أسئلة المحاضرة الرابعة امبريولوجي (قبل التعديل)

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Questions and Answers

What process occurs when two or more ova are fertilized by sperm from separate acts of coitus during the same menstrual cycle?

Cleavage

Zygotic division

Gestation

Superfecundation (correct)

What is the main characteristic of the cleavage stage in embryonic development?

Formation of organs

Formation of the umbilical cord

Development of the placenta

Repeated mitosis of blastomers (correct)

At what stage is the morula formed, and how many cells does it typically consist of?

16-32 cells, formed 3 days after fertilization (correct)

8-16 cells, formed 2 days after fertilization

4-8 cells, formed 4 days after fertilization

32-64 cells, formed 1 week after fertilization

Which component of the blastocyst develops into the fetal part of the placenta?

Trophoblast Signup and view all the answers

How many days after fertilization does the blastocyst stage occur?

4 days Signup and view all the answers

What is capacitation in the fertilization process?

The removal of seminal plasma proteins from sperm Signup and view all the answers

Where does fertilization typically occur?

In the ampulla of the uterine tube Signup and view all the answers

Which substance is released during the acrosomal reaction to aid in penetrating the zona pellucida?

Acrosin Signup and view all the answers

What is the role of the zona cortical reaction?

To make the zona pellucida impermeable to additional sperm Signup and view all the answers

What determines the sex of the embryo during fertilization?

Whether the sperm carries an X or Y chromosome Signup and view all the answers

What happens immediately after the fertilization process completes?

The initiation of zygote cell division Signup and view all the answers

Which of the following is an anomaly related to fertilization?

Parthenogenesis Signup and view all the answers

What is the outcome of dispermy during fertilization?

Triploidy zygote Signup and view all the answers

What is the correct sequence of cell division stages during cleavage after fertilization?

2 cell stage, 4 cell stage, 8 cell stage Signup and view all the answers

Which of the following correctly describes the morula stage of embryonic development?

It consists of 16-32 cells and is formed 3 days after fertilization. Signup and view all the answers

What structures are included in the blastocyst stage?

Trophoblast, blastocele, and inner cell mass Signup and view all the answers

How many days after fertilization does the formation of the blastocyst occur?

4 days Signup and view all the answers

Which of the following statements about the trophoblast is true?

It consists of outer flat cells and contributes to the placenta. Signup and view all the answers

What is the primary aim of capacitation during fertilization?

To enhance the motility of the sperm Signup and view all the answers

Which enzyme released during the acrosomal reaction is responsible for aiding sperm in penetrating the corona radiata?

Hyaluourinidase Signup and view all the answers

What is the significance of the zona cortical reaction following fertilization?

It prevents further sperm from fertilizing the oocyte Signup and view all the answers

At which point in fertilization does the male pro-nucleus formation occur?

Once the sperm's tail is lost and nucleus enlarges Signup and view all the answers

How many chromosomes are present in the zygote formed after the fusion of male and female pro-nuclei?

46 chromosomes Signup and view all the answers

Which of the following describes parthenogenesis?

An embryo developing without fertilization Signup and view all the answers

Which is the correct sequence of events leading to the formation of a zygote?

Capacitation, acrosomal reaction, fusion, meiosis Signup and view all the answers

What happens to the female gamete during fertilization after the second meiosis resumes?

It results in the formation of a female pro-nucleus Signup and view all the answers

In which stage of early embryonic development is the blastocyst formed?

4th day after fertilization Signup and view all the answers

What is the primary characteristic of the morula stage in embryonic development?

It consists of 16 to 32 cells. Signup and view all the answers

Which component of the blastocyst develops into the embryo?

Inner cell mass (embryoblast) Signup and view all the answers

What is the process of repeated mitosis of the zygote called?

Segmentation Signup and view all the answers

What forms the fetal part of the placenta during the blastocyst stage?

Trophoblast Signup and view all the answers

What is the primary role of hyaluronidase during fertilization?

To penetrate the corona radiata Signup and view all the answers

Which statement accurately describes the process of capacitation?

It involves the removal of seminal plasma proteins from the sperm's head. Signup and view all the answers

Which of the following best describes the outcome of the zona cortical reaction?

It makes the zona pellucida impermeable to additional sperm. Signup and view all the answers

What is the significance of the site known as the ampulla in fertilization?

It is the ideal location for the fertilization of the ovum. Signup and view all the answers

What happens during the acrosomal reaction?

Enzymes are released to facilitate penetration of the zona pellucida. Signup and view all the answers

Which chromosome configuration occurs when a sperm carrying an X chromosome fertilizes an ovum?

XX leading to a female embryo Signup and view all the answers

What process results in triploidy during fertilization?

Dispermy, with two sperms penetrating one ovum Signup and view all the answers

What is the key outcome of the fusion of the male and female pro-nuclei?

Formation of the embryo with 46 chromosomes Signup and view all the answers

Study Notes

Fertilization

Definition: Meeting and union of male and female gametes
Site: Ampulla of uterine tube
Steps:
- Sperm deposited in posterior fornix of vagina (200-600 x 10⁶ sperms)
- Capacitation: Removal of seminal plasma proteins from sperm head, making sperm more active for fertilization
- Acrosomal reaction: Enzymes released from sperm's acrosome, penetrating the corona radiata and zona pellucida
- Fusion of sperm and egg membranes
- Zona cortical reaction: Zona pellucida becomes impermeable to other sperm, preventing polyspermy
- Second meiosis of the ovum
- Formation of male and female pronuclei
- Union of pronuclei: Forming the zygote

Results of Fertilization

Sex determination: Y chromosome = male, X chromosome = female
Embryonic health: Assessment of embryo's health
Restoration of diploid number: Restores normal 46 chromosomes
Initiation of cell division: Begins zygote cell division

Anomalies

Parthenogenesis: Pregnancy without fertilization (all offspring female)
Dispermy triploidy: Two sperm fertilize one egg, resulting in a triploid zygote
Superfecundation: Fertilization of more than one egg released during the same menstrual cycle

Cleavage (Segmentation)

Definition: Repeated mitosis of blastomeres, increasing cell number rapidly
Steps:
- 2, 4, 8 cell stage
- Blastomeres undergo mitosis as zygote travels through uterine tube
- Morula formation: 16-32 cells within zona pellucida (3 days post fertilization), enters uterine cavity
- Blastocyst formation: 4th day after fertilization
  - Blastocele: Fluid-filled cavity inside the blastocyst
  - Trophoblast: Outer layer of cells, forms fetal part of placenta
  - Inner cell mass (embryoblast): Mass of cells that forms the embryo

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