LYMPHETIC SYSTEM

Lymphatic system

Introduction:

•        Components:

–       Lymph is the fluid

–       Lymphatics nodes

–       Structures & organs

•         Functions:

–       Return tissue fluid to the bloodstream.

–       Transport fats from the digestive tract to the bloodstream.

–       Surveillance & defense.

Lymphatics:

•        Originate as lymph capillaries

•         Capillaries unite to form larger vessels

–       Resemble veins in structure

–       Connect to lymph nodes at various intervals

•         Lymphatics ultimately deliver lymph into 2 main channels:

–       Right lymphatic duct:

§  Drains the right side of head & neck, right arm, right thorax

§  Empties into the right subclavian vein

–       Thoracic duct:

§  Drains the rest of the body

§  Empties into the left subclavian vein.

Main channels of lymphatics:

Lymphatic tissues:

•        3 types:

–        Diffuse lymphatic tissue:

§  No capsule present.

§  Found in the connective tissue of almost all organs.

–        Lymphatic nodules:

§  No capsule presents.

§  Oval-shaped masses.

§  Found singly or in clusters.

–        Lymphatic organs:

§  Capsule present.

§  Lymph nodes, spleen, thymus gland.

Lymph nodes:

•        Oval structures located along lymphatics.

•         Enclosed by a fibrous capsule.

•         Cortex: outer portion

–       Germinal centers produce lymphocytes

•        Medulla: the inner portion

Medullary cords:

•         Lymph enters nodes through afferent lymphatics, flows through sinuses, exits through efferent lymphatic.

Tonsils:

•        Multiple groups of large lymphatic nodules.

•         Location: mucous membrane of the oral and pharyngeal cavities

•         Palatine tonsils:

–       Posterior-lateral walls of the oropharynx

•         Pharyngeal tonsil:

–       The posterior wall of the nasopharynx

•         Lingual tonsils:

–       Base of tongue

Spleen:

•        Largest lymphatic organ

•         Located between the stomach & diaphragm

•         A structure like a node:

–       Capsule present

–       But no afferent vessels or sinuses

•         Histology:

–       The red pulp contains all the components of circulating blood

–       White pulp is like lymphatic nodules

•         Functions:

–       Filters blood

–       Stores blood

Thymus gland:

•        Location: behind the sternum in the mediastinum

•         The capsule divides it into 2 lobes

•         Development

–       Infant: conspicuous

–       Puberty: the maximum size

–       Maturity:  decreases in size

•         Function

–       Differentiation and maturation of t cells

The function of the lymphatic system:

•        Defense against harmful organisms and chemicals

•         2 types of defense:

–       Nonspecific

–       Specific

•         Specific defense: immunity:

–       Humoral immunity involves b cells that become plasma cells that produce antibodies that bind with specific antigens.

–       Cell-mediated immunity involves t cells that directly destroy foreign cells.