Physiology of venous system

Blood flow in veins Blood flows through the blood vessels, including the veins, primarily, because of the pumping action of the heart, although venous flow is aided by the heartbeat, the increase in the negative intrathoracic pressure during each inspiration, and contractions of skeletal muscles that compress the veins (muscle pump).

Morpho-functional properties of venous system Veins are the vessels, which are carry out blood from organs, tissues to heart in right atrium. Only pulmonary vein carry out blood from lungs in left atrium. There are superficial (skin) and deep veins. They are very stretching and have a low elasticity. Valves are present in veins. Plexus venosus are depo of blood. Blood moving in veins under gravity.

Mechanism of regulation Difference of pressure in venous system is a cause of blood moving. From the place of high pressure blood moving to the place of low pressure. Negative pressure in chest is a cause of blood moving. Contraction of skeletal muscles, diaphragm pump, peristaltic movement of veins walls are the causes of moving.

Venous pressure Venous pressure is pressure of blood, which are circulated in veins. Venous pressure in healthy person is from 50 to 100 mm H2O. Increase of venous pressure in physiological condition may be in the action of physical activity. Determine of venous pressure is called phlebotonometry and give for doctors information about activity of right atrium.

Phlebography а – atria wave –contraction of right atrium с – passing of carotid artery pulse on vein х – systole of ventricles v – ventricular – filling of atrium by blood y – passing of blood in right atria

Speed of blood stream Speed of vein blood stream depend on diameter of vessels. In venuls speed of blood moving is lower. In veins of middle diameter it 7-14 cm/s, in big veins the speed is near 20 cm/s. In big veins speed of blood moving depend on breathing and heartbeat.

Venous pulse Venous pulse is a moving of walls of big veins, which are depend on heartbeat. The cause of it stop of blood flow from vein to heart during atrium systole. At these time pressure in it increase. Methods of investigation of venous pulse are phlebography.

THANCK YOU!