Embryology Quiz: Fertilization to Teratomas
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Questions and Answers

According to the embryological point of view, which period spans from fertilization to implantation?

  • First trimester
  • Period of the embryo
  • Period of the egg (correct)
  • Period of the fetus

What is the duration of pregnancy when counted from fertilization?

  • 38 weeks (correct)
  • 40 weeks
  • 42 weeks
  • 36 weeks

What is the equivalent of 'anterior' in adult anatomy, when referring to the embryo?

  • Dorsal
  • Cranial
  • Ventral (correct)
  • Caudal

In what structure do primordial germ cells reside during the 2nd week of development?

<p>Epiblast (D)</p> Signup and view all the answers

During which week do primordial germ cells migrate within the wall of the yolk sac?

<p>3rd week (A)</p> Signup and view all the answers

What is a potential consequence of primordial germ cells migrating to extragonadal sites?

<p>Teratoma formation (B)</p> Signup and view all the answers

Which of the following describes a teratoma?

<p>A neoplasm of mixed differentiation, with tissues representing all embryonic layers (A)</p> Signup and view all the answers

Which of the following is NOT a tissue commonly found in teratomas?

<p>Cartilage (D)</p> Signup and view all the answers

Which of the following best describes the outcome of meiosis for each spermatogonium?

<p>Four viable gametes. (C)</p> Signup and view all the answers

At what stage of development do oogonia begin meiosis?

<p>By the 5th month of foetal gestation. (B)</p> Signup and view all the answers

What is a key difference between meiosis in males and females?

<p>Meiosis in females is synchronous and slow, whilst in males is asynchronous. (D)</p> Signup and view all the answers

What is the role of Sertoli cells during spermatogenesis after puberty?

<p>They form the seminiferous tubules. (B)</p> Signup and view all the answers

What is the function of the blood-testis barrier during spermatogenesis?

<p>To keep primary spermatocytes separated from the blood vessels. (C)</p> Signup and view all the answers

Where do spermatogonia undergo proliferation during spermatogenesis?

<p>In the basal compartment of seminiferous tubules. (D)</p> Signup and view all the answers

What is the process called by which spermatids become mature sperm cells?

<p>Spermiogenesis. (A)</p> Signup and view all the answers

During spermiogenesis, what change occurs in the nucleus of spermatids?

<p>The nucleus reduces in size and histones are replaced by protamines. (C)</p> Signup and view all the answers

What is the primary role of lineage-specific transcription factors during blastocyst formation?

<p>To guide the formation of the first lineages in the blastocyst. (B)</p> Signup and view all the answers

During which week of embryonic development does the formation of primitive blood vessels begin?

<p>The 3rd week (D)</p> Signup and view all the answers

What is the significance of the zona pellucida in the early stages of embryonic development?

<p>It prevents implantation before the blastocyst is ready. (B)</p> Signup and view all the answers

Which of the following is NOT a location where primitive blood vessels initially form?

<p>Endoderm of the gut tube (D)</p> Signup and view all the answers

What does 'developmental potency' refer to in the context of early embryonic development?

<p>The range of cell types a precursor can potentially develop into. (D)</p> Signup and view all the answers

What is a potential consequence of a mitotic error occurring during the cleavage stage?

<p>The formation of a mosaic embryo with multiple cell lines. (C)</p> Signup and view all the answers

What is the process of blood vessel formation from precursor cells called?

<p>Vasculogenesis (B)</p> Signup and view all the answers

What is 'developmental fate' in the context of early cell differentiation?

<p>The type of cell a precursor normally becomes. (B)</p> Signup and view all the answers

Which process refers to the formation of new blood vessels by budding from existing ones?

<p>Angiogenesis (D)</p> Signup and view all the answers

What is the role of Vascular Endothelial Growth Factor A (VEGF-A) in angiogenesis?

<p>To stimulate endothelial cell proliferation and vessel formation (D)</p> Signup and view all the answers

What triggers the hatching of the blastocyst from the zona pellucida?

<p>The release of proteases from the trophoblast's microvilli. (D)</p> Signup and view all the answers

During the apposition phase of implantation, what is a notable characteristic of the blastocyst?

<p>It can still be flushed out from the uterus. (A)</p> Signup and view all the answers

Which of the following best describes vasculogenic mimicry in cancer cells?

<p>The ability of cancer cells to form vessel-like structures independently from normal blood vessels. (B)</p> Signup and view all the answers

Which of these vessels is considered part of the inflow portion of the tubular heart?

<p>Vitelline veins (C)</p> Signup and view all the answers

What specific role does the early pregnancy factor play during implantation?

