Fertilization and Gastrulation

Question 1

Process by which the glycoprotein coat and seminal plasma proteins are removed from the plasma membrane of sperm.

Answer 1

Capacitation

Question 2

Reaction by which sperm move through the corona radiata of an egg.

Answer 2

Acrosome Reaction

Question 3

What reaction of the egg blocks polyspermy?

Answer 3

Zona reaction

Question 4

Penetration of the zona pellucida is done by what enzymes and what motive force?

Answer 4

The Arcrosome reaction - Esterases, acrosin, neuraminidase.

It is also done with tail movement.

Question 5

How does the sperm enter the oocyte after passing through the zona pelucida?

What key organelle does sperm not bring in?

Answer 5

Fusion of tail and head enter the plasma membrane.

Sperm does not bring in it’s mitochondria.

Question 6

What happens after the sperm has entered an oocyte’s nucleus?

Answer 6

The egg will undergo it’s second mitotic division, a male pronucleus will form, and fushion of the male and female pronuclei will occur.

Question 7

What is significant about the size of the embryo during cleavage?

What CAM is used during this?

Answer 7

It maintains it’s size

Cadherin

Question 8

When does a morula develop? What about an early blastocyst?

Answer 8

Day 3 and Day 5

Question 9

Upon what stage and day does an embryo enter the uterus and the zona pellucida begins to degenerate?

What day does it attach to the wall?

Answer 9

As a Blastocyst around Day 5

Day 6

Question 10

Where is sperm usually capacitated?

Answer 10

Sperm is capacitated 7 hours after ejaculation, and is done so by enzymes in the uterus and uteren tubes.

Question 11

What steps are neccasary for successful implementation of in vitro fertilization?

How long can sperm be stored for?

Answer 11

1. Hormonal stimulaiton of oocyte formation and collection of them with aspirator during laparascopy.
2. Placement on pitri dish with capacitated sperms.
3. Cleavage of zygotes with 4 to eight cell stage reached.
4. Plasmit of embryos back into uterine canal by way of cathetar.

Question 12

What does early pregnacy factor do?

Answer 12

Immunosupressent that protects embryo during implantation.

Question 13

Day 5 to Day 7 what significant events occur?

Answer 13

Zona pellucida degenerates, embryo structure changes from early to late blastocyst.

Question 14

Late in week one what enzymes are realeased and what new structures form?

Answer 14

Early pregnacy factor (immunosuppresant), hCG, and proteolytic enzymes are released.

Cytotrophoblast create a stem cell layer of mitotically active Syncytiotrophoblasts

A hypoblast is present as well.

Question 15

Cell type of week 2 that releases proteolytic enzymes and chorionic gonadotropin.

Primarily responsible for implantation.

Answer 15

Syncytiotrophoblasts

Question 16

Caused by fertilization of an empty oocyte and duplication of sperm, or can have a partial pheonotype from fertilization of two sperm (zona block failure​).

BENIGN

Answer 16

Hydratidiform Mole

Question 17

Malignant tumor developing from hydratidiform mole

Answer 17

Choriocarcinomas (3-5% of moles)

Can spread to liver lungs, vagina, intestines, bone, and brain.

Question 18

Clinical features of Hydratidiform Moles

Answer 18

Vaginal Bleeding

Pelvic pressure or pain

Enlarged Uterus

Hyperemesis gravidarum (Morning sickness)

Question 19

What is the aspect of an embryo only present during week 2?

Answer 19

The hypoblast

Question 20

What does the epiblast give rise to during week 2?

Answer 20

The ectoderm, amnion, and amniotic cavity.

Question 21

What is the prechordial plate?

Answer 21

The prechordial plate is formed from the epiblast and secondary yolk sac. This is where babies are made.

Question 22

What does the hypoblast give rise to during the second week of gastrulation?

Answer 22

The hypoblast expands around the embryo forming a primary yolk sac. This yolk sac forms the extraembryonic mesoderm. The primary yolk sac pinches off forming the secondary yolk sac.

The top of the secondary yolk sac, and bottom of the amniotic membrane (really its the epiblast) form the embryo.

Question 23

The Extraembryonic Mersoderm of week 2 consists of what?

Answer 23

The extraembryonic coelem (hollow cavity outside of embryo)

The extraembryonc somatic mesoderm (around trophoblasts and covering the amnion)

Texthe raembryonic splanchnic mesoderm (lining the yolk sac)

Question 24

What are the derivatives of the extraembryonic somatic mesoderm?

Answer 24

Gives rise to the body

(Gives rise to the placental layers)

Forms connecting stalk (umbilical cord)

Creates an embryonic pole that changes position during development

Question 25

Extraembryonic splanchnic mesoderm gives rise to what?

Answer 25

Primitive blood

Forms in the wall of yolk sac

Question 26

Where does implantation occur?

What potentially deadly pregnancy is associated with some incorrect implantations?

Answer 26

Hopefully in the posterior uterus (most of the time)

If not, eptopic pregnancy may occur.

This raises hCG yet no embryo is found on ultrasound.

Question 27

What are the three types of placenta previa

Answer 27

Marginal - just a bit over cervical os

Partial placental - about half way over

Total placental - completely over

Question 28

Symptoms and treatment of placental previa

Answer 28

Vaginal bleeding beyond 20 weeks gestation

Sonograph before digital vaginal examination with antepartum bleeding

Palpation can cause severe hemmorage

Many times the placenta will move.

Question 29

What replaces the hypoblasts in week three, during formation of the germ layers.

Answer 29

Mesoblasts form the definitive endoderm

Question 30

Label

Answer 30

Question 31

Describe expansion of the intraembryonic layer of the germ layers.

Answer 31

Forms in caudal end and moves up with the notochord towards the cranial end of the germ layers.

Question 32

What doe the ectoderm, mesoderm, and endoderm give rise to?

Answer 32

Ectoderm - skin, hair, nails, CNS

Mesoderm - connective tissue of body, heart, blood, spleen

Endoderm - lungs, GI Tract, bladder, glands

Question 33

The primitive pit becomes what?

Answer 33

After fusing with the Endoderm it forms a canal which will become the neural canal.

Question 34

The alantois becomes what?

Answer 34

The alantois is an outgrowth of the yolk sac (umbillical vesical) which will become surrounded by the mesoderm of the body stalk, it becomes the urachus (fetal bladder).