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Lymphatic system

The lymphatic system is part of the circulatory system and comprises a network of lymphatic vessels that carry lymph fluid directionally towards the heart. The lymph system transports excess interstitial fluid, fatty acids, and immune cells. It has multiple functions including fluid removal from tissues, absorption and transport of fats, and transportation of white blood cells and antigen-presenting cells to lymph nodes to stimulate immune responses. The lymphatic system consists of lymphatic vessels, lymphoid tissues found throughout the body, and lymphoid organs such as lymph nodes, spleen, thymus, and tonsils that are involved in immune defenses.

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The Department of Human anatomy LYMPHATIC SYSTEM
• The lymphatic system is part of the circulatory system, comprising a network of conduits called lymphatic vessels that carry a clear fluid called lymph (from Latin lympha "water goddess") directionally towards the heart.
• The lymph system is not a closed system. The circulatory system processes an average of 20 litres of blood per day through capillary filtration which removes plasma while leaving the blood cells. Roughly 17 litres of the filtered plasma actually get reabsorbed directly into the blood vessels, while the remaining 3 litres are left behind in the interstitial fluid. • The primary function of the lymph system is to provide an accessory route for these excess 3 litres per day to get returned to the blood.Lymph is essentially recycled blood plasma.
The lymphatic system has multiple interrelated functions • It is responsible for the removal of interstitial fluid from tissues • It absorbs and transports fatty acids and fats as chyle from the digestive system • It transports white blood cells to and from the lymph nodes into the bones • The lymph transports antigen-presenting cells (APCs), such as dendritic cells, to the lymph nodes where an immune response is stimulated.
Sponsored Medical Lecture Notes – All Subjects USMLE Exam (America) – Practice
LYMPHATIC SYSTEMS consists of: 1) lymphatic vessels 2) lymphoid tissues and lymphoid organs
travel along with blood vessels. 1) lymphatic vessels
lymphatic capillary lymphatic trunks lymphatic collecting vessels lymphatic ducts Lymphatic vessels start with lymphatic capillaries
- blind ended vessels - permeable to proteins even cells
The main function - collect excess large particles and tissue fluid lymph
Special lymph capillaries --- Lacteals - collect digested fats ( in chylomicrons)
Lymph driven by rhythmic contractions Valves are present to prevent backflow.
connection to the veins
How is fluid moved? - Contraction of skeletal muscles against lymphatic vessels - Smooth muscle contraction - Valves in lymphatic vessels - Breathing Obstruction of system leads to edema
Elephantiasis – blockage by parasitic worms
Role of Lymph Vessels in Metastasis
LYMPHATIC SYSTEMS consists of: 1) lymphatic vessels 2) lymphoid tissues and lymphoid organs
LYMPHOID TISSUE - diffusely located throughout body in all organs - contains germinal centers with dense population of B lymphocytes - houses macrophages - Function: host defense
LYMPHATIC SYSTEMS consists of: 1) lymphatic vessels 2) lymphoid tissues and lymphoid organs
Include: Function: host defense eliminates abnormal (sick, aged, or cancerous) cells and pathogens Lymph Nodes Spleen Thymus Tonsils lymphoid organs
Lymph Nodes lymphoid organs - Macrophages and lymphocytes attack microorganisms Swollen lymph nodes is caused by expansion in the number of lymphocytes
Lymphocytes develop in lymph nodes (after they are formed in the bone marrow) T cells develop in the thymus and then enter the circulation Macrophages and dendritic cells “present” antigen in the lymph nodes
Lymph Nodes Spleen lymphoid organs - site for immune surveillance and response - removes debris, foreign matter, toxins, bacteria, viruses, old blood cells - readily subject to rupture from mechanical trauma
Lymph Nodes Spleen Thymus lymphoid organs - site of maturation of T lymphocytes - secretes hormones (thymopoietin and thymosins) - critical role in childhood
Lymph Nodes Spleen Thymus Tonsils lymphoid organs - trap and destroy bacteria
Defenses Against Pathogens • 1) Nonspecific defenses - broadly effective, no prior exposure 1) external barriers 2) inflammation 3) fever • 2) Specific defense - results from prior exposure, protects against only a particular pathogen – immune system
1) External Barriers • Skin – toughness of keratin – dry and nutrient-poor – defenses: peptides neutrophils attack microbes – lactic acid (acid mantle) is a component of perspiration • Subepithelial areolar tissue – tissue gel: viscous barrier of hyaluronic acid – hyaluronidase: enzyme used by pathogens (snake bites and bacterial toxins
• Mucous membranes – stickiness of mucus – lysozyme: enzyme destroys bacterial cell walls 1) External Barriers
2) Inflammation • Cardinal signs – redness (erythema) caused by hyperemia (↑ blood flow) – swelling (edema) caused by ↑ capillary permeability and filtration – heat caused by hyperemia – pain caused by inflammatory chemicals and pressure on nerves
2) Non Specific Immunity - Inflammation • Defensive response to tissue injury – limits spread of pathogens, then destroys them; removes debris, initiates tissue repair – suffix -itis denotes inflammation of specific organs