What is Sympathetic nervous system.its following parts

Sympathetic nervous system:

The preganglionic fibresThe preganglionic fibres of the sympathetic nervous spanning from the Thoracic (T1) to the Lumbar (L2) of the spinal cord. 

The Sympathetic Nervous System is made up of the following parts-

1. Sympathetic Trunks:

These represent a pair of long cords located on eithct side of the vertebral column. They extend from the foramen magnum to coccyx.every sympathetic trunk comprises of 21 Tateral or chain ganglia interconnected to each other in a sequential manner. Every ganglion is a collection of neuronal cell bodies . A white ramus communicans connects the ganglia to the spinal cord while a grey ramus communicans connects the  ganglia to the spinal nerves. 

2. Preganglionic sympathetic fibres:
These fibres are small sizes neuronal axon located along the lateral funiculus of the spinal cord. These fibres generally exit fromthe ventral root of the  spinal nerves and forms synapses with neuronal dendrome located along all the thoracic and upper three lumbar chain ganglia, thus forning outflow.

3.Postganglionic Sympathetic Fibres:-

These fibres are long sized neuronal axons of chain ganglia. Their effect is widespread as they innervate the smooth muscles and glands of visceral organs such as the heart, ciliary muscles and iris of eyes, lungs gut, liver, urinary, and reproductive systems. 

4.Collateral Ganglia:

Three collateral ganglia are present namely, coliateral ganglia coeliac, superior, mesenteric, and inferior mesenteric ganglia. Postganglionic fibre spread from neurons of collateral ganglia to visceral organs.  In general, the nerve endings of postganglionic fibres of sympathetic nervous release adrenaline or nor-adrenaline or nor-adrenaline therefore are also known as frenetic nerve fibres