Derivates mesoderm

Limb formation

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Major lineages of the mesoderm Somite Terminology: sclerotome: vertebral and rib cartilage myotome: muscles of back, rib cage, abdomen dermamyotome: dermal cells, limb muscle

syndetome: most dorsal, tendons arthrotome: most central, vertebral joints/discs, proximal ribs “unnamed”: most posterior, dorsal aorta and intervertebral arteries

Two concentrate of pattern formation

• formation of limb vertebrates

• nerve formation in vertebrates

The formation of Vertebrate Limb

• Vertebrate limb is a very complex organ with an asymmetrical pattern

• Bone at the front limbs for example on the wings, hands, and fins, consists of a proximal humerus, radius and ulna in the middle, and distal there are wrist and fingers

There are three types of pattern formation in vertebrate limbs known as "morphogenetic rules“

•1. Mechanism gradient: homogeneous cell population was ordered to act in a certain way by the concentration of solute molecules

•2. The induction of cell growth occurs when certain cells adjacent to each other

•3. Involves a chemical reaction in which the formation of cells and inhibit region mesensim out another cell

The Limb FieldMesoderm cells that form the vertebrate limb can be identified in 3 ways:•Remove certain group of cells and observed the development ekstrimitasnya•Transplant group of cells or tissue to a new location and observe whether to form the legs•Marking a group of cells with dyes or radioactive precursors and observe which play a role in limb development

Example Limb Transplants in Salamander

Limb Development is Influenced by AER

• Developing vertebrate limb of shoots (limb bud).

• Bud mesoderm messenchymal consists of a core, covered by a layer of ectodermal epithelium.

• Process: the Apical Ectodermal Ridge (AER) at the end of the shoot induce the formation of organs in part on progress zone

The Limb Axes• Information required in forming

the leg position to function in a three-dimensional coordinate system

• Polarity axis is determined in the following order: anterior-posterior, dorsal-ventral, and proximal-distal

• Anterior-posterior pattern formation is regulated by Sonic hedgehog (Shh) and the zone of polarizing activity (ZPA); dorsal-ventral pattern is controlled by the ectoderm, while the proximal-distal governed by the AER in the progress zone (PZ)

Discovery of polarization in the wing area and morphogenesis gradient models to determine the pattern digiti

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