Thoracic Regional Anatomy Flashcards
Thoracic inlet: describe the boundaries of the thoracic inlet and outlet and the structures that pass through them and their relations Mediastinum: describe the arrangement and contents of the superior, anterior, middle and posterior parts of the mediastinum Oesophagus: describe the course, major relations and neurovascular supply of the oesophagus within the thorax Vagus and Phrenic nerves: describe the origin, course and distribution of the vagus and phrenic nerves Thoracic duct: describe
What is the mediastinum?
Thick midline partition that separates the two pleural cavities. Extends between the superior thoracic aperture (inlet) to the inferior thoracic aperture.
What are the contents of the mediastinum?
Trachea – from the LARYNX to bifurcation not principal bronchi. Oesophagus – from PHARYNX – muscular tube. Heart and pericardium. Thoracic duct – lymphatic drainage (and allows spread of metastatic diseases e.g. lung cancer). Nerves. Great vessels.
What are the divisions of the mediastinum? (x5)
Superior: above the sternal angle. Inferior: below the sternal angle.
DIVISIONS OF INFERIOR MEDIASTINUM: Anterior: anterior to heart in pericardial sac. Middle: pericardial sac and heart. Posterior: posterior to pericardial sac and diaphragm.
What are the contents of the superior mediastinum from anterior to posterior?
IMPORTANT to know the POSITIONS i.e. anterior -> posterior – this is part of the specification. Thymus, phrenic nerves, great veins, main lymphatic trunks, vagus nerves, great arteries, trachea and main bronchi, upper oesophagus.
Where do the phrenic nerves originate?
From the cervical plexus from C3, 4, 5. C4 is the main one.
What do the phrenic nerves do?
Motor nerves to the diaphragm – C3, 4, 5 keep the diaphragm alive. So is sympathetic. They are also sensory to the central tendon of the diaphragm, mediastinal pleura, pericardium and peritoneum of central diaphragm.
What are the relations of the phrenic nerves to the anatomy of the mediastinum?
Right phrenic nerve – lies on the surface of the right brachiocephalic VEIN, superior vena cava and right side of the heart and pericardium – passing anteriorly of the lung root. Left phrenic nerve – lies on surface of left subclavian artery, crosses arch of aorta anteriorly, descends anteriorly of root lung.
What are the relations of the vagus nerves to the anatomy of the mediastinum? (and in the abdomen?)
Emerge from cranial nerve X and through the skull with the internal jugular veins at the jugular foramina (two holes in the base of the skull). Vagus nerves are lateral to common carotids, and emerge from diaphragm at T10 with oesophagus. LEFT: passes anterior to the aortic arch and crosses the left phrenic which crosses the aortic arch even more anteriorly. Crosses POSTERIORLY of lung root. Breaks up into branches on the oesophagus. RIGHT: lies on the trachea, crosses behind the root lung, branches on oesophagus. Left forms ANTERIOR oesophageal/gastric nerves/trunk, and right forms POSTERIOR oesophageal/gastric nerves/trunk. Become anterior and posterior as they twist from their positions on the oesophagus.
What nerves are associated with the vagus nerve, and what are their anatomical positions? Parasympathetic?
Recurrent laryngeal nerves are associated with the vagus nerves. Left: recurs (= turns back) around the ligamentum arteriosum and aortic arch. Right: recurs around the right subclavian artery, so much longer than the left. They travel back up the oesophagus and up to supply most skeletal muscles in larynx – voice. NOT parasympathetic.
What does the vagus nerve supply?
Supplies the viscera of the thorax and most of the abdomen with parasympathetic stimulation.
What are the motor and sensory components of the autonomic nervous system?
Motor to the cardiac muscle, smooth muscle and glands. Sensory to the visceral organs.
What are the divisions of the autonomic nervous system?
Sympathetic (T1-L2) and parasympathetic (cranial and S2-S4).
How is the dermatome split in the thorax?
No need to emphasise on this.
How is the sympathetic outflow organised?
Sympathetic nerves emerge from the ventral horn and root between T1 and L2 and enter sympathetic ganglia connected by longitudinally running bundles of nerves so that they form a sympathetic/paravertebral chain – which extend well above and below the T1-L2 outflow (from neck to sacrum). Sympathetic nerves enter the ganglia via the white (myelinated) communicans ramus. All sympathetic motor pathways involve a preganglionic and postganglionic neuron.
