The Lymphatic Vascular System
is a congenital malformation of the
lymphatic system that involves the skin and subcutane-
ous tissues. It occurs most often in the head and the
neck. It is characterized by multiple clusters of translu-
cent vesicles that contain lymph ﬂ uid varying from clear
to pink to dark red. These vesicles are separated from
the normal network of lymphatic vessels but have com-
munications with the superF cial lymph vesicles through
vertical and dilated lymph channels. Skin lesions range
from minute vesicles to cystic and cavernous spaces.
Clinically, it appears as a raised, soft, spongy, and
pinkish-white lesion. Surgical excision may be chosen if
vital structures are involved or for cosmetic correction,
but it has a high recurrence rate after surgery.
Small lymphatic vessels, lymph node.
lymphatic vascular system
is composed of
, which col-
lect and drain interstitial ﬂ uid from the tissue into the large veins
(for subclavian veins, see Chapter 10, “Lymphoid
(ﬂ uid in the lymphatic system) contains lym-
phocytes, immunoglobulins, plasma, foreign antigens, and other
carry lymph through the
along the lymphatic vessels.
F lter lymph
and expose lymphocytes to antigens as part of the immune
response (see Chapter 10, “Lymphoid System”). After F ltration,
the lymph is transported via large lymphatic vessels to lymphatic
ducts (the thoracic right lymphatic ducts) and F nally enters the
subclavian veins and becomes part of the blood plasma. An
small lymphatic vessels
is shown in the hilus of a
lymph node. Small lymphatic vessels have large lumens and very
thin walls, which are composed of a layer of endothelium and a
little connective tissue with a few smooth muscle cells.
Large lymphatic vessels, lymph node.
Large lymphatic vessels
have thicker walls than small
lymphatic vessels. Large lymphatic vessels are composed of
connective tissues and multiple layers of
smooth muscle cells
Contraction of smooth muscle cells helps to move the lymph
forward. Large lymphatic vessels are structurally similar to
small veins, except they have larger lumens and prominent
. Valves are present in all sizes of lymphatic vessels.
They prevent lymph from ﬂ
owing backward. Lymphatic ves-
sels are often distinguished by lumens that contain clusters of
. Lymphatic vessels can be
found in most of the tissues of the body but not in the central
nervous system, the bone marrow, or the hard tissues.