Human Physiology, 14th edition (2016)

444 Chapter 13

Adenoid

Tonsil

Right lymphatic duct

Right subclavian

vein

Axillary lymph

nodes

Bone marrow

Lymphatics of

mammary gland

Cisterna chyli

Inguinal lymph

nodes

Left subclavian

vein

Thoracic

duct

Mesenteric

lymph nodes

and Peyer’s

patches

Thymus

Spleen

Lymph node

Cervical

lymph nodes

Figure 13.38 The location of lymph nodes along the lymphatic pathways. Lymph nodes are small bean-shaped bodies,
enclosed within dense connective tissue capsules.

contain phagocytic cells, which help remove pathogens, and
germinal centers, which are sites of lymphocyte production. The
tonsils, thymus, and spleen—together called lymphoid organs —
likewise contain germinal centers and are sites of lymphocyte
production. Lymphocytes are the cells of the immune system
that respond in a specific fashion to antigens, and their func-
tions are described as part of the immune system in chapter 15.

Although the lymphatic system transports lymphocytes and

antigen-presenting cells for immune protection, it may also

transport cancer cells that can enter and later leave the porous

lymphatic capillaries, thereby seeding distant organs. The lym-

phatic system can help cancer to spread, or metastasize. Metas-

tasis to regional lymph nodes is the first step in the dissemination

of tumors for cancers of the breast, colon, prostate, and others.