Embryology Basics Quiz

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Questions and Answers

What does embryology primarily study?

Only the development of embryos.

The fertilization process alone.

Birth defects and their treatments.

The development of gametes, embryos, and congenital disorders. (correct)

What is the primary focus during the first week of human development?

The formation of the placenta.

From the ovarian cycle to blastocyst formation. (correct)

Genetic mutation occurrence.

Fetal development and organ formation.

Why is the study of embryology important?

It solely focuses on pregnancy benefits.

It is a requirement for studying adult anatomy.

It leads to improved adult disease treatments.

It helps understand the causes of birth defects and enhances prenatal care. (correct)

What percentage of infants are typically born with a birth defect?

3-4% Signup and view all the answers

Which statement is true regarding birth defects?

They can lead to disabilities and are a leading cause of infant mortality. Signup and view all the answers

Which period of prenatal development occurs from conception to 12 weeks?

Germinal Period Signup and view all the answers

What is the primary focus of the embryonic period in the context of birth defects?

Formation of structural components Signup and view all the answers

At what stage do female gametes undergo oogenesis?

Before birth Signup and view all the answers

How does oogenesis differ from spermatogenesis?

Oogenesis is associated with a finite number of gametes, while spermatogenesis is continuous. Signup and view all the answers

During which period is the risk of structural defects the highest?

Embryonic Period Signup and view all the answers

What is the primary purpose of oogenesis in females?

To produce and mature oocytes Signup and view all the answers

How many primary oocytes are present in each ovary by puberty?

60,000 – 80,000 Signup and view all the answers

Which of the following statements about Meiosis II in oogenesis is true?

It is completed only if the oocyte is fertilized. Signup and view all the answers

What is aneuploidy in relation to chromosomal abnormalities?

An abnormal number of chromosomes due to nondisjunction Signup and view all the answers

Which trisomy is commonly known as Down syndrome?

Trisomy 21 Signup and view all the answers

What typically happens during nondisjunction in the first meiotic division?

Homologous chromosomes fail to segregate. Signup and view all the answers

What is the expected outcome of having an extra chromosome due to nondisjunction?

Aneuploidy resulting in trisomy Signup and view all the answers

How many secondary oocytes typically proceed to maturation each month?

1-2 Signup and view all the answers

Study Notes

Introduction to Embryology and the First Week of Human Development

Embryology is the study of the development of a genetically unique organism.
The zygote is a diploid (half genes from mother and half from father).
The zygote does not encode its own genome (maternal effect).
Identical twins result from an early separation of the zygote into two separate cell masses.
Fraternal twins result from the formation of two separate zygotes.
The process of fertilization results in the formation of the zygote.
The first stage of development in a genetically unique organism.

Stages of Embryonic Development

Germinal period (weeks 1-2): Involves fertilization and the early divisions of the zygote within the fallopian tube.
Embryonic period (weeks 3-8): Significant development of the major organs and body systems.
Fetal period (weeks 9-birth): Continued growth and maturation of the body systems.
Stages from fertilization to implantation and development.
Early development stages - zygote, 2-cell, 4-cell, 8-cell stage, morula, blastocyst.

Oogenesis

Oogonia (germ cells): One to two million formed during development per ovary.
Primary oocytes: 60,000 - 80,000 remain in each ovary by puberty.
Secondary oocytes (follicles): About 20 proceed to maturation every month.
1-2 develop and proceed to ovulation each month. The process of forming female gametes.

Spermatogenesis

Spermatogonium (germ cell): Start of spermatogenesis.
Formation of the male gametes. Development of sperm cells, from spermatogonium to maturation.

Fertilization

Process where a male and female gamete fuse.
Occurs in the ampullary region of the uterine tube.
Only 1% of sperm enter the cervix.
The trip to the fallopian (oviduct) can take 30 mins to 6 days.

Capacitation

This happens in fallopian tube. Interactions between sperm and fallopian tube surface.
Destabilization of acrosomal sperm head membrane.
Increased motility.

Acrosome Reaction

The reaction occurs in the acrosome of the sperm.
Allows sperm to break into the zona pellucida of the egg.
Involves release of acrosin and trypsin-like enzymes.

Fertilization Stages

Phase 1: Penetration of the corona radiata.
Phase 2: Penetration of the zona pellucida.
Phase 3: Fusion of the sperm and oocyte membranes.
The egg responds in three ways to protect itself from polyspermy; altering the membrane structure, completing the second meiotic division and formation of the female pronucleus, metabolic reactivation for early embryogenesis.

Blastocyst Formation

Morula enters the uterus; fluid goes through the zona pellucida into the intercellular space.
Forming the blastocoel (blastocyst).
Inner cell mass (embryoblast) and outer cell mass (trophoblast) formation.
Zona pellucida ruptures to allow implantation.

Blastocyst Implantation

Trophoblast cells secrete enzymes to penetrate between epithelial cells of the uterine wall (endometrium).
Immune systems are modulated to accept the "foreign" embryo.
Implantation occurs in specific uterine areas. The lining (enodometrium) undergoes changes that support implantation and the embryo's early growth.

The uterine wall

It consists of three layers: Endometrium, Myometrium, Perimetrium.
Endometrium, the innermost layer, undergoes cyclical changes during the menstrual cycle.
Changes in the endometrium during the menstrual cycle.

Menstrual Cycle

Cycle Regulated by hormones released by the ovaries.
The different phases (Follicular, Secretory, menstrual, gravid).
The endometrium undergoes cyclical changes from puberty to menopause.

Ectopic Pregnancy

Occurs when the blastocyst implants outside the uterus (usually the fallopian tubes).
Most often the embryo dies during the second month of gestation.
A life-threatening pregnancy if not terminated.
This occurs with approximately 2% of all pregnancies.

Assisted Reproductive Technology (ART)

Includes medical procedures to address infertility.
About 15-30% of couples encounter infertility problems.
1% of births from ART procedures have significant complications.
IVF uses in-vitro (test tube) fertilizations.
ART risks include: increased prematurity, low birth weight, increased risk of birth defects, childhood malignancies.

Embryonic Stem Cells

Embryonic stem cells (ESCs) can be isolated from human embryos and cultured indefinitely.
ESCs are pluripotent, meaning they can differentiate into any type of cell in the body.
ESCs can be used for stem cell therapy.

Chromosomal Abnormalities

Numerical chromosomal abnormalities (e.g., trisomies, monosomies).
Trisomy 21 (Down syndrome), Trisomy 18 (Edwards syndrome), Trisomy 13 (Patau syndrome).
Sex chromosome trisomies (e.g., Klinefelter syndrome (XXY), Trisomy X (XXX), Jacob's syndrome (XYY).
Sex chromosome monosomy (e.g., Turner syndrome (45,X)).
Risk of aneuploidy increases with maternal age.

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Description

Test your knowledge on the fundamental concepts of embryology, including human development stages, importance of the study, and birth defects. This quiz covers key topics regarding gamete formation and prenatal development periods. Perfect for students in biology or health sciences.