Dissector Answers - Lungs and Mediastina

Learning Objectives:

Upon completion of this session, the student will be able to:

  1. Identify the contents of the superior mediastinum.
  2. Identify and trace the tributaries to each of the brachiocephalic veins and the formation of the superior vena cava.
  3. Identify and trace all the branches of the arch of the aorta in the region and the relationship of the vagus and phrenic nerves to them.
  4. Identify the thoracic part of the trachea and describe its blood supply and innervation.
  5. Identify and describe the location of the lungs in the thoracic cavity.
  6. Identify the relations of the pulmonary artery, pulmonary veins, and the bronchi at the hilum of each lung.
  7. Define a bronchopulmonary segment and discuss its general organization.
  8. Name the bronchopulmonary segments and give their approximate location in reference to the lobes of the lungs.
  9. Trace the lymphatic drainage of the lungs and respiratory tract.
  10. Define the boundaries of the posterior mediastinum.
  11. Describe the major contents of the posterior mediastinum and their relationships.
  12. Describe the organization of the thoracic sympathetic trunk, in addition to its visceral and splanchnic branches.

Learning Objectives and Explanations:

1. Identify the contents of the superior mediastinum. (W&B 370, M 138, 142-150, N193, N206, N209, N211, N212, N232, N240, N262, TG4-18, TG4-35A, TG4-35B, TG4-36A, TG4-36B) 2. Identify and trace the tributaries to each of the brachiocephalic veins and the formation of the superior vena cava. (W&B 384, N74, N238, TG4-37B)

3. Identify and trace all the branches of the arch of the aorta in the region and the relationship of the vagus and phrenic nerves to them. (W&B 383-384, N211, N212, N232, N237, N240, TG4-38)

As discussed above, the arch of the aorta gives off the brachiocephalic artery (which splits into right common carotid and right subclavian arteries), the left common carotid artery, and the left subclavian artery. Also consider the veins of this region, which as a rule of thumb, lie anterior to the "analogous" artery.

Most laterally, we have the phrenic nerves. They lie on the anterior aspects of the anterior scalene muscles on both sides. These muscles separate the respective subclavian veins (anterior) from the subclavian arteries (posterior). So, the phrenic nerves cross between subclavian vein and subclavian artery as they descend into the thorax.

The vagus nerves are more medial, descending into the thorax just lateral to the common carotid arteries. They are also mostly anterior to the branches and the arch proper as they descend. The right vagus nerve gives off the right recurrent laryngeal nerve, which loops around to the posterior aspect of the right subclavian artery and travels back up into the neck. The left vagus nerve gives off the left recurrent laryngeal nerve, which loops around the arch proper, next to the ligamentum arteriosum, and ascends back into the neck between the trachea and the esophagus.

4. Identify the thoracic part of the trachea and describe its blood supply and innervation. (W&B 234-235, N33, N74, N126, N207, N209, N240, TG4-33, TG4-38)

The trachea begins at the level of C6 and terminates at the level of the sternal angle, where it divides into the two main bronchi. The trachea receives arterial supply from the inferior thyroid arteries, internal thoracic arteries, and branches of the bronchial arteries. The blood drained via tracheal veins ends up in the inferior thyroid veins. Parasympathetic innervation to the smooth muscle and glands is via the vagus nerve (CN X), either directly or by the recurrent laryngeal nerves. Sympathetic innervation comes directly from the sympathetic trunk.

5. Identify and describe the location of the lungs in the thoracic cavity. (W&B 401-404, N196, N197, N199, N206, TG4-13A, TG4-13B, TG4-15, TG4-16, TG4-17, TG4-18)

The lungs occupy the large space inside the rib cage, on either side of the mediastinum, superior to the diaphragm. These spatial demarcations also define the three surfaces of each lung, namely the costal, mediastinal, and diaphragmatic surfaces. (The pleura of the same name covers the lung over that surface.) The lungs extend out of the thoracic cavity into the root of the neck at the apex, which is covered by the cervical pleura.

Each lung has a hilum on its medial aspect. The hilum of the lung is the point of entry for the root of the lung, which includes the bronchi, the pulmonary arteries, and the pulmonary veins. A pleural sleeve is created around these structures, where the pleura reflects, changing from visceral to parietal. Inferior to the hilum on each lung is the pulmonary ligament, a continuation of that pleural reflection.

