HISTOLOGY OF LYMPHATIC
SYSTEM
TUCOM
By-Dr.Elham Majed
Lecture 1 .
LYMPHOID SYSTEM
It is part of the circulatory system
and an important part of the
immune system .
It returns fluids that have leaked
from the circulatory system back
to the blood.
Lymphatic system consists of :
1- lymph vessels
2- lymphoid tissues
3- circulating lymph
4-lymhatic organs
FUNCTIONS
• Defense of body
• Phagocytosis of foreign cells
• Involved in production of lymphocytes
and plasma cells
Originate as lymph capillaries
Lymphatic Capillaries originate in tissues as tiny blind
ended sacs
∙ lie side by side with blood capillaries
∙ single layer of endothelial cells like blood capillaries
∙ but much more permeable to solvents, and large solutes
and whole cells
Major features of the lymphatic capillaries :-
Composed of simple squamous epithelium/ endothelium
Blind-ended (dead end) capillaries (NOT part of a closed loop)
Endothelial cells at capillary ends loosely overlap
Anchoring filaments attach endothelial cells to surrounding
tissues to form one way mini-valves
Highly permeable & allow interstitial fluid to enter capillary
Lacteals
are lymphatic capillaries that facilitate fat
b
ti i th
ll i t ti
LYMPHATIC VESSELS
LYMPHATIC CAPILLARIES UNION TO FORM THE LYMPHATIC VESSELS ,
REASSEMBLE TO VEINS WITH EXCEPTION THINNER WALL WITH HIGH NUMBER
OF VALVES TO PREVENT THE BACK FLOW OF THE LYMPH
LYMPHATIC CAPILLARY &
VESSEL
-LYMPHATIC VESSELS
CHANNELS OF LYMPHATICS
– Lymphatics ultimately deliver lymph into 2
main channels
• Right lymphatic duct
– Drains right side of head & neck,
right arm, right thorax
– Empties into the right subclavian vein
• Thoracic duct
– Drains the rest of the body
– Empties into the left subclavian vein
CHANNELS OF
LYMPHATICS
MAJOR LYMPHATIC VESSEL OF
THE TRUNK
WHAT IS LYMPHOID TISSUE?
Specialized form of connective tissue
Supporting framework: reticular cells & reticular fibres
.
Large number of lymphocytes T and B lymphocytes.
.Other cells: Plasma cells & macrophages
• The cells of lymphoid tissues either (regular circular
distributed forms the lymphatic nodules conceder as
the structural unit of the lymphoid system) or irregular
distributed
-LYMPHATIC TISSUE
• Diffuse lymphatic tissue
– No capsule present
– Found in connective tissue of almost all organs
• Lymphatic nodules
– No capsule present
– Oval-shaped masses
– Found singly or in clusters
-Lymphatic organs
.Capsule present
Primary lymphatic organs ,where the lymphocytes
originate and maturated (Thymus, Bone marrow)
Secondary lymphatic tissue( Lymph nods, spleen)
DIFFUSE LYMPHATIC TISSUE
• Called as mucosa associated lymphatic tissue
(MALT).
• Accumulation of lymphatic tissue in the
mucous membrane of gastrointestinal,
respiratory, urinary and reproductive tracts.
• Located where they come in direct contact
with antigens.
LYMPHATIC NODULE
• Circumscribed concentration of
lymphatic tissue (lymphocytes and
related cells).
• Not surrounded by capsule.
LYMPHATIC
NODULE
TANKS FOR LISITENING