<p>It acts as an immunosuppressant to regulate immunotolerance. (D)</p> Signup and view all the answers

Which extraembryonic membrane does NOT derive from the trophoblast?

<p>Amnion (B)</p> Signup and view all the answers

Why might the maternal environment initially reject the embryo?

<p>Because the embryo is a semi allograft, containing paternal genetic information not recognized as self. (D)</p> Signup and view all the answers

What is the primary function of interleukin 2 in the context of embryo implantation?

<p>It prevents recognition of the embryo as a foreign body by the mother's immune system. (C)</p> Signup and view all the answers

Which layer of the trophoblast is responsible for producing enzymes that digest the endometrium?

<p>Syncytiotrophoblast (C)</p> Signup and view all the answers

What is the function of lacunae that form in the syncytiotrophoblast?

<p>They facilitate the anastomosis between maternal sinusoids and the lacunar network. (D)</p> Signup and view all the answers

What is the 'coagulation plug' primarily composed of and what is its role?

<p>It's an acellular material and seals the implantation site. (C)</p> Signup and view all the answers

What is the decidual reaction?

<p>The transformation of endometrial stromal cells into metabolically active secretory cells. (C)</p> Signup and view all the answers

What is the role of progesterone during the early stages of pregnancy?

<p>It maintains the uterine wall in a favorable state for the developing embryo. (A)</p> Signup and view all the answers

What might cause vaginal bleeding during early pregnancy and why is it often misinterpreted?

<p>Bleeding is caused by erosion of the uterine wall by the blastocyst and is often misinterpreted as a menstrual cycle. (A)</p> Signup and view all the answers

Which structure is NOT a component of the foetal side of the placenta?

<p>Decidua basalis (C)</p> Signup and view all the answers

What is the primary function of molecules produced on the foetal placental surface?

<p>To inactivate maternal immune cells locally (A)</p> Signup and view all the answers

The fusion of the amnion and smooth chorion forms which membrane?

<p>Amnio-chorionic membrane (D)</p> Signup and view all the answers

What is a potential consequence of improper placental function?

<p>Intra Uterine Growth Retardation (IUGR) (C)</p> Signup and view all the answers

What is the key characteristic of placenta accreta?

<p>Abnormal adherence of chorionic villi to the myometrium (A)</p> Signup and view all the answers

Which of the following correctly describes the maternal side of the placenta?

<p>Consists of the decidua basalis covered by a foetally-derived cytotrophoblastic shell (A)</p> Signup and view all the answers

What is the term for the condition where the placenta penetrates through the myometrium to reach the perimetrium?

<p>Placenta percreta (C)</p> Signup and view all the answers

What forms the connection between the placenta and the embryo?

<p>Umbilical cord (B)</p> Signup and view all the answers

Flashcards

Period of the Egg

The first stage of human development, starting from fertilization and lasting until the embryo implants in the uterine wall.

Period of the Embryo

The stage of human development from implantation to the 8th week of gestation, during which the major body organs and systems are formed.

Period of the Fetus

The stage of human development from the 8th week to birth, characterized by growth and refinement of existing organs and tissues.

Primordial Germ Cells

Cells that will eventually develop into sperm or eggs, depending on their location.

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Migration of Primordial Germ Cells

The journey of primordial germ cells from their initial location in the epiblast to the developing gonads.

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Teratomas

Tumors that arise from pluripotent germ cells and contain different types of tissues representing all embryonic layers.

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Pluripotency

The ability of primordial germ cells to give rise to different types of tissues.

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Gametogenesis

The process of generating mature sperm or egg cells.

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Meiosis

The process of reduction in chromosomal number from diploid to haploid, occurring during sexual gamete production.

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Spermatogonia

Cells that give rise to sperm cells via meiotic division. They undergo multiple rounds of mitosis to increase their number.

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Spermatogenesis

The process of specialized cells differentiating into sperm, involving intricate morphological changes.

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Meiosis I

The first meiotic division, where homologous chromosomes pair and exchange genetic material.

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Meiosis II

The second meiotic division, where sister chromatids separate, resulting in haploid gametes.

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Spermiogenesis

The process of a spermatid transforming into a mature sperm, involving nuclear condensation, tail formation, and size reduction.

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Sertoli Cells

Cells in seminiferous tubules that nourish developing sperm cells and form the blood-testis barrier.

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Blood-testis Barrier

A barrier formed by Sertoli cells that prevents the immune system from attacking developing sperm cells, which are antigenically different from the male's body.