6. Identify the relations of the pulmonary artery, pulmonary veins, and the bronchi at the hilum of each lung. (W&B 400, N199, TG4-31AB, TG4-31CD, TG4-34A)

On both sides, the bronchus is posterior and the pulmonary vein(s) are anterior and inferior. The difference between the two involves the pulmonary artery(ies). On the right side, the artery(ies) lie more or less anterior to the bronchus. On the left side, however, the artery(ies) are the most superior structure, even superior to the bronchus.

7. Define a bronchopulmonary segment and discuss its general organization. (W&B 402, 404-407, N201, N203, N204, N205, TG4-32AB, TG4-32CD, TG4-33A)

A bronchopulmonary segment:

8. Name the bronchopulmonary segments and give their approximate location in reference to the lobes of the lungs. (W&B 402, N201, N203, TG4-32AB, TG4-32CD, TG4-33A)

Right Lung:*

Superior Lobe: a three-piece lobe - a posterior and an anterior segment next to one another with an apical segment on top
Middle Lobe: a flat, two-piece lobe that sits on the anterior aspect of the lung - a medial and a lateral segment next to one another
Inferior Lobe: a five-piece, "square-based-pyramid" - four basal segments that point to the four "sides" of the body (anterior basal, medial basal, lateral basal, and posterior basal), and a superior segment on top.

Left Lung:*

Superior Lobe: similar to the right superior lobe, except that the apical and posterior fuse to form an apicoposterior segment; there is also an anterior segment like on the right side. However, the left also has a "lingual" portion, with a superior and an inferior segment.
Inferior Lobe: a five-piece, "square-based-pyramid" - four basal segments that point to the four "sides" of the body (anterior basal, medial basal, lateral basal, and posterior basal), and a superior segment on top. NOTE: the anterior and medial basal segments often fuse, resulting in an anteromedial basal segment in the left lower lobe.

9. Trace the lymphatic drainage of the lungs and respiratory tract. (W&B 234-235, N208, TG4-42)

Lymph from the lungs drains first to pulmonary nodes, which are small nodes within the lung tissue and also beneath the visceral pleura. The numerous small pulmonary nodes drain into larger bronchopulmonary nodes located the hilum (also called hilar nodes). The bronchopulmonary nodes drain into tracheobronchial nodes located around the tracheal bifurcation. These nodes may be separated into three large groups. The large cluster of nodes below the tracheal bifurcation are called inferior tracheobronchial nodes (or carinal nodes) and they receive lymph from the lower lobes primarily. Beside the tracheal bifurcation on either side are the fairly large superior tracheobronchial nodes. Oddly, most of the lymph from the inferior tracheobronchial nodes drains up into the right superior tracheobronchial nodes, which means that lymph from the lower lobe of the left lung crosses to the right here, for the most part. The lymph drainage ascend beside the trachea, with several modest sized paratracheal nodes intercepting some of this lymph on either side. The lymph channels coalesce as they ascend to form bronchomediastinal lymph trunks on either side. The left bronchomediastinal lymph trunk drains into the termination of the thoracic duct in the root of the neck, and the right bronchomediastinal trunk usually unites with the right subclavian and right jugular lymph trunks to form a short right lymphatic duct, which drains, similar to the thoracic duct, into the junction of the subclavian and internal jugular veins on the right.

10. Define the boundaries of the posterior mediastinum. (W&B 370-371, N231, TG4-14) 11. Describe the major contents of the posterior mediastinum and their relationships. (W&B 370, 408-416, N172, N192, N193, N194, N206, N207, N212, N232, N237, N238, N240, N260, TG4-35, TG4-35, TG4-36, TG4-36, TG4-37, TG4-37)

Once the thoracic aorta goes through the aortic hiatus in the diaphragm, its name changes to abdominal aorta.

Extra Explanation: The GI tract, including the esophagus, stomach, and intestine, originally develops midline. However, as other systems develop, two things happen. First, the trachea (tough little bugger) pushes the esophagus back against the vertebrae and slightly to the right. Below the sternal angle, after the trachea has bifurcated, the esophagus is "free" to do what it wants, which leads us to the second point. The stomach is pushed anterior and to the left by the growth of the liver. So, in its quest to find the stomach (and the esophageal hiatus at T10 level, which due to the dome-shape of the diaphragm is relatively anterior), the esophagus must move anterior and left.

