Lymphatic System

 

The lymphatic system consists of lymphatic vessels and lymphatic tissues (tonsils, adenoids, spleen and the thymus gland). It is a system of vessels similar to our blood vessels except that it is not 'circulatory' in nature i.e. the vessels are not continuous. All of the lymph vessels eventually exit the lymphatic system either into the interstitial space or into the circulatory system. 

 

lymph moves via a series of one-way valves, through  muscle contraction as you move around. This squeezes the lymph vessels in your body and causes the lymph to move towards your neck.

 

Functions

• Transport lymph (a clear liquid that contains no red blood cells)

• Return extra interstitial fluid (fluid that surrounds the tissue cells) and protein to the blood

• Destroy and filter unwanted material from the body fluids

• Start an immune response

 

Lymph Vessels

The smallest lymph vessels are microscopic capillaries that form 

branches which gradually get bigger forming trunks and finally ducts.

The ducts eventually drain back into the circulatory system via the

left and right subclavian veins.

 

Lymph vessels are semipermeable allowing the movement of large

molecules e.g. proteins to be removed from the interstitial space and

eventually returned to the circulatory system.

 

Lymph Nodes 

Lymph nodes are small round bean-shaped structures.

They act as a defense system and play an important role in the

immune system by removing foreign or unwanted material from the

lymph fluid, before it re-enters the circulatory system. Lymph nodes

contain many lymphocytes and macrophages (types of white blood

cells) which help fight infection. 

                                                                                                                     https://commons.wikimedia.org/wiki/File%3ALymphatic_system_(vector).svg

 

 

 

 

 

 

 

 

 

 

 

 

                                                                           

                                 https://commons.wikimedia.org/wiki/File%3AAnatomy_and_physiology_of_animals_Lymph_node.jpg

         

 

Lymph Tissues

This includes the tonsils, spleen and thymus gland 

 

Tonsils

These are located at the back of the throat, They are soft tissue

masses that contain macrophages and lymphocytes.

 

They act as a first line of defense from invasion of external

organisms. 

 

They act as protection against bacterial infection.

 

Lymph tissue is also found on the tongue,

adenoids, appendix and in the intestines.

 

​Image by Klem - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=3131446

 

 

Spleen

Located on the left side of the abdomen, just below the

diaphragm. It has a fibrous capsule that is divided into

compartments. It contains many lymphocytes and macrophages

(white pulp). The red pulp stores the blood.

 

The spleen acts as a reservoir for blood and destroys old

blood cells and platelets. It is also part of the immune system

because as blood passes through it, macrophages destroy any

microorganisms that have invaded the blood.

 

Image by Public Domain, https://commons.wikimedia.org/w/index.php?curid=1394146

 

 

 

Thymus Gland

The thymus gland is made up of two parts (lobes) and lies in

front of the top half of the heart. 

 

It plays an essential role in the immune system; fighting infections.

The thymus gland recieves immature lymphocytes (T cells) from

the bone marrow and turns them into cells that can fight/attack

any foreign cells. 

 

Image by Public Domain, https://commons.wikimedia.org/w/index.php?curid=1394154

 

 

 

 

 

 

The Immune System

The immune and lymphatic systems are closely related organ systems because they share several organs and  functions. 

 

The immune system is composed of specialized cells (white blood cells), various proteins, tissue and organs including the lymph nodes and lymph tissue (see above). 

 

The function of the immune system is to provide a defense system against pathogens such as  viruses, bacteria, fungi and parasitic animals. The immune system helps to stop harmful agents entering  the body and attacks those that do manage to enter.

 

White blood cells

White blood cells are the cells that help the body  fight infection. There are a number of different types and sub-types of white blood cells and each have different roles to play.

 

There are three main types of white blood cell - Granulocytes, Monocytes, Lymphocytes

 

• Granulocytes are phagocytes. They fight infection by surrounding and digesting any pathogens e.g. bacteria and viruses

• Monocytes are the largest of the blood cells. There are two main types. Dendritic cells identify cells that are antigens (foreign bodies) that need to be destroyed by lymphocytes,  and Macrophages that are phagocyte cells (fight infection by surrounding and digesting any pathogens)  

• Lymphocytes are small white blood cells that fight infection by either producing antibodies which destroy bacteria and viruses outside the cell (B cells), or by attacking the body cells that have been invaded by viruses from within (T cells)