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Mediastinum, Pericardium and Heart

This lecture outlines the basic aspects of mediastinum, pericardium and heart, along with the contents and divisions of mediastinum.

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Outline of Lecture
Mediastinum, Pericardium and Heart


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


Remains of the thymus

Heart and large blood vessels



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.


Large veins

Large arteries


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.


Heart within the pericardium with the phrenic nerves on each side

Esophagus and thoracic duct

Descending aorta

Sympathetic trunks

Clinical Notes

Deflection of Mediastinum


Mediastinal Tumors or Cysts


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



Heart Features


Right atrium

Right ventricle

Left atrium

Left ventricle


Leaflet valves


Bicuspid (mitral)

Cusped (semilunar) valves



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


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


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


Bicuspid valve


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



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




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





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