lymphatic system.doc

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Lymphatic system

Lymphatic vessels

Lymphatic vessels originate as tiny hair-like capillaries in the interstitial spaces between cells.The walls of these vessels are thin and more permeable than the walls of blood capillaries. These

capillaries join together to form larger lymphatic vessels that are similar in structure to veins, butthinner. Like veins, they have valves to prevent lymph passing backwards into the tissue. Unlike

the circulatory system however, lymph is not pumped around the body, it depends on the

movement of muscles, breathing and gravity. Lymphatic vessels accompany veins and arteries

and are often found superficially.

All of the lymphatic vessels eventually converge into either the thoracic ductor the right

lymphatic duct. The thoracic duct is about 45 cm long and forms the largest confluence of

lymphatic vessels in the body. It receives lymph from the left side of the body as well as thelower right side(below abdomen). It originates at thecisterna chyli, a small pouch that lies

abdomen. From here the thoracic duct ascends the thorax, lying to the left of the vertebral

column. It then joins with vessels from the neck and empties into the left subclavian vein at its

junction with the left internal jugular vein.

The right lymphatic ductis much shorter than the thoracic duct and may only be 1 cm long. It is

formed by the confluence of several lymphatic vessels, which drain the right side of the head and

thorax, and the right arm. It drains into the junction of the right subclavian and right internal

jugular veins.

Lymphatic nodes

Lymph nodes are small bean shaped nodules that appear along the course of the lymphaticvessels. A number of afferent lymphatic vessels enter the node and disperse the lymph into the

lumen of the node. The lymph is then collected from the lumen and leaves the node in an efferent

lymphatic vessel which leaves the node at the hilum. Lymph nodes are full oflymphocytes andmacrophages,reticular tissue .in between there is gap called as trabecula. These structure is

held together by matrix of connective tissue. and function of lymphatic tissue are.

1. Filter pathogens from the lymph.

2. Provide lymphocytes for the blood.

3. Produce antibodies.

Lymph nodes usually appear in groups in certain positions of the bodyt,the common lymph node

are.

Nodes Position Drain

Facial Face Face


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Cervical Neck Head and neck

Axillary Armpit Upper limb, breast and thorax

Inguinal Groin Lower limb

Popliteal Behind the knee Leg

Abdominal Surrounding abdominal organs Abdomen

Thoracic Surrounding thoracic organs Thorax

Spleen

The spleen is involved with the circulatory and lymphatic systems. It functions to produce white

blood cells, recycle old blood cells, as well as fight infection.

The spleen is a bean shaped organ about 12 cm long and 7 cm wide. It lies high on the posteriorabdominal wall on the left side of the abdomen, behind the stomachand above the left kidney.

The spleen receives blood from the aorta via the splenic artery, and is drained by the splenic

vein. It is a mass ofsplenic pulp held together by a mesh of connective fibres which enclose it in

a capsule. The pulp is made up of many types of cell including lymphocytes andphagocytes.Pulpmay be either white pulp which contents lymphocyte and red pulp that content redcell.

Function

As blood flows through the spleen, any pathogens within it are attacked by lymphocytes in the

splenic pulp.Macrophages in the spleen also remove worn-out red and white blood cells andplatelets. This breakdown of haemoglobin produces the pigment bilirubin, which is released into

the blood plasma. Bilirubin is removed from the blood by the liver and kidneys and is excreted in

the bile and to a lesser extent in the urine. It act as immune fuction in our body. It also act asreservoir of the blood

Diffuse lymphatic tissue

Lymphatic tissue also occurs in places other than specialised lymphatic structures like the nodesor spleen. Lymphatic tissue can be found in thepalatine and pharyngeal tonsils, the thymus

gland, the small intestine and the appendix.

Functions of the lymphatic system

The lymphatic system has three main functions, to maintain fluid balance, to defend the bodyagainst disease by producing lymphocytes and to absorb fats from the intestine and transport

them to the blood.

1. Fluid balance


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The fluid which release from the arterial end of the capillaries but the total volume of the

fluid the leak from the capillaries can not go back to venous end of capillaries these

interstitial fluid is called as Lumph and get transported via lymphatic vessels so it helpsin fluid balance .

2. DefenceLymphatic vessels empty the tissue fluid into the lymph nodes before returning it back to

the blood steam. It is here that any foreign cells i.e. viruses, bacteria and fungi orchemicals which are harmful to the body (pathogens) are detected and removed bylymphocytes (white blood cells) which congregate in the lymph nodes. Once a foreign

microorganism has been detected an immune response is triggered and the lymphocytesin the lymph node multiply.

3. Digestion

Some fats are too large to pass through the capillary walls of the small intestine andtherefore can not be absorbed. Lymphatic vessels known as lacteals can absorb these

large fats and transports them into the venous circulation via the thoracic duct. When the

lymph contains fat it becomes milky and is known as chyle.

Antigen:-The foreign substance when they enter into our body they stimulate immune system toproduce antibody

Antibody:-The defensive structure that is produced by our immune system .

Imuunity:-The defensive power of our body called as immunity

Types of immunity

Innate:-That derived at the time of birth

Acquired:-Immunity that is acquired during the course of life

Acquired immunity may be active immunity of passive immunity

Active immunity is the immunity produced by our body with the stimulation of

antigen(vaccination,infections) and passive immunity means transferring preformed antibody to

our body(Inj. Of different type of immunoglobulin) called as passive immunity.

Active immunity may be long term immunity of short term immunity.


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