MICROBIOLOGY – ALCAMO
LECTURE:
Immune System, Lymph Node
Introduction
The Lymphatic System
• The Lymphatic system defends the
body from foreign invasion by disease
causing agents such as viruses,
bacteria, or fungi
The Lymphatic System
• Part of the immune system made of a
network of lymphatic vessels that carry
a clear fluid called lymph in one
direction - toward the heart
• Also includes structures dedicated to
the circulation and production of
lymphocytes (spleen, thymus, bone
marrow, lymph nodes, tonsils, etc)
The Lymphatic System
• Blood does not directly come in
contact with the cells and tissues in the
body
• Parts of the blood first exit the blood
vessels to become interstitial fluid,
which comes into contact with the cells
of the body.
• Lymph is formed when interstitial fluid
enters the initial lymphatic vessels
The Lymphatic System
• Collects and returns interstitial fluid,
including plasma protein to the blood,
and thus helps maintain fluid balance
• Defends the body against disease by
producing lymphocytes
• Absorbs lipids from the intestine and
transport them to the blood
Lymph Node
• Small ball-shaped organs distributed
widely throughout the body including
the armpit and stomach/gut and linked
by lymphatic vessels
• Lymph nodes are found all through the
body, and act as filters or traps for
foreign particles
• They are important in the proper
functioning of the immune system
Lymph Node Structure
A. Pericapsular Connective Tissue and Fat
Tissue which clings to outside of node, holds
node in place, cushions it, ready supply of blood
for energy
B. Capsule
•
Dense outer covering which surrounds node
•
Trabeculae – inner branches of capsule
C. The Substance of the lymph node is
divided into:
• outer cortex
• inner medulla
D. Germinal Centers
• Dense, darkly stained round areas just
inside the capsule where certain WBCs are
produced
Vessels
• Multiple afferent lymph vessels bring
lymph into the lymph node
• The lymph gets slowly filtered through
the substance of the lymph node where
it encounters lymphocytes
• The efferent lymph vessel carries the
lymph out of the lymph node
Vessels
A. Artery
– Carries oxygenated blood from heart to
node
– Has a thick wall and quite small inside
diameter
– May contain visible blood cells
Vessels
B. Vein
– Carries used blood from node to heart
– Has a thinner wall and larger inside
diameter than the artery
– May contain visible blood cells
Vessels
C. Lymph
– Has almost no wall
– Has a very large
inside diameter
– Never contains
visible blood cells
Maintain the pressure and volume of extracellular fluid
by returning excess water and dissolved substances
from the interstitial fluid to the circulation