Fertilization, Weeks 1 And 2 Of Development
- 1.
The amniotic cavity appears on the eighth day as a slit-like space between the trophoblast and the
- A.
Extraembryonic mesoderm
- B.
Embryoblast
- C.
Exocoelomic membrane
- D.
Connecting stalk
- E.
Chorion
Correct Answer
B. EmbryoblastExplanation
The amniotic cavity is the fluid-filled space that surrounds and protects the developing embryo. It appears on the eighth day of development as a slit-like space between the trophoblast (outer layer of cells) and the embryoblast (inner cell mass). The other options listed do not accurately describe the formation of the amniotic cavity. The extraembryonic mesoderm is a layer of cells that surrounds the amniotic cavity, but it does not directly contribute to its formation. The exocoelomic membrane, connecting stalk, and chorion are all structures associated with the development of the placenta, but they are not directly involved in the formation of the amniotic cavity.Rate this question:
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- 2.
During the 1st and 2nd week of development
- A.
The morula implants into the endometrium
- B.
The blastocyst is composed only of epiblast and syncytiotrophoblast
- C.
The cytotrophoblast cells lack plasma membranes
- D.
The syncytiotrophoblast degrades the endometrium of the uterus
- E.
The prechordal plate is composed of epiblast cells
Correct Answer
D. The syncytiotrophoblast degrades the endometrium of the uterusExplanation
During the 1st and 2nd week of development, the syncytiotrophoblast degrades the endometrium of the uterus. This is an important step in the implantation process. The syncytiotrophoblast is a layer of cells that forms on the outer surface of the blastocyst. It secretes enzymes that help to break down the endometrial tissue, allowing the blastocyst to burrow deeper into the uterine lining and establish a connection with the maternal blood supply. This degradation of the endometrium is necessary for successful implantation and subsequent development of the embryo.Rate this question:
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- 3.
A female patient with unexplained infertility is treated with menopausal gonadotropin and pure follicle stimulating hormone to induce follicular development. Several oocytes are aspirated from enlarged follicles and cultured in nutrient medium until they reach the normal second stage of meiotic arrest before they are fertilized. Fertilization is therefore carried out at which of the following stages of oocyte development?
- A.
Prophase of the primary oocyte
- B.
Metaphase of the primary oocyte
- C.
Prophase of the Secondary oocyte
- D.
Metaphase of the Secondary oocyte
- E.
Prophase of the definitive oocyte
- F.
Metaphase of the definitive oocyte
Correct Answer
D. Metaphase of the Secondary oocyteExplanation
The oocytes are cultured until they reach the normal second stage of meiotic arrest, which indicates that they are in metaphase. Therefore, fertilization is carried out at the metaphase stage of oocyte development.Rate this question:
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- 4.
The secondary oocyte completes the second meiotic division
- A.
Before ovulation
- B.
At the time of ovulation
- C.
Before birth
- D.
At fertilization
- E.
At puberty
Correct Answer
D. At fertilizationExplanation
The secondary oocyte completes the second meiotic division at fertilization. This means that when fertilization occurs, the secondary oocyte undergoes the second meiotic division, resulting in the formation of a mature egg and a polar body. This is a crucial step in the process of fertilization as it ensures that the egg is ready to fuse with the sperm and form a zygote. Once fertilization occurs, the egg is now capable of developing into an embryo.Rate this question:
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- 5.
During the reproductive cycle which substance enhances glandular secretion of the endometrium so that implantation can occur?
- A.
FSH
- B.
LH
- C.
Estrogen
- D.
Progesterone
- E.
Testosterone
Correct Answer
D. ProgesteroneExplanation
Progesterone is the correct answer because it is the hormone responsible for preparing the endometrium (lining of the uterus) for implantation of a fertilized egg. It enhances glandular secretion in the endometrium, making it more receptive to implantation. FSH and LH are involved in the regulation of the menstrual cycle and the development of eggs, while estrogen plays a role in the growth and thickening of the endometrium. Testosterone is primarily a male sex hormone and does not have a direct role in the reproductive cycle of females.Rate this question:
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- 6.
Which of the following statements concerning a primary follicle is CORRECT?
- A.
It has a large antral cavity
- B.
Is composed of secondary oocyte and many layers of granulosa cells
- C.
It contains a primary oocyte and is surrounded by a single layer of cuboidal follicular cells
- D.
