What is the inner cell mass of the blastocyst called?
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Embryoblast cells.
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What is the inner cell mass of the blastocyst called?
Embryoblast cells.
What is the role of FSH and LH in the menstrual cycle?
They regulate folliculogenesis in the ovary and the proliferative phase in the uterine endometrium.
What effects does testosterone have in males?
Stimulates development of secondary sex characteristics, growth of testes, maturation of seminiferous tubules, and commencement of spermatogenesis.
What hormone does the trophoblast produce after implantation?
Human chorionic gonadotropin (hCG).
When does the ovulatory surge in FSH and LH typically occur in the menstrual cycle?
On about day 13 or 14.
What hormonal changes control the menstrual cycle?
Monthly cycles in the secretion of hypothalamic, pituitary, and ovarian hormones.
What happens to some growing follicles during development?
Some cease to develop and eventually degenerate.
When does meiosis resume in the female oocyte?
Only if the cell is fertilized.
What is the mature follicle called when it is swollen and ready for ovulation?
Mature vesicular follicle or mature Graafian follicle.
When does the proliferative phase of the menstrual cycle begin and end?
Begins on about day 5 and is complete by day 14.
What do the cells of the morula give rise to?
The embryo proper and its associated extraembryonic membranes, including part of the placenta.
What is the stigma in the context of ovulation?
A small, nipple-shaped protrusion formed by the thinning of the follicle wall.
What can result from abnormal implantation of a blastocyst?
Ectopic pregnancy.
What cell adhesion molecule is involved in the adhesion of trophoblast cells?
E-cadherin.
What is the primary oocyte derived from in females?
The oogonium.
What are the final products of the second meiotic division in males?
Four spermatids.
What are the two vascularized layers surrounding the oocyte?
Theca externa and membrana granulosa.
What is the role of sodium/potassium ATPase in the morula?
It pumps sodium into the interior, causing water to follow through osmosis.
What happens to primary oocytes by 5 months of fetal life?
They form in the ovaries and enter the first meiotic prophase, becoming dormant.
What is the zona pellucida?
A thin layer of acellular material secreted by follicle cells and the oocyte, forming a barrier.
What are spermatogonia?
Cells that arise from dormant PGCs and are located under the basement membrane of seminiferous tubules.
What occurs if an embryo does not implant?
The corpus luteum normally degenerates after about 13 days.
What does the head of a spermatozoon contain?
The condensed nucleus and an acrosome filled with hydrolytic enzymes.
What is the duration of the typical menstrual cycle?
28 days.
What does the first meiotic division produce in males?
Two secondary spermatocytes.
What determines the genetic sex of an individual?
The combination of sex chromosomes: XY for males and XX for females.
What hormone stimulates the pituitary gland to release FSH and LH?
Gonadotropin-releasing hormone (GnRH).
What are the smaller daughter cells produced during cleavage called?
Blastomeres.
What is the decidual reaction?
The response of endometrial stroma cells differentiating into decidual cells upon blastocyst presence.
What stimulates the resumption of meiosis and ovulation?
An ovulatory surge in FSH and LH.
What is the role of luteal progesterone in the menstrual cycle?
It stimulates the uterine endometrial layer to thicken and form convoluted glands and increased vasculature.
What is the primary source of the fetal component of the placenta?
The trophoblast.
What happens to the oocyte after it is extruded from the ovary?
It is scraped off the surface of the ovary by the fimbriated mouth of the oviduct.
What forms from the ruptured follicle after ovulation?
The corpus luteum, which is an endocrine structure.
How does the timing of gametogenesis differ between males and females?
In males, PGCs remain dormant until puberty, while in females, PGCs undergo mitotic divisions and begin meiosis by the fifth month of fetal development.
What are the nuclei of the oocyte and sperm called after fertilization?
Female and male pronuclei.
What drug is commonly used to treat ectopic pregnancy?
Methotrexate, which blocks rapid division.
What is capacitation in sperm maturation?
The final step that involves changes in the acrosome to prepare for enzyme release to penetrate the zona pellucida.
What hormones maintain the uterine endometrium for embryo implantation?
Estrogens and progesterone.
What happens to the cytoplasm of developing gametes during spermiogenesis?
It shrinks dramatically.
What constitutes a primordial follicle?
A primary oocyte enclosed by a single-layered squamous capsule of epithelial follicle cells.
What is the significance of the inner cell mass in the morula?
It gives rise to the embryo proper and is also called the embryoblast.
What happens to primary spermatocytes during spermatogenesis?
They pass through both meiotic divisions, producing secondary spermatocytes and then spermatids.
How many meiotic divisions occur during meiosis?
