Gametogenesis, Fertilization, Implantation

Question 1

Gametes:

a) develop in a germ line in the form of primordial germ cells

b) they appear in the 35th week of fetal development and their development starts
few days before birth,

c) within the gonadal epithelium the gonocytes differentiate into the gamete precur-
sors – spermatogonia in the genetic male and oogonia in female,

d) since the beginning of their development they are only haploid

Answer 1

A,c

Question 2

Which statement is correct about meiosis:

a) during meiosis the cells reduce the number of chromosomes from the diploid to
haploid number

b) in the female meiosis begins in the 5th month of prenatal development
c) in the male, meiosis begins at puberty

d) in the healthy male, the meiotic division during spermatogenesis can occur any-
time after puberty

Answer 2

A,b,c,d

Question 3

Within the gonadal epithelium, gonocytes:

a) differentiate into the gamete precursors
b) differentiate into spermatogonia in the genetic male
c) are still diploid
d) contain 23 chromosomes

Answer 3

A,b,c

Question 4

Oogonia:

a) divide in mitosis and some differentate into primary oocytes

b) between the third and fifth month oogonia enter the prophase of the first meiotic
division and reach maximum number (around 7 million)

c) already at the 7th month most of the follicles containing oogonia become atretic
(due to the apoptosis)

d) only the surviving primary oocytes are surrounded by flat epithelial cells

Answer 4

A,b,c,d

Question 5

During spermatogenesis:

a) the sex cords luminize into seminiferous tubules before the birth of the male
newborn

b) just before puberty, the sex cords luminize into seminiferous tubules and the gonocytes undergo mitosis and differentiate into both reserve stem cells and in spermatogonia
c) the whole transformation from spermatogonia into spermatozoa takes 64 days
d) spermatogonia never appear after the age of 20 years

Answer 5

B,c

Question 6

The developed spermatozoon consists of:

a) a head containing the nucleus with acrosome
b) a midpiece containing the centrioles and a mitochondrial helix
c) a midpiece with no mitochondria but with mobile structures

d) a tail which consists of a highly specialized flagellum, a mobile structure, similar
to the cellular kinocilia

Answer 6

A,b,d

Question 7

Meiosis:

a) is a reduction division
b) ends by formation of two morula
c) represents a process whereby a cell nucleus divides by two divisions into four nuclei, each containing half the original number of chromosomes, forming gene- tically a haploid set of chromosomes
d) occurs only during cleavage on the way through the oviduct

Answer 7

A,c

Question 8

The process of fertilization:

a) starts under normal conditions most of the time in the ampullary region of the
tube

b) is usually supported by the entry of many sperms, so called polyspermy
c) occurs only if the whole zona pellucida is completely dissolved
d) ends with the fertilized egg with a haploid genome called morula

Answer 8

A

Question 9

The process of fertilization:

a) starts under normal conditions in the uterine cavity
b) takes around three days to end by formation of the zygote

c) occurs only if the whole corona radiata is completely dissolved prior to the
fertilization

d) ends with the fertilized egg with a diploid genome called the zygote

Answer 9

D

Question 10

Corona radiata:

a) is formed by granulosa cells and extracellular matrix
b) is formed by blastomeres and zona pellucida
c) it has protective and nutritional role during the transport of secondary oocytes
d) is lost completely before fertilization

Answer 10

A,c

Question 11

Toward the midpoint of the menstruation cycle:

a) the growing Graafian follicle reaches size of about 15–20 mm

b) the ovarial surface degenerates and the increasing intrafollicular pressure results
in extrusion of the oocyte together with the attached cells of corona radiata

c) the oocyte has finished its first maturation division and starts the second meiotic
division

d) the oocyte is carried into oviduct by sweeping movements of the fimbriae and reaches the lumen of the tube, then it is transported toward the uterus by contraction of the smooth muscles of the tube wall and activity of its ciliary lining

Answer 11

A,b,c,d

Question 12

Fertilization:

a) occurs under normal conditions in the human only in the uterine cavity
b) is the fusion of haploid gametes, egg and sperm, to form the diploid zygote

c) can be performed thanks to assisted reproduction technologies outside the hu-
man body

d) involves signaling between both sperm and egg

Answer 12

B,c,d

Question 13

Unfertilized ovum:

a) is surrounded by blastomeres,
b) is surrounded by zona pellucida and corona radiata
c) is called a zygote
d) consists of two blastomeres

Answer 13

B

Question 14

The zygote:

a) is still encased in its zona pellucida

b) it is transported through the oviduct by the activity of the ciliated lining and
muscular contractions of the tube

c) it undergoes a series of mitotic divisions called cleavage
d) cleavage results in an increase in number of daughter cells called blastomeres

