LYMPHATIC SYSTEM

Lymph

Tissue fluid (interstitial fluid) that enters the lymphatic vessels

• Essentially a drainage system accessory to venous system
• Larger particles that escape into tissue fluid can only be removed via lymphatic system

Functions

• Network that filters antigens from the interstitial fluid
• Primary site of immune response from tissue antigens
• Lymphatic drainage in all organs of the body except brain, eyes, marrow and cartilage
• Flaccid thin walled channels → progressive caliber
• 600 lymph nodes in body
• Slow flow, low pressure system returns interstitial fluid to the blood system

Components of lymphatics

• Lymph
• Lymphatic Vessels
• Lymphatic Organs
• Lymphatic cells

 Lymphatic Capillaries

Features of structure:

• Blind end
• Single layer of overlapping endothelial cells
• More permeable than that of blood capillary
• Absent from avascular structures, brain, spinal cord splenic pulp and bone marrow

Lymphatic Vessels

• Three layered wall but thinner than vein
• More numerous valves than in vein
• Interposed by lymph nodes at intervals
• Arranged in superficial and deep sets

Lymph Trunks

• Right and left jugular trunks
• Right and left subclavian trunks
• Right and left broncho mediastinal trunk
• Right and left lumbar trunks
• Intestinal trunk

Lymphatic Ducts

• Right lymphatic duct
• Thoracic duct

Lymphatic Cells

• Also called lymphoid cells
• Located in both the lymphatic system and the cardiovascular system.
• Work together to elicit an immune response.

Types of lymphatic cells are:

• Macrophages
• Epithelial cells
• Dendritic cells
• Lymphocytes

Lymphatic Organs

• Primary organs
    * Red bone marrow
    * Thymus gland
• Secondary organs
    * Lymph nodes
    * Lymph nodules
    * Spleen

Lymph nodes:

• Capsular shell
• Fibroblasts and reticulin fibers
• Macrophages
• Dendritic cells
• T cells
• B cells

Lymphangitis

• Inflammation of the lymph vessels
• Commonest cause bacteria called streptococcus pyogenes(most common).
• Lymph vessels appear as red streaks through the skin 

Lymphedema

• Occurs due to accumulation of lymphatic fluid in the interstitial tissue
• Sometimes can be appreciated after wearing tight clothing or jewelry on affected limb

Lymphadenopathy

• Means a disease of the lymph nodes
• Lymph nodes become swollen/ enlarged and may be painful to touch

Lymphomas

• Cancers originating either from the lymphocytes in the lymph nodes or the lymphatic tissue in organs

Tonsillitis

• Infection of the pharyngeal tonsils
• Tonsils are swollen, Fever and pain during swallowing usually present