superior & posterior mediastinum & diaphragm Flashcards
what is the mediastinum?
the central component of the thoracic cavity located between the 2 pleural sacs
-contains most of the thoracic organs (not lungs!)
how is the mediastinum divided?
- divided into 2 parts by an imaginary line that runs from the sternal angle to the T4 vertebrae
-superior mediastinum - extends upwards
-inferior mediastinum - extends downwards and is further subdivided into the anterior, middle and posterior mediastinum
what are the anatomical borders of the superior mediastinum?
-superior - thoracic inlet (important anatomical passageway between neck and thorax - formed by 1st rib)
-inferior - level of sternal angle
-anterior - manubrium of sternum
-posterior - T1-T4
-lateral - pleurae of lungs
what important arteries does the superior mediastinum contain?
-arch of aorta
-the 3 main branches of the arch of aorta arise in the SM - brachiocephalic, left common carotid & left subclavian
what important veins are located in the superior mediastinum?
- brachiocephalic veins (draining blood from upper bod)
-superior intercostal vein - collects blood from left 2nd & 3rd intercostal vein
-azygos vein
Describe the nerves that the superior mediastinum contains
-vagus nerve - 2 distinctive paths
- right vagus nerve - runs parallel to trachea and passes posteriorly to superior VC
-left vagus nerve - enters SM between left common carotid & left subclavian arteries
-left recurrent laryngeal nerve arises from left vagus nerve
-phrenic nerve
other than vessels and nerves, what other structures are contained within the superior mediastinum?
-thymus
-trachea
-oesophagus
-thoracic duct
what is the anterior mediastinum?
a division of the inferior mediastinum
what does the anterior mediastinum contain?
no major structures
what is the middle mediastinum?
the largest subdivision of the inferior mediastinum
what does the middle mediastinum contain?
- heart and its protective pericardium
-tracheal bifurcation
-left and right main bronchi
-ascending aorta
-pulmonary trunk - right and left pulmonary arteries
-superior vena cava
-phrenic nerves (L +R)
-cardiac plexus
what is the cardiac plexus?
a network of nerves located at the base of the heart, containing sympathetic and parasympathetic fibres
what is the posterior mediastinum?
a subdivision of the inferior mediastinum
what major structures does the posterior mediastinum contain?
-oesophagus & its nerve plexus
-descending thoracic aorta & branches
-azygos system of veins
-thoracic duct and associated lymph nodes
what is the descending thoracic aorta?
-continuation of the arch of the aorta, . -It descends through the posterior mediastinum to the left of the vertebrae
- thoracic aorta becomes the abdominal aorta later on
what is the thoracic duct?
-largest lymphatic vessel in the body, allowing return of lymph from most of the body into the venous system.
- thoracic duct receives lymphatic drainage from the intercostal spaces and neighbouring anatomical structures through a number of branches.
what are the 2 main functions of the diaphragm?
- separates the thoracic cavity from the abdominal cavity
-contracts and relaxes - aiding in inspiration & expiration
what are the 3 peripheral attachments of the diaphragm?
-lumbar vertebrae and arcuate ligaments
-costal cartilages of ribs 7-10
-xiphoid process of the sternum
what are arcuate ligaments and name the 3 of them in the diaphragm
-fibrous bands found around the diaphragm and the abdominal aorta
-median arcuate ligament, lateral arcuate ligament & the medial arcuate ligament
what do the muscle fibres of the diaphragm combine to form and what does this structure ascend to?
- a central tendon
-this tendon ascends to fuse with the inferior surface of the fibrous pericardium
what are the 2 sides of the diaphragm called?
-right and left dome
what are the 3 hiatus’ in the diaphragm?
-caval hiatus
-oesophageal hiatus
-aortic hiatus
what happens to the diaphragm and the oesophagus during inspiration?
-diaphragm pulls down to allow the expansion of the thoracic cavity
-the oesophagus narrows during inspiration to prevent reflux
what nerve gives a motor supply to the diaphragm?
the phrenic nerve
why can diaphragm pain be referred to the shoulder?
due to the shared innervation of the phrenic nerve. The phrenic nerve originates from the cervical spinal nerves C3-C5
-phrenic nerve also provides some sensory innervation to shoulder
