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==Introduction==

==Introduction==

Embryo, when applied to mammals, is the term given to the developing organism from fertilisation to birth. Developmental biology, or embryology, is the study of the embryo as it transforms from a unicellular zygote to a multicellular, mulitsystemed organism which in some cases, is ready to function autonomously. Developmental biology is of interest to vets in understanding why organs and systems are the way they are, but also in understanding genetic disease and applying cell based therapy to treat loss or damage to tissue.

Embryo, when applied to mammals, is the term given to the developing organism from fertilisation to birth. Developmental biology, or embryology, is the study of the embryo as it transforms from a unicellular zygote to a multicellular, mulitsystemed organism which in some cases is ready to function autonomously. Developmental biology is of interest to vets in understanding why organs and systems are the way they are, but also in understanding genetic disease and applying cell based therapy to treat loss or damage to tissue.

Perhaps quite remarkably, all animals follow the same developmental "plan" - until the latter stages of development, it is difficult to tell a human embryo from a chicken embryo. This suggests an evolutionary programme for cell development.

Perhaps quite remarkably, all animals follow the same developmental "plan" - until the latter stages of development, it is difficult to tell a human embryo from a chicken embryo. This suggests an evolutionary programme for cell development.

*Embryogenesis is driven by three cellular process:

*Embryogenesis is driven by three cellular process:

#'''Cell division and growth'''

#'''Cell division and growth'''

#*Fertilisation produces a unicellular zygote which undergoes a series of mitotic divisions to eventually become a multicellular organism known as a [[Fertilisation, Implantation and Early Embryonic Development -Embryonic Development of the Blastocyst- Anatomy & Physiology|blastocyst]]. Mitosis produces:

#*Fertilisation produces a unicellular zygote which undergoes a series of mitotic divisions to eventually become a multicellular organism known as a [[Fertilisation, Implantation and Early Embryonic Development -Embryonic Development of the Blastocyst- Anatomy & Physiology|blastocyst]]. Mitosis produces (i) growth by hyperplasia (ii) an increased number of cells for greater diversity of function, and thus more complex organism.  

(i) growth by hyperplasia  

(ii) an increased number of cells for greater diversity of function, and thus more complex organism.  

The first differentiation of cells creates trophoblasts that contain molecules that adhere to the endometrium during [[Developmental Biology - Implantation - Anatomy & Physiology|implantation]]. The extent of cellular growth and division and the timing of implantation varies between [[Fertilisation, Implantation and Early Embryonic Development -Implantation- Anatomy & Physiology|species]].  

The first differentiation of cells creates trophoblasts that contain molecules that adhere to the endometrium during [[Developmental Biology - Implantation - Anatomy & Physiology|implantation]]. The extent of cellular growth and division and the timing of implantation varies between [[Fertilisation, Implantation and Early Embryonic Development -Implantation- Anatomy & Physiology|species]].  

#'''Cell differentiation'''

#'''Cell differentiation'''