The pressure of the blood returning to the heart is very low, so the walls of veins are much thinner than arteries. Capillaries are tiny blood vessels that connect arteries and veins. Their walls are very thin….Share.

Our blood pressure is highest at the start of its journey from our heart – when it enters the aorta – and it is lowest at the end of its journey along progressively smaller branches of arteries.

Each time the heart beats (contracts and relaxes), pressure is created inside the arteries. The pressure is greatest when blood is pumped out of the heart into the arteries. When the heart relaxes between beats (blood is not moving out of the heart), the pressure falls in the arteries.

Blood vessels damaged by high blood pressure can narrow, rupture or leak. High blood pressure can also cause blood clots to form in the arteries leading to your brain, blocking blood flow and potentially causing a stroke.

Veins. Veins carry blood toward the heart. After blood passes through the capillaries, it enters the smallest veins, called venules. From the venules, it flows into progressively larger and larger veins until it reaches the heart.

A large vein that carries blood to the heart from other areas of the body. The vena cava has two parts: the superior vena cava and the inferior vena cava.

The inferior vena cava is the largest vein in the human body. It collects blood from veins serving the tissues inferior to the heart and returns this blood to the right atrium of the heart. Although the vena cava is very large in diameter, its walls are incredibly thin due to the low pressure exerted by venous blood.