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.