Introduction to Human Embryology – Vocabulary Review

A comprehensive set of vocabulary flashcards covering fundamental terms, developmental periods, molecular tools, and clinical correlations from the "Introduction to Human Embryology" lecture.

Embryology

The study of the molecular, cellular and structural events that lead from a single cell to a complete organism.

Embryogenesis (Organogenesis)

The first 8 weeks of human development during which the basic body plan and organ primordia are established.

Fetal Period

Developmental phase from the end of week 8 until birth, characterized by growth and functional maturation of organs.

Prenatal Development

The entire period of human growth before birth, encompassing both embryonic and fetal stages.

Teratology

The branch of embryology that investigates the causes and mechanisms of congenital anomalies (birth defects).

Teratogen

Any infectious, chemical, metabolic or physical agent that can disturb embryonic or fetal development and cause birth defects or death.

Periods of Susceptibility

Timeframes in development when embryos or fetuses are most vulnerable to teratogens; highest sensitivity is weeks 3–8.

Thalidomide Crisis (1961)

A historical event where the antinauseant thalidomide caused limb defects such as amelia and phocomelia in exposed fetuses.

Amelia

Congenital absence of one or more limbs.

Phocomelia

A limb abnormality where long bones are missing and the hand or foot is attached close to the torso.

Primitive Streak

A midline structure appearing in week 3 that establishes the body axes and initiates gastrulation.

Primitive Node

Organizer region at the anterior end of the primitive streak directing formation of axial structures.

Gametogenesis

Process by which precursor cells divide and differentiate to form mature haploid gametes (sperm or oocytes).

Fertilization

Union of a sperm and an oocyte to form a diploid zygote—the starting point of pregnancy.

Implantation

Attachment and embedding of the blastocyst into the uterine lining, usually completed by day 9–10 post-fertilization.

Blastocyst

Early pre-implantation embryo consisting of an inner cell mass, trophoblast and blastocoel cavity.

Bilaminar Germ Disc

Two-layered embryo (epiblast and hypoblast) formed from the inner cell mass at the end of week 2.

Epiblast

Outer cell layer of the bilaminar disc that gives rise to all three germ layers.

Hypoblast

Inner layer of the bilaminar disc contributing to extra-embryonic structures such as the yolk sac lining.

Trilaminar Germ Disc

Three-layered embryonic disc (ectoderm, mesoderm, endoderm) formed during gastrulation in week 3.

Ectoderm

Outer germ layer that generates nervous system, epidermis, hair, nails, and related structures.

Mesoderm

Middle germ layer producing muscle, bone, connective tissue, cardiovascular system and urogenital organs.

Endoderm

Inner germ layer forming the lining of the gut, respiratory tract, liver, pancreas and other internal organs.

Organogenesis

Formation of specific organs from the three germ layers, primarily during weeks 3–8.

Molecular Embryology

Field that applies molecular biology techniques to study gene regulation in normal and abnormal development.

Genome Sequencing

Determining the complete DNA sequence of an organism, enabling deeper insights into developmental genetics.

Reporter Gene

A genetic tag (e.g., GFP) introduced to visualize and trace cell lineages during development.

Fluorescent Probe

Molecular tool that binds specific DNA/RNA or proteins, allowing visualization of gene expression in embryos.

Gene Knockout

Experimental technique that inactivates a specific gene to study its developmental function.

Gene Knock-in

Method of inserting a gene or reporter into a precise genomic location to analyze gene activity.

Antisense Technology

Use of complementary nucleic acids to block translation of specific mRNA, reducing gene expression.

Turner Syndrome

Monosomy X (45,X) condition characterized by short stature, gonadal dysgenesis and other anomalies.

Trisomy 13 (Patau Syndrome)

Chromosomal disorder with an extra chromosome 13 leading to severe intellectual disability and multiple anomalies.

Trisomy 18 (Edwards Syndrome)

Condition with an additional chromosome 18 causing growth restriction, clenched fists and high mortality.

Angelman Syndrome

Neuro-genetic disorder (maternal 15q deletion) marked by severe intellectual disability and characteristic laughter.

Prader-Willi Syndrome

Paternal 15q deletion resulting in hypotonia, hyperphagia, obesity and cognitive impairment.

Ectopic Pregnancy

Implantation of the embryo outside the uterine cavity, commonly in the uterine tube.

Tubal Implantation

Specific form of ectopic pregnancy where the blastocyst implants in the fallopian tube.

Conjoined Twins

Monozygotic twins whose bodies are physically connected due to incomplete embryonic separation.

Sacrococcygeal Teratoma

Tumor arising from primitive streak remnants at the base of the spine; most common newborn tumor.

Caudal Dysgenesis (Sirenomelia)

Developmental defect causing underdevelopment of lower limbs and caudal structures, linked to abnormal mesoderm formation.

Cardiovascular Disease Risk

Long-term adult health outcome influenced by prenatal molecular and cellular events.

Teratogenesis

Process by which congenital malformations are produced in an embryo or fetus.