2. Heart + Vessel Anatomy

Heart location + bordering structures

Heart location + bordering structures

• Location: thorax (middle mediastinum)

• Bordered by:

  • Lungs (laterally)

  • Diaphragm (inferiorly)

  • Sternum (anteriorly)

  • Great vessels (superiorly)

  • Esophagus (posteriorly)

Layers of the heart

1. Pericardium (outer membrane enclosing heart)

2. Myocardium (heart muscle)

3. Endocardium (inner layer, wall of heart chambers)

Layers of the pericardium

1. Fibrous layer

2. Parietal layer

3. Space/cavity

4. Visceral layer (epicardium)

Chambers of the heart

1. Right atrium

2. Right ventricle

3. Left atrium

4. Left ventricle

Flow of blood through heart

1. Superior + inferior vena cava

2. Right atrium

3. Tricuspid valve

4. Right ventricle

5. Pulmonary valve

6. Pulmonary arteries

7. Lungs

8. Pulmonary veins

9. Left atrium

10. Mitral/bicuspid valve

11. Left ventricle

12. Aortic valve

13. Aorta

14. Body

Function of valves in heart

Prevent back flow

Heart valves

AV valves:

1. Tricuspid valve

2. Mitral/bicuspid valve

Semilunar valves:

1. Pulmonary valve

2. Aortic valve

Auscultating the four valves (remember the pneumonic)

All Pigs Eat Too Much

• Aortic: 2nd intercostal space; right sternal border

• Pulmonic: 2nd intercostal space; left sternal border

• Erb’s point: 3rd intercostal space; left sternal border

• Tricuspid: 4th intercostal space; left sternal border

• Mitral: 5th intercostal space; left midclavical line

What is Erb’s point good for?

Listening to the entire heart

Heart wall

• Heart is surrounded by tough membrane: fibrous pericardium

• Inside fibrous pericardium is serous (fluid) pericardium (protection and insulation)

  • Parietal layer of serous pericardium lines fibrous pericardium

  • Visceral layer is fused to heart surface

  • Potential cavity between layers called pericardial cavity

Epicardium

• Outer layer of heart wall (innermost layer of pericardium)

• Same as visceral pericardium

Myocardium

• Middle layer

• Made of cardiac muscle

Endocardium

Epithelium that lines the heart

Are atria or ventricles larger?

Ventricles

• Require more muscular force

Why are left and righthand chambers of the heart separated?

So there is no mixing of blood from one side to the other

Interatrial septum

Wall that separates the two atria

Interventricular septum

Wall between the ventricles

Are the atrial or ventricular walls thinner?

Atrial walls are thinner

• Need to create less force than ventricular walls do

Do atria or ventricles generate higher pressure?

Ventricles

Are the walls of the left ventricle or right ventricle thicker? Why?

• Left ventricle walls = thicker

• Right ventricle only pumps blood to lungs

• Left ventricle pumps blood throughout entire body

How does blood get to the right atrium?

2 veins:

1. Superior vena cava

   1. Blood from head, neck, chest, upper extremities

2. Inferior vena cava

   1. Blood from trunk, organs, abdomen, pelvic region, and lower extremities

Pulmonary veins

Bring blood back to left atrium (from lungs)

Pulmonary trunk

Carries blood from right ventricle to the lungs

Aorta

Carries blood from left ventricle to the body

Atrioventricular (AV) valves (location, names)

• Between each atrium and ventricle

• Right side: tricuspid valve

• Left side: mitral/bicuspid valve

Semilunar valves (location, names)

• Between the ventricles and large arteries that carry blood away from heart

• Right: pulmonary valve

• Left: aortic valve

Coronary vessels (location, function, main arteries)

• Location: arise just above aortic valve

• Function: provide oxygenated blood to the heart muscle

• Two main arteries:

  • Right coronary artery (RCA)

  • Left coronary artery (LCA)

    • Left anterior descending (LAD)

    • Left circumflex (LCX)

Right Coronary Artery (RCA)

Supplies:

1. Right atrium

2. Right ventricle

3. Inferior wall of left ventricle

Left Anterior Descending (LAD)

Supplies:

1. Anterior wall of left ventricle

Left Circumflex (LCX)

Supplies

1. Left atrium

2. Lateral and posterior walls of left ventricle

Coronary circulation for SA node

• RCA (55% of population)

• LCX (45% of population)

Coronary circulation for AV node

• RCA (90% of population)

• LCX (10% of population)

Coronary veins

Parallel arterial supply

Describe how the tricuspid valve works

• When the right ventricle is full of blood, the ventricle contracts

• The one-way tricuspid valve shuts as right ventricular pressure increases so blood doesn’t squirt back into right atrium

Describe how the mitral and aortic valves work to pump blood into aorta

• Ventricular pressure increases

• Mitral valve is forced shut

• Blood ejected out of left ventricle through aortic valve to ascending aorta to body

Heart innervation

• Supplied by autonomic nerve fibers from cardiac plexus

  • Sympathetic and parasympathetic fibers

  • Visceral fibers

Visceral fibers

For pain and reflexive information

Heart innervation: sympathetic supply

• From superior 5 or 6 thoracic spinal nerves

• Increases rate, conduction, force of contraction, and blood flow through coronary arteries

• Vasodilation

Heart innervation: parasympathetic supply

• From vagus nerve (CN 10)

• Vasoconstriction

Sympathetic effects on heart (innervation, hormone, effects: HR, AP conduction, contraction force)

Innervation:

• Sympathetic neurons innervate entire heart

• Release norepinephrine

Effects:

• Inc. HR (positive chronaotropic effect)

• Inc. contraction force (positive inotropic effect)

• Inc. rate of AP (action potential) conduction (positive dromotropic effect)

Parasympathetic effects on heart (innervation, hormone, effects: HR, AP conduction, contraction force)

Innervation:

• Vagus nerve (CN 10) innervates atria (does not really effect ventricles)

• Releases acetylcholine

Effects:

• Dec. HR (negative chronaotropic effect)

• Dec. rate of AP (action potential) conduction (negative dromotropic effect)

• No real effect on contraction force because ventricles are not innervated