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1. Surrounding features

a) Gross location


The heart lies within the middle mediastinum a.k.a. the pericardium.

The middle mediastinum is surrounded by the other mediastinal portions, and hence the lungs. It is externally invested by the parietal pleura of the lungs.
Hence, consider the pericardium in relation to the lungs.


The middle mediastinum is fused to the diaphragm on the bottom.


b) Associated layers

i) Major layers


Fibrous pericardium is mostly inflexible and is the outermost
Serous pericardium functions similar to other kinds of pleura; hence visceral and parietal layers.

Layer

Fibrous pericardium

Serous pericardium

Parietal

Visceral

Innervation

Phrenic nerve

Phrenic nerve

Insensitive

Gross anatomy

Forms all of pericardium outside

Fuses with all great vessels except the IVC (fused to diaphragm at T8)



Like the pleura, invests all of heart and vessels, with reflections in certain places.
(Reflections discussed later)

Function

Inflexible but slippery

Stuck to parietal pleura so lungs glide over it







Clinical

Cardiac effusions can lead to compression (cardiac tamponade)


The only source of localized pain of pericardium

No pain

The pain of angina comes from sympathetic innervations of muscles in heart.

The pain of pericarditis comes from the parietal serous pericardium. This passes through the phrenic nerve, and hence refers to the shoulder.

ii) Clinically significant reflections


The two main defects coming fom reflections of the serous pericardium are the:

  • Transverse sinus

  • Oblique sinus

Defect

Transverse sinus

Oblique sinus

Embryological origin

Breakdown of dorsal mesocardium

Leaving patency between arterial and venous ends of heart tube



Buckling of heart tube

Creates cul-de-sac



Description

Located posterior to heart
Horizontal sinus superiorly

Relation to SVC, aortic arch, pulmonary trunk and left auricle



Located posterior to heart
J-shaped cul-de-sac

Access

Pass finger superiorly through

Under apex and behind the heart

Surgical significance

Divides arteries from veins
When a finger is put through it

  • Arteries (aorta and pulmonary trunk) are pushed anteriorly

  • Veins (SVC) and left auricle are pushed posteriorly

A ligature is passed through this sinus to occlude the aorta and pulmonary trunk in certain operations.

Functional significance:

Allows left atrium to pulsate
In fact, the majority of the oblique sinus overlies the left atrium posteriorly.




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