Fertilisation & Implantation HARD MCQ

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What do the outer blastomeres primarily contribute to in embryo development?

Creation of the trophoblast (correct)

Development of embryonic tissues

Formation of the blastocoele

Formation of the inner cell mass

Which type of junctions primarily hold the outer blastomeres together?

Adherens junctions

Gap junctions

Tight junctions (correct)

Desmosomes

What initiates the formation of the blastocoele during embryo development?

Cleavage in the Fallopian tube

Transport of fluids mediated by the zona pellucida (correct)

Establishment of gap junctions

Multiplication of inner cell mass cells

What is the role of the early pregnancy factor produced by the trophoblast?

To prevent maternal immune response Signup and view all the answers

During which developmental stage does the embryo transition to producing its own genetic material?

Blastula stage Signup and view all the answers

What is the primary consequence of mosaicism during cleavage?

Persistence of cell lines with different genetic material Signup and view all the answers

Which part of the blastocyst contains the embryonic pole?

Inner cell mass Signup and view all the answers

What differentiates polar trophoblast from mural trophoblast?

Location relative to the inner cell mass Signup and view all the answers

What is the primary outcome of the demethylation of paternal DNA during fertilization?

Generation of the male pronucleus Signup and view all the answers

What is the primary advantage of the ampullary region of the Fallopian tube in fertilization?

It provides an optimal environment for the sperm to meet the oocyte. Signup and view all the answers

Which of the following accurately describes the process of cleavage after fertilization?

The cleavage process increases the number of cells without growing the size of the zygote. Signup and view all the answers

Which enzyme is released by the acrosome to aid spermatozoa in penetrating the corona radiata?

Hyaluronidase Signup and view all the answers

What role does the zona pellucida play in preventing polyspermy?

It acts as a barrier that restricts sperm entry. Signup and view all the answers

Which statement best describes the composition of the zygote after fertilization?

It is composed of 23 chromosomes from each parent. Signup and view all the answers

What is the role of ZP3 in the fertilization process?

It is a species-specific protein that sperm bind to for penetration. Signup and view all the answers

In which phase of fertilization does the spermatozoon begin to release enzymes from its acrosome?

Phase 2: attaching to the zona pellucida Signup and view all the answers

What is the result of compaction during early embryonic development?

Maximization of cell-cell contact among blastomeres. Signup and view all the answers

Which statement regarding the acrosomal reaction initiated by the zona pellucida is true?

It is critical for the first sperm to successfully penetrate the oocyte. Signup and view all the answers

What happens to the spermatozoon after it attaches to the oocyte's plasma membrane?

Only head, midpiece and tail of the spermatozoon sink into the egg cytoplasm. Signup and view all the answers

How is variation in the human species achieved through fertilization?

Through the mixing of maternal and paternal genetic material. Signup and view all the answers

Which statement best describes the final stage of the sperm's entry into the egg?

The sperm fuses its plasma membrane with that of the egg. Signup and view all the answers

What begins approximately 30 hours after fertilization?

The initiation of cleavage. Signup and view all the answers

What physiological change occurs in the spermatozoa when penetrating the zona pellucida?

Increase in calcium concentration. Signup and view all the answers

Which layer proliferates along the inside of the trophoblast to form the parietal endoderm?

Hypoblast Signup and view all the answers

What structure is NOT useful for nutrients to humans during embryonic development?

Yolk sac Signup and view all the answers

As of the 13th day of development, what happens to the vitelline sac?

It becomes much smaller Signup and view all the answers

Which structure surrounds the amniotic cavity by mesoderm during development?

Chorion Signup and view all the answers

What is the outer wall of the blastocyst formed by?

Extraembryonic mesoderm and cytotrophoblast Signup and view all the answers

What is the body stalk's role during the early stages of embryonic development?

First site for formation of blood vessels Signup and view all the answers

What does the hypoblast contribute to in the embryonic structure?

Parietal endoderm Signup and view all the answers

What is the primary role of the extraembryonic mesoderm in the formation of the villi?

It serves as a core structure for the primary villus. Signup and view all the answers

Which of the following describes a potential risk involved with the exchange of blood materials between the fetus and the mother?

Incompatibility between maternal and embryonic blood types. Signup and view all the answers

What is the most common cause of spontaneous abortion during the first trimester?

Chromosomal abnormalities in the embryo. Signup and view all the answers

During which gestational week is the incidence of spontaneous abortion typically highest?

Week 3. Signup and view all the answers

What could be a consequence if excess glucose enters the fetal circulation from maternal blood?

Increased fetal insulin production. Signup and view all the answers

What is a factor that may increase the incidence of spontaneous abortion after the 10th week of gestation?

Fetal abnormalities. Signup and view all the answers

Which complication might arise if maternal medications cross into fetal circulation?

Fetal developmental abnormalities. Signup and view all the answers

What is one reason a missed spontaneous abortion may go unnoticed?

It might resemble a late period. Signup and view all the answers

What is the role of the syncytiotrophoblast during implantation?

To erode the endometrium and establish a connection with maternal blood vessels Signup and view all the answers

What does the trophoblast release to maintain the corpus luteum during early pregnancy?