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Developmental Potency

The ability of a precursor cell to develop into different cell types, representing its potential.

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Developmental Fate

The actual type of cell a precursor cell typically develops into, its predetermined fate.

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Mosaic Cleavage-State Embryo

An embryo with cells that have inherited an error in cell division, leading to a mixture of normal and abnormal cells.

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Implantation Window

A period of several days after ovulation where the uterus is prepared for implantation, characterized by specific hormonal and cellular changes.

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Apposition

The first stage of implantation, where the blastocyst loosely attaches to the uterine lining without penetrating it.

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Adhesion

The second phase of implantation, where the blastocyst adheres more firmly to the uterine lining, mediated by adhesion molecules expressed by both embryo and uterus.

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Trophoblast

The outer layer of cells in the blastocyst that will develop into the placenta, responsible for nutrient exchange between mother and embryo.

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Early Pregnancy Factor (EPF)

A protein produced by the trophoblast cells to suppress the mother's immune response, ensuring the embryo is not rejected.

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Angiogenesis

The formation of new blood vessels from pre-existing ones, crucial for healing and growth.

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Vasculogenic mimicry

The ability of cancer cells to form their own blood vessel-like structures to obtain nutrients, bypassing normal blood vessels.

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Vasculogenesis

The formation of blood vessels from precursor cells in the early embryo.

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Umbilical cord

The structure that connects the developing embryo to the placenta, supplying nutrients and oxygen.

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Placenta

The structure that provides the interface between the mother and the developing embryo, exchanging nutrients and oxygen.

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Umbilical veins

Veins carry oxygen-rich blood from the placenta to the embryo.

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Umbilical arteries

Arteries carry oxygen-poor blood from the embryo to the placenta.

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Chorion

The outermost membrane surrounding the embryo, contributing to the placenta formation.

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Blastocyst Implantation

The process of a blastocyst embedding itself into the uterine wall, which is critical for successful pregnancy.

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Cytotrophoblast

The inner layer of the trophoblast that forms the chorionic sac and contributes to fetal development.

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Syncytiotrophoblast

The outer layer of the trophoblast that invades the uterine lining, allowing for nutrient exchange and placental formation.

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Decidual Reaction

The transformation of endometrial cells into metabolically active cells during implantation, supporting the embryo's needs.

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Lacunae

Small spaces in the syncytiotrophoblast that connect with maternal blood vessels, facilitating nutrient exchange.

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Maternal Sinusoids

The maternal blood vessels that are remodeled during early pregnancy to provide oxygen and nutrients to the developing embryo.

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Anastomosis

The process by which the maternal sinusoids are connected to the lacunar network, establishing a circulatory system between mother and embryo.

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Placenta Accreta

A condition where the chorionic villi of the placenta abnormally adhere to the myometrium, leading to complications during birth and potential hemorrhages.

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Placenta Increta

A more severe form of placenta accreta where the chorionic villi penetrate the myometrial wall.

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Placenta Percreta

The most severe form of placental adherence, where the chorionic villi pass completely through the myometrium and attach to the perimetrium. This can lead to dangerous complications impacting the rectum or bladder.

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Intra Uterine Growth Retardation (IUGR)

A condition where the placenta is not functioning properly, leading to the fetus not growing at a normal pace. This can cause health issues for the baby.

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Decidual Immune Barrier

A barrier formed by the decidua, a layer of the uterine wall that protects the fetus from the mother's immune system.

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Maternal Immune Tolerance

A state where the mother's immune system is suppressed or regulated to avoid attacking the fetus, which has foreign antigens.

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Foetal Placental Molecules

Molecules found on the placental surface of the fetus that help to suppress the activity of the mother's immune cells in the local area.

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Placental Invasion

A condition where the syncytiotrophoblast, a layer of cells in the placenta, invades too deeply into the myometrium causing complications.

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Study Notes

Human Embryology - Introduction

  • Human embryology can be divided according to medical and embryological viewpoints.
  • Medical viewpoint divides development into three trimesters (1st, 2nd, and 3rd).
  • Embryological viewpoint divides development into:
    • Period of the egg: From fertilization to implantation.
    • Period of the embryo: From implantation to the 8th week.
    • Period of the fetus: From the end of the 8th week.
  • Pregnancy lasts 38 weeks from fertilization or 40 weeks from the last menstrual period.

Embryo Shape and Axes

  • The embryo is a curved object that changes shape over time.
  • Key axes include:
    • Anterior/Posterior: Front/Back
    • Ventral/Dorsal: Belly/Back
    • Superior/Inferior: Top/Bottom
    • Cranial/Caudal: Head/Tail

Embryo Sections

  • Sections can be transverse, median (sagittal), or coronal (frontal).

