Heart Blood Flow + Internal Anatomy

Blood flow through heart:

body → SVC/IVC → right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta → body

Order of valves through heart:

Tricuspid → pulmonary semilunar → bicuspid → aortic semilunar

Fetal blood path (high volume):

IVC/SVC → right atrium → foramen ovale → left atrium → bicuspid valve → left ventricle → aorta → body

Why does fetal blood flow bypass the lungs?

Fetus receives oxygen and nutrients from the placenta

Fetal blood path (low volume):

Right atrium → right ventricle → pulmonary trunk → pulmonary vein → left atrium → left ventricle → aorta

OR right atrium → right ventricle → ductus arteriosus → aorta

Ductus arteriosus becomes:

Ligamentum arteriosum

Difference between foramen ovale and ductus arteriosus:

Both bypass lungs in fetal circulation

Foramen ovale: when there is a high volume of blood, it is shunted directly from right atrium to left atrium

Ductus arteriosus: low volume of blood, some blood is shunted from the pulmonary artery to the aorta

Musculae pectinati

Internal muscular ridges on wall of right atrium

Crista terminalis

Ridge that runs from SVC to IVC (right atrium); separates musculae pectinati from smooth part

Vessels that empty into right atrium (4):

SVC, IVC, coronary sinus, anterior cardiac veins

Fossa ovale

Depression in wall between right and left atrium; remnant of foramen ovale

Trabeculae carnae

Large muscular beams that criss-cross one another; in myocardium

Papillary muscles

Short pillars of muscle that extend from ventricular walls; contract with ventricles

Chordae tendinae

Attached to heart valves and papillary muscles; prevent backflow through valves

2 parts of interventricular septum:

Membranous part - at top, narrow

Muscular part - the rest, thicker

Moderator band (septomarginal trabecula)

Carries branch of AV bundle to IV septum

Ventricular septal defect (VSD)

Defect in membranous region of IV septum

Atrial septal defect (ASD)

Blood leaks through foramen ovale

Atrioventricular septal defect (AVSD)

Congenital; hole between atria and ventricles

Fibrous ring (skeleton of heart)

Between atria and ventricles; all valves on same plane

Functions of fibrous ring (4):

1. Structural support

2. Anchoring point for valves

3. Ventricular muscles originate + insert here

4. Insulator between atria and ventricles (prevent them from contracting at same time)

Pacemaker

SA node (can depolarize/repolarize the fastest); sets pace for right atrial contraction

Electrical conduction path:

SA node → AV node → AV bundle (bundle of His) → Purkinje fibers

3 common occlusions:

1. Anterior interventricular a.

2. Right coronary a.

3. Circumflex a.

Artificial pacemaker

Takes over for SA node; gives off electrical impulse to set pace for right atrial contraction