Bottom line: the esophagus starts slightly right of median and pinned against the spine. It moves left and anteriorly as it descends.

As for the descending aorta, it starts left of midline and somewhat anterior to the vertebrae, due mainly to the way the arch develops (again, that trachea is hogging the midline space). After the bifurcation gets the trachea out of the way, the aorta moves midline. Furthermore, since the aortic hiatus is inferior to the esophageal hiatus (T12 level), it is also posterior to it, again since the diaphragm is a dome. So, in its quest to find the aortic hiatus, the descending aorta also moves posterior to lie on the vertebrae.

Bottom line: the descending aorta starts on the left and anterior to the trachea. It moves midline and posteriorly as it descends.

This set of cross-sections might help (no guarantee!):

12. Describe the organization of the thoracic sympathetic trunk, in addition to its visceral and splanchnic branches. (W&B 413-416, N158, N160, N165, N209, N240, N254, TG4-45, TG4-46, TG8-03, TG8-14)

The thoracic sympathetic trunk is the inferior continuation of the cervical sympathetic trunk, and after piercing the diaphragm, continues as the lumbar sympathetic trunk. The trunk is really just a highway for preganglionic sympathetic nerves (thoracolumbar) that need to reach levels superior or inferior to their level of origin in the spinal cord. The chain ganglia along the trunk are the sites of synapse between preganglionic neurons and postganglionic fibers (see box below).

A preganglionic (presynaptic) sympathetic neuron originates in the lateral horn of the spinal cord gray matter. It leaves the cord via the spinal nerve and enters the trunk via a white ramus communicans. The neuron can: a) immediately synapse in the ganglion, or b) travel up or down the trunk, subsequently synapsing in a ganglion superior or inferior to the level of origination of the neuron. In either case, the postganglionic (postsynaptic) neuron then leaves the ganglion via the gray ramus communicans to rejoin the spinal nerve for the purpose of distribution to its target, either via the ventral primary ramus or the dorsal primary ramus.

Besides the three paths mentioned above (up or down via the trunk, or out via the corresponding spinal nerve) there are two other paths that a sympathetic fiber can take. First, some enter visceral branches that directly innervate the smooth muscle, cardiac muscle, and glands of the thoracic viscera. There are contributions to the cardiac, pulmonary, esophageal, and aortic plexuses. Also, there are thoracic splanchnic nerves (Greek, splanchna = viscera), which are preganglionic fibers that travel into and synapse within the abdomen to provide sympathetic innervation for most of the abdominal viscera. (This can be a confusing point. The thoracic splanchnic nerves innervate abdominal viscera. Also, the label "splanchnic" refers to the innervation of viscera, not to a specific origin or make-up. You will see lumbar, pelvic, and sacral splanchnics that are not necessarily pre-ganglionic sympathetic nerves from the sympathetic chain.) These are listed here:

Nerve Level of Origin Site of Synapse
greater thoracic splanchnic n. T5 - T9 celiac ganglion, superior mesenteric ganglion, suprarenal medulla
lesser thoracic splanchnic n. T10 - T11 aorticorenal ganglion
least thoracic splanchnic n. T12 renal plexus

Autonomic Nervous System

The autonomic nervous system, made of the parasympathetic nervous system and the sympathetic nervous system, controls all of the smooth muscle in our body, as well as performing some other specialized functions that will be presented in physiology. Smooth muscle is present throughout the body, in blood vessels and skin, but is most often considered in the context of thoracic, abdominal, and pelvic viscera.

In that it innervates muscle, causing contraction or relaxation, the ANS is similar to the system of skeletal muscle innervation. However, the structures of the two systems is different, hence the necessity to learn words like "synapse", and "ganglion". The nerves to skeletal muscle leave the CNS, travel to the muscle, and do their business at the neuromuscular junction. Sympathetic and parasympathetic nerves, however, take a detour along the way. In the ANS, there are two separate neurons that separate the spinal cord from the target, the preganglionic (presynaptic) and the postganglionic (postsynaptic) neurons. What do you suppose is in the middle of the two? Yep, a ganglion. What happens in a ganglion? A synapse.

Preganglionic sympathetic neurons will leave the spinal cord (in the thoracic and lumbar regions) and travel part-way to their target, either via the sympathetic trunk or a splanchnic nerve. Within that trunk or at the end of that splanchnic nerve, there is a ganglion within which the preganglionic sympathetic neuron will synapse with the postganglionic sympathetic neuron. The postganglionic sympathetic neuron will then travel to the target, usually smooth muscle of an arteriole, but also cardiac muscle, sweat glands, and errector pili muscles (small muscles in the skin that attach to hair follicles and can give you "goose bumps").

