Thorax 1.2 Flashcards
What does the spinal nerve divide into?
into a small posterior ramus that supplies the intrinsic muscles of the back and a larger anterior ramus (intercostal nerve) that innervates all the muscles lining the trunk
What does the anterior ramus divide into?
- a lateral cutaneous branch at the midaxillary line
- anteriorly, and lateral to the sternum, it gives rise to an anterior cutaneous branch
Where do the intercostal nerves course?
- between the internal intercostal and innermost intercostal muscles
- Intercostal arteries and veins accompany the intercostal nerves
What do the first 11 thoracic nerves give rise to?
anterior rami that constitute the intercostal nerves (T12 is the subcostal nerve, and it is inferior to the 12th rib)
Where do thoracic anterior rami run? Why is this important?
- Thoracic anterior rami (intercostal nerves) run in the costal groove at the inferior margin of each rib
- physicians must be aware of this positioning when entering the intercostal space (for injections or chest tube placements).
What is the cardiac muscle of the hear innervated by?
The autonomic nervous system
Where do the sympathetic contributions to the cardiac plexus arise from?
- from cardiac nerves that originate largely from the cervical portions of the sympathetic trunk (although their preganglionic fibers arise from neurons in the upper 4 thoracic spinal cord levels)
- but also send direct thoracic cardiac branches (postganglionic sympathetics) medially toward the heart
Where do the parasymapthetic contributions to the heart travel?
(preganglionic) travel with the vagus nerve (CN X)
What is the cardiac plexus formed from?
- the parasympathetic and sympathetic branches form a rich cardiac plexus around the great vessels arising from the heart and around the bifurcation of the trachea.
- The vagus preganglionics synapse on postganglionics in this plexus
What does sympathetic and parasympathetic innervation to the heart do?
- Sympathetic innervation to the heart increases the heart rate and contractile force 2. Parasympathetic innervation decreases the heart rate
Where is angia pectoris conveyed? Where is the referred pain?
- Pain sensation from myocardial ischemia, called angina pectoris, is conveyed to the upper 4 thoracic spinal cord levels via the sympathetic pathways
- accounting for referred pain over the T1-T4 dermatome regions, primarily on the left side. 3. This pain may be initially interpreted by the patient as somatic pain (musculoskeletal) rather than pain from the ischemic cardiac muscle of the heart
What type fo nerves are of the oesophagus and posterior thoracic wall?
somatic nerves (thoracic intercostal nerves) and autonomic nerve
What do thoracic spinal cord segments give rise to?
intercostal nerves, which are connected by rami communicantes to the sympathetic trunk
What happens in the thorax?
the latter gives rise to the greater, lesser, and least splanchnic nerves (all preganglionic sympathetics), which course through the diaphragm to the abdomen
What is the parasympathetic contribution of the oesophagus and posterior thoracic wall?
- via the vagus nerve
- As they pass through the diaphragm, the left and right vagus nerves form a plexus on the esophagus
What would a mass in posterior mediastinum present as?
- pain, neurologic symptoms, or difficulty swallowing (dysphagia)
- The most common masses include tumors of the peripheral nerves or their sheath cells (e.g., schwannomas), or tumors or diverticula of the esophagus
Where do posterior intercostal arteries arise from and course?
- from the thoracic aorta bilaterally
- course along the inferior margin of each rib between the innermost intercostal muscles and internal intercostal muscle