Pattern of limb development, Biology

Pattern of Limb Development

The first visible sign of limb development is the appearance of ridge or thickening on each lateral side of the embryo of amniotes. The ridge called Wolffian Ridge extends antero-posteriorly between the brachial and pelvic regions; but only its anterior and posterior ends persist from which the forelimb and hindlimb develop respectively. In the amphibians there is no such ridge and separate pairs of ridges arise in the respective limb regions. The ridge is formed from proliferation of cells of the somatic (parietal) layer of lateral plate mesoderm. The mesodermal cells of the ridge or disc lose their epithelial connections and become mesenchymal migrate as separate cells and form a loose mass of mesenchyme beneath the embryonic ectoderm opposite the ridge or thickening.

Their continued proliferation elevates the covering ectoderm and a limb bud is formed.  The early limb bud has a core of mesoderm and a covering of ectoderm; the ectoderm is 2-cell layered. The outer, peridermal layer is of flattened cells and the inner layer has cuboidal cells, separated from the mesoderm by a basement membrane. The bud is at fist a small mound but soon grows in size due to proliferation of mesodermal cells; as this happens the cells of the inner layer of ectodermal covering along its distal, edge become tall columnar and form a pseudostratified layer. In the amniotes (lizard, birds, mammals) this thickening of the apical ectoderm appears as a prominent ridge running antero-posteriorly along the free distal margin of the bud. It is called the Apical Ectodermal Ridge (AER). It has also been described in xenopus and at least one frog (Rana tigrina) and may be present in other amphibians also, though not so prominently. In chick limb development AEU has been found to play a very important role.

Posted Date: 1/29/2013 6:04:27 AM | Location : United States







Related Discussions:- Pattern of limb development, Assignment Help, Ask Question on Pattern of limb development, Get Answer, Expert's Help, Pattern of limb development Discussions

Write discussion on Pattern of limb development
Your posts are moderated
Related Questions
Define the Medical Complications of Bulimia Nervosa? The medical complications of bulimia nervosa range from fairly benign, transient symptoms, such as fatigue, bloating and co

Standardisation Research of Luria Nebraska There are published manuals for the Luria Nebraska that define the battery in detail and provide information pertinent to validity,

Many endangered plant species are currently being propagated by commercial growers and botanical gardens and the sold (as both plants and seeds) to government agencies. Conservatio

Examples of cloning and molecular biology cloning may produce heterozygous individuals (as mother was heterozygous) and suggests a way to get pure breeding cats molecu

A normal healthy cell is bathed in a normal extracellular saline.  The plasma membrane of the cell contains voltage-gated sodium channels, sodium-glucose co-transporters, and sodiu

Duck plague (duck virus enteritis) Duck plague is the most serious disease caused by a herpes virus (Anatid herpes virus). Though antigenically homogenous, differences in virul

Rapidly Flowing Waters - Biota of Rivers In the rapidly flowing section of the river, the water current is the dominant feature. Everything that is not attached or weighed is

discuss the stereo isomerism of monosaccharides

Q. What is the basic Role of Botanic Garden? A botanic garden makes us to simply enjoy the beauty and variety of nature. The pleasure of admiring turns us into good naturalists

Explain the types of foods used in Space? The various types of foods are enumerated herewith. Thennostabilized (T): Heat processed foods ("off-the-shelf' items) in aluminium