27 Heart

Atria

receiving chambers w weak muscular walls

Ventricles

pumping chambers w thick muscular walls

General circulation

right atrium → right ventricle → pulmonary trunk → pulmonary arteries → lungs → pulmonary veins → left atrium → left ventricle → aorta → body → IVC/SVC → right atrium

Heart surfaces

Anterior: sternocostal surface

• covers most of R ventricle

Inferior: diaphragmatic surface

• covers most of L ventricle + some R ventricle

Left: pulmonary surface

• covers most of L ventricle

• occupies cardiac area of L lung

Heart borders

Right: R atrium + SVC + IVC

Left: L ventricle + L auricle

Inferior: R ventricle

Superior: L/R atria + ascending aorta + pulmonary trunk + SVC

Right atrium posterior part

• derived from right horn of sinus venosus

• contains sinus venarum (smooth walls)

Right atrium anterior part

• derived from atrium proper

• contains pectinate muscles

Cristae terminalis

heart tissue btwn smooth + rough atrial walls

Coronary sinus

drains coronary veins

Fossa ovalis

embryonic remnant of foramen ovale

• allowed blood to go directly from right atrium to left atrium bc lungs not operational during fetal development

Triangle of Koch

location of AV node + nodal bundles

Atrial septum defect

hole btwn L + R atria

trabecula carnea

rough irregular walls in right ventricle

• makes up inflow tract of right ventricle

Conus arteriosus (infundibulum)

outflow tract of right ventricle that leads to pulmonary trunk

papillary muscles

type of trabeculae carnea that pulls chordae tendineae

• anterior papillary muscle

• posterior papillary muscle

• septal papillary muscle

septomarginal trabecula (moderator band)

trabeculum bridging lower portion of interventricular septum + base of anterior papillary muscle for cardiac conduction

tricuspid valve (right AV valve)

valve w 3 leaflets to prevent backflow of blood

Left atrium characteristics

• smaller + thicker walls than right atrium

• forms anatomical base of heart

• receives blood from foramina venarum minimarum + 4 pulmonary veins

Left ventricle characteristics

• thickest walls for powerful expulsion pump for entire body

• contains trabeculae carnae + papillary muscles + chordae tendinae

bicuspid valve (mitral valve; left AV valve)

valve w 2 leaflets that prevent blood backflow btwn L atrium + ventricle

interventricular septum

membranous + muscular wall btwn R + L ventricles

Aortic valve characteristics

• 3 semilunar cups btwn aorta + L ventricle

Auscultatory areas for valves

• Aortic: 2nd intercostal space just right-lateral to sternum

• Pulmonary: 2nd intercostal space just lateral left-lateral to sternum

• Tricuspid: 5th intercostal space just left-lateral to sternum

• Mitral: 5th intercostal space at L midclavicular line

Sinoatrial node (SA node)

site of initiation of each cardiac cycle; pacemaker

• in sinus venarum side of cristae terminalis

Atrioventricular node (AV node)

• gives rise to AV bundle (Bundle of His)

• near coronary sinus

Right AV bundle pathway

passes right fibrous trigone towards apex of right ventricle + papillary muscles

Left AV bundle pathway

passes right fibrous trigon along side of interventricular septum + papillary muscles

Layers of heart

• epicardium

  • subserous fat

• myocardium

• endocardium

Functions of cardiac skeleton (4)

• insulation

  • creates electrical discontinuity btwn atria + ventricles

• attachment for myocardium

• prevent bulging as blood is pumped

• provides stable + deformable base for valve leaflet attachment

Pulmonary trunk characteristics

• divides at TV5

• covered in pericardium

Aorta sections

• ascending

• arch

• descending

Branches from ascending aorta

• right coronary a.

• left coronary a.

branches from aortic arch

• brachiocephalic a.

  • right common carotid a.

  • right subclavian a.

• left common carotid a.

• left subclavian a.

Right coronary a. supply

• most of RV + RA

• small part of LV

• inferior half of IV septum

• part of LA

• most of SA/AV nodes

Branches off right coronary a.

• atrial + ventricular a.

• right marginal a.

• posterior interventricular a. (posterior descending a.; PDA)

• SA nodal a.

Left coronary a. supply

• most of LV + LA

• strip of anterior RV

• 2/3 of IV septum

Branches off left coronary a. (left main trunk; LMT)

• anterior interventricular a. (left anterior descending a. LAD)

  • goes towards apex of heart

• left marginal a.

• circumflex a.

Venous drainage of the heart

• great cardiac v.

  • runs w left anterior descending a.

• middle cardiac v.

  • runs w posterior descending a.

• small cardiac v.

  • runs w R marginal a.

• anterior cardiac veins

  • drains into R atrium

• vena cordis minimae

  • small veins that drain directly into heart

Most common sites of occlusion in coronary arteries

• 50% anterior interventricular LAD

• 30% right coronary artery

• 20% left circumflex artery

GVA innervation spinal levels

T1- T4

Regions most susceptible to deceleration trauma

• aortic valve

• ligamentum arteriosum

• aortic hiatus

Coronary artery anastomoses

• Right coronary a. ←→ circumflex a.

• left anterior descending a. ←→ posterior descending artery.

  • and/or within the interventricular septum