Symphathetic Trunk & Phrenic Nerve (Viva)


Q.1 What is the extent of the sympathetic trunk?

Each trunk is placed on either side of the vertebral column and extends from the base of the skull to the coccyx below.

Q.2 What is the position of the sympathetic trunk in relation to the vertebral column?

In the cervical region: Anterior to transverse processes of cervical vertebrae.

In thoracic region: Anterior to heads of ribs

In the lumbar region: Anterolateral to lumbar vertebrae.

In sacral region: Anterior to sacrum. The two join each other in front of the coccyx.

Q.3 What is the number of ganglia in the cervical sympathetic trunk?


Q.4 What is ganglion impar?

The lower fused ends of right and left sympathetic trunks are thickened in a midline ganglion called as ganglion impar.

Q.5 Where the cell body of sympathetic preganglionic neurons are present?

In the intermediolateral grey column of the spinal cord in the spinal segment T1 to L2.

Q.6 What is the location of sympathetic postganglionic neurons?

Ganglia on sympathetic trunk.

Q.7 What is the number of ganglia in the thoracic sympathetic trunk?

12, but may be reduced due to the fusion of adjacent ganglia with one another.

Q.8 What is ‘stellate ganglion’?

It is ganglion formed by fusion of first thoracic ganglion with inferior cervical ganglion.

Q.9 Name the branches of the thoracic part of the sympathetic trunk.

• Lateral branches:
Each ganglion is connected with corresponding spinal nerve, by white (preganglionic) and grey (postganglionic) rami communicans.

By from upper five ganglia

Medial branches:
Pulmonary branches to pulmonary plexus
Cardiac branches to upper cardiac plexus.
Aortic branches to aortic plexus
Oesophageal branches to oesophageal plexus

By from lower Seven Ganglia

• Greater splanchnic nerve:
By roots from ganglia 5 to 9. Ends mainly in coeliac ganglion

• Lesser splanchnic nerve:
Preganglionic roots from ganglia 10 and 11.Ends mainly in aorticorenal ganglia.

• Least splanchnic nerve:
By roots of ganglion 12. Ends in renal plexus



Q.1 How the phrenic nerve is formed?

Each nerve is formed by ventral primary rami of C3, C4, and C5 spinal nerves. The contribution from C4 is greatest.

Q.2 What is the distribution of the phrenic nerve?

Motor: To diaphragm.


  • Proprioceptive fibers from diaphragm
  • Sensory branches to the pericardium and parietal pleura.
  • Sensory branches to suprarenal glands, inferior vena cava, and gallbladder.'