Lymphatic System Gross Anatomy ANHB Avinash Bharadwaj

Blood, Tissue Fluid and Lymph Blood capillaries “Extravasation” of fluid Tissue fluid and exchange Not all the fluid returns to blood vessels. Lymph flows through lymphatic vessels before returning to larger veins. Lymph may contain micro-organisms and other “unwanted” material  Needs to be “filtered”  Lymph nodes : More than physical filters

Lymph Nodes Histological structure and function : Friday! Small structures – few mm in size Scattered all over the body Regional groups and “drainage territories” Variable number and pattern Broad principles

Lymphatic Drainage – Concepts – 1 Importance  Infections  Infectious agents carried by lymph  Immune responses in lymph nodes  Enlargement of lymph nodes  Malignancies (cancers)  Cancerous cells break loose from the main mass  Carried by lymph  Trapped in lymph nodes  further growth   Enlargement of nodes (destruction of normal structure)  Diseases of lymph nodes  Some specific infections

Lymphatic Drainage – Concepts – 2 Lymphatic vessels form plexuses Series of lymph nodes  Usually two to four sets before bloodstream Many routes of drainage  Blockage may lead to opening of alternative routes  Different descriptions and terminology

Regional Nodes – Limbs Upper limb  First nodes around the elbow (few)  Major sets in the axilla  Also drain abdominal and thoracic walls including the breast Lower limb  First nodes behind the knee  Major sets in the groin (inguinal region)  Also drain abdominal wall, lower back, perineum

Regional Nodes – Head and Neck Superficial and deep General direction of flow : superficial  deep Superficial nodes in the superficial fascia Deep nodes mainly around carotid sheath

Regional Nodes – Thorax Thoracic wall – Axillary! Thoracic viscera  Nodes around trachea and bronchi  Tracheobronchial  Bronchopulmonary  Also : paratracheal, paraoesophageal

Regional Nodes – Abdominal Wall Axillary and Inguinal  Boundary (“Watershed”) through the umbilicus No lymph nodes in the wall itself

Regional Nodes : Abdominal Viscera Multiple sets especially for the GI Tract Final set around the aorta Developmental correlation  GIT Tract – unpaired midline structures  Nodes in front of the aorta : preaortic  Other organs – paired, lateral  Kidneys, suprarenals, gonads  Nodes lateral to aorta : para-aortic

Digestive System Organs Nodes close to the wall of the organ Nodes along the arteries Preaortic nodes Illustrated by the colon here.

Abdominal Nodes at a Glance Para-aortic (also called lateral aortic)  Upper : paired glands (note : these include the gonads!)  Also drain lymphatics along lumbar arteries  Lower nodes : drain inguinal nodes Pre-aortic – grouped around the origins of the three arteries. All abdominal nodes  cisterna chyli  thoracic duct Lateral Pre- Lymphangiography Last Slide