Heart Anatomy - Comprehensive Tutorial 2 Notes (Comprehensive Study Notes)
Orientation: Anterior vs Posterior Surfaces
When viewing the heart face-to-face, you are looking at a mirror image: the right side of the heart is on your left, and the left side is on your right.
To determine anterior vs posterior surface:
Anterior surface shows two small purposefully placed triangles, the auricles (right auricle and left auricle), which are embryonic remnants; atria have largely replaced them functionally.
Posterior surface lacks auricles and features a large blue vein across the surface: the coronary sinus (the reference point indicating the posterior aspect).
The rule about mirror-imaged orientation holds for all structures discussed in this course.
Pericardial and Cardiac Membranes
Three layers of pericardium around the heart:
Fibrous pericardium: tough layer of dense connective tissue that forms a sac around the entire heart.
Parietal pericardium: thin, delicate layer lining the fibrous pericardium; secretes a small amount of pericardial fluid.
Visceral pericardium (epicardium): layer stuck to the surface of the heart; produces a small amount of fluid; gives the heart its shiny appearance.
Pericardial cavity: potential space between parietal and visceral pericardium containing pericardial fluid.
Distinguishing epicardium vs visceral pericardium: in questions about the heart surface, epicardium refers to the outer layer of the heart wall; visceral pericardium refers to the membrane directly on the heart surface (same layer, different naming depending on perspective).
Heart Wall Layers (from exterior to interior)
Epicardium: outer surface layer, also called visceral pericardium.
Myocardium: thick muscular middle layer; the厚ness varies by chamber; the left ventricle has the thickest myocardium due to workload.
Endocardium: inner lining of the heart chambers; a layer of simple squamous epithelium (think of it as a “Teflon lining” to prevent sticking of blood cells).
Chambers of the Heart
There are four chambers:
Atria (upper chambers): right atrium and left atrium.
Ventricles (lower chambers): right ventricle and left ventricle.
The heart is a double pump: right heart (right atrium + right ventricle) pumps blood to the pulmonary circuit; left heart (left atrium + left ventricle) pumps blood to the systemic circuit.
A note on naming: right/left orientation in anatomy relates to the patient’s right/left, not the observer’s; when discussing structures on the model, still use the patient’s right/left orientation.
Atria: Features to Know
Interatrial septum: solid wall after birth preventing cross-flow between right and left atria; pre-birth there is an opening (foramen ovale).
Fossa ovalis: shallow oval depression in the interatrial septum, remnant of the foramen ovale.
Pectinate muscles: muscular ridges lining the atria.
Ventricles: Features to Know
Interventricular septum: thick muscular wall separating the right and left ventricles.
Trabeculae carneae: muscular ridges on the inner walls of the ventricles.
Atrioventricular (AV) valves: located between atria and ventricles; anchored to the ventricles by papillary muscles via chordae tendineae.
Papillary muscles: finger-like muscles anchored by chordae tendineae; their role is to tense the AV valves during ventricular contraction to prevent regurgitation; they do not open/close the valves themselves.
Valves: Structure and Function
Four valves in total:
Atrioventricular valves (between atria and ventricles):
Right AV valve = tricuspid valve (three cusps).
Left AV valve = mitral (bicuspid) valve (two cusps).
Semilunar valves (between ventricles and the arteries they pump into):
Pulmonary valve: between the right ventricle and the pulmonary trunk; color-coded blue on many models because it deals with deoxygenated blood on the right side; has three cusps/pockets.
Aortic valve: between the left ventricle and the aorta; color-coded red; has three cusps/pockets.
General function: valves are one-way pressure valves that open when the ventricle contracts and pressure pushes blood through; they close to prevent backflow into the atria (for AV valves) or into the ventricles (for semilunar valves).
Important nomenclature note: lab exams will accept multiple names for valves as long as they refer to the correct structure (e.g., tricuspid = right AV valve; mitral = left AV valve).
Conduction System (Electrical Coordination of the Heartbeat)
Purpose: coordinate contraction of heart muscle so blood moves efficiently.
Sinoatrial (SA) node: the natural pacemaker; initiates the heartbeat; located in the right atrium.
Atrioventricular (AV) node: located in the floor of the right atrium; creates a built‑in pause to allow atrial contraction before ventricular conduction.
Atrioventricular (AV) bundle (Bundle of His): begins in the interventricular septum; splits quickly into right and left bundle branches.
Right bundle branch and Left bundle branch: conduct impulses to the right and left ventricles respectively.
Purkinje fibers: terminate the conduction pathway and deliver the impulse to ventricular myocardium for coordinated contraction.
