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.