Deck 3: Embryology

Question 1

Differentiation refers to the

A)moment of conception (when sperm and egg unite).
B)time when the blastocyst implants in the uterine wall.
C)formation and organization of the diverse cell types in the body.
D)formation of the various organ systems in the body.
E)separation of the placenta from the fetus at birth.

Answer 1

C

Question 2

The formation of sex cells in the human is termed

A)gametogenesis.
B)karyogenesis.
C)sporogenesis.
D)typogenesis.
E)differentiation.

Answer 2

A

Question 3

Oogenesis is the formation of

A)a new autosomal cell.
B)a new somatosomal cell.
C)a sperm.
D)an egg.
E)new ovaries.

Answer 3

D

Question 4

Reduction division occurs during

A)mitosis.
B)meiosis.
C)both mitosis and meiosis.

Question 5

A polar body is formed during

A)mitosis.
B)meiosis I.
C)meiosis II.
D)meiosis I and meiosis II.
E)ovulation.

Question 6

The event called "crossing over" in meiosis results in

A)greater genetic variety in sex cells and thus in embryos.
B)less genetic variety in sex cells.
C)greater vitality of sex cells making them more active.
D)a change in the gender (sex)of the embryo.
E)irreversible mutations.

Question 7

The process of separating homologous chromosomes is termed

A)replication.
B)reduction division.
C)nondisjunction.
D)cleavage.
E)differentiation.

Question 8

In the human,the diploid genetic condition occurs

A)when the number of chromosomes equals the number of genes.
B)when a cell has 23 pairs of chromosomes.
C)when a cell has the (n)number of chromosomes.
D)when a cell has 23 chromosomes.
E)in each gamete just before fertilization.

Question 9

The fetal period occurs during the

A)first three weeks of development.
B)third through the eighth week of development.
C)eighth through the twenty-fourth week of development.
D)last 30 weeks of development.
E)full term of pregnancy.

Question 10

The embryonic period occurs during the

A)first three weeks of development.
B)third through the eighth week of development.
C)eighth through the twenty-fourth week of development.
D)last eight weeks of development.
E)full term of pregnancy.

Question 11

Why does meiosis pass through two complete cycles?

A)To assure that the gametes will be of the correct size
B)To allow crossing over to occur
C)So that the zygote will have the diploid number of chromosomes
D)Because two cycles are necessary to produce the proper shape of the gametes
E)Because the chromosomes are still double-stranded at the end of meiosis I

Question 12

Spermiogenesis is

A)the formation of a spermatid.
B)the transformation of a spermatid into a functional sperm.
C)the process of a sperm finding an oocyte.
D)reduction division of a spermatogonium.
E)the process of a sperm losing its tail following fertilization.

Question 13

The secondary oocyte enters into an arrested state during its development.In what stage of development does this occur?

A)During metaphase I
B)During telophase I
C)During prophase II
D)During metaphase II
E)During telophase II

Question 14

The number of chromosomes in a secondary oocyte is

A)greater than the number in a mature sperm.
B)less than the number in a mature sperm.
C)the same as the number in a mature sperm.
D)greater than the number in a polar body.
E)less than the number in a polar body.

Question 15

In what developmental stage does the human embryo implant in the wall of the uterus?

A)As a zygote
B)In the morula stage
C)In the blastocyst stage
D)In the gastrula stage
E)During organogenesis

Question 16

The human sex cells are called

A)spores.
B)genes.
C)gonads.
D)gametes.

Question 17

Which is regarding the process of meiosis?

A)Meiosis begins in a haploid state and concludes in the diploid condition.
B)Meiosis forms haploid daughter cells from a diploid cell.
C)Meiosis is represented by the notation: n $\rightarrow$ 2n.
D)Most growth in the body is accomplished through meiosis.
E)Meiosis results in identical sex cells.

Question 18

The two items that form protective layers around the secondary oocyte are the zona pellucida and

A)polar body.
B)transverse membrane.
C) corona radiata.
D)acrosome.
E)primary oocyte.

Question 19

A major difference between oogenesis and spermatogenesis is that each cycle of oogenesis results in

A)four viable eggs,whereas a single cycle of spermatogenesis produces only one sperm.
B)three viable eggs,whereas a single cycle of spermatogenesis produces only one sperm.
C)only one viable egg,whereas a single cycle of spermatogenesis produces four spermatozoa.
D)three viable polar bodies,whereas a single cycle of spermatogenesis produces no polar bodies.
E)a tiny viable egg,whereas a single cycle of spermatogenesis produces four sperm,each much larger than the egg.

