In the preceding chapters, we examined cardiovascular regulation at several different levels. Powerful systemic mechanisms operate over both the short term and the long term to control mean arterial pressure and cardiac output. Operating independently of these are local mechanisms…
When faced with a patient who appears seriously ill, clinicians focus their immediate attention on the patient's vital signs: temperature, respiratory rate, pulse, and blood pressure. These parameters are aptly named vital because they reflect the most fundamental aspects of…
The Cardiac Cycle The sequence of mechanical and electrical events that repeats with every heartbeat is called the cardiac cycle. The duration of the cardiac cycle is the reciprocal of the heart rate: For example, for a heart rate of…
The microcirculation serves both nutritional and non-nutritional roles The primary function of the cardiovascular system is to maintain a suitable environment for the tissues. The microcirculation is the “business end” of the system. The capillary is the principal site for…
Arterial Distribution and Venous Collection Systems Hemodynamics is the study of the physical laws of blood circulation. It therefore addresses the properties of both the “content” (i.e., blood) and the “container” (i.e., blood vessels). In Chapter 18 , we discussed…
Blood is a complex fluid consisting of plasma—extracellular fluid rich in proteins—and of formed elements—red blood cells (RBCs), white blood cells (WBCs), and platelets. Total blood volume is ~70 mL/kg body weight in the adult woman and ~80 mL/kg body weight in…
Elements of the Cardiovascular System The circulation is an evolutionary consequence of body size Isolated single cells and small organisms do not have a circulatory system. They can meet their metabolic needs by the simple processes of diffusion and convection…
The cells of the human body live in a carefully regulated fluid environment. The fluid inside the cells, the intracellular fluid (ICF), occupies what is called the intracellular compartment, and the fluid outside the cells, the extracellular fluid (ECF), occupies…
What is physiology? Physiology is the dynamic study of life. Physiology describes the “vital” functions of living organisms and their organs, cells, and molecules. For centuries, the discipline of physiology has been closely intertwined with medicine. Although physiology is not…