Assignment 8b
As the capillaries contain small holes for nutrient exchange, plasma from the blood can leak
out into the tissues creating a substance known as interstitial fluid. It lacks red blood cells,
which are too big to leak out, so it’s not classed as blood. Instead it’s a mixture of proteins,
fat, water and white blood cells. As well as other things. Without enough fluid however, the
blood thickens and oxygen carrying gets harder. And excess fluid in the tissues causes that
area to swell. So the lymphatic system collects it, the fluid now being called lymph, and
transports it back to the bloodstream. It also removes and recycles cellular waste, as well as
transports the white blood cell filled lymph around the body. The latter is what makes
it part of the immune system.
(P3)The Structure of the Lymphatic system
The spleen is located in the upper left abdomen, where it stores and filters the blood. It
recycles aged blood cells, mostly red ones, and produces lymphocyte white blood cells. It is
made of two types of tissue: white pulp produces lymphocytes and red pulp is responsible
for filtration.
The thymus gland is found between the lungs and behind the sternum. It’s the site of
lymphocyte T cell development.
The tonsils protect the body from bacteria that are inhaled. They’re located at the rear of the
throat.
Lymph vessels are a network of thin tubes that transport lymph back to the blood. They’re
found throughout the body. The thinner ones are called lymph capillaries or lacteals,
they pick up the lymph from the interstitial space. The larger ones contain valves to maintain
the one way system, the surrounding layers of muscle contract rhythmically. As they join
together they get larger and form ducts, the body has two: the right lymphatic duct and the
thoracic duct.