The heart

❤ BIOM2020 – HEART: The Complete, Exam‑Ready Summary

1. Location & Mediastinum

  • The heart sits in the middle mediastinum.

  • The mediastinum is divided by a plane from:

    • Manubriosternal joint (Angle of Louis) → T4 vertebra

  • Above this plane = superior mediastinum

  • Below = inferior mediastinum, subdivided into:

    • Anterior mediastinum (in front of pericardium)

    • Middle mediastinum (heart + pericardium)

    • Posterior mediastinum (behind pericardium)

2. Pericardium

Two major layers:

A. Fibrous pericardium

  • Tough, collagen‑rich, non‑stretchable

  • Anchors heart to diaphragm & great vessels

B. Serous pericardium

Two layers:

  • Parietal layer – lines inside of fibrous pericardium

  • Visceral layer – adherent to heart surface (also called epicardium)

Between them: pericardial cavity with a thin film of fluid → reduces friction.

3. External Features of the Heart

Think of the heart as a pyramid:

Apex

  • Formed by left ventricle

  • Points inferolaterally to the left 5th intercostal space

Base

  • Posterior surface

  • Formed mainly by left atrium

Surfaces

  • Sternocostal surface → mostly right ventricle

  • Diaphragmatic surface → mostly left ventricle

4. Internal Anatomy

Atria

Right atrium

Key features:

  • Smooth posterior wall

  • Rough anterior wall with musculi pectinati

  • Crista terminalis – ridge separating smooth & rough regions

  • Openings:

    • SVC

    • IVC

    • Coronary sinus

  • Fossa ovalis – embryological remnant of foramen ovale

Left atrium

  • Mostly smooth

  • Receives 4 pulmonary veins

  • Small region of musculi pectinati in auricle

Heart (right and left atrium): Anatomy and function | Kenhub

Ventricles

Shared features

  • Papillary muscles

  • Chordae tendineae

  • Trabeculae carneae

Right ventricle

  • Thinner wall

  • Pumps to low‑pressure pulmonary circulation

  • Outflow → pulmonary trunk via pulmonary valve

Left ventricle

  • Thickest wall (high systemic pressure)

  • Outflow → aorta via aortic valve

5. Heart Valves

Atrioventricular (AV) valves

  • Right AV valve = tricuspid (3 cusps)

  • Left AV valve = bicuspid / mitral (2 cusps)

Function:

  • Prevent backflow from ventricles → atria

  • Papillary muscles + chordae tendineae prevent cusp prolapse

Semilunar valves

  • Pulmonary valve

  • Aortic valve

Function:

  • Prevent backflow from arteries → ventricles

  • No chordae tendineae

6. Coronary Circulation

The heart receives the best oxygenated blood directly from the aorta.

Right coronary artery (RCA)

Supplies:

  • Right atrium

  • Right ventricle

  • SA node (in most people)

  • AV node (in many people)

Left coronary artery (LCA)

Branches:

  • Left anterior descending (LAD)

  • Circumflex artery

Supplies:

  • Left ventricle (majority)

  • Interventricular septum

  • Left atrium

Venous drainage

  • Great cardiac vein

  • Middle cardiac vein
    → drain into coronary sinus → right atrium

7. Conduction System

(Not heavily tested in BIOM2020 but know the sequence)

  1. SA node (pacemaker)

  2. AV node

  3. Bundle of His

  4. Right & left bundle branches

  5. Purkinje fibres

8. Foetal Circulation & Adult Remnants

Foetal shunts bypass lungs & liver.

Foetal structures → Adult remnants

  • Foramen ovale → Fossa ovalis

  • Ductus arteriosus → Ligamentum arteriosum

  • Ductus venosus → Ligamentum venosum

Purpose:

  • Bypass non‑functional foetal lungs

  • Bypass developing liver

Closure triggered by first breath → pressure changes.

9. Clinical Notes

Angina

  • Caused by coronary artery narrowing

  • Reversible ischaemia

Myocardial infarction

  • Irreversible death of myocardium

  • Subendocardial region most vulnerable

    • Endocardium survives longer because it receives oxygen directly from chamber blood

Broken heart syndrome (Takotsubo cardiomyopathy)

  • Stress‑induced

  • Catecholamine surge

✔ What you should absolutely memorise for BIOM2020

  • Surfaces: sternocostal = RV, diaphragmatic = LV

  • Right atrium landmarks: crista terminalis, musculi pectinati, fossa ovalis, coronary sinus

  • Valve names & functions

  • Coronary arteries (RCA, LCA, LAD, circumflex)

  • Foetal → adult remnants

  • Differences between ventricles (wall thickness + pressure)

  • Pericardium layers