It lacks a basal lamina
- E.
It is surrounded by the theca interna and theca externa
Correct Answer
C. It contains a primary oocyte and is surrounded by a single layer of cuboidal follicular cellsExplanation
A primary follicle is the initial stage of follicle development in the ovary. It contains a primary oocyte, which is an immature egg, and is surrounded by a single layer of cuboidal follicular cells. This stage does not have a large antral cavity, which is present in later stages of follicle development. The theca interna and theca externa are not present in the primary follicle.Rate this question:
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- 7.
During meiosis I what is the amount of DNA / chromosomal number during prophase I?
- A.
2n DNA 23 chromosomes
- B.
2n DNA 46 chromosomes
- C.
4n DNA 23 chromosomes
- D.
4n DNA 46 chromosomes
- E.
1n DNA 23 chromosomes
Correct Answer
D. 4n DNA 46 chromosomesExplanation
During prophase I of meiosis I, the amount of DNA is 4n and the number of chromosomes is 46. This is because during meiosis I, the DNA replicates once in the S phase of interphase, resulting in the formation of sister chromatids. These sister chromatids pair up during prophase I to form homologous chromosomes, and each homologous pair consists of two sister chromatids, hence the 4n DNA. The number of chromosomes remains the same as the diploid number, which is 46 in humans.Rate this question:
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- 8.
During the 2nd week of development
- A.
The amniotic sac lies below the hypoblast layer
- B.
The syncytiotrophoblast layer surrounds the lacunae spaces
- C.
The definitive yolk sac is formed by day 8
- D.
Epiblast cells migrate into the primitive streak
- E.
The yolk sac is lined by epiblast cells
Correct Answer
B. The syncytiotrophoblast layer surrounds the lacunae spacesExplanation
During the 2nd week of development, the syncytiotrophoblast layer surrounds the lacunae spaces. This layer is responsible for the formation of the placenta and plays a crucial role in nutrient and gas exchange between the mother and the developing embryo. The syncytiotrophoblast layer also helps in implantation of the embryo into the uterine wall.Rate this question:
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- 9.
Which of the following processes concerning fertilization of the ovum is CORRECT?
- A.
The mature spermatid fuses with the oocyte plasma membrane
- B.
Release of cortical granules causes hyaluronic acid of the corona radiata to be altered in composition
- C.
The corona radiata is composed of theca interna cells
- D.
The sperm releases acrosomal enzymes which break down the zone pellucida
- E.
About 2 million sperms surrounds the oocyte at the time
Correct Answer
D. The sperm releases acrosomal enzymes which break down the zone pellucidaExplanation
During fertilization, the sperm releases acrosomal enzymes which break down the zone pellucida. The zone pellucida is a glycoprotein layer surrounding the oocyte. The acrosomal enzymes help the sperm penetrate through this layer and reach the oocyte for fertilization to occur. This process allows the sperm to fuse with the oocyte and release its genetic material, leading to the formation of a zygote.Rate this question:
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- 10.
The secondary oocyte is arrested
- A.
3 hours before ovulation
- B.
Just after ovulation
- C.
Before birth
- D.
At fertilization
- E.
At puberty
Correct Answer
A. 3 hours before ovulationExplanation
The secondary oocyte is arrested 3 hours before ovulation. This is because the secondary oocyte, which is released during ovulation, needs time to complete its maturation process before it can be fertilized. The arrest allows for the necessary changes to occur within the oocyte, such as the completion of meiosis, before it can be released from the ovary. Once ovulation occurs, the secondary oocyte is then able to be fertilized by a sperm cell.Rate this question:
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- 11.
During the reproductive cycle which substance stimulates the theca interna?
- A.
FSH
- B.
LH
- C.
Estrogen
- D.
Progesterone
- E.
Testosterone
Correct Answer
B. LHExplanation
LH, or luteinizing hormone, stimulates the theca interna during the reproductive cycle. The theca interna is a layer of cells surrounding the ovarian follicle, and it plays a crucial role in the production of estrogen. LH triggers the theca interna to produce androgens, which are then converted into estrogen by the granulosa cells. This estrogen production is important for the maturation of the follicle and the preparation of the uterus for potential pregnancy. Therefore, LH is the correct answer as it directly stimulates the theca interna.Rate this question:
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- 12.
Which of the following statements concerning a secondary follicle is CORRECT?
