Lymph also returns to the bloodstream most of the small
proteins that the blood capillaries F ltered. At the same time,
lymph transports foreign particles, such as bacteria and
viruses, to lymph nodes.
Lymphatic capillaries are adapted to receive proteins and
foreign particles in a way that blood capillaries are not. The
epithelial cells that form the walls of lymphatic vessels over-
lap but are not attached to each other. This conF guration,
, creates ﬂ
aplike valves in the lymphatic
capillary wall. The valves are pushed inward when the pres-
sure is greater on the outside of the capillary but close when
the pressure is greater on the inside.
The epithelial cells of the lymphatic capillary wall are
also attached to surrounding connective tissue cells by thin
protein F laments. As a result, the lumen of a lymphatic capil-
lary remains open even when the outside pressure is greater
than the pressure inside the lymph capillary.
What is the relationship between tissue f
uid and lymph?
How do plasma proteins in tissue f
ect lymph ±ormation?
What are the major ±unctions o± lymph?
the tissue ﬂ
uid hydrostatic pressure moving tissue ﬂ uid into
lymphatic capillaries, forming lymph. Thus, lymph forma-
tion prevents the accumulation of excess tissue fluid, or
Lymphatic vessels in the small intestine play a major role
in the absorption of dietary fats (chapter 17, pp. 684–685).
by right lymphatic duct
Right lymphatic duct
Right internal jugular vein
Afferent lymphatic vessel
Efferent lymphatic vessel
Lymphatic pathways. (
) The right lymphatic duct
drains lymph ±rom the upper right side o± the body, whereas the
thoracic duct drains lymph ±rom the rest o± the body. (
drainage o± the right breast illustrates a localized ±unction o± the
lymphatic system. Surgery to remove a cancerous breast can disrupt
this drainage, causing pain±ul swelling.
The lymphatic pathway.