertilization?
Centrioles
Sperm cell binding to the oocyte membrane initiates the “cortical reaction”. What does that mean?
Cortical granule enzyme release “hardens” the zona pellucida
What is amphimixis?
Male/female nuclear fusion
Correct sequence of structures would be:
Zygote, morula, blastocysts, gastrula, neurula
Why is compaction important?
Cells segregate into inner cell mass (embryoblast) and outer cell mass (trophoblast)
Why is the zona pellucida important?
Prevents polyspermia, prevents premature implantation, and prevents maternal immune system from attacking the conceptus
Which two ovarian cells are responsible for estrogen/progesterone production?
Theca cell and Granulosa cells
Following compaction, the morula constists of 2 cell populations; the inner cell mass and the outer cell mass. What is the fate of the outer cell mass?
it forms the trophoblast
Once implantation begins, the syncytiotrophoblast rapidly becomes the source of which critical hormone?
human chorionic gonadotropin
Which structure is not present on day 7 post fertilization?
Heuser’s (exocoelomic) membrane
What is the decidual reaction?
endometrial cells accumulate glycogen and lipids
The primitive streak marks the beginning of gastrulation. What will be the fate of the first cells to pass through the primitive streak?
will become intraembryonic endoderm
The neurenteric canal provides a transient passageway btw which 2 area?
amnion and yolk sac
The notochord develops from which cell population?
axial mesoderm
Blood Island and thus bloood cell formation begin where?
extraembryonic splanchnic mesoderm
Following primitive streak and embyonic endoderm formation, the initial mesoderm cells that migrate anteriorly along the midline become which population of cells?
prechordal plate
The first somites develop from which somitomeres?
8
The somites develop from which area or layer?
paraxial mesoderm
Based on amnion/chorion arrangement, which situation would most likely produce conjoined twins?
monochorionic, monoamnionic twins
Splitting of the embryo at the inner cell mass stage would result is which membrane arrangment?
monochorionic, diamnionic twins
Which extraembyonic membrane actually cober the umbilical cord?
amnion
The placental barrier “thins” during gestation to improve exchange. How does this occur?
Loss of mesenchyme and cytotrophoblast within the placental villi
The somatopleure is a membrane comprised of which two tissues?
ectoderm and somatic mesoderm
What is the primary source of amnionic fluid after 12 weeks of gestation?
fetal urine production
Why is the allantois important?
umbililcal cord blood vessel formation
Which layer disappears during gestation?
decidua capsularis
A woman has a difficult time delivering an infant because of a large bulging mass in the posterior area of the infants buttocks. After delivery, gentle rectal palpation indicated that this tissue extended up into the pelvis. Biopsy of the tissue revealed the presence of shin, cartilage, bone, nervous tissue, cardiac and skeletal muscle, and intestinal epithelium. What is the diagnosis?
sacrococcygeal teratoma
List 3 ectoderm derived cell populations that result from neurulation.
neuroepithelial cells, neural crest cells, surface ectoderm
List 3 components that make up the chorion.
syncytiotrophoblast, cytotrophoblast, and extraembryonic somatic mesoderm
List 3 layers that make up the late gestation placental membrane.
syncytiotrophoblast, fused basal lamina, and fetal endothelium
Explain why meiosis is important.
it reduces the number of chromosomes, enables genetic variability in conceptus through synapsis and crossing over, exchange of genes through independent assortment and crossing over
Describe the structure of a mature Graafian follicle
has a secondary oocyte, zona pellucida, corona radiata, cumulus cells, cumulus oophorus, large fluid-filled antrum, granulosa cells, theca externa and theca interna
What is the site of action (specific cells) for FSH and LH in males and females.
FSH: males - sertoli cells. females - granulosa cells
LH: males - Leydig cells, females - theca cells
Outline the major epiblast derivatives during human gastrulation (primitive streak).
Endoderm: primitive gut
Messoderm: axial - prechordal plate and notochord; paraxial - somites; intermediate - genitourinary system; lateral - somatic (somatopleure) and splanchnic (splanchnopleure)
Ectoderm: skin ectoderm, neural plate/fold ectroderm - neural tube neuroepithelial and neural crest cells
