Running parallel to the arteries is the system of deep veins. Immediately beneath
the skin is a network of superficial veins. These veins collect and then join the
deep veins in the axillae (armpits) and the inguinal region (groin).
Collecting the blood from the head, neck, and upper members is the superior vena
cava. Collecting the blood from the rest of the body is the inferior vena cava.
Thus, the final major veins, emptying the returned blood into the right atrium of the
Except the veins from the head, veins are generally supplied with valves to assist
Carrying absorbed substances from the gut to the liver is the hepatic portal venous
system. After being specially treated and conditioned, this blood is returned to the
Located in the interstitial spaces, where they absorb excess interstitial fluid, are
the lymphatic capillaries. A tributary system collects this fluid, now called lymph.
To help maintain lymph flow in one direction, lymphatic vessels are supplied with
valves. The major lymph vessel (which passes from the abdomen, up through the
thorax, and into the root of the neck) is the thoracic duct. Lymph nodes are
special structures which interrupt lymphatic vessels and serve as special filters for
the lymph fluid passing through. Tonsils are special collections of lymphoid tissue.
They are protective structures located primarily at the entrances of the respiratory
End of Lesson 9