Lymphatic system Flashcards
Lymph
Coagulable fluid in the lymphatic system that has similar contents to plasma.
Except:
Contains white blood cells
Lipids
The word ‘lymph’ only applies to interstitial fluid in the lymphatic vessels.
Interstitial fluid
Environment surrounding tissues
Receives nutrients from arteries and removes waste products from veins.
When in the lymphatic vessels, interstitial fluid is called ‘lymph’
Pathway of lymph through lymphatic system
Arterial capillary ---> Interstitial space ----> Lymphatic capillary -----> Afferent lymphatic vessel ----> Lymph node -----> Efferent lymphatic vessel ----> Lymphatic trunk -----> Collecting duct -----> Jugular/ subclavian vein.
Lymphatic tissues around the body (8)
Cervical nodes Thymus Axillary nodes Thoracic duct Spleen Iliac nodes Bone marrow Interstitial nodes
Lymphatic capillaries
A plexus formed in tissue space
10-50 micrometres in diameter.
Composed of unicellular endothelial cells that allow unidirectional flow of lymph due to overlapping of cells.
Contains pores in the endothelial cells, allows flow of lymph into vessel.
Function of the lymphatic system
Drains fluid from tissue- prevent oedema
Absorbs fatty acid from the intestines
Provides immunological defence, through white blood cells.
Pathological significance of the lymphatic system
Can allow the spread of cancer- metastasis
Can allow the spread of infection
Lacteals
Lymphatic capillaries in the small intestines that carries chyle.
Chyle has more lipids compared to normal interstitial fluid.
Lymphatic afferent vessels
Vessels that carry lymph to the lymph nodes.
Formed from the joining of lymphatic capillaries.
Composed of three layers:
Endothelium- inner layer, one cell thick
Tunica intima- Middle layer, composed of smooth muscle
Tunica adventitia: Outer layer, connective tissue. This prevents vessel from expanding.
Contains valves- prevents backflow of lymph, due to low pressure in vessels,
Describe the flow of lymph through a lymph node
Afferent lymphatic vessel----> Subcapsular sinus ----> Trabecular sinus ----> Cortex -----> Medulla -----> Efferent lymphatic vessel
Lymphatic nodules
Smaller version of lymph nodes without a capsule.
Formed from a collection of lymphatic tissue.
Located:
Tonsils
Peyer’s patches in the small intestines
Appendix
Nodules act as a first line of defence due to their locations. This is what pathogens would usually meet first if they enter through the mouth or stomach.
Structure and function of the lymph nodes
Lymphatic tissue found in clusters, around 600 in the body. This is where lymph is processed.
Structure:
Capsule- outer layer of connective tissue. Prevents node from swelling
Subcapsular sinus- space between cortex and capsule
Trabecular sinus: drains lymph from the subcapsular sinus, connects to the cortex
Cortex: divided in outer and paracortex region.
Outer contains B cells and macrophages.
Paracortex contains T cells.
Medulla: The deepest region of the node. Contains B cells and macrophages
Lymphatic chain
Line of lymph nodes connected by lymphatic vessels.
A primary node is at the start of the chain, whilst the terminal node is at the end of the chain.
This allows all the lymph to be filtered efficiently.
How is lymph moved in the lymph vessels?
Contraction of skeletal muscles.
Respiratory movements
Contraction in the lymphatic vessel walls.
How is lymph moved into the lymphatic capillaries?
Filtration pressure:
build up of interstitial fluid is forced into the capillaries.
Lymphatic drainage of the breast
Contains a lymphatic plexus around the nipple.
75% of lymph drains out the axillary region
25% drains out the parasternal.
This is important for when cancer treatment is targetted
Axillary lymph nodes and vessels
Axillary lymphatic plexus drains 75% of the breast into the axillary lymph nodes.
Lymph is also collected from the upper limb vessels.
There are around 20-30 axillary lymph nodes
The nodes drain into the subclavian trunk.
Primary cervical lymph nodes
Collects lymph from the nose to the base of the neck.
How are lymphatic vessels/ nodes classified
Deep or superficial
When deep: close to the viscera. Usually close to arteries
Named according to the organ is is next to
I.e Left pulmonary lymph node
When superficial: named according to the anatomical region. Usually close to veins.
I.e right superficial inguinal lymph nodes
Spleen
Largest lymphatic organ, around 12cm.
Located in the left hypochondrium (below costal cartilage).
Supplies by splenic vein and artery.
Divided into:
White pulp- inner region with white blood cells. Central to the arteries.
Red pulp- outer region with red blood cells. Next to venous spaces
Functions:
Filters blood
Stores and removes platelets
Thymus
Primary lymphatic organ that is larger in children. Shrinks from 70g in children to 3g in adults.
Contains 2 lobes- cortex and medulla
Located between the aorta and sternum at the T4/5 space.
Function:
Contain T cells and macrophages
Thoracic duct
Left thoracic collecting duct- 40 cm in length
Vessel that ascends between the azygos vein and the oesophagus.
Passes through the diaphragm and aortic hiatus.
Extends from the base of the neck to L2
Function:
Collects chyle from the cisterna chyli and drains into the left venous angle- between the left subclavian vein and left internal jugular
Right collect duct
Lymphatic vessel around 1.2cm in length, located at the right venous angle- between right internal jugular vein and right subclavian vein
Drains:
Upper right section of the trunk
The right arm
The right side of the head and neck
Formed from the joining of;
Right jugular trunk
Right subclavian trunke
Right bronchomediastinal trunk
Jugular trunk
Lymphatic vessel that runs along the internal jugular vein.
There is the right and left jugular trunk.
Carries lymph from the head and neck.
Left drains into Thoracic duct whilst right drains into the right collecting duct.
