ANATOMY
Lymphatic System
THYMUS
OUTLINE
I. Lymphatic organs • bilobed mass of tissue located in the mediastinum
a. Tonsils along the trachea behind the sternum
b. Spleen • involved in immunity
c. Thymus gland • site for lymphocyte production and maturation
d. Peyer’s patches • helps develop T lymphocytes in the fetus and in
e. Vermiform appendix infants for a few months after birth
f. Bone marrow
II. Lymph PEYER’S PATCHES (AGGREGATED LYMPHATIC
a. Lymphatic circulation FOLLICLES)
III. Lymph nodes
a. Structure • found in the wall of the SI
b. Function • resemble tonsils
• their macrophages destroy bacteria
LYMPHATIC ORGANS VERMIFORM APPENDIX
TONSILS • worm-like
• attached to the cecum (1st portion of the colon) and
• Form a protective ring (Waldeyer’s lymphatic ring) of contains a small lumen lined w/ mucosa and rich in
reticulo-endothelial cells against harmful lymphatic nodules
microorganisms that might enter the nose or oral • After birth, lymphoid tissue begins to develop in
cavity appendix, reaching peak amounts around age of 25
• More functional in children • assists in the maturing of B lymphocytes and produces
• As we age, tonsils decrease in size and may even Ig A antibodies
disappear in some individuals
TYPES
• Palatine- visible when you open your mouth and say
“ah”
• Pharyngeal- when enlarged and inflamed they are
called adenoids
• Lingual- located on the base of tongue
BONE MARROW
• occupies the marrow cavity in long & short bones and
the interstices of the cancellous bone in flat & irregular
bones
SPLEEN • At birth, the marrow is red and hematopoietic
o This blood-forming activity gradually lessens
• Oval in shape w/ age, and the red marrow is replaced by
• Single, largest mas of lymphatic tissue in the body yellow marrow
• Found in the left upper corner of the abdominal cavity • At 7 years of age, yellow marrow begins to appear in
• Filters blood and phagocytoses bacteria and worn-out the distal bones of the limbs
platelets and RBCs o This replacement of marrow gradually moves
o This action releases Hgb to be recycled proximally, so that by the time the person
• Also produces lymphocytes and plasma cells becomes an adult, red marrow is restricted to
the bones of the skull, vertebral column,
thoracic cage, girdle bones, and head of
humerus & femur
LYMPH
• After blood travels through capillary beds and is
moved to the venous system, some of its fluid is left
behind in the tissues and is called lymph
• clear, colorless liquid with a composition similar to
blood plasma
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Lymphatic System
THYMUS
OUTLINE
I. Lymphatic organs • bilobed mass of tissue located in the mediastinum
a. Tonsils along the trachea behind the sternum
b. Spleen • involved in immunity
c. Thymus gland • site for lymphocyte production and maturation
d. Peyer’s patches • helps develop T lymphocytes in the fetus and in
e. Vermiform appendix infants for a few months after birth
f. Bone marrow
II. Lymph PEYER’S PATCHES (AGGREGATED LYMPHATIC
a. Lymphatic circulation FOLLICLES)
III. Lymph nodes
a. Structure • found in the wall of the SI
b. Function • resemble tonsils
• their macrophages destroy bacteria
LYMPHATIC ORGANS VERMIFORM APPENDIX
TONSILS • worm-like
• attached to the cecum (1st portion of the colon) and
• Form a protective ring (Waldeyer’s lymphatic ring) of contains a small lumen lined w/ mucosa and rich in
reticulo-endothelial cells against harmful lymphatic nodules
microorganisms that might enter the nose or oral • After birth, lymphoid tissue begins to develop in
cavity appendix, reaching peak amounts around age of 25
• More functional in children • assists in the maturing of B lymphocytes and produces
• As we age, tonsils decrease in size and may even Ig A antibodies
disappear in some individuals
TYPES
• Palatine- visible when you open your mouth and say
“ah”
• Pharyngeal- when enlarged and inflamed they are
called adenoids
• Lingual- located on the base of tongue
BONE MARROW
• occupies the marrow cavity in long & short bones and
the interstices of the cancellous bone in flat & irregular
bones
SPLEEN • At birth, the marrow is red and hematopoietic
o This blood-forming activity gradually lessens
• Oval in shape w/ age, and the red marrow is replaced by
• Single, largest mas of lymphatic tissue in the body yellow marrow
• Found in the left upper corner of the abdominal cavity • At 7 years of age, yellow marrow begins to appear in
• Filters blood and phagocytoses bacteria and worn-out the distal bones of the limbs
platelets and RBCs o This replacement of marrow gradually moves
o This action releases Hgb to be recycled proximally, so that by the time the person
• Also produces lymphocytes and plasma cells becomes an adult, red marrow is restricted to
the bones of the skull, vertebral column,
thoracic cage, girdle bones, and head of
humerus & femur
LYMPH
• After blood travels through capillary beds and is
moved to the venous system, some of its fluid is left
behind in the tissues and is called lymph
• clear, colorless liquid with a composition similar to
blood plasma
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