4. Mediastinum + Heart I Flashcards
Mediastinum (def)
Midline region between R and L pleural cavities
Houses all thoracic organs except lungs
Mediastinum (borders, plane)
Superior: superior thoracic aperture
Inferior: diaphragm
Divided into superior and inferior mediastinum by horizontal plane through sternal angle
Superior Thoracic Aperture
Ring of bones
T1 vertebrae, Rib 1, Manubrium
Thymus
Lymphoid organ
Important in development and maintenance of immune system
Gradual involution: shrinks and replaced with fat
Thymus (location)
Posterior to manubrium, body
Anterior to pericardium
Pericardium
AKA Pericardial Sac
Fiberoserous membrane surrounding heart, roots of great vessels
Phrenic Nerves
Motor: diaphragm
Sensory: diaphragm, parietal pleura, fibrous pericardium, parietal layer of serous pericardium
Pericardium (layers)
Fibrous
Parietal Serous
Visceral Serous
Fibrous Pericardium
Tough
External layer
Inelastic (prevents heart from overfilling)
Attached to central tendon of diaphragm
Serous Pericardium
Parietal lines fibrous pericardium
Visceral lines heart
Continuous w/ each other
Pericardial Cavity
Potential space between parietal and visceral layers of serous pericardium
Contains serous fluid
Pericarditis
Inflammation of serous pericardium
Leads to roughened surfaces and pericardial friction
Auscultation sign: fabric rubbing together
Cardiac Tamponade
Accumulation of fluid in pericardial cavity
This leads to compression and restriction of heart’s ability to fill to capacity
Pericardiocentesis
Drains fluids from pericardial cavity
Need to avoid lungs
- intercostal nerve block
- subxiphoid approach or parasternal approach
Subxiphoid Approach
Insert needle to the left of the xiphoid process, directly superiorly deep to costal margin
Parasternal Approach
Insert needle to the left of the sternum in the left 5th or 6th intercostal space – cardiac notch!!
Heart Chambers
Right Atrium
Left Atrium
Right Ventricle
Left Ventricle
Heart Chamber (orientation)
R Ventricle: anterior
L Atrium: posterior
Borders of the Heart
Superior: B atria
Inferior: L ventricle
Left: L ventricle
Right: R atrium
Apex of the Heart
Look at a picture
Directed anteroinferiorly and to the left
Formed by L ventricle
Base of the Heart
Look at a picture
Directed posteriorly
Formed by L atrium
Great Vessels (veins)
Look at a picture
Internal jugular veins
Subclavian veins
Brachiocephalic veins
Superior Vena Cava (SVC)
Brachiocephalic Veins
L is longer than R because it must cross midline to reach SVC
Superior Vena Cava
returns oxygen poor blood to R atrium from structures superior to diaphragm (except heart)
Inferior Vena Cava
returns oxygen poor blood to R atrium from structures inferior to diaphragm
Great Vessels (Aorta)
Ascending Aorta (emerges from L ventricle)
Arch of Aorta
Descending (Thoracic) Aorta
Name changes at sternal angle
Great Vessels (Arch of the Aorta)
Brachiocephalic Trunk (R Subclavian, R Common Carotid)
L Common Carotid
L Subclavian
Transverse Pericardial Sinus
Posterior to aorta and pulmonary trunk
Good for ligation - allows control of arterial outflow
Vagus Nerve
CN X
Parasympathetic innervation
Slows down heart rate, reduces force of contractions
Vagus Nerve (pathway)
Pre cell bodies: brain
Pre fiber: vagus nerve
Post cell bodies: heart
Post fiber: heart
Right Recurrent Laryngeal Nerve
Branch of Vagus
Courses posterior to R subclavian artery - makes a U turn back up to larynx
Contributes to cardiac plexus, R pulmonary plexus, esophageal plexus
Left Recurrent Laryngeal Nerve
Branch of Vagus
Courses under arch of aorta - makes a U turn in mediastinum back up to larynx
Contributes to cardiac plexus, esophageal plexus
Clinical significance: aneurysm of aortic arch/enlargement of lymph nodes compresses nerve -> hoarseness of voice
Sympathetic Innervation
Increases heart rate
Lateral horn Ventral root Spinal nerve Ventral ramus White ramus communicans Sympathetic trunk Paravertebral ganglia (upper thoracic, cervical) Cardiac nerves Heart
Cardiac Nerves
Arise from upper thoracic and cervical sympathetic trunk
Referred Cardiac Pain
Visceral sensory fibers follow pathway of sympathetic nerves
Visceral pain (normally vague) misinterpreted as somatic pain (sharp)