Preganglionic parasympathetic neurons usually leave the spinal cord (in the cranial and sacral regions) and travel directly to their target organ, sometimes piggybacking on splanchnic or other nerves. They will synapse in very small ganglia in or on the target organ. The postganglionic parasympathetic neurons, then, do not travel very far to reach their target tissue (usually smooth muscle or glands, but also cardiac muscle).

One more thing: You will come across abbreviations, either in the anatomy tables or some texts, like GVE, SVA, GSE, etc. This is old terminology that divided innervation up into general vs. special, visceral vs. somatic, and efferent vs. afferent. The current way of thinking, and the way that this course will be taught, divides innervation up functionally, as described above, with skeletal, sympathetic, and parasympathetic nerves, some of which are efferent and some of which are afferent.
Cultural enrichment: Check out these sections from the 1918 version of Gray's Anatomy of the Human Body! Some of the terms are (of course) out-of-date, but the illustrations are timeless.

The Trachea and Bronchi - The Lungs - The Pulmonary Veins - The Thoracic Duct - The Vagus Nerve - Surface Anatomy of the Thorax - Surface Markings of the Thorax

Questions and Answers:

1. Are there plexuses of nerves on the pulmonary arteries? (N209, TG4-45, TG8-14, TG8-15)

The pulmonary plexuses lie around the roots of the lungs, and the pulmonary artery is one of the structures of the lung roots. Therefore, there are plexuses on the arteries.

2. Determine the relation of the left superior intercostal vein to the aortic arch, the phrenic nerve, and vagus nerves. (N231, TG4-36B)

The left superior intercostal vein runs between the vagus and phrenic nerves. It crosses the aortic arch horizontally passing from the heads of the ribs anteriorly to end in the left brachiocephalic vein.

3. Observe the formation of the superior vena cava (confluence of both brachiocephalic veins), and relate its position to the manubrium and other great vessels. (N N196, N206, N212, TG4-37B, TG4-15, TG4-19)

The superior vena cava lies immediately to the right of the manubrium. It is overlapped on its left margin by the ascending aorta. Posteriorly, it lies against the right pulmonary artery and the right superior pulmonary vein.

4. Are there cardiac nerves arising from the left vagus? (N209, N240, TG4-45, TG8-15)

The left vagus normally gives parasympathetic branches to the cardiac plexus. They are most easily seen where the vagus crosses the aortic arch.

5. Do you find a vertebral artery from the arch of the aorta? (N33)

Sometimes the left vertebral artery will branch directly from the aortic arch.

6. Pull the aortic arch toward the left and observe the thoracic portion of the trachea. What innervates it and how? (N209, N240, TG4-35, TG4-45)

The recurrent laryngeal nerves innervate the upper trachea and esophagus as they pass superiorly in the tracheoesophageal groove to reach the larynx, which they also innervate. Recurrent laryngeal nerves provide skeletal motor innervation to the voluntary muscle of upper esophagus and larynx and parasympathetic motor innervation to the smooth muscle of the trachea. They also provide parasympathetic motor innervation to the mucous glands of all of these structures.

7. What is the blood supply of the trachea? What structure does it lie upon? (N33, N207, TG7-14, Objective 4)

For the blood supply, see Objective #4 above. The trachea lies upon the esophagus.

8. Locate the right and left bronchial arteries. What is their source? How do the two sides differ in number? (N207, TG4-39)

The two left bronchial arteries are branches from the highest part of descending aorta. The single right bronchial artery is either a branch of one of the left bronchial arteries or it may branch from the right 3rd posterior intercostal artery, in which case the common trunk is called the intercostobronchial trunk.

9. What is the difference between the "root" of the lung and the "hilum"? (N199, TG4-31AB, TG4-31CD)

The root of the lung is the collection of structures that connect the lung to the mediastinum. This includes the pulmonary arteries and veins, the primary bronchi and bronchial arteries, and the pulmonary nerve plexuses and lymphatics. The hilum is the place on the lung where these structures enter and leave the lung.

