Intro to Circulation

Series Organization

The systemic and pulmonary circulations are arranged in series, meaning total cardiac output passes through both circuits in sequence

Flow equivalence

At steady state, Cardiac Output=Total Tissue Blood Flow=Venous Return=Pulmonary Flow

What % of Cardiac Output is contained in the Sphlanic?

27%

What % of Cardiac Output is contained in the Kidneys?

22%

What % of Cardiac Output is contained in the Skin and other tissues?

18%

What % of Cardiac Output is contained in the Inactive Skeletal Muscles?

15%

What % of Cardiac Output is contained in the Brain?

14%

What % of Cardiac Output is contained in the Heart (Coronary Circulation)

4%

Total Blood Volume Distribution

5000 mL

Where does the majority of blood volume reside?

Venous system

What % blood volume does the systemic circulation contain?

84%

What % blood volume do the small veins contain?

46% (largest blood reservoir)

What % blood volume do the large veins contain?

18%

What % blood volume do the small arteries contain?

8%

What % blood volume do the aorta, large arteries and small arteries contain?

6%

What % blood volume does the heart contain?

7.6%

What % blood volume does the pulmonary circulation contain?

8.8% (Arteries=2.6%, Capillaries=2.2%, Veins=4.0%)

Where is mean pressure the highest?

The aorta (~100 mmHg)

Where does pressure experience its steepest decline?

The arterioles, making arterioles the primary site of vascular resistance

Capillary and Venous Pressure

Pressure drops further through capillaries

Where does pressure reach its lowest level?

The vena cava (0.5mmHg)

The pulmonary circulation operates at significantly _____ pressures compared to the systemic circulation

lower

Microvascular Control

Perfusion through the true capillaries is controlled by precapillary sphincters along metarterioles

What does contraction of precapillary sphincters cause?

Blood to bypass capillary beds

Myocardial Wall Layers from Inside to Outside

Endocardium—>Myocardium—>Epicardium

What surrounds the Myocardial Wall Layers?

Pericardial cavity, and the parietal/fibrous pericardium