Overview
- Lecture covers heart anatomy: position, shape, chambers, great vessels, valves, and important internal structures.
- Emphasis on clinical relevance for nursing: apical pulse, medication checks, endocarditis, and heart failure.
Location and Shape
- Heart lies in the mediastinum, slightly left of midline, posterior to the sternum.
- Shape: a cone oriented upside down (base superior toward right shoulder; apex inferior toward left).
- Apex location: left 5th intercostal space at midclavicular line — site for apical (point of maximal impulse) pulse.
- Base location: near the 2nd intercostal space behind the sternum.
Blood Flow Overview
- Right heart handles deoxygenated blood → pulmonary circulation.
- Left heart handles oxygenated blood → systemic circulation.
- Sequence: systemic veins → right atrium → right ventricle → pulmonary artery → lungs → pulmonary veins → left atrium → left ventricle → aorta → body.
Chambers And Major Incoming/Outgoing Vessels
| Chamber | Function / Major Vessels |
| Right Atrium | Receives deoxygenated blood from SVC, IVC, and coronary sinus. |
| Right Ventricle | Pumps deoxygenated blood into pulmonary artery (pulmonary trunk). |
| Left Atrium | Receives oxygenated blood from four pulmonary veins. |
| Left Ventricle | Pumps oxygenated blood into the aorta for systemic circulation. |
Right Atrium Details
- Receives blood from superior vena cava (head, neck, upper limbs/chest), inferior vena cava (lower limbs, abdomen, pelvis), and coronary sinus (myocardial drainage).
- Wall thinner than left atrium due to lower pressure on right side.
- Fossa ovalis in interatrial septum — remnant of fetal foramen ovale; patent foramen ovale (PFO) can persist and increase stroke risk via clot passage.
- Inner anterior surface: pectinate muscles (comb-like ridges) concentrated in the auricle; aid atrial contraction and provide extra blood storage during increased demand.
- Crista terminalis: smooth ridge guiding electrical impulses from SA node toward AV node.
Right Ventricle Details
- Separated from right atrium by tricuspid valve (atrioventricular valve with three cusps).
- Walls thinner and chamber smaller than left ventricle because pulmonary circulation is lower pressure.
- Internal structures:
- Trabeculae carneae: meaty ridges for structural support during contraction.
- Papillary muscles and chordae tendineae: attach to tricuspid cusps to prevent valve prolapse during systole.
- Outflow: pulmonary (pulmonic) valve → pulmonary artery.
Pulmonary Artery / Pulmonary Valve
- Pulmonary (pulmonic) valve: semilunar valve with three crescent-shaped cusps; prevents backflow into right ventricle via pressure changes.
- Pulmonary artery (pulmonary trunk): carries deoxygenated blood away from heart (exception to "arteries carry oxygenated blood"); divides into right and left pulmonary arteries to each lung.
- Pulmonary artery walls thinner than aorta to avoid high pressure damaging lungs.
Left Atrium Details
- Located posteriorly; slightly smaller than right atrium but with thicker walls due to higher pressure.
- Receives oxygenated blood from four pulmonary veins (two from each lung).
- Inner surface smoother with fewer pectinate muscles.
- Blood flows from left atrium through mitral (bicuspid) valve to left ventricle.
Left Ventricle Details
- Separated from right ventricle by interventricular septum; forms the cardiac apex.
- Much larger and thicker myocardium than right ventricle to generate systemic pressure.
- Contains trabeculae carneae, papillary muscles, and chordae tendineae supporting the mitral valve.
- If left ventricle function is impaired (e.g., myocardial infarction), patient may develop heart failure.
- Outflow: aortic valve → aorta.
Valves: Types And Function
| Valve | Location | Type / Structure | Primary Function |
| Tricuspid Valve | Between right atrium and right ventricle | Atrioventricular; three cusps; supported by chordae tendineae and papillary muscles | Allows flow to RV; prevents backflow during ventricular contraction |
| Mitral (Bicuspid) Valve | Between left atrium and left ventricle | Atrioventricular; two cusps; supported by chordae tendineae and papillary muscles | Allows flow to LV; prevents backflow during ventricular contraction |
| Pulmonic Valve | Between right ventricle and pulmonary artery | Semilunar; three crescent cusps; pressure-dependent closure | Prevents backflow into RV after systole |
| Aortic Valve | Between left ventricle and aorta | Semilunar; three crescent cusps; pressure-dependent closure | Prevents backflow into LV after systole |
- Mnemonic: “Try Before You Buy” — tricuspid (right) then bicuspid/mitral (left).
- Atrioventricular valves are mechanically supported by chordae tendineae and papillary muscles.
- Semilunar valves rely on pressure changes, not chordae tendineae.
Coronary Circulation
- Aorta gives rise to right and left coronary arteries immediately after aortic valve.
- Coronary arteries encircle the heart to supply myocardium with oxygenated blood.
- Coronary sinus drains myocardial deoxygenated blood into right atrium.
Clinical Points For Nursing
- Apical pulse (PMI) location critical before administering drugs like digoxin.
- PFO can allow paradoxical emboli and increase stroke risk.
- Endocarditis: valves susceptible to vegetations from IV drug use or bacteremia; may require valve replacement.
- Left ventricular dysfunction leads to heart failure because of systemic pump failure.
- Recognize arterial/venous exceptions: pulmonary artery carries deoxygenated blood; pulmonary veins carry oxygenated blood.
Key Terms And Definitions
- Apex: inferior tip of the heart, points left; location of apical pulse.
- Base: superior portion toward the right shoulder.
- Mediastinum: central thoracic cavity housing the heart.
- Pectinate Muscles: comb-like ridges in atria, aid contraction and storage (especially in auricles).
- Crista Terminalis: smooth ridge guiding atrial conduction.
- Trabeculae Carneae: muscular ridges in ventricles.
- Papillary Muscles / Chordae Tendineae: structures preventing AV valve prolapse.
- Fossa Ovalis / Foramen Ovale: neonatal shunt remnant; PFO if patent after birth.
- Semilunar Valves: pulmonic and aortic; three cusps; pressure-dependent.
Action Items / Next Steps
- For further study: review coronary artery branching and layers of the heart (myocardium, endocardium, epicardium).
- Practice locating apical pulse and valve auscultation points clinically.
- Review pathologies: endocarditis signs, PFO implications, and left ventricular failure mechanisms.