Lymphatic System
MAIN FUNCTION OF LYMPHATIC SYSTEM
All body tissues
are bathed in a watery fluid derived from the blood stream. This intercellular
or tissue fluid is formed when blood passes trough the capillaries. The
capillary walls are permeable to all components of blood except the R.B.C’s
& blood proteins. The fluid passes from the capillary into the
intercellular spaces as the inter-cellular or tissue fluid. About 85% of the
tissue fluid returns into the blood at the venous end of capillary. The rest 15
% of tissue fluid drains into lymphatic capillaries as lymph along with
W.B.C’s, cell debris & micro organism like Bacteria , are transported back
to the heart through lymphatic system.
COMPONENTS OF LYMPHATIC SYSTEM
Lymphatic System
Consists of
1. Lymph
2. Lymphatic tissues
3. Lymphatic vessels or Lymphatics
4. Lymph nodes (type of lymphatic tissue)
DETAILS OF COMPONENTS
1. LYMPH
DEFINITION
“Lymph is the name given to the
tissue fluid once it has entered a lymphatic vessel. OR It can be defined as
“Colour less body fluid that contains lymphocytes (agranular WBC’S), small
proteins & fats”.
EXPLANATION
Lymph is a medium of exchange between blood & body
cells. It takes the fluid substances from cell of tissues & intercellular
spaces, which cannot penetrate the blood capillaries.
2.LYMPHATIC TISSUES
DEFINITION
“Lymphatic tissues are a type
of connective tissues that contain large no. of lymphocytes”
ORGANS THAT CONTAIN LYMPHATIC
TISSUES
Lymphatic tissue is organized into following structures
(organs).
§ Lymph nodes
§ Thymus
§ Spleen
§ Tonsils
§ Some of the patches of tissues in vermiform appendix & in
small intestine.
FUNCTION
Lymphatic tissue is essential for immunologic defenses of
the body against viruses & bacteria.
3. LYMPHATICS
DEFINITION
Lymphatic vessels or lymphatics are blind tubes that
assist the cardiovascular system in removal of tissue fluid from tissues spaces
of the body, the vessels then return the fluid to the blood.
AREAS WHERE LYMPHATIC ARE NOT
PRESENT
Lymphatics are present in all tissues & organs of the body
except.
§ Central Nervous System
§ The eye ball
§ Internal Ear
§ Epidermis of Skin
§ Cartilage & bone
TYPES
Two Types of Lymphatics are there:-
SMALL - LYMPH CAPILLARIES
LARGE - LYMPH VESSELS.
1. LYMPH CAPILLARIES
DEFINITION
“Lymph capillaries are a network of thin walled,
anastomosing, microscopic vessels which are closed towards the tissue sinuses
& drain the Lymph from tissues.”
2. LYMPH VESSELS
DEFINATION
The capillaries are in turn drained by lymph tubes having larger diameters
& beaded appearance, called the Lymph vessels.
These vessels contain smooth muscles in them as well as Internal valves to
prevent the back flow of Lymph. The Lymph circulates through the Lymph vessels
by the contraction of surrounding skeletal muscles in one direction (towards
the heart). These vessels converge into collecting ducts i.e right
Lymphatic duct & thoracic duct that drain into large veins at the root of
neck.
4. LYMPH NODES
DEFINITION
“Lymph nodes are lymphoid
tissue which are present through out the course of Lymphatics, through which
the lymph must passes”
INTERNAL STRUCTURE
Each node consists of a thin, fibrous, outer capsule &
an inner mass of lymphoid tissue.
AFFERENT VESSELS
Several small Lymphatics which carry the lymph into the
lymph node are referred to as “Afferent vessels.”
EFFERENT VESSEL
A single large vessel which carry the lymph away from the
node is called “Efferent vessel”
FUNCTION
Lymph nodes act as filters that trap the microorganisms
& other foreign bodies in the lymph. The Lymphocytes & macro-phages
present here, neutralize & engulf the microorganisms, respectively.
MAJOR FUNCTIONS OF LYMPHATIC SYSTEM.
From Text Book Pg.
379.
EDEMA
DEFINITION
“Whenever the tissue fluid
accumulates rather than being drained into the blood by the lymphatic system,
tissue & body cavities become swollen. This condition is known as “Edema”.
TYPES OF EDEMA
There are two types
of Edema.
1. INTRACELLULAR
2. EXTRACELLULAR
1. INTRACELLULAR EDEMA
“Accumulation of
excess of fluid within the cells causing cellular swelling is called “Intra
cellular Edema. It usually occurs after severe extracellular Edema.
2. EXTRACELLULAR EDEMA
“Excess fluid
accumulation in extra cellular spaces is called Extracellular Edema. ”
It is the most commonly occurring form of Edema.
FACTORS CAUSING EDEMA
Any factor that
increases the tissue fluid high enough than normal value can cause excess
tissue fluid volume causing edema. Some of these factor are as follows.
§ High blood pressure
§ Kidney failure
§ Hart failure & etc.
CAUSES OF EDEMA
Following are three
main causes of Edema.
1. HYPOPROTEINEMIA (SEVERE
DIETARY PROTEIN DEFICIENCY)
When body is starving for Amino acids, it consumes its own
blood proteins. This reduces the osmotic potential of the blood causing tissue
fluid to accumulate in body tissues rather than being drawn back into
capillaries, resulting in Edema.
2. LYMPHATIC OBSTRUCITON
(COMMONEST CAUSE –FILARIASIS )
Another cause of edema is lymphatic obstruction, which
results in more & more protein collection in the local tissue fluid hence,
the increased volume. Commonest cause of lymphatic obstruction is FILARIASIS
(infection by NEMOTODES) such condition is also called as “Elephantiasis”
(because of swollen legs).
3. INCREASED PERMEABILITY OF
CAPILLARIES (CAUSES-BURNS & ALLERGIC REACTIONS)
Sometimes the permeability of capillaries increase due to
burns or allergic reactions, so blood proteins & plasma come out of
capillaries & enter the tissue fluid thus causing Edema.
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