Nerves of the Thorax PDF

Nerves of the Thorax Fraser Chisholm [email protected] https://www.latimes.com/entertainment-arts/movies/story/2020-06-17/ultimate-summer-movie-showdown-finding-nemo Learning Outcomes After this lecture, time spent in the dissecting room, and further private study you should be able to: • De...

Nerves of the Thorax Fraser Chisholm [email protected] https://www.latimes.com/entertainment-arts/movies/story/2020-06-17/ultimate-summer-movie-showdown-finding-nemo Learning Outcomes After this lecture, time spent in the dissecting room, and further private study you should be able to: • Describe the course and distribution of the right and left vagus nerves • Describe (again) the clinical importance of the anatomy of the left recurrent laryngeal nerve • Describe the position and extent of the sympathetic trunks and ganglia • Describe the pre- and post-ganglionic neural connections of the sympathetic trunks • Describe the functions of the sympathetic trunks and their branches • State the signs of Horner’s syndrome • Describe the pre- and post-ganglionic neural connections of theparasympathetic system • Compare and contrast the functional anatomy of the sympathetic and parasympathetic systems 2 Overview of the nervous system CNS brain & spinal cord PNS Cranial and spinal nerves Sensory (afferent) Somatic sensory Visceral sensory Enteric Motor (efferent) Somatic motor Visceral motor Parasympathetic Sympathetic 3 Autonomic nervous system • Under the control of the hypothalamus. • Dual innervation: Sympathetics and parasympathetics exert opposite effects in a particular organ/tissue but they functionally complement each other to keep the body functioning normally. • Certain blood vessels, errector pili muscle and sweat glands are supplied by sympathetics only 4 Autonomic nervous system • STABLE INTERNAL ENVIRONMENT • Regulates the visceral activity (Circulation, respiration, digestion, excretion, reproduction) • Supplies smooth muscles (walls of the blood vessels, bronchi, intestines) – Supplies the cardiac muscle – Supplies the glands • Regulates body temperature • Autonomic fibres “accompany” the general visceral afferent fibres 5 Autonomic nervous system • Reach the end organ with two neurons • Cell body of the 1st neuron (preganglionic neuron) is at grey matter of the spinal cord or brain stem • axon is myelinated • Cell body of the 2nd neuron (postganglionic neuron) is at an autonomic ganglion • axon is unmyelinated 6 Basic anatomy of the ANS Two-neuron system – Pre-ganglionic fibers originate from the CNS – Post-ganglionic fibers originate from autonomic ganglia Fiber origins Sympathetic Parasympathetic Pre-ganglionic Thoracolumbar Craniosacral Paravertebral Chain Post-ganglionic Prevertebral Ganglia In or Near Target Organ Parasympathetic • • • • • • Rest & digest or Rest & repose - conserves energy Slows breathing and heart rate, reducing cardiac output and BP Stimulates digestion (secretion of digestive enzymes) Opens sphincters Secretomotor to glands (salivary, lacrimal) Constricts pupils (accommodation for close focus) 8 Vagus nerve • The parasympathetic innervation of the thoracic viscera is by the 10th cranial nerve, vagus • Vagus leaves cranial cavity through jugular foramen, descends betweeninternal jugular vein and internal (then common) carotid artery 9 Vagus • Right Vagus enters the thoracic cavity between the right subclavian artery and Brachiocephalic vein • Left vagus enters the thoracic cavity posterior to the left Brachiocephalic vein, between the • subclavian and common carotid arteries 10 Right Vagus nerve Left Vagus nerve 11 Recurrent Laryngeal Nerves • The right vagus gives off recurrent laryngeal nerve, which winds around right subclavian artery • The left vagus gives off recurrent laryngeal nerve, which winds around the aortic arch (aortopulmonary window), just posterolateral to the ligamentum arteriosum 12 Recurrent Laryngeal Nerves • Recurrent laryngeal nerves supply – Intrinsic laryngeal muscles (Except 1) – Middle and inferior pharyngeal constrictor muscles – sensory to the laryngeal cavity below the level of the vocal folds 13 Sympathetic Nervous system • It prepares the body to “Fight or flight” situations • Increases heart rate and strength of heart beat • Dilates coronary arteries (indirectly, by local metabolic factors) • Constricts peripheral arteries • Relaxes bronchial smooth muscles (Increases respiratory efficiency) • Closes sphincters • Controls body temperature (blood vessels, sweat glands) 14 Sympathetic • THORACOLUMBAR OUTFLOW • Preganglionic cell bodies lie in the intermediolateral horn of T1-L2 spinal cord Segments • Postganglionic cell bodies lie either: • In paravertebral sympathetic ganglia – Anterior to the neck of the ribs lateral aspect of the vertebral bodies – Covered by the parietal pleura – Interconnected sympathetic chain (sympathetic trunk) • OR in pre vertebral (pre aortic ganglia) – abdomen 15 Sympathetic Trunk • Each sympathetic trunk extends between the atlas and coccyx • Trunks fuse with each other in the single ganglion impar, opposite the coccyx • Number of paravertebral sympathetic ganglia<number of vertebra – Superior (C1-4), middle (C5-6) and inferior (C7-8) cervical ganglia – Inferior cervical+T1 can fuse = Stellate Ganglion (cervicothoracic ganglion) (C7-T1) 16 17 18 Sympathetic Neurones 1. Synapse at its level • Postganglionic axons (unmyelinated, grey) pass in the GRC and join T1-L2 Spinal nerves GRC = Grey Rami Communicantes WRC = White Rami Communicantes 19 Rami communicantes = approx. 1mm Intercostal nerve 20 Sympathetic Neurones GRC = Grey Rami Communicantes WRC = White Rami Communicantes 2. Ascend then synapse • Postganglionic axons (unmyelinated, grey) pass in the GRC and join Cervical Spinal nerves • OR leave via cardiopulmonary splanchnic nerves 21 Sympathetic Neurones 3. Travel down the chain to synapse in a lumbar/sacral ganglion GRC = Grey Rami Communicantes WRC = White Rami Communicantes • Postganglionic axons pass in the GRC and join lumbar/sacral spinal nerves 22 Sympathetic Neurones Aorta Prevertebral ganglion 4. Preganglionic branches pass through the sympathetic trunk without synapsing • Travel in Thoracic splanchnic nerves to the abdomen • Synapse in a prevertebral ganglion GRC = Grey Rami Communicantes WRC = White Rami Communicantes • Supply abdominal viscera 23 Thoracic Splanchnic nerves • Greater – T5-9 • Lesser – From T10 + 11 • Least – From T12 • Also – Lumbar splanchnic nerves – Pelvic splanchnic nerves 24 Thoracic Splanchnic Nerves Greater Splanchnic nerve Lesser Splanchnic nerve Least Splanchnic nerve 25 Adrenal supply 5. The adrenal medulla is supplied directly (it is itself like a ganglion) 26 Areas of Supply • • • • Sympathetics of the head from T1 - T3 segments Sympathetics of the upper limb from T4 - T6 segments Sympathetics to the heart from T1-5 Sympathetics of the thoracic and abdominal walls from T1 - T12 segments • Sympathetics of the lower limb from T12 to L2 segments • Remember the referred pain from visceral structures to the matching dermatome 27 Visceral Plexuses • Sympathetic and parasympathetic fibres mix and form autonomic or visceral plexuses in the thorax, abdomen or pelvis • Visceral plexuses in the thorax – Cardiac plexus: Anterior to the bifurcation of the trachea and posterior to the ascending aorta – Pulmonary plexus: Anterior and (mainly) posterior to the roots of the lungs – Oesophageal plexus: Around the oesophagus 28 Cardiac plexus • Sympathetics from T1-5 → T1-5 ganglia + inferior and middle cervical ganglia • Visceral afferent fibres travel alongside the sympathetic nerves • Referred pain from heart to T1 /T2 dermatomes (medial aspect of left arm) +T3-5 • Parasympathetics from Vagus 29 Pulmonary plexus • Sympathetics from T2-4 → T2-4 ganglia • Parasympathetics from Vagus 30 Phrenic nerve • Sole motor supply to the diaphragm • Also supplies sensory fibres to the – mediastinal parietal – pleura parietal pericardium – peritoneum and pleura related to the central tendon 31 Netter Fig. 190B Intercostal nerves • Anterior rami of the thoracic spinal nerves • Mixed nerves • Motor branches to intercostal and abdominal wall muscles • Visceromotor branches to vessels • Lateral cutaneous branch • Anterior cutaneous branch 32 Pancoast’s Tumour 33 Sources of figures and Images • • • • • • • DAFFNER: Daffner & Hartman. Clinical Radiology. The Essentials ,4th Ed, 2014 © Lippincott Williams & Wilkins. DRAKE: Drake et al. Gray’s Atlas of Anatomy 2nd Ed, 2018 © Elsevier. GILROY: Gilroy et al. Atlas of Anatomy 2nd Ed, 2012 © Thieme KELLEY: Kelly&Petersen. Sectional Anatomy for Imaging Professionals, 3rd Edition, 2013 © Mosby, Elsevier Inc MOORE: Moore et al. Clinically Oriented Anatomy 8th Ed, 2018 © Wolters Kluver. NETTER: Hansen. Netter's Clinical Anatomy, 3rd Edition, 2014 © Saunders, Elsevier Inc SOBOTTA: Putz&Pabst. Sobotta Atlas of Human Anatomy, 14th Edition, 2006 © Urban and Fischer Verlag, Elsevier Inc 34