Great Vessels and Blood Flow: Key Relationships
Superior vena cava (blue; deoxygenated): drains the upper body (arms and head) into the right atrium.
Inferior vena cava (blue; deoxygenated): drains the lower body into the right atrium.
Pulmonary trunk: arises from the right ventricle; quickly divides into the right and left pulmonary arteries (the horizontal split forms part of a rough “T” shape on cross‑section in models).
Pulmonary arteries: carry deoxygenated blood from the right ventricle to the lungs; right and left branches.
Pulmonary veins (red on many models due to oxygenated blood): four total; two visible in this view carry oxygenated blood from the lungs to the left atrium; other two lie behind the heart (not visible in this view).
Aorta: the largest artery; has an ascending portion, an arch, and a descending portion.
Ascending aorta: rises from the left ventricle.
Aortic arch: curves and gives off three characteristic branches (typical: brachiocephalic trunk, left common carotid, left subclavian).
Descending aorta: continues downward to supply systemic circulation.
Coronary arteries (to supply the heart muscle itself):
Right coronary artery (RCA): travels to the right side; gives off branches to the right ventricle (marginal artery) and the posterior interventricular artery.
Left coronary artery (LCA): quickly divides into two main branches:
Anterior interventricular artery (also called the left anterior descending, LAD): runs on the anterior surface down between the ventricles.
Circumflex artery: curves around to the posterior aspect of the heart.
Cardiac veins: blue structures that drain the heart muscle into the coronary sinus; the coronary sinus then drains into the right atrium.
The coronary sinus is a key posterior reference point for identifying the heart’s posterior surface.
The pulmonary veins are the exception to the usual color-coding rule (they carry oxygenated blood back to the left atrium). Some models show them in purple to remind you of their oxygenation status; others show them red.
Practical Anatomy Observations and Exam Tips
If asked to identify the epicardium vs visceral pericardium, consider the context: epicardium refers to the outer layer of the heart wall; visceral pericardium refers to the surface covering of the heart (same layer, different naming). If the question asks for the outer surface layer, answer epicardium; if it asks for the membrane on the heart surface, answer visceral pericardium.
Auricles indicate the anterior surface; absence of auricles suggests posterior surface on the model.
The five great vessels include the major arteries and veins entering/leaving the heart: superior/inferior vena cavae, pulmonary trunk, pulmonary veins, aorta, and the coronary vessels emerging from the aorta.
Blood flow sequence (for holistic understanding):
Right atrium → right ventricle → pulmonary trunk → lungs (gas exchange) → pulmonary veins → left atrium → left ventricle → aorta → systemic circulation.
Remember the “three” rules:
AV valves have cusps: tricuspid (right, 3 cusps) and mitral (left, 2 cusps).
Semilunar valves have three cusps/pockets each: pulmonary valve and aortic valve.
The right atrial coronary-related branches include the marginal artery and posterior interventricular artery arising from the RCA; the left coronary artery divides into the LAD and circumflex.
Color cues on models are helpful but not universal: blue typically indicates deoxygenated blood (right heart/venous side) while red indicates oxygenated blood (left heart/pulmonary veins); exceptions exist for pulmonary veins which return oxygenated blood but are sometimes shown in blue or purple depending on the diagram.
Embryology remnants: fossa ovalis marks the former foramen ovale; its presence in the interatrial septum is a key developmental indicator.
The heart’s internal surfaces have distinct textures: pectinate muscles in the atria, trabeculae carneae in the ventricles, and the relatively smooth endocardial lining to reduce turbulence.
The conduction system is a critical driver of synchronized heart function and is a common exam topic: SA node, AV node, AV bundle, right/left bundle branches, Purkinje fibers.
The model highlights the coronary circulation as the mechanism by which the heart muscle itself receives oxygenated blood to support its own pumping action.
Summary of Structural Relationships (Flow Snapshot)
Outer coverings: fibrous pericardium → parietal pericardium → pericardial cavity with fluid → visceral pericardium (epicardium) → myocardium → endocardium (inner lining).
Chambers: RA (right atrium) receives venous blood via SVC and IVC; RV pumps to pulmonary trunk; LA receives oxygenated blood from pulmonary veins; LV pumps to the aorta.
Valves ensure one-way flow: AV valves open with atrial pressure, close to prevent backflow to atria; semilunar valves open with ventricular pressure, close to prevent backflow to ventricles.
Coronary circulation nourishes myocardium: RCA and LCA originate from the aorta; branches supply the ventricles and interventricular septum; venous drainage via coronary sinus back to the right atrium.
Conduction system coordinates timing: SA node → AV node pause → AV bundle → bundle branches → Purkinje fibers delivering synchronized contraction.