Layers of the Heart Lecture Notes

Overview

• The heart is surrounded by a sac called the pericardium, which acts as a protective and supportive covering.
• Functions of the pericardium:
  • Prevents overstretching of the heart.
  • Keeps out invaders that could cause infection.
  • Keeps the heart in place, preventing it from moving excessively.

Pericardium Layers

1. Fibrous Pericardium

   • Outer layer made of tough connective tissue.
   • Provides anchorage to nearby structures like great vessels and the diaphragm.
   • Prevents the heart from overstretching during increases in blood volume.

2. Serous Pericardium

   • Produces serous fluid to lubricate the heart, reducing friction during heartbeats.
   • Made up of two continuous layers that form the pericardial space which stores serous fluid.
   • Parietal Layer
     • Contacts the fibrous pericardium.
   • Visceral Layer (Epicardium)
     • Adheres to the heart itself.
     • Also known as the outermost layer of the heart wall.

Visceral vs. Parietal Layers

• Visceral Layers: Surround the vital organ itself. Think Visceral = Vital.
• Parietal Layers: Surround the cavity or outer layer enclosing the organ.

Pericardial Cavity

• Space formed by the continuous layers of the serous pericardium, filled with serous fluid.
• Functions as a protective barrier against infection or trauma.

Clinical Relevance: Pericardium

• Pericardial Effusion: Excess fluid in the pericardial space.
• Pericarditis: Inflammation of the pericardial layers.
  • Symptoms include pericardial friction rub, a grating sound heard best at the left sternal border when the patient sits up and leans forward.

Layers of the Heart Wall

1. Epicardium (Visceral Layer of Serous Pericardium)

   • Outermost layer.

2. Myocardium

   • Middle layer and the thickest layer.
   • Made up of myocytes (cardiac muscle cells) responsible for rhythmic, continuous contractions.
   • Contains and supports electrical structures of the heart.
   • Supplied by coronary arteries.
   • Diseases include myocardial infarction (heart attack) and myocarditis (inflammation).

3. Endocardium

   • Innermost layer, covering the inside of the heart including chambers and valves.
   • Smooth layer that helps prevent clot formation.
   • Endocarditis: Inflammation of the endocardium caused by infection entering the bloodstream, affecting valves.

Summary

• The heart has multiple protective layers that ensure proper function and protection from external factors and infections.
• Nurses need to know the different layers and potential diseases affecting each to provide proper care to patients.