751
T
hey can’t all be superstars!
When we mentally tick off the names of the
body’s organ systems, the lymphatic (lim-fat
9
ik) system and the lymphoid organs
and tissues are probably not the first to come to mind. Yet if they failed their quiet
background work, our cardiovascular system would stop working and our immune sys-
tem would be hopelessly impaired.
Tis chapter is a bit unusual in that we will explore two functionally different but
structurally overlapping systems, the
lymphatic system
and the
lymphoid organs and
tissues
. Te
lymphatic system
returns fluids that have leaked from the blood vascular
system back to the blood. It actually consists of three parts:
A meandering network of
lymphatic vessels
Lymph
, the fluid contained in those vessels
Lymph nodes
that cleanse the lymph as it passes through them
Te
lymphoid organs and tissues
provide the structural basis of the immune system.
Tese organs and tissues house phagocytic cells and lymphocytes, which play essential
roles in the body’s defense mechanisms and its resistance to disease. Tese structures
include the spleen, thymus, tonsils, and other lymphoid tissues scattered throughout the
body. Te lymph nodes are also part of this system, and like a keystone, they have im-
portant roles to play in both the lymphoid organs and tissues and the lymphatic system.
Let’s begin by looking at the lymphatic system.
20
The Lymphatic System and
Lymphoid Organs and Tissues
Lymphatic System
(pp. 752–754)
Distribution and Structure of Lymphatic
Vessels (pp. 752–754)
Lymph Transport (p. 754)
Lymphoid Cells and Tissues
(pp. 754–755)
Lymphoid Cells (p. 754)
Lymphoid Tissue (pp. 754–755)
Lymph Nodes
(pp. 755–757)
Structure of a Lymph Node (p. 755)
Circulation in the Lymph Nodes
(pp. 755–757)
Other Lymphoid Organs
(pp. 757–759)
Spleen (pp. 757–758)
Thymus (pp. 758–759)
Mucosa-Associated Lymphoid Tissue
(MALT) (p. 759)
Developmental Aspects of the Lymphatic
System and Lymphoid Organs
and Tissues
(pp. 759–760)
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