Introduction and overview of development and cell specification

Embryology lecture 1 specifically PNU curriculum

What is the main difference between you and a machine

machines arent required to function until after its built. organisms on the other hand function as theyre built

Definition of Embryology according to science

the study of growth, formation , and difference that takes place in living organisms

Embryology is considered by some reserachers to

study the life cycle of and individual from fertilization to sexual maturity

Branches of Embryology

1. Descriptive

2. Comparative

3. Development

4. Experiment

5. Ontogeny

6. Molecular

7. Teratology

Descriptive Embroylogy

Seeks to explain the morphology. example : formation of gametes, fertilization operations, etc..

Comparative Embryology

Compares descriptive studies between different colonies

Experimental Embryology

Focuses on the research and lab experiment. example ; Subjecting different stages of fetus to experiments, and Interpretation and analysis, etc….

How did scientists bridge the gap between the inacuracy of using animal fetus and the unethical use of human fetus for human experiments ?

The used cell and tissue culture from a skin graft and reverse engineered it to its primative self

Development Biology

Includes all branches of life science

Molecular Embryology

studies all stages of embryogensis at a molecular level

Ontogeny

studies the stages of embryonic formation of the individual example: Doctors only studying human embryology

Teratology

studies the causes that lead to congenital malformation such as chemicals, hormones etc..

The Cycle of Life

Most animals pass through similar stages of development

embryogenesis

the stages between fertilization and hatching

The stages of development

1. fertilization

2. Cleavage

3. Gastrulation

4. Organogenesis

5. Hatching / Birth

6. Metamorphosis

7. Gametogensis

Fertilization

Involves the fusion of mature sex cells

Cleavage

A series of mitotic divisions that immediately follows fertilization. Starts of as Blastomeres and ends as 100s of blastula

Gastrulation

The Blastomeres undergo dramatic movements and change their position relative to one another.

The embryo in the gastrulation stage is called

gastrula stage

The result of gastrulation

the embryo contains three germ layers (endoderm, ectoderm, mesoderm) that will interact with interact to generate the organ of the organ of the body.

Organogensis

The production of tissue and organ. This stage includes chemical signals between the cells of the germ layers

What are the cells that under long migrations

precursors of blood cells, lymph cells, pigment cells and gametes

Metamorphosis

when the organism hatches / is born but yet to be sexually mature

Gametogenesis

precursors of the gametes, and is often one of the first differentiations to occur during animal development

how do cells become specified to a specific fate

1. specification

2. determination

3. differentiation

Specification

Capable of differentiating autonomously when placed in an environment that is neutral with respect to the developmental pathway. It is still capable of being reversed

Determination

The stage of commitment, irreversible, capable of differentiating autonomously even when placed into a non-neutral environment

Differentiation

Unspecialized cell becomes specialized into one of the many cell types that make up the body

Mechanisms of Developmental Patterning

1. Autonomous

2. Conditional

3. Syncytial

Autonoumous Specification

1. Cells develop only according to early fate

2. without receiving external signals

3. If a section is removed, the surrounding cells will still produce the same cells they intended to

4. Prospective potency = Prospective fate

5. Shows mosaic development

6. Seen in invertebrates

Autonoumous Specification

Conditional Identity

1. Depends on the surrounding cells

2. Found in Vertebrates and a few invertebrates

3. Inductive signal is responsible for fate determination

4. Regulative development

5. Prospective potency > Prospective fate

Conditional Identity

Syncytium

the nuclear division which is not followed by cell division

Cellularization

The process of creating individual cells out of a multinucleated cell by separating the nuclei by cell membranes

Syncytial specification

1. Interactions between regions of cells before cellularization

2. No specific cell fate before cellularization

3. a mix of both auto and conditional, but mostly conditional after cellularization

4. The morphogens can affect nuclei in a concentration dependent fashion

5. Mostly in insects

Syncytial specification

Mechanism of developmental patterning