10. How do the cardiac and pulmonary plexuses differ? Where do they distribute? (N209, N240, TG4-45)

The cardiac and pulmonary plexuses are continuous at the tracheal bifurcation. The heart receives the cardiac plexus and lungs the pulmonary plexus.

11. Where and what is the cardiac notch? (N199, TG4-30AB, TG4-31AB)

The cardiac notch is a lateral deviation in the anterior border of the left lung, caused by the position of the heart. The lingula is an anterior projection of the left superior lobe below the cardiac notch.

12. What is the average projection of each lung and its fissures to the rib cage? (N196, N 197, N200, TG4-15, TG4-16, TG4-30C)

The anterior borders of each lung generally follow the sternal margin, although the cardiac notch causes a lateral deviation to the left anterior border between the 4th and 6th ribs. The apex of each lung projects to the level of T1, which means, due to the declination of the first rib anteriorly, that the apex rises above the first rib. The inferior border of each lung is located at rib 6 in the midclavicular line, rib 8 at midaxillary line, and rib 10 in the paravertebral line. (Recall that the pleura goes 8, 10, 12.) Both oblique fissures begin posteriorly at the spine of T3, passing obliquely (like the name implies) to reach the 6th costal cartilage near the midclavicular line. The horizontal fissure of the right lung begins at rib 5 in the midaxillary line, then reaches rib 4 to follow it anteriorly to the sternal margin.

13. What is the lingular bronchus? (N202, N 203, TG4-33A)

The left superior lobe bronchus has two divisions: superior and lingular. The lingular division or lingular bronchus has two segmental bronchi: superior lingular and inferior lingular.

14. What is its significance of the superior segmental branch of the right inferior lobar bronchus? (N203, TG4-33A)

Due to its larger caliber and more vertical orientation, the right primary bronchus is more likely to receive foreign bodies that enter the airway. The superior segmental bronchus branches posteriorly off of the intermediate bronchus or the inferior lobe bronchus, so it is the most likely segmental bronchus to receive those foreign bodies that enter the right bronchus. This is especially true if the patient is in a supine position.

15. Are there sympathetic branches to the lung? Along what do they distribute? (N209, N240, TG4-45, TG4-46, TG8-14)

Sympathetic fibers reach the lungs via the pulmonary plexuses, which are located along the roots of the lungs. Pulmonary plexuses are continuous with the cardiac plexus at the tracheal bifurcation. Additional sympathetics reach the pulmonary plexuses via the thoracic visceral nerves, which are branches from T1-T4/T5 sympathetic chain ganglia.

16. Where does the esophagus begin? Where does it pass into the abdomen? Where does it terminate? (N63, N194, N195, N232, N234, N235, TG4-45, TG4-46)

The laryngopharynx "becomes" the esophagus at the C6 level. The esophagus passes through the esophageal hiatus of the diaphragm, which is at the T10 level, to end in the cardiac portion of the stomach.

17. Consider the course, relations, constrictions of the esophagus. (N232, TG4-49, TG7-91)
For course and relations, see above. Constrictions of the esophagus are found at its beginning, at the tracheal bifurcation, and at the esophageal hiatus.
18. Describe the blood supply and venous drainage of the esophagus. Are there venous collaterals to stomach? (N238, TG4-49, TG7-91)

Two or three esophageal arteries branch from the descending aorta. Esophageal veins drain into the azygos system, which eventually reaches the superior vena cava. The esophageal tributaries of the left gastric vein drain the terminal esophagus. Since the gastric veins first drain into the portal system before going to the heart, this part of the esophagus is an important site of portal-caval (portal-systemic) anastomosis in cases of portal hypertension.

19. Do the right and left mediastinal pleurae come together? (N194, TG4-49)

Very low in the posterior mediastinum the esophagus sweeps forward, so there is potential for the right and left mediastinal parietal pleurae to touch one another posterior to esophagus and anterior to aorta. However, typically the anterior deviation of the esophagus is not sufficient to allow enough space for this contact of the pleurae.

20. Through what and at what level does the aorta enter the abdominal cavity? (N194, N195, TG4-37, TG4-38, TG4-39)

The descending thoracic aorta passes through the diaphragm at the aortic hiatus, a passageway between the two diaphragmatic crura, located at the T12 level.

21. What is the subcostal artery? (N264, TG4-49, TG7-91, TG4-39)

Below the 12th rib, there is no intercostal space or intercostal artery, so we call the segmental neurovascular structures subcostal.

