Lympathic system Flashcards
What does the lympatic system consist of?
Lymph
Lymph vessels
Lymph nodes
Lymph organs
Lymphoid tissue
Bone marrow
What are the 3 functions of the lymphatic system?
Tissue drainage
Immunity
Absorption in the small intestine
What happen during tissue drainage?
Fluid carrying substances escapes capillaries into tissue
Most is returned to the bloodstream by capillaries at the venous end
About 3-4l is not and this drains in to the lymphatic system
What happens at absoption in the small intestines?
Breakdown products of fat and fat-soluble materials are absorbed into the lymphatic vessels of the villi.
They drain into larger lymphatic vessels and eventually into the blood stream.
How is the lymphatic system involved in immunity?
Lymphatic organs are concerned with the production and maturation of lymphocytes.
Where are B-lymphocytes produced and matured?
Bone marrow
Where are T-lymphocytes matured?
Thymus
What is lymph?
Clear, watery fluid with identicial composition to intersitial fluid and simular to plasma but less protien
What does lymph do?
Carries particles e.g., cell debris, bacteria that is filtered and destoryed by nodes
Transport plasma proteins back to the blood
What are lymph capilaries?
These originate as blind-ended tubes in the interstitial spaces.
Permeable to all interstitial fluid including protein and cell debris.
Capillaries join up to make larger lymph vessels.
What are lymph vessels?
Often found running alongside arteries and veins serving the area.
Cup-shaped valves to ensure that lymph flows in a way one system towards the thorax.
Vessels become larger as they join together
What drains into the thoratic duct?
Lymph from both legs, the pelvic and abdominal cavities, the left half of the thorax, head and neck and left arm.
What side is the thoracic duct?
Left
What drains into the right lymphatic duct?
Lymph from the right half of the thorax, head, neck and right arm.
Where does lymph from the ducts drain into?
Subclavian veins
How is lymph circulated?
Large lymph vessels have the ability to contract
Compression from activity
Changes in thoracic pressure
What are lymph nodes?
Oval or bean-shaped organs that lie along the length of lymph vessels.
Lymph drains through a number of nodes before returning to venous circulation.
Packed with immune and defence cells.
4 or 5 afferent lymph vessels may enter the node but there is only one efferent vessel that carries lymph away.
Positioned at strategic positions throughout the body.
Arranged in deep and superficial groups.
What are the 2 lymph node functions?
Defence
Maturation and proliferation of lymphocytes
What are the tonsils?
Collections of lymphoid tissue located in the back of the mouth and throat to intercept swallowed or inhaled antigens.
Deep pits and clefts to trap bacteria, which are then destroyed by the defence cells in the tonsil.
What is the spleen?
Contains reticular and lymphatic tissue.
Largest lymph organ in the body.
Lies in the left hypochondriac region of the abdominal cavity.
Vascular and contains red blood cells, macrophages, lymphocytes and plasma cells.
What are the 4 functions of the spleen?
- Phagocytosis
Old and abnormal erythrocytes are destroyed in the spleen,
Other cellular material e.g., leukocytes, platelets and bacteria is phagocytosed here. - Storage of blood
The spleen contains up to 350ml of blood and in response to sympathetic stimulation can rapidly return it to circulation. - Immune response
The spleen contains T and B lymphocytes which are activated by the presence of antigens. - Erythropoiesis
It is important for fetal blood cell production and the spleen can also fulfil this function in adults when needed.
What is the thymus gland?
Lies in the upper part of the mediastinum behind the sternum and extends to the root of the next.
It weights more at birth, grows until puberty and then begins to atrophy.
What are the functions of the thymus gland?
Lymphocytes that enter develop into T-lymphocytes.
T-lymphocytes that can distinguish self-tissue from foreign tissue
What is mucosa-assocated lymphoid tissue?
Collections of lymphoid tissue that are not enclosed in a capsule.
They contain B and T lymphocytes.
However, as they have no lymphatic vessels, they do not filter lymph and are therefore exposed to disease spread by lymph.
What is the largest collection of lymphoid tissue called?
Spleen
Which duct has the largest proportion of lymphatic drainage?
Thoracic duct
Where does excess interstitial fluid drains directly into?
Lymphatic capillaries
