Difference between revisions of "Developmental Biology Overview - Anatomy & Physiology"

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==Introduction==
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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 at birth. Developmental biology is of interest to vets in understanding why organs and systems are the way they are, but also in understanding genetic diseases and applying cell based therapies to treat loss or damage to tissues.
 
  
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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.
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==Introduction==
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Embryogenesis is driven by three cellular process:
 
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#'''Cell division and growth'''
 
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#:Fertilisation produces a unicellular zygote which undergoes a series of mitotic divisions to eventually become a multicellular organism known as a [[Blastocyst Embryonic Development - 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 [[Implantation - Anatomy & Physiology|timing]] of implantation varies between species.
 
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#'''Cell differentiation'''
 
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#: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. 
 
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#'''Morphogenesis'''
 
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#:During embryogenesis two cell types exist; mesenchymal and epithelial. Mesenchymal cells are single cells or loosely linked to other cells and irregularly shaped. Epithelial cells are tightly attached to each other or a membrane and have a regular shape (cuboidal or columnar).
 
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==The Development of Anatomical Structures==
 
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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.
 
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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]].
 
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The mesoderm also gives rise to the [[Kidney and Urinary Tract Development - 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 [[Sexual Differentiation - Anatomy & Physiology|genetic sex]] of the embryo.
 
  
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Lateral plate mesoderm differentiates into the [[Heart Development - 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.  
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'''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.
  
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The formation of bone, or [[Bone & Cartilage 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 - Anatomy & Physiology|bones]] and [[Cartilage - Anatomy & Physiology#Structure_and_Function_of_Cartilage|cartilage]] continue to develop into several well differentiated types specific to their anatomical position and function.
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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 cells.
  
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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.
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*Embryogenesis is driven by three cellular process:
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#Cell division and growth
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#*Fertilisation produces a unicellular zygote which undergoes a series of mitotic divisions to eventually become a multicellular organism. Mitosis produces (i) growth by hyperplasia (ii) an increased number of cells for greater diversity of function, and thus more complex organism.  
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#Cell differentiation
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#*As embryogenesis progresses, cells become specialised in structure and function. Regulation of gene expression allows different proteins to be expressed in some cells, allowing different tissues to exists despite all cells containing 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 cells become '''pluripotent''', meaning they can form several but not all cell types. Eventually, most cells terminally differentiate and can no longer form any other cell type. 
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#Morphogenesis
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#*During embryogenesis two cell types exist; mesenchymal and epithelial. Mesenchymal cells are single or loosely linked to other cells and irregularly shaped. Epithelial cells are tightly attached to each other or a membrane and have a regular shape (cuboidal or columnar).
  
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==The Development of Specialised Structures==
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==[[Fertilisation, Implantation and Early Embryonic Development -Embryonic Development of the Blastocyst- Anatomy & Physiology|Early Embryonic Development]]==
  
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===Alimentary===
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==[[Developmental Biology - Implantation - Anatomy & Physiology|Implantation]]==
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*[[Tooth Development|Tooth Development]]
 
  
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===Reproductive===
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==[[Developmental Biology - Gastrulation - Anatomy & Physiology|Gastrulation]]==
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*[[Testes and Epididymis - Anatomy & Physiology#Testicular Descent|Testicular Descent]]
 
  
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===Integumentary===
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==[[Developmental Biology - Neurogenesis - Anatomy & Physiology|Neurogenesis]]==
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*[[Hair - Anatomy & Physiology#Development|Hair Development]]
 
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*[[Mammary Gland - Anatomy & Physiology#Development of the Mammary Gland (prenatal mammogenesis)|Mammary Gland Development]].
 
  
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===Endocrine===
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==[[Developmental Biology - Somite Development - Anatomy & Physiology|Somite Development]]==
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*[[Pituitary Gland - Anatomy & Physiology#Anatomy|Pituitary Gland Development]]
 
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*[[Adrenal Glands - Anatomy & Physiology#Embryological Origin|Adrenal Gland Development]]
 
  
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===Lymphatic===
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==[[Developmental Biology - Limb Development - Anatomy & Physiology|Limb Development]]==
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*[[Bone Marrow - Anatomy & Physiology#Development|Bone Marrow Development]]
 
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*[[Bursa of Fabricius - Anatomy & Physiology#Development|Bursa of Farbricus Development]]
 
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*[[Thymus - Anatomy & Physiology#Embryology|Thymus Development]]
 
  
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==Test yourself with the embryology quiz==
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==[[Developmental Biology - Muscle, Bone & Joint Development - Anatomy & Physiology|Muscle, Bone & Joint Development]]==
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[[Embryology_quiz|Embryology quiz]]
 
  
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==References==
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==[[Developmental Biology - Endoderm & Mesoderm Development - Anatomy & Physiology|Endoderm & Mesoderm Development]]==
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*Scott F. Gilbert '''Developmental Biology''', 6th edition
 
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*T.A.McGeady, P.J. Quinn, E.S.Fitzpatrick, M.T.Ryan '''Veterinary Embryology'''
 
  
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[[Category:Developmental Biology]]
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[[Category:A&P Reviewed]]
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Revision as of 15:22, 19 August 2008

()Map ANATOMY & PHYSIOLOGY (Map)



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.

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 cells.

  • Embryogenesis is driven by three cellular process:
  1. Cell division and growth
    • Fertilisation produces a unicellular zygote which undergoes a series of mitotic divisions to eventually become a multicellular organism. Mitosis produces (i) growth by hyperplasia (ii) an increased number of cells for greater diversity of function, and thus more complex organism.
  2. 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 different tissues to exists despite all cells containing 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 cells become pluripotent, meaning they can form several but not all cell types. Eventually, most cells terminally differentiate and can no longer form any other cell type.
  3. Morphogenesis
    • During embryogenesis two cell types exist; mesenchymal and epithelial. Mesenchymal cells are single or loosely linked to other cells and irregularly shaped. Epithelial cells are tightly attached to each other or a membrane and have a regular shape (cuboidal or columnar).

Early Embryonic Development

Implantation

Gastrulation

Neurogenesis

Somite Development

Limb Development

Muscle, Bone & Joint Development

Endoderm & Mesoderm Development

()Map ANATOMY & PHYSIOLOGY (Map)


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