22. Completely review the blood supply to an intercostal space. (N33, N191, N192, TG4-43)

Intercostal spaces in general are supplied by posterior and anterior intercostal arteries. Posterior intercostal arteries 3 through 11 are branches of the descending thoracic aorta. The first two posterior intercostal arteries are branches of the highest intercostal artery, which is a branch of the costocervical trunk from subclavian artery. Anterior intercostals are branches of the internal thoracic or the musculophrenic arteries.

23. What are the posterior branches of the posterior intercostal (segmental) arteries? What do they supply? (N171, N172, TG4-39, TG4-08)

The posterior branches of posterior intercostal arteries supply the deep and superficial back muscles, skin of the back, and the vertebral column. They have radicular branches that reach the spinal cord along the dorsal and ventral rootlets.

24. Observe the azygos venous system. If you have two primary veins, do they communicate with one another? How? Where? What is the pattern of venous drainage in your specimen? Are all the veins present? If not, where does the drainage go? (N238, TG4-38, TG4-39, TG4-40)

Hemiazygos and accessory hemiazygos usually cross the midline at T7, 8, or 9 to empty into the azygos vein. There are also connections between the various left-sided venous channels.

25. What vein drains the first intercostal space? Into what? What veins drain into the azygos system? (N238, TG4-38, TG4-39, TG4-40)

Both first posterior intercostal veins drain directly into their respective brachiocephalic veins. Bronchial and esophageal veins drain into the azygos system, the latter being a significant site of portal-caval anastomosis in cases of portal hypertension. (This is the second mention... could be important!)

26. How does the thoracic duct get into the thorax? At what level does it deviate to the left side? (N206, N266, TG4-43, TG4-44)

The thoracic duct enters the chest through the aortic hiatus along the right side of the aorta. It deviates to the left at the level of the sternal angle. (The trachea pushes the esophagus against the vertebral bodies which pushes thoracic duct to the left.)

27. Do you find posterior mediastinal lymph nodes or afferent lymph channels? (N239, TG4-43, TG4-44)

The thoracic duct is usually paralleled by posterior mediastinal nodes.

28. What are bronchomediastinal lymph trunks? (N208, TG4-43, TG4-44)

The lymph from the lungs and chest passes through the paratracheal nodes to form the bronchomediastinal lymph trunks. These drain to the thoracic duct on the left and the right lymphatic duct on the right.

29. Is the sympathetic trunk located within the posterior mediastinum? Does it change positions in different regions of the chest? (N N180, N254, TG4-45, TG4-46, TG8-14)

The sympathetic trunk lies on the heads of the ribs through most of the chest, so it is almost, but not quite, within the posterior mediastinum. It deviates anteromedially as it travels inferiorly to its exit through the diaphragm.

30. How many thoracic ganglia do you find? (N209, N240, TG4-45, TG4-46, TG8-14)

There are typically 12 thoracic ganglia, although the first may be fused with the inferior cervical ganglion to form a cervicothoracic (stellate) ganglion.

31. Identify white and gray rami communicans. What is their significance and distribution? What do they contain? (N164, N180, N209, N240, N254, TG4-45, TG4-46, TG8-14)

Since the preganglionic sympathetic neurons live within the spinal cord at T1 to L2 levels, these are the only levels where white rami communicans are found. Gray rami, on the other hand, are found at every level at which there are spinal nerves. Gray rami carry postganglionic sympathetic fibers back to the ventral primary rami, to be distributed along their branches (and also the branches of the dorsal primary rami).

32. Do you see thoracic visceral nerves to the aorta, esophagus, and trachea? What about to the cardiac and pulmonary plexuses? (N209, N240, TG4-45, TG4-46, TG8-03, TG8-14)

The first 4 or 5 thoracic ganglia (T1-4) give small visceral branches that pass anteroinferiorly to reach the cardiac, pulmonary, esophageal, and aortic plexuses, as well as the trachea.

33. Expose the greater (thoracic) splanchnic nerve. From what does it come? At what level? What types of fibers does it contain? To what does it distribute? (N209, TG4-45, TG4-46, TG8-03, TG8-14)

The greater thoracic splanchnic nerve is made by contributions from sympathetic chain ganglia at T5 to T9 (or T10) levels. These are preganglionic fibers that leave the chest to enter the abdomen. They synapse in the celiac ganglion and innervate the abdominal viscera that is supplied by the celiac trunk.