Answer 14

A,b,c,d

Question 15

Blastomeres:

a) are cells that form the embryo during cleavage

b) after two cells stage the cleavage becomes asynchronous and the blastomeres
become smaller in each division

c) after three divisions undergo condensation, called compaction, to form a tightly
grouped ball of cells

d) can be observed during the cleavage after in vitro fertilization

Answer 15

A,b,c,d

Question 16

Cleavage:

a) proceeds at the rate of roughly one cleavage division per day for the first two
days

b) takes place in the uterine cavity only, and nowhere else

c) becomes at some point asynchronous and the blastomeres become smaller in
each division

d) results in condensation (called compaction) to form a tightly grouped ball of
cells

Answer 16

A,c,d

Question 17

Morula:

a) is a ball of usually 16 compacted blastomeres
b) consist of usually 6 to 8 cells called blastocysts
c) enters the uterine cavity on the 4th day after fertilization
d) enter the oviduct for the further development into blastocyst

Answer 17

A,c

Question 18

Morula:

a) is a ball of usually 4 compacted blastomeres
b) consist of usually 6 to 8 cells called blastocysts
c) enters the uterine cavity on the 1st day after fertilization
d) appears around the 4th or 5th day of development

Answer 18

D

Question 19

At the end of the first week of development:

a) the oocyte is being fertilized
b) the cleavage starts
c) the implantation occurs
d) the fusion of the male and the female pronucleus occurs

Answer 19

C

Question 20

The blastocyst:

a) consists of the inner cell mass and trophoblast
b) has no cavity

c) consists of totipotent cells of the embryoblast and trophoblastic cells that will
form the extraembryonic structures, such as the fetal part of the placenta

d) can divide into two blastocysts and develop into twin pregnancy

Answer 20

A,c,d

Question 21

Blastocyst is usually formed by:

a) only 2 blastomeres
b) embryoblast and trophoblast
c) only 3 blastomeres
d) only 4 blastomeres

Answer 21

B

Question 22

The embryonic stem cells:

a) are located between trophoblast cells inside the syncytiotrophoblast
b) form the inner cell mass
c) form the zygote
d) can differentiate into all germ layers

Answer 22

B,d

Question 23

The embryonic pole:

a) is the region of the contact of trophoblast with embryoblast
b) it is also called the animal pole
c) it is also called the vegetative pole
d) is also called the regenerative pole

Answer 23

A,b

Question 24

The embryonic stem cells:

a) form the embryoblast which is also called the inner cell mass
b) form the syncytiotrophoblast
c) form the oocyte
d) can differentiate into all germ layers

Answer 24

A,d

Question 25

Implantation:

a) is the term used to describe process of attachment and invasion of the uterine
endometrium by the blastocyst (conceptus) in placental animals

b) begins at approximately the sixth day after fertilization
c) begins by invasion of zygote
d) begins with adhesion of the blastocyst to the uterine wall

Answer 25

A,b,d

Question 26

Implantation:

a) is the term used to describe process of cleavage
b) begins at approximately at the 12th day after fertilization
c) begins usually by invasion of morula
d) begins with adhesion of the blastocyst into the uterine wall

Answer 26

D

Question 27

Before the implantation of a blastocyst into the uterine cavity:

a) the uterine endometrial cells as well as the trophoblastic cells express a variety
of adhesive molecules

b) the trophoblast differentiates into an inner single layer of mononucleated and mitotically active cuboidal cells of cytotrophoblast and an outer layer of multi- nucleated syncytiotrophoblast

c) the cells of the cytotrophoblast differentiate also inside the blastocyst – at first
proximal to embryoblast and gradually around the whole blastocyst

d) there are three germ layers already present

Answer 27

A,b,c

Question 28

Ectopic pregnancy occurs after an ectopic embryo implantation which is:

a) any implantation outside the uterine cavity
b) e.g. the implantation inside the uterine cavity
c) e.g. the implantation in the uterine cervix
d) e.g. the implantation in the interstitial (intramural) part of the oviduct

Answer 28

A,c,d

Question 29

Embryo implantation inside the uterine cervix:

a) is a normal, physiological site of embryo implantation
b) is considered as an ectopic implantation
c) ends usually by the delivery of a healthy term newborn

d) ends usually by some obstetrical pathology – e.g. spontaneous abortion or pre-
term delivery

Answer 29

B,d

Question 30

The embryo implantation inside the interstitial part of the oviduct:

a) is a normal, physiologic site of embryo implantation
b) is considered as an ectopic implantation
c) ends usually by the delivery of a healthy term newborn
d) ends usually by rupture of the uterine horn and severe bleeding

Answer 30

B,d