198
UNIT 3
Organ Systems
Organ
Epithelium/
Capsule
Covering
Cortex and
Medulla
Cords and
Sinuses
B-cell Main
Region
T-cell Main
Region
Special Features (1)
and Functions (2)
Tonsils
Incomplete
epithelium
and capsule
No
No
Primary and
secondary nodules
Outside of
the lymphatic
nodules
1. Epithelial covering
2.
Promotes B cells to
proliferate and to
produce IgA; immune
defense against upper
respiratory infections,
where B and T cells
encounter foreign
antigens and initiate
immune response
Lymph
nodes
Capsule
(thin)
Cortex, paracortex,
and medulla
Medullary
cords and
medullary
sinuses
Primary and
secondary nodules
(most nodules
are secondary);
medullary cords
Paracortex
1.
Afferent lymphatic
vessels and
subcapsular sinuses
2.
Filter lymph and
recirculate both B
and T cells; provide
place for lymphocytes
to meet antigens and
start immune response
Thymus
Capsule
(thin)
Cortex (without
lymphatic nodules);
medulla (with
Hassall corpuscles)
No
No
Cortex and
medulla
1.
Epithelial reticular
cells and Hassall
corpuscles; no
lymphatic nodules
2.
Development and
maturation of T cells
Spleen
Capsule
(thick)
No, arranged in
white pulp and red
pulp
Splenic cords
and venous
sinuses
Secondary nodules
(splenic nodules)
PALS
1.
Central arteries and
PALS
2.
Red pulp ±
lters
blood, removes aged
erythrocytes, and
acts as a reservoir
for erythrocytes and
platelets; the white
pulp hosts B and T
lymphocytes, where
they meet antigens,
mature and prolif-
erate, and initiate
immune response
TABLE 10-2
Lymphoid Organs
SYNOPSIS 10-3
Pathological and Clinical Terms for the Lymphoid System
Lymphadenopathy
: Enlarged lymph nodes due to a variety of causes including lymphoma, infection, autoimmune disease,
medications, and metastatic disease (Fig. 10-9C).
Myalgia
: Muscle pain that may be caused by a variety of conditions including exercise, autoimmune disease, medications,
infections, and neoplasms (Fig. 10-9C).
Lymphoid hyperplasia
: A reactive proliferative process of lymphoid tissues, particularly lymph nodes, characterized by
enlarged follicles with abundant macrophages within the germinal center (Fig. 10-9C).
Reed-Sternberg cell
: Characteristic cell of classical Hodgkin lymphoma containing two nuclei or nuclear lobes, each with
a prominent nucleolus (Fig. 10-12C).
Waldeyer ring
: Lymphoid tissues of the nasopharynx including the palatine tonsils and pharyngeal tonsils (adenoids) that
may be an extranodal site of lymphoma development (Fig. 10-9B).
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