Download What is the lymphatic system?

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
1. Lymphatic capillaries
2.Lymphatic vessels
3.Lymph nodes
4.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
Lymph – Structure
• Structure: plasma, lymphocytes, proteins and
waste products
Functions of Lymphatic
System
1. Transports fat
2. Controls swelling
3. 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
1. Contraction of skeletal muscles collapses vessels and
because valves are present, lymph is directed towards the
upper part of body
2. There is a slight oncoming pressure from tissue fluids
3. Movement of lymph towards thorax during inspiration
4. Negative suction pressure helps pull lymph upwards
Structure of lymph node
Functions of lymph
nodes
1. Filter lymph, remove and destroy harmful microorganisms, tumour cells, damaged or dead tissue
cells; filtering system prevents toxic materials from
reaching bloodstream and causing septicaemia
2. Produce new lymphocytes and antibodies
3. Lymphatic tissue cells within node may become
activated to form antibodies against a particular
infection
Main lymphatic ducts
Lymphatic nodes – head
and neck
1. Superficial parotid nodes – in front of ears
2. Mastoid nodes – behind ears
3. Submandibular – beneath mandible
4. Occipital nodes – base of skull
5. Deep cervical nodes – deep within neck
6. Superficial cervical nodes – side of neck
Lymphatic nodes – body
1. Axillary nodes – armpit
2. Supratrochlear nodes – elbow crease
3. Iliac nodes – abdomen
4. Inguinal nodes – groin
5. Popliteal nodes – knee
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
Axillary
Abdominal
Cubital
Pelvic
Inguinal
Popliteal