Veterinary Histology and Embryology

AXON OR AXIS CYLINDER

• The single axon arises from a special part of the periphery of cell body called axon hillock. This area is devoid of nissl bodies and golgi apparatus.
• Length of axon varies from a fraction of a millimeter to several feet.
• Branches arise at right angles form axons and are called collaterals axon is made up of fibrillae embedded.
• In axioplasm and covered by a membrane axolemma.
• Nerves fibres are formed by the axon and its sheaths.
• All peripheral nerve fibres consist of the axon covered with a thin protoplasmic sheath called neurolemma or sheath of schwann.
• Another sheath myelin or medullary sheath seen in some nerve fibres is next to the axis cylinder and nuerolemma. These latter fibres showing myelin sheath are called myelinated or medullated nerve fibres.
• Those without myelin sheath are amyelinated or non medullated nerve fibres.