This lecture outlines the basic aspects of mediastinum, pericardium and heart, along with the contents and divisions of mediastinum.
Outline of Lecture
Mediastinum, Pericardium and Heart
Mediastinum
The mediastinum, though thick, is a movable partition that extends superiorly to the thoracic outlet and the root of the neck and inferiorly to the diaphragm.
It extends anteriorly to the sternum and posteriorly to the vertebral column
Contents
Remains of the thymus
Heart and large blood vessels
Trachea
Esophagus
Thoracic duct
Lymph nodes
Vagus and phrenic nerves
Sympathetic trunks
Division of mediastinum
Superior Mediastinum
The superior mediastinum is bounded in front
by the manubrium sterni and behind by the
first four thoracic vertebrae.
Thymus
Large veins
Large arteries
Trachea
Esophagus and thoracic duct
Sympathetic trunks
Inferior Mediastinum
The inferior mediastinum is bounded in front
by the body of the sternum and behind by the
lower eight thoracic vertebrae.
Thymus
Heart within the pericardium with the phrenic nerves on each side
Esophagus and thoracic duct
Descending aorta
Sympathetic trunks
Clinical Notes
Deflection of Mediastinum
Mediastinitis
Mediastinal Tumors or Cysts
Mediastinoscopy
Pericardium
Pericardium is a fibroserous sac that encloses the heart and the roots of its great vessels.
Fibrous Pericardium
Serous Pericardium
Pericardial Sinuses
Arterial supply and venous drainage of the pericardium
Nerve Supply of the Pericardium
The Heart
Facts, location, & orientation
Oblique orientation
Apex points inferiosinister (down and left)
5th intercostal space
Base is superior near origins of great vessels
2nd intercostal space
2/3 lies left of the midline
For the most part
Anterior/inferior aspect of the heart
right atrium/ventricle
Posterior/superior aspect
left atrium/ventricle
Structure of the Heart – Coverings
Fibrous pericardium
Serous pericardium
Parietal pericardium
Visceral pericardium
Coronary sulcus
Atrioventricular sulcus
Circumvents the heart
Interventricular sulcus
Anterior
Posterior
Heart Features
Chambers
Right atrium
Right ventricle
Left atrium
Left ventricle
Valves
Leaflet valves
Tricuspid
Bicuspid (mitral)
Cusped (semilunar) valves
Aortic
Pulmonic
Position of heart
Surfaces of the Heart
The sternocostal surface
The diaphragmatic surface
The base of the heart
The apex of the heart
Borders of the Heart
Chambers of the Heart
Fibrous Skeleton Of Heart
Right Atrium
Right atrium
Auricle (ear)
Pectinate muscles (rough)
Sinus venarum (smooth)
Crista terminalis
Division between rough to smooth
Openings (ostia)
SVC/IVC/Coronary sinus
Fossa ovalis
Foramen ovale in fetus
Limbus
Right atrium “valves”
Superior vena cava
No valve
Inferior vena cava
Eustachian valve
Incompetent in adult, directs IVC blood though Foramen ovale in fetus
Coronary Sinus
Thebesian valve
Prevents backflow into coronary sinus during atrial systole
Openings into the Right Atrium
Fetal Remnants
Right Ventricle
Right ventricle
Most anterior aspect of heart
Tricuspid valve (RA-RV)
Anterior/Posterior/Septal cusps (leafs)
Papillary muscles
Connected to cusps via Chordae tendinae
Contract to prevent Tricuspid valve regurgitation
Named same as cusps
Trabeculae carnae
Moderator band
The tricuspid valve
The pulmonary valve
Left Atrium
Left atrium
Ostia of 4 pulmonary veins
2 superior
2 inferior
Auricle
Openings into the Left Atrium
Left Ventricle
Left ventricle
Trabeculae carnae
Bicuspid (mitral) valve
Anterior/Posterior cusps
Papillary muscles
Chordae tendinae
Usually a greater number than the right, due to the increased pressures and strength necessary to prevent regurgutation
Heart Valves
Tricuspid valve
RA – RV
Bicuspid valve
LA – LV
aka “Mitral valve”
Aortic valve
LV – aorta
Pulmonic valve
RV – pulmonary trunk
The mitral valve
The aortic valve
Aortic valve
Posterior to pulmonic valve
Just superior lies the Sinus of Valsalva
Helps to dampen aortic outflow and prevent cusps from adhering to walls of aorta
3 cusps
Posterior (non-coronary) cusp
Right
Left
Just superior to right and left cusps in the Sinus of Valsalva are the openings of the right and left coronary arteries, respectively
Pulmonic valve
From RV to pulmonary trunk
Lies just anterior to aortic valve
3 semilunar cusps
Anterior
Right
Left
Structure of the Heart
Conducting System of the Heart
Conducting system
Arterial Supply of the Heart
Variations in the Coronary Arteries
Coronary Artery Anastomoses
Anastomoses between the terminal branches of the right and left coronary arteries (collateral circulation) exist, but they are usually not large enough to provide an adequate blood supply to the cardiac muscle should one of the large branches become blocked by disease.
A sudden block of one of the larger branches of either coronary artery usually leads to myocardial death (myocardial infarction), although sometimes the collateral circulation is enough to sustain the muscle.
Clinical Notes
Coronary Artery Disease
Arteriosclerotic disease of the coronary arteries may present in three ways, depending on the rate of narrowing of the lumina of the arteries:
General degeneration and fibrosis of the myocardium
Angina pectoris
Myocardial infarction
Venous Drainage of the Heart
Nerve Supply of the Heart
Surface markings
Reading Assignments
Gray’s Anatomy: 39th Edition (Reference book).
Last’s Anatomy, 11th Edition.
Clinical Anatomy by Richard S. Snell, 8th Edition.
Clinically Oriented Anatomy by Keith L. Moore,
6th Edition
