Changes

*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 (i) growth by hyperplasia (ii) an increased number of cells for greater diversity of function, and thus more a 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 [[Fertilisation, Implantation and Early Embryonic Development -Implantation- Anatomy & Physiology|timing]] of implantation varies between species.  

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

#'''Cell differentiation'''

#'''Cell differentiation'''

#*As embryogenesis progresses, cells become specialised in structure and function. Regulation of gene expression allows different proteins to be expressed in some cells, allowing tissue differentiation even though all cells contain the same DNA. At the blastomere stage (16 cells) cells are '''totipotent''', meaning they have the capacity to form every adult cell type. As the embryo progresses and enters [[Gastrulation - Anatomy & Physiology|gastrulation]] cells become '''pluripotent''', meaning they can form several but not all cell types. Gastrulation is the process of forming the three germ layers; ectoderm, mesoderm and endoderm. Eventually, most cells terminally differentiate and can no longer form any other cell type.   

#*As embryogenesis progresses, cells become specialised in structure and function. Regulation of gene expression allows different proteins to be expressed in some cells, allowing tissue differentiation even though all cells contain the same DNA. At the blastomere stage (16 cells) cells are '''totipotent''', meaning they have the capacity to form every adult cell type. As the embryo progresses and enters [[Gastrulation - Anatomy & Physiology|gastrulation]] cells become '''pluripotent''', meaning they can form several but not all cell types. Gastrulation is the process of forming the three germ layers; ectoderm, mesoderm and endoderm. Eventually, most cells terminally differentiate and can no longer form any other cell type.   

==The Development of Anatomical Structures==

==The Development of Anatomical Structures==

The [[Developmental Biology - Neurogenesis - Anatomy & Physiology|nervous system]] develops from ectoderm in the anterior part of the embryo, beginning with the formation of the neural plate. Some of the ectoderm will also develop into the [[Skin - Anatomy & Physiology#Origin of the epidermis|epidermis]] in response to signalling factors from elsewhere in the embryo; formation of the neural ectoderm is the default pathway. The neural plate develops into the [[CNS Development - Anatomy & Physiology|neural tube]], which is the precursor to the brain and spinal cord.

The [[Neurogenesis - Anatomy & Physiology|nervous system]] develops from ectoderm in the anterior part of the embryo, beginning with the formation of the neural plate. Some of the ectoderm will also develop into the [[Skin - Anatomy & Physiology#Origin of the epidermis|epidermis]] in response to signalling factors from elsewhere in the embryo; formation of the neural ectoderm is the default pathway. The neural plate develops into the [[CNS Development - Anatomy & Physiology|neural tube]], which is the precursor to the brain and spinal cord.

In the verterbrate embryo, the anterior of the embryo also begins to form into blocks of cells known as [[Somite Development - Anatomy & Physiology|somites]]. Somites are transient structures that will give rise to the vertebrae and ribs, the dermis of the dorsum, and the skeletal [[Developmental Biology - Muscle Development - Anatomy & Physiology|muscle]] of the body wall, back and limbs; they originate from the subsection of mesoderm known as [[Gastrulation - Anatomy & Physiology|paraxial mesoderm]].  

In the verterbrate embryo, the anterior of the embryo also begins to form into blocks of cells known as [[Somite Development - Anatomy & Physiology|somites]]. Somites are transient structures that will give rise to the vertebrae and ribs, the dermis of the dorsum, and the skeletal [[Muscle Development - Anatomy & Physiology|muscle]] of the body wall, back and limbs; they originate from the subsection of mesoderm known as [[Gastrulation - Anatomy & Physiology|paraxial mesoderm]].  

The mesoderm also gives rise to the [[Developmental Anatomy of the Kidneys and Urinary Tract - Anatomy & Physiology|urinary system]] and some parts of the reproductive system; these develop from intermediate mesoderm. The development of the male or female reproductive system is mediated by the [[Fertilisation, Implantation and Early Embryonic Development -Sexual Differentiation- Anatomy & Physiology|genetic sex]] of the embryo.

The mesoderm also gives rise to the [[Developmental Anatomy of the Kidneys and Urinary Tract - Anatomy & Physiology|urinary system]] and some parts of the reproductive system; these develop from intermediate mesoderm. The development of the male or female reproductive system is mediated by the [[Fertilisation, Implantation and Early Embryonic Development -Sexual Differentiation- Anatomy & Physiology|genetic sex]] of the embryo.

Lateral plate mesoderm differentiates into the [[Developmental Anatomy of the Heart - Anatomy & Physiology|heart]], the [[Vascular Development - Anatomy & Physiology|vascular system]], the lymphatic system, the [[Developmental Biology - Limb Development - Anatomy & Physiology|limbs]], and the tissue and smooth muscle surrounding the alimentary canal, or digestive system.  

Lateral plate mesoderm differentiates into the [[Developmental Anatomy of the Heart - Anatomy & Physiology|heart]], the [[Vascular Development - Anatomy & Physiology|vascular system]], the lymphatic system, the [[Limb Development - Anatomy & Physiology|limbs]], and the tissue and smooth muscle surrounding the alimentary canal, or digestive system.  

The formation of bone, or [[Developmental Biology - Bone & Joint Development - Anatomy & Physiology|osteogenesis]] has several different origins - the skull develops at the junction of the neural plate and the epidermis, the limb skeleton develops from lateral plate mesoderm, and the axial skeleton develops from paraxial mesoderm. Both [[Bones and Cartilage - Anatomy & Physiology|bones]] and [[Bones_and_Cartilage_-_Anatomy_%26_Physiology#Structure_and_Function_of_Cartilage|cartilage]] continue to develop into several well differentiated types specific to their anatomical position and function.

The formation of bone, or [[Bone & Joint Development - Anatomy & Physiology|osteogenesis]] has several different origins - the skull develops at the junction of the neural plate and the epidermis, the limb skeleton develops from lateral plate mesoderm, and the axial skeleton develops from paraxial mesoderm. Both [[Bones and Cartilage - Anatomy & Physiology|bones]] and [[Bones_and_Cartilage_-_Anatomy_%26_Physiology#Structure_and_Function_of_Cartilage|cartilage]] continue to develop into several well differentiated types specific to their anatomical position and function.

The endoderm will form the lining of the [[Developmental Biology - Gut Development - Anatomy & Physiology|alimentary canal]] and the glandular structures that develop within it. Endoderm also develops into other digestive organs such as the [[Pancreas - Anatomy & Physiology#Development|pancreas]]; it also gives rise to non digestive structures such as the [[Thyroid Gland - Anatomy & Physiology#Embryological Origin|thyroid gland]] which is formed from a downgrowth of the pharyngeal endoderm of the developing tongue. Initially, the alimentary canal is supended within two compartments; further development alters this arrangement so that a single [[Peritoneal Cavity - Anatomy & Physiology#Development|peritoneal cavity]] is formed.

The endoderm will form the lining of the [[Gut Development - Anatomy & Physiology|alimentary canal]] and the glandular structures that develop within it. Endoderm also develops into other digestive organs such as the [[Pancreas - Anatomy & Physiology#Development|pancreas]]; it also gives rise to non digestive structures such as the [[Thyroid Gland - Anatomy & Physiology#Embryological Origin|thyroid gland]] which is formed from a downgrowth of the pharyngeal endoderm of the developing tongue. Initially, the alimentary canal is supended within two compartments; further development alters this arrangement so that a single [[Peritoneal Cavity - Anatomy & Physiology#Development|peritoneal cavity]] is formed.

==The Development of Specialised Structures==

==The Development of Specialised Structures==