Structure and Functions of Lymphatic Tissue (Lymph)
1.0 Introduction to Lymphatic Tissues:
What is the Lymphatic System ?
The Lymphatic System is
one of the two systems of circulation of fluid around the body
(the other being blood
The lymphatic system consists of lymphatic fluid (called "lymph")
flowing through a system of lymphatic
vessels, including lymphatic
capillaries, other lymphatic vessels of various
sizes (which can be compared with blood
vessels), and lymph nodes (which
are encapsulated masses of B Cells and T Cells).
The Blood System and
System are interconnected. The clear fluid
that is known as "lymph" when flowing through the lympatic vessels,
initially passes into those vessels as "interstitial fluid" contained
in spaces between tissue cells - spaces into which it had been
filtered from blood. Ultimately, after travelling through lymphatic
vessels, the same lymph passes back into the blood system -
junctions of the jugular and subclavian veins (on both the
right- and left- sides of the body).
2.0 The tissues that form the Lymphatic
Several different types of tissues form the structures of the
They are listed according to the parts
of of the lymphatic system that they form:
(a) Primary Lymphatic Organs
The locations at which stem cells divide and mature into
B Cells and T Cells:
- Red Bone Marrow -
- The Thymus
- This is a two-lobed organ located in the chest.
The tissue of the thymus itself consists of
T cells, macrophages and epithelial cells. Each
lobe is encapsulated by a layer of connective
(b) Secondary Lymphatic Organs and Tissues
The locations at which most immune responses occur:
- Lymph Nodes -
These are small bean-shaped organs located throughout
the body and consisting of B cells that develop into
plasma cells - which secrete antibodies, T cells, and
macrophages. Each node is covered by a capsule of dense
- The Spleen
- This is the largest single mass of lymphatic
tissue in the human body.
The outer covering of the spleen is formed by
dense connective tissue.
The spleen itself consists of two types of tissue, called white
pulp and red pulp.
- Lymphatic Nodules -
Lymphatic Nodules differ from Lymph Nodes in that lymphatic
nodules are not surrounded by
capsules (of dense connective tissue). They are also
known as mucosa-associated lymphatic tissue (MALT).
(c) Lymph (Fluid)
The fluid "lymph" can be described
as a tissue in its own right - in the same way
as the fluid "blood" can be described
tissue". Lymph is a clear fluid that
is similar to plasma but contains less protein.
It flows through lymphatic vessels throughout
the body and includes chemicals and cells whose
composition varies according to location within
Despite being a fluid, lymph is classified
as a connective tissue.
3.0 Where in the body are the
As explained above, there are lymphatic
tissues throughout the body.
However, the structure of lymphatic tissues vary
according to the particular type of lymphatic tissue or organ
they form a part of - (a), (b)
or (c) above, and possibly also it's location in the body -
especially in the case of (c) Lymph (Fluid).
4.0 The Structure (Physical Description)
Lymph is a clear fluid that is similar to (blood)
but contains less protein.
5.0 The Functions of
The lymphatic tissues throughout the body operate in conjunction
with each other to perform the functions of the lymphatic system.
The lymphatic system is part of the body's immune system. The
functions of the lymphatic system include:
- Draining interstitial fluid.
- Transporting dietry lipids.
- Protecting the body (organism) against invasion/infection
See also related pages about: the
structure and functions of blood (similar information
to that on this page - but in more detail;
most of the information on this page is extracted from
the main "The Structure and Functions of Blood"
page), the Glossary Pages about the
components of blood, the
structure and functions of blood vessels (related
information), and blood
pressure (related information).