Organisation of Nerves in the Thorax

Question 1

What do somatic spinal nerves provide somatic sensory innervation to?

Answer 1

Body wall but NOT to viscera

Question 2

What is a dermatome?

Answer 2

An area of skin that is supplied by a single spinal nerve on one side or from a single spinal cord level

Question 3

What is a myotome?

Answer 3

Part of a skeletal muscle that is supplied by a single spinal nerve on one side or from a single spinal cord level

Question 4

How many intercostal nerves are there?

Answer 4

11 intercostal + 1 subcostal

Question 5

What are the branches of the intercostal nerves?

Answer 5

There is a lateral cutaneous branch (anterior and posterior branches) and an anterior cutaneous branch (medial and lateral branches)

Question 6

What structures do the phrenic nerves provide sensory and motor innervation to?

Answer 6

Motor = diaphragm
Sensory:
Central diaphragm
Mediastinal pleura
Pericardium
Peritoneum of central diaphragm

Question 7

Where do sympathetic preganglionic neurones to the body wall synapse?

Answer 7

In the ganglia of the sympathetic trunk

Question 8

Where do sympathetic preganglionic neurons to the viscera synapse?

Answer 8

In unpaired ganglia

Question 9

The sympathetic trunk receive which spinal nerves?

Answer 9

T1-L2

Question 10

What is the significance of sympathetic fibres in spinal nerves T5-T12?

Answer 10

These are the thoracic splanchnic nerves that carry sympathetic fibres to the abdomen.

Question 11

What are the five sets of nerves that contain parasympathetic fibres?

Answer 11

Occulomotor (III)
Facial (VII)
Glossopharyngeal (IX)
Vagus (X) 
Sacral spinal nerves (S2-S4)

Question 12

Which spinal nerves do sympathetic fibres to the heart and lungs come from?

Answer 12

T2-T4 passing through cervical and upper thoracic ganglia

Question 13

Where do many of these fibres synapse?

Answer 13

In ganglia of the pulmonary and cardiac plexuses rather than in the trunk ganglia

Question 14

What effect do sympathetic and parasympathetic nerves have on bronchioles?

Answer 14

Sympathetic - bronchodilation

Parasympathetic - bronchoconstriction

Question 15

What are the effect of sympathetic and parasympathetic efferents to the heart?

Answer 15

Sympathetic - increase heart rate and force of contraction (inotropic and chronotropic effect)
Parasympathetic - decrease heart rate and vasoconstrict coronary arteries

Question 16

What are the roles of sympathetic and parasympathetic afferents from the heart?

Answer 16

Sympathetic - relay pain sensations from the heart

Parasympathetic - relay blood pressure and chemical information from the heart

Question 17

Where does the vagus nerve arise and where does it leave the skull?

Answer 17

Vagus nerves arise in the medulla and it leaves the skull via the jugular foramina

Question 18

Describe the path of descent of the vagus nerve.

Answer 18

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

Question 19

What are roles of sympathetic and parasympathetic efferents from the oesophageal plexus?

Answer 19

Sympathetic - relays pain sensation from the oesophagus

Parasympathetic - senses normal physiological information from the oesophagus

Question 20

Branches of the vagus provide sensory content from…?

Answer 20

Gut and lungs

REMEMBER: branches of the vagus provide NO AUTONOMIC SUPPLY to the body wall.

Question 21

State a feature of the left recurrent laryngeal nerve. What does it innervate?

Answer 21

It is NOT parasympathetic

It innervates most of the skeletal muscle of the larynx

Question 22

How do the vagi in the posterior and anterior mediastinum differ?

Answer 22

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.

Question 23

Label this diagram.

Answer 23

o Remember you are above the plane of the arch of the aorta so you will NOT see the aorta
o You will see the right and left brachiocephalic vein but not its branches
o Vagus is posterior to phrenic nerves