Lecture 1 Intro to Embryo

Pregunta	Respuesta
Development	The processes relating to how a multicellular organism forms from a single cell.
Development (text)	The process of progressive and continuous change that generates a complex multicellular organism from a single cell. Development occurs throughout embryogenesis, maturation to the adult form, and continues into senescence.
Zygote	A fertilized egg. Parent haploid + Parent haploid = Diploid zygote
Embryo	The development of an organism from fertilization to birth.
Embryology	The study of organism development from fertilization to birth.
Generalized Life Cycle (6 stages)	Fertilization Cleavage Gastrulation Organogenesis Metamorphosis Gametogenesis
Fertilization	1. Fusion of male and female gametes. 2. Fusion of haploid gamete nuclei. 3. Initiation of reactions which allow for development.
Gamete	A specialized reproductive cell. i.e sperm or egg
Genome	Complete DNA sequence of an organism.
Cleavage	Series of rapid mitotic cell divisions, post fertilization. Cleavage divides embryo without increasing its mass
Blastomere	A cleavage stage cell. (from mitotic division)
Morula	Vertebrate embryo of 16-64 cells.
Blastula	Early-stage embryo consisting of a sphere of cells surrounding an inner fluid cavity known as blastocoel.
Gastrulation	A process involving the movement of blastomeres to form three germ layers of the embryo.
Gastrula	Stage after gastrulation, that contains 3 germ layers which will interact to form organs.
Germ Layer	Layer which forms all of the tissues of the body except for germ cells. Has 3 layers of its own: Ectoderm, mesoderm, endoderm.
Tripoblastic	Having 3 germ layers. Most animals are like this.
Ectoderm	The cells that remain on outside/dorsal surface of the embryo post to gastrulation. -Forms the nervous system from neural tube and rural crest. -Forms epidermis of embryo.
Endoderm	Innermost germ layer. Forms: -epithelial lining of respiratory tract -gastrointestinal tract -accessory organs of digestive tract (liver & pancreas) i.e stomach cell, thyroid cell, lung cell
Mesoderm	Middle layer of three germ layers. Gives rise to muscles & skeleton, connective tissue, reproductive organs, kidneys, blood, and majority of cardiovascular tissue.
Organogenesis	Interactions between, and rearrangement of, the cells of the 3 germ layers to produce tissues and organs.
Metamorphosis	Changing from one form to another i.e tadpole to frog or caterpillar to butterfly
Germ Cells	Cells for reproduction. Consist of cells of the gonads (testis and ovary) which undergo meiotic cell division to form gametes.
Somatic cells	Cells that form the body excluding germ cells.
Gametogenesis	Production of gametes.
Aristotle	Recognize two types of cleavage: Holoblastic - cleavage pattern where entire egg is divided into smaller cells; i.e frogs and mammals Meroblastic - cell division pattern in zygotes containing large amount of yolk where only part of the cytoplasm is cleaved. Cleavage does not interfere with yolk which serves as nutrition for embryo i.e insects, fish, reptiles, birds, etc.
Harvey	All animals originate from eggs. Suggested humans were reproduced by fertilization of egg and sperm. Also observed blood tissue forms before heart.
Describe average eukaryotic cell	-average diameter of 10-20 micrometers -colourless and translucent
Malpighi	-first microscopic account of chick development -saw neural groove, somites (muscle forming, and arteries & veins -- to and from yolk.
Epigenesis vs. Preformation	Aristotle & Harvey said organs of the embryo were formed from scratch (de novo). Malpighi concluded organs were already present in mini form.
Wolff	Supports epigenesis but without the concept of cells and the cell doctrine, Wolff postulated an unknown force “vis essentialis” that directs embryogenesis.
Christian Pander, Karl Ernst von Baer, Heinrich Rathke	established epigenesis
Von Baer's Laws	1) all embryos go through a similar stage 2) generalized features appear early in development 3) specialized features arise from generalized ones 4) adult forms of lower animals are not embryos of higher animals
Schwann & Schließen	cell theory – all living things are built of cells Virchow added the bit that cells are derived from pre-existing cells in 1858 (S&S were still suggesting that cells arose spontaneously)
Epithelial Cells	- form sheets connected by junctional complexes - sheets act as a barrier - move in harmony - have a clear polar character from one side to another -basal lamina is a foundation contacts only one surface of the cell
Mesenchymal Cells	-loosely organized and loosely attached cells (more like bold individuals) - can migrate as individual cells - can also adhere in 3-dimensional clumps -basal lamina may surround the cells (muscle or fat cells)
Morphogenesis	The organization of the cells of the body into functional structures via coordinated cell growth, cell migration, and cell death. Refer to powerpoint for more details
Fate Map	Lets us tell what cell will become what when looking at an early embryo
Understanding Fate Maps	Blue - epidermal ectoderm Dark blue - neural ectoderm Red - mesoderm Dark Red - notochord Dark Yellow - Endoderm Light Yellow -yolk
How is a fate map constructed?	Vital Dyes -stain that can be used on living cells without killing them. Fluorescent Dyes - injected into embryo and photo activated be laser which allows small groups of cells to be tagged & you can trace their movement - much better than vital dyes
Homologous Structures	are similar because they are derived from a common ancestral structure – our arms and the bat’s wings are homologous structures (but they do not necessarily perform similar functions).
Analogous Structures	are similar because they perform similar functions, but they do not necessarily share a common ancestral form – the bat’s wing and the butterfly’s wing are analogous structures (used in generating flight).
Disruption	Abnormality or congenital defect caused by exogenous agents (teratogens) such as plants, chemicals, viruses, radiation, or hyperthermia.
Malformation	Abnormalities caused by genetic events such as gene mutations, chromosomal aneuploidies, and translocations. Often associated with a phenotypic syndrome.
Teratogen	The agents associated with such disruptions are called teratogens. The largest class of teratogens includes drugs and chemicals, but viruses, radiation, hyperthermia, and metabolic conditions in the mother can also act as teratogens. Examples are alcohol, warfarin, bromine, lead, heroin, etc.

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