Lymphatic System

CHAPTER 20-THE LYMPHATIC SYSTEM

I. FUNCTIONS OF THE LYMPHATIC SYSTEM

A. Draining Excess Interstitial Fluid

B. Transporting dietary lipids

1. Lymphatic vessels transport lipids and lipid-soluble vitamins (A, D, E, and K) absorbed in

the gastrointestinal tract throughout the body.

C. Immune responses

II. THE LYMPHATIC SYSTEM

A. This system is composed of two primary parts:

1. Lymphatic Vessels which transport fluids back to the blood that have escaped from the blood.

2. Lymphatic Organs which are scattered throughout the body.

III. TYPES OF LYMPHOID CELLS

A. Lymphocytes-serve as the primary cells of the immune system.

1. These develop in red bone marrow and mature into one of two types of immunocompetent cells:

a. T Cells (T Lymphocytes)-these manage immune responses and some directly attack

and destroy foreign cells.

b. B Cells (B Lymphocytes)-protect the body by producing plasma cells. Plasma cells secrete

antibodies into the blood. Antibodies attach to and immobilize antigens until they can be

destroyed.

B. Lymphatic Macrophages-protect the body by phagocytizing foreign substances and by activating T Cells.

C. Dendritic Cells-are also phagocytes on foreign substances.

D. Reticular Cells-produce a network of protein fibers that support cells in the lymphoid organs.

IV. LYMPHATIC VESSELS

A. These vessels remove interstitial fluid and proteins and return them to the bloodstream. Once the

Interstitial fluid enters lymphatic vessels, it is known as lymph.

B. The Lymphatic Vessels

1. These vessels begin as Lymphatic Capillaries which are small vessels located in the spaces

between cells. Lymphatic capillaries are typically closed at one end (unlike capillaries).

a. Lymphatic capillaries are not found in bone marrow or nervous tissue.

b. Lymphatic capillaries are composed of very thin endothelial cells whose ends overlap.

1) The ends of these cells are easily...