Heart Anatomy and Physiology

Homework Information

  • Homework One has been posted.
    • DUE: This Friday at midnight.
  • Office Hours:
    • Tomorrow, office hours will be dedicated to discussing homework.
    • Laura will have office hours on Thursday at 5 PM.
    • May be conducted via Zoom if the room isn't arranged on time.
  • Friday office hours are also being finalized.
  • Discussion sessions are important for understanding the homework and are highly recommended for follow-up if attendance isn't possible.

Anatomy and Physiology of the Heart

Overview

  • Today's lecture focuses on the anatomy and physiology of the heart.
    • It is assumed that not all students have covered this in Anatomy One or Two.
  • Key points from the previous lecture will be revisited:
    • In physiology, quantitative science is crucial; emphasis is on flows and flux.

Important Definitions and Equations

  • Flux:
    • Defined as the flow per unit area.
    • The flux is driven by a driving force.
    • Generalized equation for flux:
      ext{Flux} = ext{Phenomenological Constant} imes ext{Driving Force}
    • For pressure-driven flow, the volumetric flux formula is:
      ext{Volumetric Flux} = ext{Hydraulic Conductivity Coefficient} imes rac{dP}{dx}
  • Derivative Definition:
    • A derivative represents the rate of change of one variable concerning another, i.e., rac{dY}{dX} indicates the change in Y as X changes.
  • Continuity Equation:
    • rac{dC}{dt} = - rac{dQ}{dx}
    • Where C is concentration and Q is flux.
    • Steady state occurs when there's no change concerning time, resulting in rac{dC}{dt} = 0.
  • Integration leads to the equation of a line from the continuity equation.

Blood Circulation Overview

Heart Functionality

  • Blood flow through the heart:
    • Deoxygenated blood returns from the body via the superior and inferior vena cava, which feeds into:
    • Superior Vena Cava: Collects blood from areas above the heart (arms, head, upper chest).
    • Inferior Vena Cava: Collects blood from areas below the heart (abdomen, legs).
  • Blood enters the heart:
    • Right Atrium: Blood fills this chamber passively from above and below.
    • Right Ventricle: Blood is pumped out into the pulmonary trunk, directed to the lungs for oxygenation.
  • Gas exchange occurs in the lungs:
    • Oxygen enters the bloodstream while carbon dioxide is removed.
  • Oxygenated blood returns:
    • Via pulmonary veins to the Left Atrium, which then flows into:
    • Left Ventricle, where it is pumped out via the aorta throughout the body.
  • The heart operates as a closed circulatory system to maintain blood circulation.

Pressure Gradients and Valves

  • Blood flows through the heart due to:
    • Pressure Gradients: Blood moves from regions of high pressure to low pressure.
    • E.g., Blood moves from the right atrium to the right ventricle when the atrial pressure is higher.
  • Valves: Ensure unidirectional blood flow and prevent regurgitation.
    • The important valves include:
    • Tricuspid Valve: Between right atrium and right ventricle.
    • Pulmonary Valve: Between right ventricle and pulmonary trunk.
    • Mitral (Bicuspid) Valve: Between left atrium and left ventricle.
    • Aortic Valve: Between left ventricle and aorta.

Physiological Implications

  • Blood Pooling: Lack of movement can lead to blood pooling in the legs.
    • Important during long travels to avoid clots (e.g., swollen feet post-flight).
  • Varicose Veins: Results from inefficient valves in veins due to aging, leading to blood stretching the walls of veins.

Anatomy of the Heart

Location and Size

  • The human heart is slightly larger than a fist, located to the left side of the thoracic cavity, behind the sternum.
    • Approximate location can be estimated by placing the base of a hand across the sternum with fingers pointing towards shoulders.

Major Structures

  • Chambers of the Heart:
    • Right Atrium: Receives deoxygenated blood from the body.
    • Right Ventricle: Pumps blood to the lungs.
    • Left Atrium: Receives oxygenated blood from the lungs.
    • Left Ventricle: Pumps oxygenated blood to the body.
  • Valves: explained above; play vital roles in blood flow control.
  • Heart Sounds: Created by the closure of valves:
    • First sound: Closure of mitral and tricuspid valves.
    • Second sound: Closure of aortic and pulmonary valves.

Electrical Conduction System of the Heart

Overview

  • The heart has its electrical conduction system that controls heart muscle contraction:
    • Initiates in the Right Atrium and directs signals to the rest of the heart.
  • Two neural responses:
    • Sympathetic Nervous System: Increases heart rate and force of contraction (Fight or Flight response).
    • Parasympathetic Nervous System: Decreases heart rate and force of contraction (Rest and Digest response).
  • The contraction begins at the apex, squeezing towards the top for efficient blood ejection.

Coronary Artery System

Vascular Health

  • Importance of coronary arteries as they supply blood to the heart muscle.
    • Commonly affected by blockages leading to heart diseases.
  • Main coronary arteries:
    • Right Coronary Artery: Wraps around the right ventricle and atrium.
    • Left Coronary Artery: Supplies the left side of the heart, branches into anterior and circumflex arteries.
  • Bypass Procedures: Utilized for blocked arteries, replacing the function of damaged sections using grafts.

Coronary Anatomy: Key structures include:

  • Anterior descending artery (LAD)
  • Posterior and middle cardiac veins.
  • The coronary sinus returns deoxygenated blood from the heart muscle back to the right atrium.