- A.
It has a large antral cavity
- B.
Is composed of secondary oocyte and many layers of granulose cells
- C.
It contains a primary oocyte and is surrounded by a single layer of cuboidal follicular cells
- D.
It lacks a basal lamina
- E.
It is surrounded by the theca interna and theca externa
Correct Answer
E. It is surrounded by the theca interna and theca externaExplanation
A secondary follicle is surrounded by two layers of cells called the theca interna and the theca externa. These layers provide support and nourishment to the developing follicle. The theca interna is responsible for producing androgens, which are converted into estrogen by the granulosa cells within the follicle. The theca externa is a connective tissue layer that provides structural support. Together, these layers play a crucial role in the growth and maturation of the secondary follicle.Rate this question:
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- 13.
Which of the following chromosomal numbers in a sperm normally results in a male embryo if it fertilizes on oocyte (ovum)?
- A.
22 + 0
- B.
22 + X
- C.
22, X
- D.
23 + X
- E.
23, Y
- F.
23 + Y
- G.
23, X
Correct Answer
E. 23, YExplanation
During fertilization, when a sperm with 23 chromosomes (including one Y chromosome) fertilizes an oocyte (which also has 23 chromosomes), it results in a male embryo. This is because the presence of the Y chromosome determines the development of male characteristics. Therefore, the correct answer is 23, Y.Rate this question:
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- 14.
Ultrasound examination of an anovulatory patient with polycystic ovary syndrome (PCOS) reveals that her ovaries contain multiple enlarged but immature follicles. The oocytes within these follicles have advanced to which of the following stages of meiosis?
- A.
First meiotic prophase
- B.
First meiotic metaphase
- C.
Second meiotic prophase
- D.
Second meiotic metaphase
- E.
Pronuclear stage
Correct Answer
A. First meiotic prophaseExplanation
The ultrasound examination of an anovulatory patient with PCOS reveals multiple enlarged but immature follicles in her ovaries. This indicates that the oocytes within these follicles have not yet matured fully. The first meiotic prophase is the stage in which oocytes undergo DNA replication and begin to divide, but they have not yet completed the division into two cells. Therefore, the oocytes in this patient's ovaries have advanced to the first meiotic prophase stage of meiosis.Rate this question:
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- 15.
An undescended testis of a prepubertal male is removed since it is at higher risk to develop testicular cancer. Histologic analysis reveals that cells of the germ line in this testis have have advanced as far as which of the following stages of development?
- A.
Primordial germ cell
- B.
Spermatogonium
- C.
Primary spermatocyte
- D.
Secondary spermatocyte
- E.
Definitive spermatocyte
Correct Answer
A. Primordial germ cellExplanation
An undescended testis of a prepubertal male is removed because it is at a higher risk of developing testicular cancer. The histologic analysis reveals the stage of development of the germ line cells in this testis. The germ line cells are the cells that give rise to sperm. In this case, the cells have advanced as far as the primordial germ cell stage. Primordial germ cells are the earliest stage of development of germ line cells, and they are the precursors to all other stages of sperm development. Therefore, the correct answer is primordial germ cell.Rate this question:
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- 16.
Chromosome analysis is carried out on the polar bodies of a woman for screening prior to in vitro fertilization. Polar bodies removed from some oocytes contain two copies of chromosome 21 while others contain no copies of chromosome 21. The woman displays none of the characteristics of Down syndrome and so the nondisjunction that resulted in this condition must have occurred in which of the following cells?
- A.
Primary oocyte in her mother's germline
- B.
Secondary oocyte in her mother's germline germline
- C.
Blastomere in her mother's germline
- D.
Primary oocyte in her own germ line
- E.
Secondary oocyte in her own germline
- F.
Blastomere in her own germ line
Correct Answer
F. Blastomere in her own germ lineExplanation
The question states that the woman displays none of the characteristics of Down syndrome, which suggests that the nondisjunction leading to the presence of two copies of chromosome 21 in some polar bodies did not occur in the primary oocyte in her mother's germline. It also suggests that the nondisjunction did not occur in the primary oocyte in her own germ line, as this would result in the presence of two copies of chromosome 21 in all polar bodies. Therefore, the most likely explanation is that the nondisjunction occurred in a blastomere in her own germ line, leading to the presence of two copies of chromosome 21 in some polar bodies and no copies in others.Rate this question:
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