Three pathways for sympathetic neurones?
- Synapse in these ganglia, travel down the grey (unmyelinated) ramus communicans with sensory nerves too. The nerves involved in this pathway are SOMATIC. 2. Some neurones move up or down via sympathetic trunks to the region of the paravertebral ganglia where their target tissue lies, then synapse in the ganglia, then emerge. The nerves involved in this pathway are VISCERAL, BUT TO SMOOTH MUSCLE AND GLANDS. 3. Some neurones pass through the paravertebral ganglia and synapse instead in unpaired, local microganglia e.g. pre-ganglionic sympathetic nerves that supply the heart and lungs synapse in the cardiac and pulmonary plexi which sit in front of the aorta. THIS PATHWAY IS USED FOR MOTOR NEURONES THAT GO TO THE VISCERA. The grey ramus contains post-ganglionic fibres; the white ramus contains pre-ganglionic fibres.
What is the advantage and disadvantage of this two-stage arrangement (pre- and post- ganglionic nerves) in sympathetic nerves? BUT…
Reduces the number of cell bodies in the CNS. Reduces the precision of targeting of the other nerves. In view of the functions of the autonomic target organs, precise targeting is not of such great importance.
What sympathetic spinal nerves go to the abdomen and lower? What are they called?
From T5-T12. Called splanchnic nerves.
What are sympathetic TRUNKS? Two functions?
RECEIVE branches from spinal nerve T1-L2. Send sympathetic nerve fibres to different paravertebral ganglia (different spinal nerves). Purpose: for distribution to smooth muscle and glands throughout body. They also bring back PAIN fibres to the CNS from the VISCERA.
Where do sympathetic nerves of the thorax emerge from in the vertebral column, and what paravertebral ganglia do they pass through?
Emerge mainly from T2-T4 and from T1. And pass through cervical and upper thoracic ganglia of sympathetic trunk.
What is the difference between sympathetic and parasympathetic neurones that supply the thorax? (x3)
Parasympathetics are only distributed to the viscera – NO SOMATIC SUPPLY. The entire parasympathetic supply of the thorax is supplied by the VAGUS nerve. Come from different regions of the vertebral column. NB: remember, parasympathetic still have pre- and post- ganglionic neurones.
What is the relationship between the number of pre-ganglionic sympathetic and parasympathetic neurones and post-ganglionic neurones?
There are more post-ganglionic neurones than pre-ganglionic neurones. When pre-ganglionic neurones synapse, they synapse onto SEVERAL post-ganglionic neurones. What does afferent and efferent refer to in neurology vs. in relation to an organ? NEURONAL: afferent = towards the CNS (sensory). ORGAN: afferent = towards the organ e.g. kidneys.
What do the pulmonary sympathetic nerves do?
Dilate the bronchioles.
What do the cardiac sympathetic nerves do? (x3)
Increase force of contraction in the heart and increases heart rate efferently. Sympathetic afferents also relay pain and sensations from the heart afferently.
What does the parasympathetic vagus nerve do in the thorax? (x4)
Constrict the bronchioles. Decrease heart rate. Constrict coronary arteries. Relay blood pressure and chemistry information from the heart.
What are the functions of the oesophageal plexus? (x2) IMPORTANT
Describes the ganglia and neurones that concern the oesophagus. Sympathetic afferents relay pain sensations from the oesophagus. Parasympathetic afferents (VAGUS) senses normal physiological information from the oesophagus.
What are the sensory receptors called in the vagus nerve?
Enteroceptors. Content from the gut and lungs.
Where does the lymphatic system drain?
Into the circulatory system in the neck. Three quarters of the body is drained into the left subclavian vein via the thoracic duct (both lower limbs, left upper limp, and left side of head). The upper right quadrant of the body (right head, neck, upper right limb, right of thorax) drains into the right subclavian vein.
What are the names of lymph nodes found in the thorax? (x3) Anatomical positions?
Remember, lymph in relation to the thorax, travels UPWARDS towards the neck. THREE TYPES: Parasternal nodes – drain the anterior chest wall and are associated with internal thoracic arteries. Diaphragmatic nodes – drain the diaphragm and are associated with the diaphragm. Intercostal nodes – drain the posterior chest wall and are associated with the posterior aspects of the ribs.
