General Embryology and Histology: Molecular Fundamentals

Vocabulary flashcards covering key terms in embryology, histology, molecular signaling, transcription factors, morphogens, developmental periods, and signal-transduction mechanisms.

Embryology

The study of an animal’s development from fertilization to birth.

Histology

The study of tissues and how they are organized to form organs.

Cell Differentiation

Process by which unspecialized cells become specialized in structure and function.

Morphogen

A signaling molecule that diffuses from a localized source to form a concentration gradient, dictating cell fate and tissue patterning.

Transcription Factor

A protein that binds DNA to switch specific genes on or off, guiding developmental processes.

Hox Genes

Homeotic transcription factors that establish structures along the anterior-posterior body axis.

Pax Genes

Transcription factors critical for sense-organ and nervous-system development.

Msx Genes

Genes involved in mesenchymal-to-epithelial transitions during limb and facial formation.

Tbox Genes

Transcription factors coordinating outgrowth of limbs (arms and legs).

Fox Genes

Transcription factors expressed broadly to drive formation of multiple organs.

Helix-Loop-Helix Proteins

A family of transcription factors that regulate muscle formation.

Wt1 Gene

Transcription factor essential for kidney and gonad development.

Dlx Genes

Genes that help shape the jaws and inner ear.

Sonic Hedgehog (Shh)

A morphogen involved in retina patterning and formation of notochord, lung epithelium, hair, and more.

Bone Morphogenetic Proteins (BMP)

Morphogens that induce formation of many structures, often by inhibiting alternative developmental pathways.

Transforming Growth Factor-β (TGF-β)

Morphogen that induces mesoderm formation and stimulates myoblast proliferation.

Wnt Signaling

Pathway that governs gastrulation movements and establishes cell polarity.

Chordin

BMP-inhibiting morphogen contributing to dorsal patterning.

Noggin

BMP antagonist that shapes neural and skeletal development.

Gremlin

BMP inhibitor influencing limb and kidney development.

Retinol / Retinoic Acid

Vitamin A derivative acting as a morphogen that organizes hindbrain and pharyngeal neural-crest patterning.

Totipotent

Describes a stem cell (e.g., zygote) capable of forming all embryonic and extra-embryonic tissues.

Pluripotent

Describes inner-cell-mass cells able to become any cell of the embryo proper but not extra-embryonic tissues.

Morula

Solid ball of cells (~3 days post-fertilization) preceding blastocyst formation.

Blastocyst

Hollow sphere of cells (~4 days) containing an inner cell mass and trophoblast layer.

Germinal Period

First 0–2 weeks of development, from fertilization to implantation.

Embryonic Period

Weeks 3–8 when major organs and body structures begin to form.

Fetal Period

Weeks 9 to birth, characterized by growth and functional maturation.

Receptor Tyrosine Kinase (RTK)

Cell-surface receptor with intrinsic kinase activity that phosphorylates tyrosine residues upon ligand binding.

Signal Transduction

Cascade that transmits an extracellular signal to the nucleus to influence gene expression.

Second Messenger

Intracellular molecule (e.g., cAMP) activated downstream of a membrane receptor to propagate signals.

Intrinsic Kinase Activity

Receptor’s built-in enzymatic ability to add phosphate groups to itself or other proteins.

Ras-MAPK Pathway

RTK-linked signaling cascade (RAS → RAF → MEK → ERK) that regulates proliferation, differentiation, and survival.

Primary Cilium

Microtubule-based cellular projection essential for Hedgehog signal reception and processing.

Hippo Pathway

Signaling network controlling organ size by regulating cell proliferation and apoptosis.

Vitamin A Pathway

Developmental signaling route mediated by retinoic acid and its nuclear receptors to control gene expression.