The Lymphatic System

By Emily Lopez, Alejandro Campos, and Jennifer Leon

What Is the Lymphatic System?

It is the network of vessels in which lymph drains from the tissue into the blood

It is composed of lymph vessels, lymph nodes, the spleen, the thymus, tonsils, and bone marrow.

Functions of the Lymphatic System

The functions of this system include: the absorption of excess fluid and its return to

the blood stream Absorption of fat (In the villi and small intestine) Its Immune System Response

Lymph Vessels

Thin walled, valve structures that carry lymph Complementary to the cardiovascular system Lined by endothelial cells, a thin layer of smooth

muscles, and adventitia(binds lymph vessels to surrounding tissue)

Types of vessels: Afferent vessels, Efferent vessels, and Lymph Trunks

Different types of Lymph Vessels

Afferent lymph vessels: Carries unfiltered lymph into the node Found only in the lymph nodes

Efferent lymph vessels: Carries filtered lymph out of the node Found in the thymus and spleen

Lymph Trunk: Carries lymph and is formed by confluence of many efferent lymph vessels

Different types of Lymph Vessels(Cont…)

Lymph Trunks carry lymph and then drain them into either the right lymph duct, or the thoracic duct.

There are four pairs and one unpaired lymph trunk: Jugular Lymph Trunk Subclavian Lymph Trunk Bronchomediastinal Lymph Trunk Lumbar Lymph Trunk Intestinal Trunk(unpaired)

Lymph Nodes

Lymph nodes are areas of concentrated lymphocytes and macrophages along the lymphatic veins.

Located in the neck, armpit, groin, center of chest and abdomen

Act as filters for foreign particles and cancer cells Do NOT deal with toxicity

They become inflamed or enlarged in various infections and diseases

The Spleen

It is a reservoir for blood It filters the blood and lymph fluid that flows

through It sits under the rib cage in the upper left part of the

abdomen towards the back

The Thymus

secretes hormone, thymosin, that causes pre-T-cells to mature into the T-cells

The Bone Marrow

contains tissue that produces lymphocytes All lymphocytes derive from stem cells in the

bone marrow

Absorption(and return) of Fluid

The Lymphatic System returns excess interstitial fluid(A.K.A tissue fluid) to the blood

Lymph capillaries pick up the excess interstitial fluid and proteins and return them to the venous blood When the fluid enters the lymph capillaries it is

called lymph

Fluid Formation

Lymph starts as Interstitial fluid The interstitial fluid forms at the end of

the arterial end of capillaries, through which hydrostatic pressure pushes outward, creating a fluid similar to plasma in terms of function. Interstitial fluid maintains equilibrium by osmotic pressure, which pushes water into the capillaries due to solubility.

90% returns to the venules. The other 10% enters the lymph capillaries making it now lymph

Absorption of Fat

The Lymphatic system’s second function is the absorption of fats and fat-soluble vitamins from the digestive system, and the transport of these to the venous circulation

There are lymph capillaries called lacteals in the villi of the small intestine that absorb fats and fat solubles

Immune System Function

Lymph nodes and other lymphatic organs filter the lymph to remove microorganisms and other foreign particles

The nonspecific responses are the first line of defense

Highly specific responses are the second line of defense and are tailored to an individual threat

Non-specific vs. Specific

Non-specific vs. Specific

The immune response includes both specific and nonspecific components

Nonspecific responses block the entry and spread of disease-causing agents.

examples: Physical Barriers(skin), Inflammation, the Complement system, and Immune Response

Non-specific vs. Specific(cont…)

Specific responses generate to specific invaders. The immune system is more effective than the

nonspecific methods, and has a memory component that improves response time when an invader of the same type (or species) is again encountered(antibodies)

Specific Cells

T-Cells

A.K.A “T lymphocytes” Act as helpers to other immune cells or attack

pathogens directly After an infection, memory T cells persist in the

body to provide faster reaction to the same antigen

B-Cells

A.K.A “B lymphocytes” Form plasma cells to produce antibodies These antibodies neutralize the pathogen until other

immune cells destroy it

NK-Cells

A.K.A Natural Killer Cells Lymphocytes that respond to a wide range of

pathogens and cancerous cells

Non-Specific Cells

Macrophages

A phagocyte that consumes pathogens, destroys cells, and debris by phagocytestosis

Dendritic Cells

They detect pathogenic antigens which activate T and B cells to help body fight off parasites

Eosinophils

granular leukocytes that reduce allergic inflammation and help body fight off parasites

Basophils

granular leukocytes that trigger inflammation by releasing heparin and histamine

Neutrophils

granular leukocytes that act as the first responder to the site of infection

Neutrophils use chemotaxis to detect chemicals produced by the infection agents

Inflammatory Response

1. Damaged cells release histamine, a chemical messenger, that increases blood flow to the infection site

2. Inflammation produces heat; unfavorable to microbes; promotes healing; raises mobility of W. blood cells; increases metabolic rate of cells

3. Capillaries pass fluid into interstitial areas, which causes swelling

4. Clotting factors trigger blood clots

5. Monocytes clean up dead microbes, cells, and debris

Allergen Response

Allergies result from immune system hypersensitivity to weak antigens that do not cause an immune response in most people

Some allergens include dust, molds, pollen, certain foods and some medicines

1. After an exposure to an allergen, some people make IgE antibodies as well as B and T memory cells

2. Subsequent exposure to the same allergen releases IgE antibodies

3. IgE antibodies bind to mast cells, which then releases histamine

1. In some individuals, histamine causes life-threatening anaphylaxis

The Cardiovascular System vs. The

Lymphatic System

The Cardiovascular System

I. Carries oxygen throughout the body

II. Flows in a continues loop

III. Uses a pumping action

IV. Blood is filtered by kidneys

The Lymphatic System

I. collects and removes waste left behind in tissue

II. Flows in an open circuit and only one direction

III. Flows passively into the lymph capillaries by movement such as breathing, muscle movement and blood pumping

IV. Invisible and difficult to detect damage

V. Filtered by lymph nodes throughout the body

Bibliography

Boundless. Cardiovascular and Lymphatic System Defenses. 1 January 2015. Webpage. 23 March 2015.

Farabee, M.J. Lymphatic System and Immunity. 2001. Webpage. 23 March 2015.

Knowedgebase. Lymphatic versus Cardiovascular Systems. 11 December 2013. Article. 23 March 2015.