Blood Vessels

Filtration

-Blood pressure causes plasma fluid to be pushed out into the interstitial fluid -As fluid is pushed out, blood Colloid Osmotic Pressure increases -Interstitial fluid is drawn back into the capillaries when osmotic pressure exceeds blood pressure -More fluid is forced out than pulled in

Muscular Arteries

-Changes slightly as the pressure of the blood rises and falls during the heart's pumping activity -Arterioles and small muscular arteries have lumina which provide greater resistance to blood flow through the arterial system.

Elastic Arteries

-Expand when the pressure of the blood rises as a result of the ventricles contraction -Recoil when the blood pressure falls during relaxation of ventricles

Capillary Properties -High Surface Area

-Extensive Branching (close to all cells)

Discontinuous Capillaries

-Found in the bone marrow,liver,and spleen -There is a huge distance between the endothelial cells that they look like tiny cavities in the organ

Capillary Properties -Slow Blood Flow

-Increases time for exchange to occur

Types of Capillaries -Fenestrated Capillaries

-Occur in the Kidneys, Endocrine Glands, and Intestines -Wide intercellular pores that are covered by a layer of mucoprotein.

Mucoprotein

-Serves as a basement membrane over the capillary endothelium -Restricts passage of certain molecules that might through the large capillary pores.

Capillary Properties -Short Diffusion Distance

-Thin Capillary Walls -Narrow diameter

Veins

A blood vessel that returns blood to the heart -Able to expand as they accumulate amounts of blood -Pass between skeletal muscle groups

Arteries

A vessel that carries blood away from the heart

Types of capillaries -Continuous Capillaries

Adjacent endothelial cells are closely joined together. -Found in muscle,lungs,adipose tissue, and CNS -In other organs, Continuous Capillaries have narrow intercellular channels that permit the passage of molecules other than protein between the capillary blood and tissue fluid.

Venous Valves

As veins are squeezed by contracting muscles, a one-way flow of blood to the heart is ensured -The ability of valves prevent the flow of blood away from the heart

Blood passing through many capillaries undergoes...

Filtration

Arterioles

Small muscular artery -In some tissues, blood from arterioles can enter the venules directly through Arteriovenous Anastomoses

Skeletal Muscle Pump

The effect of the massaging action of skeletal muscles on venous blood flow -The rate of venous return to the heart is dependent on Skeletal Muscle pump

What are Capillaries?

The smallest vessel in the vascular system. Capillary walls are only one cell thick wall,and all exchanges of molecules between the blood and tissue fluid occur across the capillary wall.

Resistance to blood flow is increased by...

Vasoconstriction of arterioles -Decreases the blood flow downstream in the capillaries

When pumps are less active...

blood accumulates in the veins and causes them to bulge

When a pumps are more active...

blood returns to the heart at a faster rate and less is left in the venous system

Vasolidation of Arterioles...

decreases the resistance and increases the flow through the arterioles to the capillaries

Capillary growth...

is promoted by Vascular Endothelial Growth Factor -can also be promoted by Adenosine, which stimulates vasolidation of arterioles and thereby increases blood flow to the hypoxic tissue