Overview
This lecture reviews the structure of the heart, focusing on blood flow, heart valves, the interventricular septum, and the heart wall layers.
Blood Flow in the Heart
- Blood flows from the right atrium to the right ventricle, then to the lungs, left atrium, and left ventricle.
- Heart valves ensure blood flows in one direction and prevent backflow.
Heart Valves and Their Support Structures
- The atrioventricular valves (between atria and ventricles) are the tricuspid (right side) and mitral (left side) valves.
- These valves are tethered by chordae tendineae to papillary muscles in the ventricles.
- Chordae tendineae prevent valve flapping and backward blood flow during ventricular contraction.
- Damage to chordae tendineae can cause valves to malfunction, leading to backward blood flow.
Interventricular Septum Structure and Defects
- The interventricular septum is the wall separating the right and left ventricles.
- It has two parts: a thin membranous part (upper) and a thick muscular part (lower).
- Ventricular septal defects (VSD) often occur in the membranous part, allowing abnormal blood flow between ventricles.
Layers of the Heart Wall
- The heart wall has three layers: endocardium (inner), myocardium (middle, muscular), and pericardium (outer).
- The endocardium lines the heart chambers and valves and is similar to blood vessel inner lining.
- The myocardium is the thick, muscular layer responsible for heart contraction and energy use.
- The pericardium has two layers: visceral (epicardium, inner, attached to the heart) and parietal (outer, forms a sac).
- A fluid-filled space exists between the visceral and parietal pericardium.
Key Terms & Definitions
- Atrioventricular valves — The tricuspid and mitral valves between atria and ventricles.
- Chordae tendineae — Tendon-like cords tethering valves to papillary muscles, preventing backflow.
- Papillary muscles — Muscles in ventricles anchoring chordae tendineae.
- Interventricular septum — Wall dividing right and left ventricles.
- Ventricular septal defect (VSD) — Hole in the interventricular septum, usually in the membranous part.
- Endocardium — Inner heart lining; interfaces with blood.
- Myocardium — Middle, muscular heart wall layer.
- Pericardium — Outer heart covering with visceral (epicardium) and parietal layers.
- Visceral pericardium (epicardium) — Inner pericardium layer closely covering the heart.
- Parietal pericardium — Outer layer of the pericardium.
Action Items / Next Steps
- Review diagrams of the heart to identify the valves, septum parts, and wall layers.
- Remember the definitions and relationships among key heart structures for future quizzes or exams.