Fertilization and prenatal development

Question 1

define Fertilization

Answer 1

fusion of gametes to initiate the
development of a new individual organism

Question 2

parts of a spermatozoa

Answer 2

head, neck, mid piece, tail

Question 3

where are sperm produced

Answer 3

seminiferous tubules in the testes

Question 4

Sperm maturation

Answer 4

1., 2. caput epididymis 0%
3. corpus epididymis 14%
4. corpus epididymis 97%
5.,6. cauda epididymis 99%

complete in approx. 60 days

Question 5

Ovum nucleus at fertilization is at what divisional phase

Answer 5

At the time of fertilization, most mammal ovum do not yet have a haploid number of chromosomes. Only after fertilization do the final divisions complete.

Exceptions: dogs and foxes.

Question 6

define Capacitation

Answer 6

Capacitation is required to render spermatozoa competent to fertilize an oocyte. This step is a biochemical event; the sperm move normally and look mature prior to capacitation.

Their motility changes, they become hyperactive.

Question 7

define Acrosome reaction

Answer 7

The spermatozoa fusing to the egg cell usually causes little problem, whereas penetrating through the egg’s hard shell or extracellular matrix can be more difficult.

Therefore, sperm cells go through the acrosome reaction to facilitate penetration.

the acrosome fuses with the plasma membrane of the sperm’s head, exposing the contents of the acrosome.

The contents include surface antigens necessary for binding to the egg’s cell membrane, and numerous enzymes which are responsible for breaking through the egg’s tough coating and allowing fertilization to occur.

Question 8

what enzymes are involved in the acrosomem reaction

Answer 8

acrosin & hyaluronidase

Question 9

The steps of Fertilization

Answer 9

Question 10

What is the SRY gene?

Answer 10

Sex-determining region Y protein found on the Y chromosome that is responsible for the initiation of male sex determination in therian mammals.

Those without it develop into females.

Question 11

Prerequisites for embryo implantation (4)

Answer 11

• Development inside ZP –7p
• Hatching 7-10p
• Maternal recognition of pregnancy
• Placentation

Question 12

Early stages of a developing zygote?

Answer 12

zygote
morula
blastocyst
gastrula

Question 13

what is the elongation stage of embryo development

Answer 13

Embryonic elongation is therefore a late phase of the embryonic development. It consists of the extension of the embryo along its longitudinal axis and a reduction of its transverse diameter. This involves a dramatic modification of the shape of the hypodermal cells.

Rapid growth from 2mm to 1 m in some species (30-40mm/h).

Question 14

Maternal recognition of pregnancy is necessary to

Answer 14

prevent luteolysis and keep high progesterone concentration

Question 15

What does the embryo produce in cows and the ewe, in order to prevent luteolysis?

Answer 15

Cow and ewe – embryo produces proteins that prevent luteolysis

Question 16

What does the embryo produce in sows, in order to prevent luteolysis?

Answer 16

embryo produces estradiol that gives a signal about
pregnancy to female and stimulates myometric
contractions to support even distribution of embryos in uterus

Question 17

What does the embryo produce in mares in order to prevent luteolysis?

Answer 17

presence of embryo prevents luteolysis

Necessary migration of embryo from one uterine horn to another 12-14x/day in between 12-14 days of pregnancy.

• Embryo has round shape and needs to pass the signal to endometrium cells.

Question 18

Development of placenta

Answer 18

mesoderm and endoderm form in blastocele.
the endoderm grows smaller, will form the yolk sack.

Trophoblast + primitive endo- and
mesoderm form chorion and amnion.

Chorion attaches to the uterine surface.

Amnion is filled with fluid and protects
embryo.

Allantois functions as liquid waste reservoir.

The expanding allantois forms the allantochorion when united with the chorion.

Question 19

Explain placental Implantation

Answer 19

attachment of the placenta to the uterine endometrium

Chorion – fetal side. The chorion forms finger-like projections calle dchorionic villi. Uterine endometrium is the maternal side.

• Attachment occurs only in certain zones
• Platcenta produces hormones for pregnancy and birth

Question 20

Placental classification is based on

Answer 20

placental shape and contact points

Question 21

species with diffuse placenta

Answer 21

sow, mare

Question 22

cotyledonary placenta in what animal

Answer 22

cow

can contain even 120+ cotyledons

are called caruncles from the maternal side but caruncle + cotyledon together are placentomes.

Question 23

species with discoid placenta

Answer 23

rodents, primates

Question 24

species with zonary placenta

Answer 24

cat, dog

Question 25

Placental Classification Based on Layers Between
Fetal and Maternal Blood

Answer 25

(max 6-min 3 layers)

Prefix = mother side + suffix = fetal side

• Epitheliochorial
• Synepitheliochorial (cow,sheep)
• Endotheliochorial
• Hemochorial

Question 26

Transport through placenta

Answer 26

• Water, gases, electrolytes – diffusion along osmolar gradient
• Glucose -simplified transport
• Proteins – too large
• Peptides, amino acids – active transport
• Immunoglobulins – only in hemo- and
  endoteliochorial placenta
• Low molecular mass hormones
  (steroids, thyroid hormones, epinephrine, norepinephrin), vitamins, minerals pass placenta
• Lipids and triglycerides are decomposed in the placenta, where

Question 27

Teratogens

Answer 27

agents that can disturb the development of an embryo or fetus by passing through teh palcental barrier.

• Toxins (alcohol, tin, phosphor, mercury)
• Drugs (opiates, barbiturates, antibiotics)
• Microorganisms (viruses, bacteria)

Question 28

the placenta secretes hormones that:

Answer 28

preserve pregnancy, (progesterone)
stimulate fetal growth, (lactogens)
stimulate growth of mammary gland, (lactogens)
help during calving (estrogens)

Question 29

progesterone functions

Answer 29

suppression of contractility in uterine smooth
muscle, inhibits release of GnRH from hypothalamus, prepares the mammary gland

Question 30

Sow needs progesterone from CL when?

Answer 30

during whole pregnancy

Question 31

for ewe placental progesterone is enough starting from

Answer 31

day 50 of gestation

Question 32

for mare placental progesterone is enough starting from

Answer 32

day 70 of gestation

Question 33

for cow placental progesterone is enough starting from

Answer 33

month 6-8 of gestation

Question 34

Mare loses the CL on what day of gestation?

Answer 34

150-180 day of pregnancy

Question 35

function of relaxin

Answer 35

softens connective tissue,
enables uterus to enlarge and accomodate the growing fetus,
widens the pelvis, concentration increases
before birth.

Mare - placenta produces relaxin
Cow, sow - CL produces relaxin

Question 36

function of estrogen during pregnancy

Answer 36

increases the blood circulation in uterus, prepares the mammary gland

Question 37

function of placental lactogens

Answer 37

prepares the mammary gland

Question 38

function of eCG

Answer 38

Mare placenta produces equine chorionic gonadotropin – eCG which helps maintain primary CL and form additional CL; if administered to other
species initiates follicular growth (similar to FSH).

Question 39

function of hCG

Answer 39

Human chorionic gonadotropin (hCG) is secreted from d. 8-10, is the basis of pregnancy tests, supports the maintaining of CL and progesterone
production, if administered to animals induces ovulation.

Question 40

it can be called a fetus from what point

Answer 40

a fetus is developing organism whose organs are
formed depending on species 28-50 d after
fertilization, bovine fetus 45d.