7 - anatomy of the heart

What is the heart?

What is the heart?

Cone shaped muscular pump (upside down pyramid)

Where is the heart located (simple)?

In the thorax between the lungs (middle mediastinum)

Location of the heart (complex)

• Protected by ribcage

• Lies behind sternum

• Between ribs 2-5 (left of midline)

• Apex found in 5th intercostal space, midclavicular line

What is the fibrous pericardium, where is it and and what purpose does it serve?

What: Inelastic sac of dense connective tissue

Where: Fuses inferiorly with the diaphragm and superiorly with the great vessels

Why: ‘Seatbelt’ - prevents overfilling of heart and anchors it into position

What is the serous pericardium, what does it consist of and what purpose does it serve?

• Double layered serous membrane that lies deep to the fibrous pericardium. Contains Parietal and Visceral portions

• Contains :

  • Parietal pericardium - lines inner surface of fibrous pericardium

  • Visceral pericardium (epicardium) - adheres tightly to surface of heart

  • Pericardial cavity - space between the two layers, contains tissue fluid

• Function: Prevents friction

What are the 3 layers of the heart wall?

• Endocardium : Inner layer - endothelium (simple squamous epithelium)

• Myocardium: middle layer - cardiac muscle

• Epicardium: outer layer - visceral pericardium

what are the two aortas?

Ascending aorta, Descending thoracic Aorta

What is the fibrous skeleton of the heart?

Bands of fibrous connective tissues between the atria and ventricles

What does the fibrous skeleton of the heart do?

Electrically seperates atria from the ventricles

Encircles the pulmonary trunk, aorta, semilunar and AV valves

What are the AV valves?

Tricuspid - right

Bicuspid - left

What are the semilunar valves?

Pulmonary

Aortic

What features do the AV valves have?

Anchored by chordae tendinae to papilllary muscles

What happens when the papillary muscles contract?

Prevents eversion of valves therefore backflow of blood into the atria

Where are the semilunar valves?

Guards entrances of aorta and pulmonary trunk

How much blood does the heart recieve every minute? (coronary circulation)

250ml

How is blood delivered to the heart?

To myocardium during ventricular relaxation

What does the left coronary artery (LCA) consist of?

Anterior interventricular

Circumflex

What does the right coronary artery consist of?

Marginal artery

Posterior interventricular

What is angiography and what can it detect?

Medical imaging technique used to examine the patency of vessels

restricted blood vessels - angina

What does the conducting system do and consist of?

Coordinates heart contraction

Consists of non-contractile cells that initiate electrical impulses

What does the conducting system consist of? (complex)

SA node

AV node

AV bundle (bundle of his)
Right and left bundle branches

Purkinje fibres

What does an electrocardiogram (ECG) do?

Records the electrical activity of the heart

Why is the foetal circulation different ?

Oxygen and nutrients received from placenta via umbilical vein

Need to bypass non-functional lungs

What are the 3 circulatory shortcuts of foetal circulation?

• ductus venosus connects umbilical veins to inferior vena cava

• Foramen ovale connects right and left atria

• Ductus arteriosus connects pulmonary trunk to arch of aorta

What happens when a newborn takes its first breath?

• Lungs expand → blood rushes into pulmonary circulation → O2 levels rise → constricts ductus arteriosus

• LA pressure increases → Foramen ovale closes to become fossa ovalis

• Umbilical cord ties → Umbilical vessels close → Ductus venosus fibroses