Where do the lymph nodes of the thorax drain into? (plus an additional cluster of nodes)
Parasternal and upper intercostal nodes drain UP into bronchomediastinal trunks. Lower intercostal nodes drain into the thoracic ducts. Diaphragmatic nodes drain into the brachiocephalic (nodes/trunk) and aortic/lumbar trunks. Lymph nodes found superficially drain into the axillary or parasternal NODES.
What is the anatomic relation of the thoracic duct? Including where it terminates.
Begins at L2 at the cisterna chyli (a large vessel that drains the abdomen, pelvis, perineum and limbs). It ascends up behind the oesophagus with the vertebral column and pierces the diaphragm at T10. It ascends right of the midline between the descending aorta and azygous vein, then switches to the left of the midline at T5. Empties into the junction between the left internal jugular vein and left subclavian vein – this is the definition you need to use in exams for termination!
What are the lymphatics of the posterior mediastinum?
Nodes on aorta receive lymph from oesophagus, diaphragm, liver and pericardium and drain into the thoracic duct and posterior mediastinal nodes.
What is the lymphatic flow through the lymphatic system in the thorax?
IMPORTANT.
What are the contents of the middle mediastinum?
The heart. And the pericardium. The phrenic nerves. Lymphatic nodes and vessels.
What are the contents of the anterior mediastinum?
Bound laterally to the pleurae, posteriorly by the pericardium and anteriorly to the sternum. It contains loose areolar tissue, lymphatic vessels, anterior mediastinal lymph nodes, the mediastinal branches of the internal thoracic artery, and the thymus.
What is the anatomy of the superior mediastinum from an axial plane?
REALLY IMPORTANT! This is all in relation with the ‘Heart and Great Vessels revision notes’. NOTE THAT the brachiocephalic trunk lies medially.
How many constrictions are there in the oesophagus and where are they?
Oesophagus has constrictions at four locations – things don’t just drop into the stomach. Occur at: Junction of the pharynx and the oesophagus (C7) and posterior to the trachea. Where the arch of the aorta squashes the oesophagus to the right as it turns into the descending aorta. Where oesophagus is compressed by the left main bronchus anteriorly. At the oesophageal hiatus – where it crosses the diaphragm.
What is the superior thoracic aperture? Alternative name?
Defined as the ring created by the vertebral body (the anterior part of the vertebrate) T1 vertebrate, the medial margins of the first rib, and the anterior wall of the manubrium. The aperture is at an oblique angle (not 90 degrees) – this is because the rib is upwards sloping from the manubrium – which attaches at the horizontal plane TII/III. The oesophagus, trachea, superior vena cava and major blood vessels pass through the aperture to access the upper limbs and neck. Also called the thoracic INLET.
What is the inferior thoracic aperture? Alternative name?
Defined as the ring formed by the TXII vertebrate, rib XII and end of rib XI, the cartilage VII to X, and the xiphoid process. It is enclosed by the diaphragm to separate the abdomen from the thorax. Also called the inferior thoracic INLET.
What are the differences between the images in a CT scan and an X-ray?
- Higher resolution. 2. We can identify water differently from soft tissue in CT scans, which we would not be able to see in an X-ray. This means that there is some contrast between the densities of different soft tissues depending on water content e.g. photo shows liver tissue as denser than the kidneys etc. 3. We can also display the imaging in different ‘windows’. CT windows changes the interpretation of the image to expose different details based on focusing on different densities – seen in photo. 4. We can display any cross-section we want e.g. we can view sagittal, axial and coronal planes.
How do image colours differ for different tissues between CT scans and MRI images? (x3)
The three colours that change (noticeably) are: bone, water, and fat. Bone is black in an MRI because protons are so packed together.
What is the mechanism of referred pain in the T1-5 sympathetic afferents to the chest wall?
Thoracic sympathetic afferents (from the heart and lungs) pass through their plexuses and return to the CNS. These visceral afferents associated with the sympathetic system conduct pain sensation from the heart and lungs. These afferents converge on neurons that receive information from the skin at the same spinal cord level. The sympathetic afferents have a low sensory input, whereas the sensory inputs from the skin is very high. As a result, this pain is often ‘referred’ to cutaneous regions supplied by the same spinal cord levels by the CNS. T2-4 sympathetic nerves supply the heart. E.g. heart attack = pain interpreted as coming from the skin in the left of the chest and arm.