Two sequential divisions, known as meiosis I and II.
How long does a cycle of spermatogenesis take in humans?
About 74 days.
What process allows homologous chromosomes to exchange DNA segments?
Crossing over.
What triggers the development of ovarian follicles in females?
The monthly surge of pituitary gonadotropic hormones starting at puberty.
What is the role of the ampulla in the oviduct?
It is where sperm survive and retain their capacity to fertilize an oocyte for 1 to 3 days.
Where does capacitation take place?
Within the female genital tract, requiring contact with oviduct secretions.
What happens to the corpus luteum if an embryo does not implant?
It degenerates after about 14 days and becomes the corpus albicans.
What initiates the cascade of events leading to ovulation?
The secretion of histamine and prostaglandins.
What maintains the uterine lining during early pregnancy?
Progesterone secreted by the corpus luteum.
What visual change occurs in the oocyte about 15 hours after the ovulatory surge?
The membrane of the swollen germinal vesicle breaks down.
What happens to the morula by 4 days of development?
It begins to absorb fluid and develops a fluid-filled cavity, transforming into a blastocyst.
What is the role of the midpiece in a spermatozoon?
It contains mitochondria that generate energy for swimming.
What is the primary spermatocyte derived from in males?
The spermatogonium.
Why do ectopic pregnancies threaten the life of the mother?
Because blood vessels at the abnormal site can rupture due to the growth of the embryo and placenta.
What marks the beginning of the menstrual cycle?
Menstruation, the shedding of the degenerated uterine endometrium.
What is the C value?
The number of copies of each unique double-stranded DNA molecule in the nucleus.
What happens to primordial follicles at the beginning of a cycle?
The follicular epithelium thickens, converting them into primary follicles.
What is the term for the embryo at the 16 to 32 cell stage?
Morula.
What changes occur in the follicle as ovulation approaches?
The follicle becomes more vascularized and forms a bulge on the surface of the ovary.
What is the outcome of meiosis in females?
One massive haploid definitive oocyte and typically one polar body.
At what stage is the secondary oocyte arrested before ovulation?
Second meiotic metaphase.
How do Sertoli cells assist in spermiogenesis?
They are connected to maturing spermatocytes and spermatids, facilitating their differentiation.
What is the result of crossing over in terms of genetic variability?
Increases genetic variability of future gametes.
What is the outcome of meiosis in sex cells?
The number of chromosomes is halved, resulting in cells with 23 chromosomes.
What is formed after the oocyte completes meiosis upon fertilization?
A definitive oocyte and a polar body.
What interventions are usually required for ectopic pregnancy?
Drug or surgical intervention to interrupt the pregnancy.
What happens to the majority of follicles recruited during the cycle?
They degenerate (undergo atresia).
What hormone is secreted by the testes at puberty?
Testosterone.
What type of cells are haploid?
Mature gametes.
What is the role of tubulobulbar complexes in spermiogenesis?
They provide a mechanism for transferring excess cytoplasm to Sertoli cells.
How many primordial follicles are present in the ovaries at their peak?
About 7 million by 5 months of fetal life.
What differentiates the connective tissue of the ovarian stroma surrounding follicles?
It differentiates into two layers: theca interna and theca externa.
What is spermiogenesis?
The process of sperm cell differentiation as spermatids mature into sperm.
What occurs when a spermatozoon binds to ZP2?
The acrosome releases enzymes that allow the sperm to penetrate the zona pellucida.
What is formed during prophase when homologous chromosomes match up?
Chiasma.
What occurs during the second meiotic division regarding DNA replication?
No DNA replication occurs.
What is gametogenesis?
The process that converts primordial germ cells (PGCs) into mature male and female gametes (spermatozoa and definitive oocytes).
What is the role of the acrosome reaction in fertilization?
It exposes sperm-specific proteins that bind to egg-specific receptors.
What does ploidy refer to?
The number of copies of each type of chromosome present in a cell nucleus.
What is the role of hyaluronic acid in cumulus expansion?
It contributes to the secretion of an abundant extracellular matrix, causing the cumulus cell mass to expand several-fold.
How does cumulus expansion affect the oocyte?
It may play a role in regulating meiotic progress and ovulation.
What happens during mitosis?
A diploid (2n), 2C cell replicates its DNA and undergoes a single division to yield two diploid, 2C daughter cells.
What is the final step of spermatogenesis called?
Spermiation.
What marks the beginning of the menstrual phase?
The sloughing of the thickened endometrium along with blood and the unfertilized oocyte.
What is menarche?
The onset of menstruation and the beginning of the menstrual cycle after puberty.
