Blood Flow & Cardiomyocytes - Chapter 19

Basic pathway of blood in the body (the 2 circuits):

• Pulmonary Circuit: Heart → Lungs → Heart

• Systemic Circuit: Heart → Body → Heart

Pulmonary Circuit Full Pathway:

1. Deoxyginated blood enters into the Right Atrium

2. Blood travels through the tricuspid valve

3. Blood enters the Right Ventricle

4. Blood passes through the pulmonary semi lunar valve

5. To the pulmonary turnk

6. To the pulmonary artery

7. Into the lungs

8. Oxyginated blood travels to the pulmonary veins

9. Oxyginated blood is deposited in the left atrium.

Lower pressure

Systemic Circuit Full Pathway:

1. Oxyginated blood enters into the Left Atrium.

2. Blood travels through the mitral (bicuspid) valve

3. Blood enters the left ventricle

4. Blood passes through the aortic semilunar valve.

5. Blood enters the aorta

6. Blood enters into systemic circulation

7. Deoxyginated blood enters the inferior and superior vena cava

8. Deoxyginated blood enters into the Right Atrium.

Higher pressure

Blood Vessel Names

• Arteries bring blood away from the heart.

• Veins bring blood to the heart.

Coronary Circulation Overview

• Blood supply for the muscles on the heart.

• This blood gets delivered when the heart is relaxed, and most of it goes towards the left ventricle.

• Arterial blood supply varies among individuals.

• Contains many anastomoses (junctions). These provide additional routes for blood delivery, but cannot compensate for coronary artery occlusion (blocked artery)

Coronary Arteries and Their Divisions

• Left Coronary Artery: Anterior interventricular artery, Cirumflex Artery

• Right Coronary Artery: Right interventricular artery, Posterior interventricular artery

Left Coronary Artery Supplies what

• Interventricular septum

• Anterior ventricular walls

• left atrium

• and the posterior wall of the left ventricle

Anterior Interventricular Artery

• Runs in the anterior interventricular artery

• Forms an anastomosis with the posterior interventricular artery

Circumflex Artery

• Runs in the coronary sulcus

• Forms an anastomosis with the posterior interventricular artery

Right ventricular sulcus supplies what

Supplies the right atrium and most of the right ventricle

Right Marginal Artery

Runs in the right coronary sulcus

Posterior interventricular sulcus

Runs within the posterior interventricular sulcus

Forms anastomosis with both left branches

Cardiac Veins

collect blood from capillary beds

Coronary Sinuses

Empties into the right atrium

• Is formed by the cardiac veins

1. Great Cardiac Vein

2. Middle Cardiac Vein

3. Small Cardiac Vein

Great Cardiac Vein

• Runs alongside the Anterior Interventricular Artery

• Runs inside the interventricular Sulcus

Middle Cardiac Vein

• Runs with the posterior interventricular artery

• Located in the posterior interventricular sulcus

Small Cardiac Vein

• Runs with the marginal artery

• Located in the inferior margin

Several Small Cardiac Veins

• They just drain directly into the right atrium

Cardiac Muscle Cells

cells of da heart muscle

Anatomy of Cardiac Muscle Cells:

• They are striated, branched, and interconnected.

• Is wrapped by an endomesium that provides blood supply to cardiac muscles

• Contains T-Tubules, albiet wider and less numerous than skeletal muscle cells

• Has many mitochondira that takes up 25%-35% of the cell

• Contains intercalated discs

Intercalated Discs

• They contain Desmosomes, which help to prevent the heart from pulling apart when contracting and relaxing.

• They contain gap junctions, allowing for ions to pass in between cells. All the heart musculature contracts and relaxes at once because of this.

Three Similarities with Skeletal Muscles:

1. Both cells suddenly depolarize with an influx of sodium in the sarcolemma. Membrane potential from -90mv to 30mv. Brief; na+ channels close rapidly.

2. Depolarization wave travels down T-Tubules to triads; sarcoplasmic reticulum releases calcium

3. Calcium attatches to troponin, troponin pulls tropomyosin off filaments, excitation contraction coupling occurs.

Unique Features of Cardiac Muscle Functioning:

• Around 1% of cardiac muscle cells have automaticity, meaning that they contrat without nervous system stimulation. Due to gap junctions, this causes the rest of the cells to contract as well.

• The nervous system controls the rate at which the heart contracts, not if it does or does not.

• Because of gap junctions, either all the cells contract, or all the cells relax. They work as a single unit.

Cardiac Cell Respiration

• Cardiac cells use a lot of energy, so they heavily rely on aerobic respiration and do not fare well with aerobic respiraton

• In an emergency, the cells can use lactic acid, fat, and even ketones, but this is not ideal and will usually lead to a heart attack.