Heart & Borders

Cardiac Output at Rest

5L/min

(7200 L/day)

Describe the blood flow route from body to heart to body

Blood enters heart through the superior & inferior vena cava → right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary artery → lungs → pulmonary vein → left atrium → mitral valve → left ventricle → aortic valve → aorta → body

Where is the heart located

Located in thoracic cavity between 2 pleural cavities in the mediastinum

Transverse sections we are looking at it from the feet up to body (inferior view)

subdivisions of the mediastinum

Superior

Inferior

The inferior subdivision is further divided:

• Anterior:

• Middle

• Posterior

Borders of superior subdivision of the mediastinum

Superior border: Superior thoracic aperture

Inferior border: Sternal angle

Borders of the anterior inferior subdivision of the mediastinum

Superior: T4/T5 (sternal angle)

Inferior: T12 (diaphragm).

Anterior: Posterior surface of sternum

Posterior: Pericardium

Borders of the posterior inferior subdivision of the mediastinum

Superior: T4/T5 (sternal angle)

Inferior: T12 (diaphragm).

Anterior: Pericardium and diaphragm.

Posterior: Vertebral bodies of T5–T12.

Blood vessels, Nerves & Structures of superior subdivision of the mediastinum

Arteries:

• Arch of the aorta

• Left common carotid artery & left subclavian artery (both come directly off aorta)

• Right common carotid artery & right subclavian artery (come off the aorta through the brachiocephalic trunk)

 

Veins

• Superior Vena Cava

• Right & Left Brachiocephalic veins (come from SVC)

• Left superior intercostal vein

Nerves

• Phrenic nerves

• Vagus nerves

• Left recurrent laryngeal branch (of left vagus nerve)

Structures

• Oesophagus

• Trachea

• Thymus

• Thoracic duct

Contents of the anterior inferior subdivision of the mediastinum

Thymus gland

(Active in children - gradually regresses during childhood)

(Extends from cricoid to retrosternal area)

Contents of the middle inferior subdivision of the mediastinum

Pericardium

Heart

Roots of great vessels

Contents of the posterior inferior subdivision of the mediastinum

Thoracic aorta

Azygous system of veins

Oesophagus

Trachea

Thoracic duct

Sympathetic trunks

1st division off the aorta

Brachiocephalic trunk

Ligamentum arteriosum

Ligamentum arteriosum is a foetal blood vessel used when lungs weren't functional in utero (it is the remnants of a duct that connected the pulmonary trunk to the arch of the aorta)

Why don’t left & right vagus nerves have the same route

The aorta is in the left’s way

Which nerve is closely to the oesophagus

Vagus nerve

The vagus nerve goes under the _____vein

azygous

Layers to the pericardium

Outer fibrous layer

Inner double layer of serous membrane consisting of:

• parietal layer (lines fibrous layer)

• visceral layer (lines heart)(epicardium)

(outer fibrous layer & inner parietal layer are attached)

What is the fibrous pericardium attached to

Great vessels

Sternum (sternopericardial ligament)

Central tendon of the diaphragm

Parietal layer of serous pericardium

What is the space between the 2 internal serous pericardium layers called, filled with & used for

Called:

• Pericardial cavity

• Potential space

Filled with: Pericardial fluid

Used for: Facilitating gliding movements (beating of heart)

Cardiac tamponade

Excess fluid in pericardial cavity puts pressure on heart

Work through the layers between the chest cavity & the Blood inside the heart

How do pericardial sinuses come about

Naturally occurring open spaces in the pericardium caused by reflection of serous pericardium on the posterior surface of the heart

Name 2 pericardial sinuses

Oblique sinus

Transverse sinus

Where are each of the pericardial sinuses located

Oblique sinus is behind the heart (reflection surrounding veins)

Transverse sinus is between the great arteries & veins (posterior to the aorta & pulmonary trunk & anterior to the superior vena cava)

Lots of arteries supply the pericardium. Where are their branches from

branches from the internal thoracic, pericardiacophrenic, musculophrenic, inferior phrenic and the thoracic aorta

What veins drain the pericardium

pericardial veins drain into the azygos system of veins, the internal thoracic veins & the superior phrenic veins

What nerves supply the pericardium

the vagus nerve, sympathetic trunks and phrenic nerves

Why is pericardial related pain referred to the supraclavicular region or lateral neck

Pain from parietal pericardium is carried in somatic afferent fibres in phrenic nerves.

What can be seen in a T3 axial CT

What can be seen in a T4 axial CT

What is the auscultation position for the aortic valve

RHS 2nd intercostal space

What is the auscultation position for the pulmonary valve

LHS 2nd intercostal space

What is the auscultation position for the tricuspid valve

LHS 5th intercostal space at sternal border

What is the auscultation position for the mitral valve

LHS 5th intercostal space at the mid-clavicular line

What is the apex beat

The lowest and most lateral point on the chest wall where you can feel the heart beating

Where is the apex beat

LHS 5th intercostal space, mid clavicular line

Dextrocardia

Relatively uncommon embryological abnormality where the heart is positioned on the right hand side of the chest