1.5 - Nerves of the Thorax Flashcards
What do somatic spinal nerves provide somatic sensory innervation to?
Body wall but NOT to viscera
Whats a dermatome?
An area of skin that is supplied by a single spinal nerve on one side or from a single spinal cord level
What is a myotome?
Part of a skeletal muscle that is supplied by a single spinal nerve on one side or from a single spinal cord level
How many intercostal nerves are there?
11 intercostal + 1 subcostal
What are the branches of the intercostal nerves?
There is a lateral cutaneous branch (anterior and posterior branches) and an anterior cutaneous branch (medial and lateral branches)
What structures do the phrenic nerves provide sensory and motor innervation to?
Motor = diaphragm
Sensory:
Central diaphragm
Mediastinal pleura
Pericardium
Peritoneum of central diaphragm
Where do sympathetic preganglionic neurones to the body wall synapse?
In the ganglia of the sympathetic trunk
Where do sympathetic preganglionic neurons to the viscera synapse?
In unpaired ganglia
The sympathetic trunk receive which spinal nerves?
T1-L2
What is the significance of sympathetic fibres in spinal nerves T5-T12?
These are the thoracic splanchnic nerves that carry sympathetic fibres to the abdomen.
What are the five sets of nerves that contain parasympathetic fibres?
Occulomotor (III)
Facial (VII)
Glossopharyngeal (IX)
Vagus (X)
Sacral spinal nerves (S2-S4)
Which spinal nerves do sympathetic fibres to the heart and lungs come from?
T2-T4 passing through cervical and upper thoracic ganglia
Where do many of these fibres synapse?
In ganglia of the pulmonary and cardiac plexuses rather than in the trunk ganglia
What effect do sympathetic and parasympathetic nerves have on bronchioles?
Sympathetic - Bronchodilation
Parasympathetic - Bronchoconstriction
What are the effect of sympathetic and parasympathetic efferents to the heart?
Sympathetic - increase heart rate and force of contraction (inotropic and chronotropic effect)
Parasympathetic - decrease heart rate and vasoconstrict coronary arteries
What are the roles of sympathetic and parasympathetic afferents from the heart?
Sympathetic - relay pain sensations from the heart
Parasympathetic - relay blood pressure and chemical information from the heart
Where does the vagus nerve arise and where does it leave the skull?
Vagus nerves arise in the medulla and it leaves the skull via the jugular foramina
Describe the path of descent of the vagus nerve.
The two vagus nerves pass postero-laterally to the common carotid arteries.
Right vagus passes posterior to the right lung root
Left vagus nerve crosses over anterior to the aortic arch and then posterior to the left main bronchus
What are roles of sympathetic and parasympathetic efferents from the oesophageal plexus?
Sympathetic - relays pain sensation from the oesophagus
Parasympathetic - senses normal physiological information from the oesophagus
Branches of the vagus provide sensory content from…?
Gut and Lungs
State a feature of the left recurrent laryngeal nerve. What does it innervate?
Its not parasympathetic. Innervates the skeletal muscle of the larynx.
How do the vagi in the posterior and anterior mediastinum differ?
In the posterior part of the oesophagus, you form the posterior oesophageal nerve which mainly takes right vagal fibres through the diaphragm to the abdominal viscera.
The left vagus provides fibres to the oesophageal plexus and then continutes as the anterior oesophageal nerve.
What is the position of the phrenic nerve relative to the vagus nerve?
Vagus nerves are posterior
What are the left and right main branches from the coronary arteries?
Right main branches: Sino-atrial nodal artery Right marginal artery Posterior descending artery
Left main branches: Circumflex artery Left anterior descending (LAD)
What is the difference between left and right dominant in terms of coronary arteries?
Right dominant (2/3) - PDA and SAN coronary arteries come off the right coronary artery
Left dominant (1/3) - PDA comes off the left circumflex artery. SAN artery comes of the left coronary
The dominant will serve the posterior wall of the left ventricle.
