The lymphatic system consists of lymphatic vessels, lymph nodes, and lymphoid organs that work together to drain excess tissue fluid, absorb fatty acids, and recognize and fight foreign pathogens. Lymphatic vessels are made up of a network of lymph capillaries, collecting vessels, and trunks that drain into the subclavian veins or thoracic duct. Lymph nodes filter lymph and initiate immune responses. Major lymphoid organs include the spleen, thymus, tonsils, and clusters of lymphoid tissue in the digestive system that help fight infection and remove old blood cells and platelets.

1. Lecture Topic:
Lymphatic
system

2. One way system: to the heart
Return plasma protein and
excess tissue fluid (2-4 L/day
Lacteals in small intestine
absorb dietary lipids
Recognizes specific foreign
molecules.
Lymphatic system

3. Lymphatic
system
Cardiovascular
system
Lymphatic system

4. Lymphatic
Vessels

5. 1).Lymph capillaries
 Have one way mini-valves allowing excess fluid to
enter but not leave
 Picks up bacteria and viruses as well as proteins,
electrolytes and fluid
 Absent in bones, bone marrow, teeth, CNS

8. 2).Lymphatic collecting vessels
 Similar to blood vessels (3 layers), but thin &
delicate
 Superficial ones in skin travel with superficial veins.
 Deep ones ( in trunk and digestive viscera) travel
with deep arteries.
 Drain into superficial and deep lymph nodes.

9. 3).Lymphatic Trunks
 Lumbar
 Intestinal
Receives fatty lymph (chyle) absorbed
through lacteals of intestines
 Broncho-mediastinal
 Subclavian
 Jugular
(Paired, except intestinal)
Drain into cisterna chyli

10. Lymphatic Trunks
Right
Broncho-
Mediastinal
Trunk
Right subclavian trunk
Left
Broncho-
Mediastinal
Trunk
Left subclavian
trunk
Right lumber Trunk Left lumber Trunk
Thoracic Duct
Cisterna Chyli
Right jugular trunk Left jugular trunk
Intestinal Trunk

11. 4).Lymphatic ducts:
 Thoracic duct (always present)
(drain into left subclavian vein)
 20% also have a right lymphatic duct
(drain into right subclavian vein)

13. Lymphoid
Organs

14.  Lymph nodes
 Spleen
 Thymus
 Tonsils
 Small intestine &
appendix
(lymphoid nodules)

15. Lymphatic system
L

16. Function of lymph nodes
FILTERING THEM FROM LYMPH TO INITIATE AN
IMMUNE RESPONSE.
DISTROY MOST PATHOGENS
BY

17. LYMPH NODES ARE FOUND IN
GROUPS
Superficial groups:
-Cervical
-Axillary
-Inguinal
Deep groups:
-Tracheobronchial
-Aortic
-Iliac

19. Lymph Nodes Structure
 Bean shaped masses of lymphoid tissue( Conn. Tissue &
lymphocytes.
 Covered by Capsule, gives off trabiculae.
 In between trabiculae, Cortical and Medullary sinuses.
 Sinuses contain lymph. follicles (nodules)
 Follicles are masses of B-Lymphocytes.

20. Afferent
Lymphatic
vessels
Efferent
Lymphatic
vessel

22. Nodules (also called follicles)
(Spherical masses of mostly B-lymphocytes).
1. Scattered Lymphatic nodules. (in submucosa of GIT).
2. Aggregated lymphatic nodules. (“Payer's Patches”)
About 40 follicles / 1 cm area.
Distal ileum and Appendix

25. The thymus
Secrete hormones (thymopoietin, thymulin and
thymosin) for the development of T-lymphocytes
Thymus is the organ where T-cells become
mature and differentiate.

26. Very large in fetus, after age 14 begins involution
(in elderly mostly fatty and fibrous tissue)

27. Structure of the thymus
 Capsule gives off trabeculae, divides
parenchyma into lobules of cortex and medulla
 Cortex is darker than the medulla.
 Medulla has more mature T-lymphocytes.
 Medulla contains Hassall's corpuscles.
(Masses of aged, degenerated cells)

28. Thymus Gland

29. Structure of the thymus

30. SPLEEN
This is the largest lymphoid organ,
posterior to the stomach.

32. SPLEEN STRUCTURE
(spleen is about the size of a fist).
a. Capsule
b. Trabeculae
c. Red pulp
d. White pulp

33. RED PULP:
(made of sinuosoid capillaries)
WHITE PULP:
(made of masses of lymphocytes)

35. FUNCTIONS OF THE SPLEEN
 Phagocytizes bacteria and other foreign
materials : “white pulp”
 Removal & destruction of aged or defective
blood cells: “red pulp”
 Stores platelets
 In fetus: hematopoiesis

36. TONSILS. LOCATION
 Palatine tonsils:
 pair at posterior margin of oral cavity
 most often infected
 Lingual tonsils:
 pair at root of tongue
 Pharyngeal tonsil (adenoid):

37. STRUCTURE OF PHARYNGEAL TONSILS
 Covered by epithelium
 Tonsillar crypts
 Lymph Nodules (Follicles)
 Lymphocytes

38. Tonsils

39. Hematopoiesis

40. thank you for attention.
THE END!