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Embryology Practice Questions with Answers.
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Embryology Practice Questions with Answers1. The part of the sperm containing proteolytic enzymes to digest the
zona pellucida is the:
A. capacitor
B. head
C. corona
D. acrosome
E. cumulus Correct Answer-D. is correct.
The acrosome is the part of the sperm containing proteolytic enzymes to
digest the zona pellucida. It is exposed by the process of capacitation.
Then, under the influence of substances released by corona radiata cells,
it releases its proteolytic enzymes and penetrates the oocyte.
2. The ovulated mammalian oocyte is arrested at:
A. prophase of meiosis I
B. metaphase of meiosis I
C. prophase of meiosis II
D. metaphase of meiosis II
E. none of the above Correct Answer-D. is correct.
The long arrest in meiosis occurs in the primary oocyte. These
descendants of oogonia begin meiosis before birth and stop dividing
during prophase of the first division. Years later, this first division is
,completed just prior to ovulation. Ovulated secondary oocytes then stop
at metaphase II until fertilized.
3. The seven-day blastocyst:
A. has a single layer of trophoblast at the embryonic pole
B. has an amniotic cavity
C. is attached to the endometrial epithelium
D. is surrounded by a degenerating zona pellucida
E. is called the hypoblast Correct Answer-C. is correct.
The decidual reaction of the endometrium creates a nourishing
environment for the conceptus a it buries itself by invasion of the uterine
endometrial wall. Progesterone produced by the corpus luteum
stimulates glandular secretion in the endometrium during the secretory
phase of menstruation or early pregnancy.
4. Haploid nuclei that fuse at fertilization are called:
A. homunculi
B. mitotic figures
C. centrioles
D. nucleoli
E. pronuclei Correct Answer-E. is correct.
After the sperm reaches the ovum, it deposits its genetic load, the male
pronucleus, into the cytoplasm of the egg. After finally completing the
,meiotic division that had begun years before, the female pronucleus
fuses with the male pronucleus to create the diploid nucleus of the
zygote
5. The first week of human development is characterized by formation
of the:
A. inner cell mass
B. hypoblast
C. trophoblast
D. blastocyst
E. all of the above Correct Answer-E. is correct.
At four days, the blastocyst cavity of blastocele forms within the morula.
Trophoblast are outer cells of the blastocyst, while a knot of cells
appears, protruding into the blastocele. This is the inner cell mass.
Trophoblast becomes 2 layers: syncytiotrophoblast and cytotrophoblast.
Inner cell mass becomes epiblast and hypoblast.
6. During implantation, the blastocyst:
A. implants in the endometrium
B. usually attaches to endometrial epithelium at its embryonic pole
C. usually implants in the posterior wall of the body of the uterus
D. causes change in the endometrial tissues
E. all of the above are correct Correct Answer-E. is correct.
, Implantation occurs when the trophoblast cells at the embryonic pole
secrete proteolytic enzymes that allow the blastocyst to penetrate the
wall of the uterus, usually the posterior wall. The endometrial lining
responds to implantation through the decidua reaction, by which it
becomes more succulent for nourishing the blastocyst.
7. Capacitation of the sperm:
A. is caused by the zona pellucida
B. occurs in the male
C. prevents polyspermy
D. is essential for fertilization
E. removes the head of the sperm Correct Answer-D. is correct.
Capacitation involves removing the glycoprotein coat and seminal
plasma proteins from the head of the sperm, exposing the acrosome and
allowing the acrosome reaction to occur. Capacitation occurs within the
female genital tract, and without its occurrence, fertilization could not
occur.
8. The early stages of cleavage are characterized by:
A. formation of a hollow ball of cells
B. formation of the zona pellucida
C. increase in the size of the cells in the zygote
D. increase in the number of cells in the zygote
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