Where are sperm stored after being produced in the seminiferous tubules?
In the lower part of the epididymis.
How many spermatozoa can be deposited in the vagina during ejaculation?
As many as 300 million.
What structure joins sister chromatids together?
Centromere.
What does the first meiotic division produce in females?
A secondary oocyte and a first polar body.
What proteins mediate sperm-egg fusion?
IZUMO1 (sperm-specific) and JUNO (egg-specific).
What forms within the morula as hydrostatic pressure increases?
The blastocyst cavity (blastocoel).
What is the process called that the zygote initiates within 24 hours after fertilization?
Cleavage.
What happens to the blastocyst by day 5 of development?
It hatches from the zona pellucida.
What is a germinal vesicle?
The large, watery nucleus of a dormant primary oocyte that protects its DNA during meiotic arrest.
What hormone is secreted by luteal cells after ovulation?
Progesterone.
What is the function of tight junctions between Sertoli cells?
To help establish a blood-testis barrier.
What marks the beginning of gametogenesis?
The replication of each chromosomal DNA molecule during meiosis I.
What is the role of the zona pellucida in fertilization?
It surrounds the oocyte and contains a sperm receptor molecule called ZP2.
What do luteal cells of the corpus luteum secrete?
Steroid hormones.
What is the state of primary oocytes in females until sexual maturity?
They enter a state of dormancy and remain in meiotic arrest.
What is the response of abnormal sites to an implanting blastocyst?
Increased vascularity and other supportive changes.
What are common symptoms of ectopic pregnancy?
Abdominal pain and/or vaginal bleeding.
What is X-inactivation in females?
The random inactivation of one X chromosome in each cell.
What phase of meiotic arrest does the oocyte enter in females?
The second meiotic metaphase before replication of the centromeres.
What happens to cumulus cells surrounding the oocyte during ovulation?
They lose their cell-to-cell connections and disaggregate.
What is the small mass of follicle cells surrounding the oocyte called?
Cumulus oophorus.
What is the ploidy of somatic cells and PGCs?
Diploid (2n).
Does the embryo increase in size during cleavage?
No, it remains the same size and is enclosed in the zona pellucida.
Why do only 5 to 12 primordial follicles commence folliculogenesis each month?
Follicles become progressively more sensitive to FSH as they advance in development.
What do Sertoli cells differentiate into under the influence of testosterone?
A system of seminiferous tubules.
What are growing follicles?
Primary follicles that proliferate to form a multilayered capsule of follicle cells around the oocyte.
What is the outcome of meiosis in males?
Four identical spermatozoa.
What are antral or vesicular follicles?
Follicles that develop a central fluid-filled cavity called the antrum in response to rising levels of FSH.
What are the three main parts of a spermatozoon?
Head, midpiece, and tail.
How is the follicle ruptured during ovulation?
Through a combination of tension from smooth muscle cells and the release of collagen-degrading enzymes.
What happens to spermatozoa in the female reproductive tract?
They become hypermobile and ascend toward the ampulla of the oviduct.
What is the function of the acrosome in spermatozoa?
It plays an essential role in fertilization.
How long can the oocyte remain viable in the ampulla of the oviduct?
Up to 24 hours before losing its capacity to be fertilized.
What happens when a spermatozoon successfully penetrates the zona pellucida?
The cell membranes of the sperm and oocyte fuse.
What process prepares sperm for fertilization as they travel to the oviduct?
Capacitation.
What type of nuclei are produced after the first meiotic division?
Haploid (1n) but 2C.
What happens to PGCs in males during puberty?
They differentiate into spermatogonia and undergo successive waves of meiosis to mature into spermatozoa.
What are the two types of sex chromosomes?
X and Y chromosomes.
What role does the sodium/potassium ATPase play in trophoblast cells?
It helps transport and regulate the exchange of metabolites between the morula and the maternal environment.
What protein holds sister chromatids together?
Cohesion.
What is produced in females during the second meiotic division?
A large definitive oocyte and a diminutive polar body.
What happens to the oocyte after sperm fusion?
The oocyte resumes meiosis and completes the second meiotic division.
What is the process of cleavage in relation to the zygote?
Cleavage subdivides the zygote without increasing its size.
What is the purpose of the calcium wave during fertilization?
It alters sperm receptor molecules to prevent polyspermy.
What is the genetic composition of a zygote?
Diploid (2n) complement of chromosomes and a 2C quantity of DNA.
What immediate events occur after sperm-egg membrane fusion?
Formation of a calcium wave and release of cortical granules.
What happens to the nuclear membranes of the pronuclei in the zygote?
They quickly disappear as chromosomes are replicated.
