Mediastinum & Nerves Flashcards
Where are cell bodies of the sympathetic efferent fibres found?
In the lateral horn, T1-L2.
Where does the spinal nerve start?
Where the dorsal and ventral roots merge, before passing through intervertebral foramen.
What is the function of the dorsal rami?
Innervate epaxial muscles and overlying skin.
What is the function of the ventral rami?
Innervate lateral and ventral body wall muscle and skin.
What is the function of communicating rami?
Carry sympathetic fibres to and from the sympathetic chain.
What is the brachial plexus?
Bilateral network of nerves supplying the forelimb which is transected when removed the forelimb in disection. Formed from ventral rami of C6-8, T1 & T2.
What is the phrenic nerve?
Sole motor supply to diaphgram.
Formed from ventral rami C5, 6, 7 (bi lateral).
Also contain some sensory and sympathetic fibres.
What are thoracic spinal nerves?
Leave vertebral column from T1, T2 etc.
Contain motor, sensory and sympathetic fibres.
Branch to skin and muscle wall.
Supply intercostal muscles thus have a respiratory role.
Where do sympathetic fibres leave the spinal cord?
Only in the thoracolumbar region (T1 - L2).
What is the largest sympathetic ganglia in the thoracic cavity?
Cervicothoracic (stellate) ganglion (CTG). The size is due to the cell bodies of the pre-ganglionic nerve fibres located here.
What is the ansa subclavia?
Where the cervicothoracic ganglion loops around the subclavian artery and joins the middle cardiac ganglion.
Where do sympathetic nerves in the medastinum synampse and where do they terminate?
At any ganglion in the sympathetic chain, cervicothoracic or middle cervical ganglion. They terminate at either the heart or lungs (fine network of nerves surrounding both organs called cardiac or pulmonary plexi).
What is the root of parasympathetic fibres?
“Cranialsacral outflow”.
Cranial nerves III, VI, IX, X and sacral spinal cord.
NB. Cell bodies of postganglionic neurons are in ganglia on or near thoracic and abdominal viscera (long pre, short post ganglionic fibres).
What is the vagus journey in the thorax?
The vagus trunk is a mixed nerve. At the first rib the vagus nerve leaves the trunk and continues caudally. Preganglionic fibres will exit the main nerve and synapse on ganglion near or on the heart and lungs.
At the base of the heart, a nerve departs (the recurrent laryngeal) wrapping around the aortic arch, and back up the next to supply laryngeal structures. The vagus loses all somatic fibres to this nerve branch, and is now mostly parasympathetic fibres.
Each vagus divides into dorsal and ventral branches before passing into the abdomen (where branches fuse and become left and right vagus nerves).
How do sympathetic fibres reach the head?
Via the communicating rami. From the sympathetic chain, fibres travel via the bilateral vago-sympathetic trunk, and synapse with the cranial cervical sympathetic ganglia (CCSG) at the base of the skull to supply fibres such as the pupil (dilatation).
