Blood Flow of The Heart

College of Engineering

Department of Biomedical Engineering

Prof. Cathal J. Kearney

Module I. Lecture 2: The Anatomy And Physiology Of The Heart

BME330: Quantitative Physiology

Instructor: Prof. Cathal J. Kearney
All figures are from Gray’s Anatomy unless stated

1. Driving Forces and Flux

• Flux: Linearly related to a driving force. Increasing the force results in a linear increase in flux.

• Denotation of Driving Force:

  • F is the “driving force” for the flux.

  • Mathematically represented: $J = -L <br>\nabla F$, where $L$ is a phenomenologically defined linear coefficient.

• Note: The “driving forces” do not have units of Newtons.

• This format is applicable for various types of fluxes:

  • Pressure-driven flow:
    $J<em>V = -L</em>P \frac{dP}{dx}$

  • Ohm’s Law:
    $J_E = -\sigma \frac{dV}{dx}$

  • Fick’s Law of Diffusion:
    $J_S = -D \frac{dC}{dx}$

  • Where:

  • $J<em>V$ = volume flux; $\frac{dP}{dx}$ = pressure gradient; $L</em>P$ = hydraulic conductivity

  • $J_E$ = electrical current flux; $\frac{dV}{dx}$ = voltage gradient; $\sigma$ = electrical conductivity

  • $J_S$ = solute flux; $\frac{dC}{dx}$ = concentration gradient; $D$ = diffusion coefficient

  • General Formula: $J = -L<em>f F</em>f$

2. Continuity Equation

• Definition:

  • Describes the conservation of mass within a control volume:

• Mathematical Representation:
  $\frac{\partial C}{\partial t} = -\frac{\partial J}{\partial x}$

3. Continuity Equation: Steady State

• Substituting variables into the continuity equation leads to the conclusion that:

  • Slope is constant

  • Variable varies linearly with respect to $x$.

• Key terms:

  • $J_S$ = solute flux; $\frac{dC}{dx}$ = concentration gradient; $D$ = diffusion coefficient;

  • $J<em>V$ = volume flux; $\frac{dP}{dx}$ = pressure gradient; $L</em>P$ = hydraulic conductivity

  • Where:

  • $C$ = compliance; $V$ = volume

4. Learning Outcomes

• Students should be able to:

  1. Describe the anatomy of the chambers of the heart.

  2. Discuss the function of the heart and circulatory system.

  3. Describe the electrical conduction system of the heart.

  4. Explain blood flow through the heart.

  5. Describe systemic circulation.

5. Circulation of Blood in the Heart

• Key Questions:

  • How is blood kept flowing in the correct direction?

6. Anatomy of the Heart: Chambers

• Chambers:

  • Right Atrium: Receives blood from the superior and inferior vena cavae.

  • Right Ventricle: Pumps blood into the pulmonary arteries.

  • Left Atrium: Receives blood from the pulmonary veins.

  • Left Ventricle: Pumps blood into the aorta.

7. Heart Valves

• Valves ensure unidirectional blood flow:

  • Right AV (Tricuspid) Valve: Between right atrium and right ventricle.

  • Pulmonary Valve: Between right ventricle and pulmonary trunk; contains 3 semilunar cusps.

  • Left AV (Bicuspid) Valve (Mitral Valve): Between left atrium and left ventricle.

  • Aortic Valve: Between left ventricle and aorta; contains 3 semilunar cusps.

8. The Conduction System of the Heart

• Functions:

  • Controls:

  • Heart rate

  • Contraction force

  • Cardiac output

  • Sympathetic System:

  • Increases heart rate and force of contraction.

  • Parasympathetic System:

  • Decreases heart rate and force of contraction.

  • Constricts coronary arteries.

9. Pathway of the Conduction System

• Components:

  • Sinoatrial Node → Atrioventricular Node → Bundle of His → Right and Left Bundle Branches → Purkinje Fibres.

  • Septomarginal Band:

  • Located in the right ventricle, it contains the right bundle branch and coordinates contraction.

10. Coronary Artery System

• Anastomoses:

  • Between termination of arteries in the atrioventricular groove and interventricular branches at the apex are insignificant.

  • There are significant anastomoses at the arteriolar level.

  • Slow occlusion allows time for arterioles to open; abrupt occlusion does not permit this.

11. Venous Drainage of the Heart

• Key Veins:

  • Anterior veins of the right ventricle

  • Posterior cardiac vein

  • Great cardiac vein

  • Small cardiac vein

  • Middle cardiac vein

  • Coronary sinus: Major vessel collecting venous blood from the heart.

12. Summary of the Heart's Physiology

• Key Concepts to Remember:

  1. Blood flow through the heart.

  2. Timing of events (e.g., which valves are open or closed).

  3. Electrical conduction system of the heart.

  4. Key features of pressure, volume, sounds, EKGs.

• It is important to review these concepts regularly to ensure a solid understanding.