Question 20

A double-stranded chromosome consists of two genetically identical sister chromatids.What important biological event produced the sister chromatids?

A)Crossing over
B)Genetic mutation
C)Mitosis
D) DNA replication
E)Reduction division

Question 21

Which is not one of the extraembryonic membranes that form early in the development of the embryo?

A)Chorion
B)Placenta
C)Amnion
D)Yolk sac
E)All of these are correct.

Question 22

Which is not correct about fertilization?

A)It establishes the three primary germ layers.
B)It combines male and female genetic material.
C)It determines the sex of the organism.
D)It initiates cleavage.
E)It restores the diploid number of chromosomes.

Question 23

What is capacitation?

A)Another term for fertilization
B)Implantation of the embryo into the uterine wall
C)Movement of the fertilized egg down the fallopian tube
D)Release of the secondary oocyte from the ovary
E)Conditioning of the sperm within the female reproductive tract

Question 24

The correct chronological pathway of fertilization is

A)zona pellucida penetration $\rightarrow$ corona radiata penetration $\rightarrow$ pronuclei fusion.
B)corona radiata penetration $\rightarrow$ zona pellucida penetration $\rightarrow$ pronuclei fusion.
C)pronuclei fusion $\rightarrow$ corona radiata penetration $\rightarrow$ zona pellucida penetration.
D)pronuclei fusion $\rightarrow$ zona pellucida penetration $\rightarrow$ corona radiata penetration.
E)corona radiata penetration $\rightarrow$ pronuclei fusion $\rightarrow$ zona pellucida penetration.

Question 25

The implantation process begins by about day _____ following fertilization.

A)2
B)4
C)7
D)10
E)12

Question 26

What process does the pre-embryo undergo in order to from into a tightly grouped ball of cells?

A)Meiosis
B)Implantation
C)Dissolution
D)Compaction
E)Morulation

Question 27

The fetal portion of the placenta forms from the

A)amnion.
B)yolk sac.
C)inner cell mass.
D)chorion.
E)blastocoel.

Question 28

The function of the chorion is to

A)prevent desiccation of the embryo.
B)assist in the formation of the circulatory system.
C)form red blood cells.
D)aid in the formation of the placenta.
E)cover the embryo in a protective layer of mucus.

Question 29

The acrosome

A)carries the DNA.
B)is responsible for movement of a spermatozoan.
C)provides nourishment to the sperm.
D)contains enzymes to break through protective layers surrounding the secondary oocyte.
E)initiates growth of the sperm tail.

Question 30

Which is not a function of the placenta in humans?

A)Exchange of nutrients
B)Exchange of respiratory gases
C)Transmission of maternal antibodies
D)Transfer of blood between mother and embryo
E)Production of hormones

Question 31

The amnion is one of the extraembryonic membranes,and its function is to

A)prevent desiccation of the embryo.
B)allow fluid to enter the placenta.
C)form the plasma portion of the blood.
D)give the embryo nourishment.
E)permit implantation to occur.

Question 32

At its formation,a morula consists of ______ cells.

A)4
B)8
C)16
D)32
E)64

Question 33

The single cell resulting from fertilization is a(n)

A)blastocyst.
B)morula.
C)trophoblast.
D)embryoblast.
E)zygote.

Question 34

The blastodisc (bilaminar germinal disc)of the early embryo consists of the

A)hypoblast and the epiblast.
B)hypoblast and the trophoblast.
C)epiblast and the trophoblast.
D)hypoblast and the cytotrophoblast.
E)cytotrophoblast and the epiblast.

Question 35

The hormone hCG (human chorionic gonadotropin)is produced by the

A)chorion.
B)cytotrophoblast.
C)endometrium.
D)corpus luteum.
E)syncytiotrophoblast.

Question 36

Some estimates claim that approximately ______ percent of all pregnancies result in spontaneous abortion,many due to chromosomal abnormalities.

A)10
B)20
C)30
D)40
E)50

Question 37

Following ovulation,how long does a secondary oocyte remain viable?

A)For about 1-2 hours
B)Approximately 12 hours
C)For about 1 day
D)Between 3-5 days
E)For approximately 1 week

Question 38

Once implantation takes place the pre-embryo is divided into two general areas.Which of these two actually gives rise to the embryo?