Human Chorionic Gonadotropin (hCG) Signup and view all the answers

How does the decidual reaction affect the endometrium?

It induces changes in the lamina propria of the endometrium Signup and view all the answers

What is the primary function of the corpus luteum during early pregnancy?

To synthesize progesterone and regulate endometrial functions Signup and view all the answers

What homeostatic mechanism do decidual cells engage in during implantation?

They secrete interleukins and growth factors to modulate implantation Signup and view all the answers

During early implantation, what might a woman mistakenly interpret as a menstrual period?

Erosion of blood vessels in the endometrium Signup and view all the answers

Which statement about the cytotrophoblast is correct?

It forms the inner layer of the trophoblast Signup and view all the answers

What potential role do anti-invasive factors from decidual cells play?

They regulate the erosion process to prevent excessive damage Signup and view all the answers

Study Notes

Fertilization

Egg size: The egg cell is significantly larger than the sperm cell, about 10 million times larger in volume.
Meeting place: Fertilization occurs in the ampullary region of the Fallopian tube. The folds in the uterine tube slow down the egg and create an optimal environment for sperm.
Phase 1 of Fertilization: Sperm travel through the corona radiata (granulosa cells) aided by hyaluronidase (released from the acrosome). The sperm then moves to the zona pellucida. Uterine tube enzymes may also aid this process.
Phase 2 of Fertilization: Sperm binding to the zona pellucida, specifically to ZP3 proteins. The acrosome releases enzymes (like acrosin). The sperm head fuses with the acrosome's anterior part in response to increased intracellular pH. Sperm penetrates the zona pellucida and arrives in the perivitelline space. Only one sperm will attach to the oocyte's plasma membrane.
Phase 3 of Fertilization: A single sperm attaches to the oocyte's microvilli using Izumo1 (on the sperm) and Juno (on the egg). This triggers the fusion of the membranes. Mitochondria of the sperm are excluded from the egg cytoplasm.
Phase 4 of Fertilization: Prevention of polyspermy (multiple sperm entry). The egg membrane depolarizes quickly after one sperm enters. Cortical granules are released into the perivitelline space causing hardening of the zona pellucida making it impenetrable to other sperm.
Phase 5 of Fertilization: Oocyte completes meiosis II. Two pronuclei (from the egg and sperm) are formed. Meiosis is completed.
Other key facts:
Paternal mitochondria are eliminated after fertilization
Mutations in Mitochondrial DNA can cause diseases
Increase in calcium concentration causes cortical granule release.
Increased permeability in the sperm's nucleus allows chromatin spreading to occur

Cleavage

Cleavage Definition: Series of cell divisions that increase the number of cells in the zygote. Cytoplasm doesn't increase in size during cleavage.
Timing: Cleavage begins around 30 hours after fertilization. Mammalian cleavage takes days.
Blastomeres: Resulting cells from cleavage.
Morula: 16 blastomeres form a solid ball called a morula. (takes 3 days);
Blastocyst: The morula develops into a blastocyst, containing a fluid-filled cavity (blastocoele). The outer layer is called trophoblast and inner cells form the embryoblast. (takes 4 days).

Blastocyst and Implantation

Polarity: The blastocyst is polarised– it has an embryonic pole and an abembryonic pole.
Trophoblast: The outer layer, responsible for implantation and placenta formation
Inner cell mass: This layer is responsible for the formation of the embryo.
Implantation: The blastocyst implants in the uterine wall. The embryo attaches to the endometrium in a location where it's ready, aided by adhesion molecules.
Invasion: The blastocyst penetrates the endometrium. It doesn't reach the myometrium. Syncytiotrophoblast helps erode the endometrium.
Immunotolerance: The embryo is a semi-allograft; the endometrium produces cytokines (like LIF) to promote tolerance.
Early pregnancy factor: The trophoblast produces this before implantation. This helps protect the embryo from the mother's immune system.
Decidua: The uterine tissue surrounding the implanting blastocyst is called decidua.

Maintenance of early pregnancy

Corpus luteum: Produces progesterone to maintain the uterine environment.
hCG: Human Chorionic Gonadotropin is produced by the trophoblast keeping the corpus luteum functioning (important for the first 10 days). This can be detected in maternal blood or urine by day 10.

Ectopic Pregnancy

Abnormal implantation: Implanted outside the uterus, usually in the fallopian tube.
Potential complications: Rupture of the fallopian tube and internal haemorrhage.
Signs and Symptoms: May be mistaken for other conditions, especially in the early stages.
Importance of diagnosis: Timely diagnosis is critical to prevent potentially serious complications.

Second Week of Development

Bilaminar Embryo: The inner cell mass separates to form the epiblast and hypoblast.
Amniotic Cavity: Forms from the epiblast.
Yolk Sac: Forms from the hypoblast.
Extraembryonic Coelom: Forms the cavity between the yolk sac and the trophoblast.
Chorion: The outer layer is called chorion, inside this the cavity is called chorionic cavity.
Primitive Blood Vessels:
Develop in the extraembryonic mesoderm.
Important for placental development.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on key concepts in embryology with this Chapter 3 quiz. Explore topics such as blastomere roles, junction types, and the formation of the blastocoele. Additionally, discover the effects of mosaicism and differences in trophoblast types.