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?

Epiblast Signup and view all the answers

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

3rd week Signup and view all the answers

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

Teratoma formation Signup and view all the answers

Which of the following describes a teratoma?

A neoplasm of mixed differentiation, with tissues representing all embryonic layers Signup and view all the answers

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

Cartilage Signup and view all the answers

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

Four viable gametes. Signup and view all the answers

At what stage of development do oogonia begin meiosis?

By the 5th month of foetal gestation. Signup and view all the answers

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

Meiosis in females is synchronous and slow, whilst in males is asynchronous. Signup and view all the answers

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

They form the seminiferous tubules. Signup and view all the answers

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

To keep primary spermatocytes separated from the blood vessels. Signup and view all the answers

Where do spermatogonia undergo proliferation during spermatogenesis?

In the basal compartment of seminiferous tubules. Signup and view all the answers

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

Spermiogenesis. Signup and view all the answers

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

The nucleus reduces in size and histones are replaced by protamines. Signup and view all the answers

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

To guide the formation of the first lineages in the blastocyst. Signup and view all the answers

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

The 3rd week Signup and view all the answers

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

It prevents implantation before the blastocyst is ready. Signup and view all the answers

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

Endoderm of the gut tube Signup and view all the answers

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

The range of cell types a precursor can potentially develop into. Signup and view all the answers

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

The formation of a mosaic embryo with multiple cell lines. Signup and view all the answers

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

Vasculogenesis Signup and view all the answers

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

The type of cell a precursor normally becomes. Signup and view all the answers

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

Angiogenesis Signup and view all the answers

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

To stimulate endothelial cell proliferation and vessel formation Signup and view all the answers

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

The release of proteases from the trophoblast's microvilli. Signup and view all the answers

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

It can still be flushed out from the uterus. Signup and view all the answers

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

The ability of cancer cells to form vessel-like structures independently from normal blood vessels. Signup and view all the answers

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

Vitelline veins Signup and view all the answers

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

It acts as an immunosuppressant to regulate immunotolerance. Signup and view all the answers

Which extraembryonic membrane does NOT derive from the trophoblast?

Amnion Signup and view all the answers

Why might the maternal environment initially reject the embryo?

Because the embryo is a semi allograft, containing paternal genetic information not recognized as self. Signup and view all the answers

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

It prevents recognition of the embryo as a foreign body by the mother's immune system. Signup and view all the answers

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

Syncytiotrophoblast Signup and view all the answers

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

They facilitate the anastomosis between maternal sinusoids and the lacunar network. Signup and view all the answers

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

It's an acellular material and seals the implantation site. Signup and view all the answers

What is the decidual reaction?

The transformation of endometrial stromal cells into metabolically active secretory cells. Signup and view all the answers

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

It maintains the uterine wall in a favorable state for the developing embryo. Signup and view all the answers

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

Bleeding is caused by erosion of the uterine wall by the blastocyst and is often misinterpreted as a menstrual cycle. Signup and view all the answers

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

Decidua basalis Signup and view all the answers

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

To inactivate maternal immune cells locally Signup and view all the answers

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

Amnio-chorionic membrane Signup and view all the answers

What is a potential consequence of improper placental function?

Intra Uterine Growth Retardation (IUGR) Signup and view all the answers

What is the key characteristic of placenta accreta?

Abnormal adherence of chorionic villi to the myometrium Signup and view all the answers

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

Consists of the decidua basalis covered by a foetally-derived cytotrophoblastic shell Signup and view all the answers

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

Placenta percreta Signup and view all the answers

What forms the connection between the placenta and the embryo?

Umbilical cord Signup and view all the answers

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.