Ch. 20 Notes: Lymphatic System
Lymphatic Vessels
Overview of Lymphoid Cells, Tissues, & Organs
Lymph Nodes
Other Lymphoid Organs
Ch. 20 Notes: Lymphatic System
Lymphatic Vessels
Distribution & Structure
Capillaries
Collecting Vessels
Lymph Transport
Valves
Propulsion by skeletal muscle contraction, thoracic pressure fluctuations with breathing.
Overview of Lymphoid Cells, Tissues, & Organs
Cells
Lymphocytes: B and T
Antigen-presenting cells: dendritic cells and macrophages
Tissues
Organs
Lymph nodes: hundreds; cluster along lymphatic vessels
Spleen
Thymus
MALT: Tonsils, etc.
Lymph Nodes
Act as monitoring sites for foreign objects (bacteria, viruses, etc.) in lymph. Contain lots of immune
cells, especially lymphocytes, which can mount a response to foreign particles.
Structure
Lima bean shaped
Circulation
Lymph enters on the convex "outer" side, via afferent lymphatic vessels; percolates slowly
through lymph node, and exits on the concave "inner" side via efferent lymphatics.
Other Lymphoid Organs
Spleen
Fist sized, left of stomach, below diaphragm
Site of lymphocyte proliferation, immune surveillance of blood, and immune response when
needed. (Lymph nodes watch lymph, not blood.)
Stores large amount of red blood cells, platelets, monocytes (parent cells of macrophages).
Filters out old erythrocytes and platelets. Begins the recycling of hemoglobin. Stores iron.
Thymus
At front of neck.
Site of maturation of T lymphocytes in childhood.
Thymus inactive in adulthood.
MALT
Mucosa-associated lymphoid tissue
Includes tonsils, Peyer’s patches, appendix
Tonsils
Clusters of lymphoid tissue which guard the entrance to the body through the nose and
mouth.
Pharyngeal tonsil (nasopharyngeal tonsil, adenoid) on posterior wall of nasopharynx,
behind & above uvula
Palatine tonsils (commonly called "tonsils") on R, L sides of back of oral cavity
Lingual tonsil at base of tongue
Tubal tonsils near nasopharyngeal opening of auditory tubes (Eustachian tubes,
pharyngotympanic tubes)
Peyer’s patches
In wall of ileum (last & longest part of small intestine)
Appendix
Small extension from lower end of cecum (ascending colon)
Copyright © 2015, William C. Rose