Organisation of nerves in thorax Flashcards
Where do somatic nerves innervate?
Skin and skeletal muscles
Where do autonomic/visceral nerves innervate?
Organs, smooth muscle
What are the functions of somatic spinal nerves?
Motor - skeletal muscle only
Sensory to body wall NOT viscera
What do segmental nerves combine to?
Plexi - supply specialised areas
What type of innervation enters the posterior dorsal horn?
Sensory
What type of innervation leaves the ventral horn?
Motor - to muscles
What is the difference between the posterior root and ramus?
Root: Sensory nerves
Ramus: Post. has sensory and motor nerves and Ant. has all others (skin/muscle)
What is a dermatome?
Area of skin which is supplied by a single spinal nerve on one side/from a single spinal cord
What is a myotome?
Part of skeletal muscle supplied by a single spinal nerve on one side/ from single spinal cord level
What are spinal levels?
The levels on innervation which the spinal nerves innervate
What spinal levels innervate the arm?
C5-8 and T1
Why is T1 spinal level relevant?
Cardiac referred pain
Why is T3 spinal level relevant?
3rd and 4th intercostal space
Why is T4 spinal level relavant?
Nipple line, 4-5th interspace
Why T6 spinal level relevant?
Xiphoid process
Why is T10 spinal level relevant?
Navel
Why is T12 spinal level relevant?
Pubis
Where do IC nerves originate?
Only from spinal cord - so can be spinal or segmental - anterior 1ry rami
Where are IC nerves present in the thorax?
Under the ridge of the ribs, between the innermost and internal layers
How many IC nerves do we have?
11 pairs and 1 subcostal
What kind of innervation do the IC muscles carry?
Both motor and sensory
Where does the lateral cutaneous branch of IC nerves supply?
The anterior and posterior IC spaces, supplies skin
Where does the anterior cutaneous branch of IC nerves supply?
The lateral and medial IC spaces, including skin outside of chest wall
What nerves supply the IC muscles?
The IC nerves from the anterior ramus
At which level does the IVC cross the diaphragm?
T8
What does the phrenic nerve motor fibres supply?
Skeletal muscle of the diaphragm
Where are the phrenic nerves derived from?
Anterior Rami of C3-5
What kind of nerves are the phrenics?
Somatic so no autonomical function or visceral distribution
What do the sensory fibres of the phrenic supply?
Central diaphragm, pleural covering, mediastinal pleura and pericardium (peritoneum on inf surface of diaphragm)
Where do sympathetic nerves have cell bodies?
Thoraco-lumbar cord
How do the symp nerves reach their destination?
Travel with vessels
Where do the autonomic motor nerves innervate?
Cardiac muscle, smooth muscle and glands
Where do the autonomic sensory nerves innervate?
Visceral organs
Where does the parasympathetic division originate from?
Brainstem CNIII, VII, IX, X and S2-4 - craniosacral
Where does the sympathetic division originate from?
T1-L2
Where do sympathetic pathways to body wall synapse?
In ganglia of sympathetic trunk
Where do symp pathways to viscera synapse?
In unpaired ganglia
What do the sympathetic trunks do?
They take fibres up or down the body
What is the intermediate/lateral horn?
Place where efferent cell bodies send out signals to be relayed
What happens when the nerve gets to the paravertebral ganglion?
Either synapse onto a different nerve and ride on spinal nerve (blood vessels) OR to prevertebral ganglion to synapse on viscera
OR transmitted up or down symp trunk and then synapse
What symp nerve supplies the brain?
T1
Where is there not a lateral horn?
Outside T1, superior to T1 and inferior L2
Where do the symp trunks receive branches from?
T1-L2
What is the role of the symp trunks?
Distribute symp nerves to smooth muscle, glands throughout the body
What does the symp trunk bring back to CNS from viscera?
Pain fibres
What are spanchnic nerves?
Bundle of fibres from lower than T5-12 that reach the abdomen
What are the important parasymp nerves?
Vagus (CNX) which supplies viscera of thorax and abdomen
What is the path of the vagus?
Emerges through jugular foramina to thorax, through diaphragm and to supply the abdomen
Where is the biggest outflow of symp system?
T1 - efferents can make way up to head or to heart and pulmonary plexi
What are the names of the presymp ganglia to the heart and lungs?
Superior, middle and inferior ganglia
Where are many of the synapses located for the symp nerves to heart and lungs?
Micro-ganglia in pulm and cardiac plexi rather than trunk ganglia
What are the functions of symp and parasymp nerves in pulm plexus?
Symp: dilate bronchioles
Parasymp (Vagus) constricts bronchioles
What are the functions of symp and parasymp nerves in cardiac plexus to do with the heart (efferents)?
Symp: ^ HR and force of contraction
Parasymp: decrease HR via pacemaker tissue and constrict coronary arteries
What are the enlargements present on the plexus?
Where post-ganglionic nerves are located
Where is the vagus nerve located?
Anterior to aortic arch
What is the path of the left recurrent laryngeal nerve?
Comes down and wraps around aorta and then moves back up again to larynx
What is the path of the right recurrent laryngeal nerve?
Comes down and wraps around right subclavian artery
How many branches does the vagus nerve have?
Left and right
What eventually happens to the vagus nerve?
Forms the oesophageal plexus
Where are the oesophageal plexus located?
Either anterior (left vagus) or posterior (right vagus) side of oesophagus
What is the function of the parasymp and symp nerves in the cardiac plexus to do with relaying (afferents)?
Symp: Relay pain sensations from heart
Parasymp: Relay BP and chem info from heart
Where does the deep cardiac plexus sit?
Between the aortic arch and trachea
Where does the superficial cardiac plexus sit?
In front of the aortic arch
What does the cardiac plexus do?
Distribute nerves to heart so opposing actions can occur
Where does cardiac visceral pain relay back to?
Tends to relay back from heart to spinal cord T1-4
Why is different pain felt between pericardium and heart?
Pericardium supplied by somatic phrenic nerves to C3-5 and cardiac pain supplied back to spinal cord to T1-4
Where does CNX arise?
Medulla and leaves skull through jugular formaina
What vessel does CNX follow from brain?
Common carotid artery (posterolateral)
How does the left vagus pass by the lungs?
Crosses ant to aortic arch and posterior to left hilum
How does right vagus pass by lungs?
Crosses posterior to right lung root
What happens to the vagus after the oesophageal plexi?
Separate to form ant and post oesophageal/gastric nerves (cross diaphragm at T10)
What is the function of the parasymp and symp nerves in the oesophageal plexus to do with relaying (afferents)?
Symp: Pain sensations from oesophagus
Parasymp: Senses normal physiological info from oesophagus
What are the parasymp branches of vagus?
To chest and abdomen - control smooth and cardiac muscle, glands)
What do the parasymp NOT supply?
Blood vessels
What type of nerves are the recurrent laryngeal nerves?
NOT parasymp - Somatic (supplies most skeletal muscles of larynx)
Where does vagus get a large sensory content?
From gut and lungs (enteroreceptor)
What do the plexi receive as well as parasymp nerves?
Symp fibres which are distributed via these plexi into heart and lungs/abdomen
What is the enteric NS?
Plexus of ganglia and axons within the oesophageal wall
What is the function of the intrinsic nerves of the oesophagus?
Coordinates the activity of oesophagus and can be up/down-regulated by autonomic nerves
Compare the positions of phrenic vs vagus
Phrenic is further anteriorally than the vagus
