The immune and lymphatic systems are two closely related organ systems that share several organs and physiological functions.

The immune system is our body’s defense against infectious pathogenic viruses, bacteria, and fungi as well as parasite and protists.

The immune system works to keep these harmful agents out of the body and attacks those that manage to enter

Introduction

Immune systemFunction of the immune system:

1. Has the ability to distinguish "self" from "non-self“

molecules (foreign substances).

2. Has the ability to neutralize or inactivate foreign molecules

(such as soluble molecules present in viruses, bacteria, and

parasites)

3. Destroy microorganisms or other cells (such as virus

infected cells, cells of transplanted organs, and cancer

cells).

Immune system

Autoimmune diseases :

The immune system of an individual reacts against its own

normal body tissues or molecules, causing autoimmune

diseases.

Immune system

The cells of the immune system:

1. Are distributed throughout the body in the blood, lymph,

epithelial and connective tissues.

2. Are arranged in small spherical nodules called lymphoid

nodules found in connective tissues and inside several

organs.

3. Are organized in larger lymphoid organs—the lymph nodes,

the spleen, the thymus, and the bone marrow.

4. Example to the immune cells- neutrophils, macrophages,

cytotoxic natural killer (NK). B .cell, T .cell, dendritic cell……

The lymphatic system is part of the circulatory system, comprising a network of lymphatic vessels that carry a clear fluid called lymph (from Latin lympha meaning water) directionally towards the heart . The lymph has a number of functions, including:Helps the body to get rid of toxins, waste and other unwanted materials Removal of interstitial fluid ( extracellular fluid of most tissue). It also acts as a highway, transporting white blood cells to and from the lymph nodes, and antigen-presenting cells to the lymph nodes.

LYMPHATIC SYSTEM

LYMPHATIC SYSTEM

1.Lymphatic vessel

2.Lymphoid organs

The lymphatic system is comprised of :

Lymphatic system

1. Lymphatic vessels:

which transport interstitial fluid (lymph) back to the blood

circulation

2. Lymphoid organs:

which house lymphocytes and other cells of the body's immune

defense system

Lymphoid organs

Lymphoid organs

Primary lymphoid organs

Secondary lymphoid organs

• Bone marrow• Thymus

• Lymph node• Spleen• Tonsils

Thymus

Thymus: primary lymphoid organ, composed of two identical

lobes and is located anatomically in front of the heart and

behind the sternum(is a long flat bony plate shaped like a capital

"T" located anteriorly to the heart in the center of the chest)

Thymus

Lobule :

Each lobule contain lymphoid tissue

Consist of :

Peripheral cortex

Central medullas

Interlobular septum

Thymic corpuscle

ThymusCortex: The cortical portion is mainly composed of lymphocytes, supported by a network of finely-branched epithelial reticular cells, which is continuous with a similar network in the medullary portion. The cortex is the location of the earliest events in thymocyte development Medulla: In the medullary portion, the reticulum is coarser than in the cortex, the lymphoid cells are relatively fewer in number. The medulla is the location of the latter events in thymocyte development.

Both cortex and medulla contain small lymphocyte (Called in this particular location as thymocytes.No lymphatic nodules are present in the thymus.

Thymus

Function of the thymus:

1.Production of T-Lymphocyte

2.Production of Thymosin

Function of Thymosin:

stimulates the development of T cells

Thymus

Development of thymus gland:

• This organ varies in size and development with the age of

the individual.

• After birth it continues to grow and attains its maximum

development around puberty.

• It decrease in size and its is gradually replaced by fat and

connective tissue

• In the old age very little thymatic tissue remains.

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