1. The Lymphatic System Major components:
lymphatic vellse,s lymph organs, tissues, and cells
A. Functions
1) helps maintain fluid balance of tissues by transporting interstitial fluid back to the bloodstream
2) provides transport route for absorbed fat
3) helps mediate immunological defenses against diseases

2. Lymphatic Vessels
B. Lymphatic vessels transport fluids that have leaked out of blood vessels back into the blood
One way transport system- all lymph fluid moves to the heart.
Lymph capillaries-sites of fluid collection; located in loose connective tissue; present where blood capillaries are except bone, teeth and CNS; very porous and permeable; walls made of endothelial cells
Collecting vessels-collect fluid from lymph capillaries; get successively larger as they move toward heart; run along veins

3. Fig 20.2a

5. Lymphatic Vessels( Con’t)
Trunks-collect lymph from largest collecting vessels
Ducts-collect lymph from trunks; sites of drainage into vascular system
Right lymphatic duct to right subclavical and jugular vein junction.
Left lymphatic duct to left subclavian and jugular vein junction.
C. Transport of Lymph-no direct pumping action; flow driven by:
1) skeletal muscle movement
2) smooth muscle movement in walls of trunks and ducts moves fluid toward veins
3) lymph vessels bundled with blood vessels by CT-pulsation of blood vessels moves lymph fluid

6. D. Lymphoid Cells, Tissues and Organs
lymphocytes-arise from hematopoetic cells in bone marrow migrate to lymphoid tissue and mature into: B lymphocytes-
T lymphocytes-
macrophages-phagocytic cells; also activate T cells
dendritic cells-spiny cells that activate T cells
reticular cells-fibroblast cells that produce the reticular network that supports cells

7. D. Lymphoid Cells, Tissues and Organs
lymphocytes-arise from hematopoetic cells in bone marrow migrate to lymphoid tissue and mature into: B lymphocytes- produce plasma cells that secrete antibodies T lymphocytes- carry out cell-mediated immune responses
macrophages-phagocytic cells; also activate T cells
dendritic cells-spiny cells that activate T cells
reticular cells-fibroblasts that produce the reticular network that supports cells
(from monocytes)

8. D. Lymphoid Cells, Tissues and Organs (con’t)
Lymphoid Organs
Lymph nodes-oval-shaped lymphoid tissue enclosed in a fibrous capsule
large clusters in inguinal, axillary, and cervical regions of the body
Functions: 1) act as lymph filters- remove debris and infectious cells ) trapped antigens activate immune cells

9. Fig.20.4

10. D. Lymphoid Cells, Tissues and Organs (con’t)
Spleen-largest lymphoid organ located near the left side of the stomach
Functions: )site for lymphocyte proliferation and immune surveillance
2) removes debris, pathogens from lymph and blood
3) extracts aged erythrocytes and platelets
4) mediates iron recycling
5) site of fetal erythrocyte production
6) stores platelets
Filters blood.

11. Fig. 20.5

12. Fig. 20.6

13. Lymphoid Organs (con’t)
Thymus-bi-lobed organ located in lower neck; site of maturation of T lymphocytes-stomach
Tonsils-Ring of lymphatic tissue structures around the entrance to the pharynx
nodules- contain lymphocytes
crypts-trap bacteria and debris
lingual-base of tongue
palantine-posterier sides of oral cavity
pharnygeal-nasopharynx
tubal-surround pharyngotympanic tube

14. Lymphoid Organs (con’t)
Lymphoid nodules-scattered in various regions
Ex:Peyers patches-small intestine
MALT (mucosa-associated lymphatic tissue)