A)Trophoblast
B)Cytotrophoblast
C)Syncytiotrophoblast
D)Embryoblast
E)Morula

Question 39

Of the millions of sperm deposited into the vagina during intercourse,only a few hundred reach the secondary oocyte.What happens to the rest?

A)Many leak out of the vagina.
B)Some never become motile.
C)They may be destroyed by the acidic environment of the female tract.
D)They may become disoriented and lose direction.
E)All of the choices are correct.

Question 40

Although the early digestive system maintains contact with the embryonic yolk sac,it does not gain any nourishment from the sac.Instead,the yolk sac is involved with the formation of

A)the heart and lungs.
B)the reproductive organs.
C)blood vessels and blood cells.
D)bones.
E)skeletal muscle tissue.

Question 41

During embryonic development,a process called transverse folding creates the

A)digestive and respiratory tracts.
B)pelvic girdle and lower appendages.
C)cylindrical trunk or torso region of the embryo.
D)primary germ layers.
E)neural tube.

Question 42

What structure produces estrogen and progesterone until the placenta is fully formed?

A)Endometrium
B)Corpus luteum
C)Pituitary gland
D)Amnion
E)Yolk sac

Question 43

From which primary germ layer is the lining of the digestive tract derived?

A)Ectoderm
B)Mesoderm
C)Endoderm

Question 44

From which primary germ layer is the dermis of the skin derived?

A)Ectoderm
B)Mesoderm
C)Endoderm

Question 45

When does the embryonic period officially begin?

A)With the onset of cleavage
B)At the time of implantation
C)With the establishment of the three primary germ layers
D)When the umbilical cord becomes functional
E)At fertilization

Question 46

The axial skeleton,most muscle,cartilage,dermis,and connective tissues are derived from blocklike embryonic structures called

A)teratogens.
B)dermatomes.
C)notochords.
D)lateral plates.
E)somites.

Question 47

From which primary germ layer is the thyroid gland derived?

A)Ectoderm
B)Mesoderm
C)Endoderm

Question 48

Neural crest cells give rise to

A)melanocytes.
B)the adrenal medulla.
C)spinal ganglia
D)skeletal and muscular components of the head.
E)All of the choices are correct.

Question 49

What is the feature that first signals gastrulation?

A)Invagination of cells from the epiblast occurs.
B)Folding of the embryonic disc occurs.
C)The yolk sac disappears.
D)The embryonic disc forms.
E)The primitive streak forms.

Question 50

It takes about _______ for the placenta to become fully formed.

A)1 week
B)2 weeks
C)1 month
D)2 months
E)3 months

Question 51

Formation of the neural tube

A)begins at the anterior (head)end and proceeds toward the posterior (tail).
B)begins at the posterior and proceeds toward the anterior.
C)begins in the middle and proceeds toward the head and the tail.
D)is random in that it can begin and proceed at any location along the neural plate.
E)is caused by compaction of the neural plate.

Question 52

From which primary germ layer are muscles derived?

A)Ectoderm
B)Mesoderm
C)Endoderm

Question 53

What happens during gastrulation?

A)The three primary germ layers are formed.
B)The embryo implants in the wall of the uterus.
C)The placenta becomes functional.
D)The chorion disintegrates.
E)The amnionic fluid appears.

Question 54

From which primary germ layer is the heart derived?

A)Ectoderm
B)Mesoderm
C)Endoderm

Question 55

What is the name given to substances that can cause birth defects or even death if exposure to them occurs during the embryonic period?

A)Mutagens
B)Antibiotics
C)Fungicides
D)Teratogens
E)Pesticides

Question 56

From which primary germ layer is the gall bladder derived?

A)Ectoderm
B)Mesoderm
C)Endoderm

Question 57

Neurulation is an example of

A)compaction.
B)blastulation.
C)gastrulation.
D)induction.
E)organogenesis.

Question 58

From which primary germ layer is the epidermis of the skin derived?

A)Ectoderm
B)Mesoderm
C)Endoderm

Question 59

Which is not correct concerning cephalocaudal folding of the embryonic disc?

A)It occurs before the primary germ layers have formed.
B)It occurs in the cephalic and caudal regions of the embryo.
C)It occurs because of differential growth in different regions of the embryonic disc.
D)It occurs during the late third and fourth weeks of development.
E)It helps create the future head and buttocks regions of the embryo.

