An overview of the circulatory system, and related anatomy and physiology of the peripheral vascular system
At the end of this chapter, the practitioner will be able to:
Discuss the structure of the circulatory system
Have a basic understanding of the anatomy and physiology of the peripheral vascular system
Identify the structural differences between an artery and a vein
Identify the most common anatomical sites for venepuncture and cannulation.
It is important to have a good knowledge of anatomy and physiology and to understand how the circulatory system works. This chapter will provide a brief overview; you may wish to read a dedicated anatomy and physiology text if you require more detailed information.
The heart is a four-chambered pump. The heart’s pumping action can appear confusing. It may be helpful to separate functions to the right and left side of the heart.
Table 2.1 Right-side heart functions
Deoxygenated blood is delivered to the right atrium by two of the largest veins in the body – the inferior and superior venae cavae.
The right atrium pumps blood to the right ventricle.
The right ventricle pumps blood to the lungs for oxygenation via the pulmonary artery.
The right side of the heart contains two of the heart’s four chambers – the right atrium and ventricle. The primary role of the right side is to pump deoxygenated blood to the lungs (Nair & Peate 2013). Deoxygenated blood enters the right side of the heart. From there, it travels to the lungs.
At this point it is useful to highlight one of the key differences between arteries and veins:
Arteries carry blood away from the heart; veins carry blood back to the heart.
You will notice from the description above that the venae cavae (large veins) are carrying blood back to the heart, while the pulmonary artery carries blood away from the heart. Once blood has been oxygenated, it takes the following journey from the lungs to the left side of the heart and on to the rest of the body:
Table 2.2 Left-side heart functions
Once blood has been oxygenated in the lungs it is carried back to the left atrium via the pulmonary vein.
The left atrium pumps blood into the left ventricle.
The left ventricle is the most powerful chamber of the heart and pumps blood via the aorta (the largest artery in the body).