Gametogenesis

  • Primordial germ cells (PGCs): Develop in the epiblast during the second week and migrate to the yolk sac by the third week, then to the developing gonads by weeks 5-6.
  • Teratomas: Tumours resulting from migrating PGCs to abnormal sites. These tumours may contain several tissue types, including hair, muscle, and bone.
  • Large Sacrococcygeal Teratomas: Can cause complications such as hydrops (fluid buildup), polyhydramnios (excess amniotic fluid), and potential dystocia.
  • Oogenesis (Female Gametogenesis):
    • All oogonia in the ovary enter meiosis I by the 5th month of gestation.
    • By birth, there are about 2 million primary oocytes.
    • Some oocytes degenerate before puberty.
    • Only about 400 oocytes will be ovulated during a woman's reproductive life.
  • Spermatogenesis (Male Gametogenesis):
    • Process continues throughout a man's reproductive life.
    • Spermatogonia produce primary spermatocytes.
    • Meiosis occurs, producing spermatids.

Spermatogenesis

  • Puberty: Sertoli cells differentiate into seminiferous tubules.
  • Basal Compartment: Spermatogonia proliferate within the basal compartment.
  • Adluminal Compartment: Spermatogonia undergo changes in the adluminal compartment.
  • Blood-Testis Barrier: Spermatocytes are separated from the blood vessels to prevent an immune response.
  • Spermiogenesis: Spermatids mature into spermatozoa.
  • Maturation: Final steps of maturation occur in the epididymis (mobility, functional maturation).
  • Motility and Sperm Count: Essential for successful fertilization.

Oogenesis

  • Oogenesis is the maturation of the oocyte and surrounding follicle.
  • Primordial follicles: present at birth, where cells will differentiate.
  • Follicle Stages: Different phases of development, from primordial follicle to primary follicle.
  • Hormonal Regulation: FSH and LH regulate folliculogenesis.
  • Meiosis I: The process is completed at ovulation, which starts at puberty.
  • Meiosis II: Process completed upon fertilization.

Ovulation

  • Ovulation occurs about 14 days prior to the onset of the menstrual period.
  • The cumulus oophorus surrounds the oocyte as it ovulates.
  • The released oocyte is immediately captured by the fimbriae of the uterine tube.

Fertilization

  • Spermatozoa must reach and penetrate the ovum.
  • Sperm undergo capacitation, removing surface proteins in the female reproductive tract.
  • Acrosome reaction exposes enzymes to digest the corona radiata and zona pellucida.
  • Fusion of sperm and egg membranes triggers completion of meiosis II and formation of the zygote.
  • Sperm and egg nuclei fuse (syngamy), resulting in the diploid zygote.

Cleavage

  • The zygote undergoes a series of rapid mitotic divisions, not associated with substantial cell growth; cleavage.
  • Blastomeres are the cells produced during cleavage.
  • Compaction results from an increase in cell-to-cell contact.
  • Morula develops into a blastocyst.
  • Blastocyst contains a fluid-filled cavity (blastocoel).

Implantation

  • The blastocyst implants into the uterine wall (endometrium) between 6 and 10 days after fertilization.
  • Different phases (apposition, adhesion, and invasion) occur during implantation.
  • Trophoblast cells in the blastocyst participate in constructing the placenta to aid in nutrient exchange.

Third Week Embryology

  • Gastrulation: Key process that forms three germ layers (ectoderm, mesoderm and endoderm)
  • Primitive streak: Thickening structure appears on the epiblast as the start of gastrulation
  • Migration and Invagination: Epiblast cells move inward at the primitive streak; forms endoderm
  • Mesoderm: Forms from the epiblast cells, which migrate into the space between the epiblast and endoderm.
  • Bilaminar embryonic disc transformed into trilaminar embryonic disc.
  • Neural Plate: Forms from the ectoderm in order to generate the central nervous system.

Fourth Week Embryology

  • Segmentation: formation of somites from paraxial mesoderm (key structure in the creation of the vertebrae).
  • Folding: Cranial and caudal regions fold in order to create an elongated body-shape, creating the primitive gut.

Fifth to Eight Week Embryology

  • Continuation of organ development from the germ layers
  • Limb-buds start appearing

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Description

Test your knowledge on embryological development with this quiz covering topics from fertilization to teratomas. Learn about germ cell migration, meiotic processes, and key anatomical terms in human development. Perfect for students in embryology or anatomy courses.

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