many veins contain these, thin folds of tunica interna that form flap like cusps that project into the lumen pointing towards the heart. They prevent the back flow of blood in their aiding of venous return.
is a vein with a thin endothelial wall that has no smooth muscle to alter its diameter. The surrounding dense connective tissue provides support and replaces the media and externa tunica
the union of the branches of two or more arteries suppling the same body region. Between arteries they provide alternate routes for blood to reach a tissue or organ. These helps maintain a constant blood flow no matter what damage is done to primary routes.
the alternate route of blood flow to a body part through an anastomoses.
veins, venules, from which blood can be diverted quickly if the need arises
the movement of substances between the blood and interstitial fluids.
the most important method of capillary exchange. Oxygen, CO2, glucose, amino acids and hormones enter and leave capillaries through this process
in this process, substances in blood plasma become enclosed within tiny pinocytic vesicles that first enter endothelial cells by endocytosis then move across the cell and exit on the other side. Important for large lipid-soluble molecules that cannot cross the capillary walls in any other way
is a passive process in which large numbers of ions, molecules or particles in a fluid move together in the same direction. It occurs from an area of higher pressure to an area of lower pressure and it continues as long as a pressure difference exists. It is important for the relative volumes of blood and interstitial fluid
pressure driven movement of fluid and solutes from blood capillaries into interstitial fluid.
pressure driven movement from interstitial fluids into the blood capillaries
Blood hydrostatic pressure (BHP)
promotes filtration. It is the pressure generated by the pumping action of the heart.
interstitial fluid osmotic pressure
blood colloid osmotic pressure
the main pressure promoting reabsorption of fluid.
net filtration pressure
is the balance of these pressures
if filtration greatly exceeds reabsorption. An abnormal increase in interstitial fluid volume
is the volume of blood that flows through any tissue in a given time period (ml/min)
created by the contraction of the ventricles it is the hydrostatic pressure exerted by blood on the walls of a blood vessel. It is determined by cardiac output, blood volume and vascular resistance.
systolic blood pressure
is the highest pressure attained in arteries during systole
diastolic blood pressure
is the lowest arterial pressure during diastole
mean arterial blood pressure
the average blood pressure in arteries, is roughly one-third of the way between diastolic and systolic pressures
is the opposition to blood flow due to friction between blood and the walls of blood vessels
factors in vascular resistance
size of lumen, blood viscosity, total blood vessel length,
systemic vascular resistance
refers to all the vascular resistances offered by systemic blood vessels