Question 60

From which primary germ layer is the nervous system derived?

A)Ectoderm
B)Mesoderm
C)Endoderm

Question 61

This figure shows a cross-sectional view of the developing embryo.Which of the three primary germ layers does number 1 indicate?

A)Ectoderm
B)Mesoderm
C)Endoderm

Question 62

What happens to the polar bodies that are produced during oogenesis?

A)They participate in the formation of the extra-embryonic membranes.
B)They provide yolk to nourish the early embryo.
C)They help to form the placenta.
D)They degenerate.
E)They are incorporated into the inner cell mass.

Question 63

Trisomy refers to

A)the development of three primary germ layers.
B)three layers of cells.
C)the formation of triplets.
D)there being three copies of a given chromosome instead of two.
E)the formation of the three extra-embryonic membranes.

Question 64

The process of embryogenesis includes

A)gastrulation.
B)fertilization.
C)gametogenesis.
D)formation of a zygote.

Question 65

During which fetal stage do reproductive organs and permanent kidneys begin to develop?

A)Weeks 1-8
B)Weeks 9-12
C)Weeks 13-16
D)Weeks 17-20
E)Weeks 21-38

Question 66

Two standard measurements are used to determine fetal length.Which of these would be the longer of the two measurements on any normal fetus?

A)CHL
B)CRL
C)HTL
D)HRL
E)CFL

Question 67

What would happen if capacitation did not occur?

A)The egg (oogonium)would not mature.
B)Ejaculation could not occur.
C)The sperm could not reach the egg.
D)Ovulation could not occur.
E)Spermiogenesis would be impeded.

Question 68

The number of possible combinations of genes in humans is virtually limitless.One reason is random assortment of chromosomes and the other is

A)random mating.
B)crossing over.
C)reduction division.
D)nondisjunction.
E)spermiogenesis.

Question 69

What would be the result if the notochord failed to develop?

A)The digestive system could not develop properly.
B)The circulatory system could not develop properly.
C)The skeletal system could not develop properly.
D)The nervous system could not develop properly.
E)The reproductive system could not develop properly.

Question 70

Which statement is not correct concerning fertilization?

A)Digestive enzymes released from the acrosome eat away the intercellular connections in the corona radiata.
B)Once a sperm has penetrated the oocyte,the zona pellucida hardens to prevent additional sperm from penetrating.
C)Only the sperm nucleus enters the oocyte cytoplasm.
D) Fusion of pronuclei produces a haploid nucleus.

Question 71

Which position of the three primary germ layers in the early embryo is correct?

A)Ectoderm on the inside,endoderm on the outside,and mesoderm in the middle
B)Endoderm on the inside,ectoderm on the outside,and mesoderm in the middle
C)Mesoderm on the inside,endoderm on the outside,and ectoderm in the middle
D)Ectoderm on the inside,mesoderm on the outside,and endoderm in the middle
E)Mesoderm on the inside,ectoderm on the outside,and endoderm in the middle

Question 72

During this fetal stage,lanugo covers the skin and the limbs near their final proportions.

A)Weeks 1-8
B)Weeks 9-12
C)Weeks 13-16
D)Weeks 17-20
E)Weeks 21-38

Question 73

The fetal period

A)extends from the beginning of the 9th week until birth.
B)extends from the beginning of the 12th week until birth.
C)includes only the middle trimester.
D)includes only the last trimester.
E)extends from the end of the 4th week until birth.

Question 74

What would happen if more than one sperm penetrated a secondary oocyte,an event termed polyspermy?

A)Identical twins would result.
B)The sperm with the most advanced chromosomes would merge with the female nucleus.
C)The extra sperm would most likely fertilize one of the polar bodies.
D)The resulting zygote would not develop.
E)This never happens due to genetic controls.

Question 75

This figure shows a superior view of the developing embryo.What structure does number 1 indicate?

A)Yolk sac
B)Notochord
C)Primitive streak
D)Epiblast
E)Hypoblast

Question 76

During this critical period the subcutaneous fat is deposited and testes descend into the scrotum.

A)Weeks 1-8
B)Weeks 9-12
C)Weeks 13-16
D)Weeks 17-20
E)Weeks 21-38

Question 77

Down syndrome is the result of

A)improper crossing over.
B)nondisjunction.
C)improper implantation.
D)incomplete capacitation.
E)disassociation.