Lesson objectives To describe the structure of the lymphatic system To explain how the lymphatic system works To identify the main lymph nodes of the body

Structure of Lymphatic System Lymphatic capillaries Lymphatic vessels Lymph nodes Lymphatic ducts

Lymphatic capillaries Structure: fine, blunt-ended permeable tubes, composed of a single layer of thin cells

Lymphatic vessels Structure: thin-walled, collapsible vessels similar to veins but carrying lymph not blood

Lymph nodes Structure: each node is made of lymphatic tissue, surrounded by a wall of tough, white fibrous tissue

Right lymphatic duct Empties into right subclavian vein to rejoin circulatory system Function: receives all drained lymph from right side of head, chest and neck and from right arm

Thoracic duct Empties into subclavian vein to rejoin circulatory system Function: collects and drains lymph from left side of head, the neck, both lower limbs, left side of trunk and left arm

What is the lymphatic system? Lymphatic system is a secondary circulation, helping blood circulation carry out its functions Blood travels to and from the tissues delivering nutrients and removing waste Whole blood never leaves capillaries but leucocytes, oxygen, food and water can

What is the lymphatic system? Once outside the capillaries they are carried by a derivative of blood plasma called tissue/interstitial fluid This fluid circulates throughout the tissues, delivering food, oxygen and water to cells and collecting carbon dioxide When it has finished its work not all of it can pass through capillary walls because the pressure is too high

What is the lymphatic system? Fluid that is left is picked up by the lymphatic capillaries These have larger pores in their walls than blood capillaries and the pressure inside is lower Excess tissue fluid and substances made of large molecules etc. drain away into them The fluid – called lymph – is filtered by lymph nodes then collected by the lymphatic ducts before entering right/left subclavian veins and returning to the bloodstream

Connection between blood and lymph

Simplified lymph circuit

Structure: plasma, lymphocytes, proteins and waste products Lymph – Structure Structure: plasma, lymphocytes, proteins and waste products

Functions of Lymphatic System Transports fat Controls swelling Fights infection

Effect of Lymphatic System on Skin and Muscles Removes waste and toxins from skin and muscles so they can work more efficiently

Movement of lymph Contraction of skeletal muscles collapses vessels and because valves are present, lymph is directed towards the upper part of body There is a slight oncoming pressure from tissue fluids Movement of lymph towards thorax during inspiration Negative suction pressure helps pull lymph upwards

Structure of lymph node

Functions of lymph nodes Filter lymph, remove and destroy harmful micro-organisms, tumour cells, damaged or dead tissue cells; filtering system prevents toxic materials from reaching bloodstream and causing septicaemia Produce new lymphocytes and antibodies Lymphatic tissue cells within node may become activated to form antibodies against a particular infection

Main lymphatic ducts

Lymphatic nodes – head and neck Superficial parotid nodes – in front of ears Mastoid nodes – behind ears Submandibular – beneath mandible Occipital nodes – base of skull Deep cervical nodes – deep within neck Superficial cervical nodes – side of neck

Lymphatic nodes – body Axillary nodes – armpit Supratrochlear nodes – elbow crease Iliac nodes – abdomen Inguinal nodes – groin Popliteal nodes – knee

Lies on upper left-hand side of abdomen Spleen Lies on upper left-hand side of abdomen

Spleen – Functions 1. Forms new lymphocytes 2. Destroys thrombocytes and erythrocytes 3. Helps fight infection

Tonsils

Tonsils Lymphoid tissue that plays role in immune function Tonsils help to fight infection

Main Lymphatic Nodes